JP4255755B2

JP4255755B2 - Secondary battery remaining capacity calculation device and remaining capacity calculation method thereof

Info

Publication number: JP4255755B2
Application number: JP2003162036A
Authority: JP
Inventors: 利史植田; 展安森下; 和宏大川; 善忠中尾
Original assignee: パナソニックＥｖエナジー株式会社
Priority date: 2003-06-06
Filing date: 2003-06-06
Publication date: 2009-04-15
Anticipated expiration: 2023-06-06
Also published as: JP2004361313A

Description

【０００１】
【発明の属する技術分野】
本発明は、二次電池の残存容量演算装置及びその残存容量演算方法に関する。
【０００２】
【従来の技術】
従来、携帯電話基地局などの設備で使用される電子・電気機器のバックアップ用電源には鉛蓄電池が多く用いられていたが、最近はニッケル−金属水素化物電池の需要が高まっている。ニッケル−金属水素化物電池は鉛蓄電池に比べて高エネルギー密度で、軽量・小型化が可能であることがその要因である。
バックアップ用電源として使用されるニッケル−金属水素化物電池は、通常は負荷に電力を供給せず、間欠充電される。停電時に、負荷に電力を供給する（放電する。）。停電時にはユーザが、バックアップ用電源が放電可能な間に電力の復旧作業等の処置を行わなくてはならないため、バックアップ用電源の残存容量又は使用可能時間を、特に放電末期に正確に演算し表示する必要がある。以下、「残存容量」は、「その時点から放電可能な電気量」を表す。
【０００３】
特許文献１（特開平９−１７８８２７号公報）に開示された電池容量の残量検出装置は、電池の放電中に所定時間内の電圧値変化量を測定し、所定時間値と電圧値変化量から、電池容量の残量（残存容量）に対応する残量時間を計算し、表示する。
【０００４】
【特許文献１】
特開平９−１７８８２７号公報
【０００５】
【発明が解決しようとする課題】
一般に二次電池をほぼ定電流で放電する場合、放電電気量（又は放電開始からの時間）に対して電池電圧は単調に減少する。放電末期には二次電池の放電電圧が急激に低下する。特許文献１に開示された二次電池の残存容量演算装置は、放電電圧が急激に低下することを検出して、放電末期に入ったこと（放電末期の残存容量）を表示した。しかし、メモリ効果を有する二次電池の場合、放電末期以外においても放電電圧が急激に低下することがある。それ故に、特許文献１に開示された二次電池の残存容量演算装置は、実際には残存容量が十分あるにも関わらず、小さな残存容量を表示する可能性があった。
【０００６】
二次電池の残存容量が所定の範囲においては、二次電池の電圧はほとんど変化しない。放電電圧に基づいて残存容量を算出する二次電池の残存容量演算装置（特許文献１）は、二次電池の電圧がほとんど変化しない区間において、残存容量を正確に演算することは困難であった。
放電電流に基づいて放電電気量を積算し、残存容量から放電電気量を減算して、新たな残存容量を算出する二次電池の残存容量演算装置がある。しかし、この装置によれば、演算において考慮されない種々の要因により、演算された残存容量と実際の残存容量との間にわずかの誤差が生じる。放電末期においてはその誤差が累積する。放電末期において、残存容量演算装置が残存容量が未だあると表示しているにもかかわらず、実際には二次電池が完全放電状態に突然陥る恐れがあった。
【０００７】
本発明は上記従来の課題を解決するもので、放電末期の二次電池の残存容量を正確に演算する二次電池の残存容量演算装置及びその残存容量演算方法を提供することを目的とする。
本発明は、メモリ効果に起因して残存容量を誤って表示する恐れがなく、且つ放電末期の二次電池の残存容量を正確に演算する二次電池の残存容量演算装置及びその残存容量演算方法を提供することを目的とする。
本発明は、二次電池の電圧がほとんど変化しない区間においても、放電末期においても、二次電池の残存容量を正確に演算する二次電池の残存容量演算装置及びその残存容量演算方法を提供することを目的とする。
【０００８】
【課題を解決するための手段】
上記課題を解決するため、本発明は以下の構成を有する。請求項１に記載の発明は、二次電池の放電電圧を検出する電圧検出部と、前記二次電池の放電電流を検出する電流検出部と、前記二次電池の放電に伴って放電電圧の時間微分値が減少する放電末期における所定残存容量のときの前記放電電圧の時間微分値である第２の所定値と、二次電池が完全放電した後における、前記二次電池が不完全放電状態から充電状態に変化したときの各放電終了時残存容量の最小値である最小放電終了時残存容量と、を記憶する記憶部と、前記電流検出部によって検出された放電電流の積算値に基づき前記二次電池の残存容量を演算する残存容量演算部と、前記残存容量を表示する表示部と、を有し、前記残存容量演算部は放電中に、前記残存容量が前記記憶部に記憶された前記最小放電終了時残存容量より小さく、且つ前記放電電圧の時間微分値が前記記憶部に記憶された第２の所定値になった時、前記残存容量を前記所定残存容量に置き換える、ことを特徴とする二次電池の残存容量演算装置である。
【０００９】
請求項６に記載の発明は、二次電池の放電電圧を検出する電圧検出ステップと、前記二次電池の放電電流を検出する電流検出ステップと、前記二次電池の放電に伴って放電電圧の時間微分値が減少する放電末期における所定残存容量のときの前記放電電圧の時間微分値である第２の所定値と、前記二次電池が完全放電した後における、前記二次電池が不完全放電状態から充電状態に変化したときの各放電終了時残存容量の最小値である最小放電終了時残存容量と、を記憶する記憶ステップと、前記電流検出ステップにおいて検出された放電電流の積算値に基づき前記二次電池の残存容量を演算する残存容量演算ステップと、前記残存容量を表示する表示ステップと、を有し、放電中の前記残存容量演算ステップにおいて、前記残存容量が前記記憶ステップにおいて記憶した前記最小放電終了時残存容量より小さく、且つ前記放電電圧の時間微分値が前記記憶ステップにおいて記憶した第２の所定値になった時、前記残存容量を所定残存容量に置き換える、ことを特徴とする二次電池の残存容量演算方法である。
【００１０】
請求項２に記載の発明は、二次電池の放電電圧を検出する電圧検出部と、前記二次電池の放電電流を検出する電流検出部と、前記二次電池の放電に伴って放電電圧の時間微分値が減少する放電末期における所定残存容量のときの前記放電電圧の時間微分値である第２の所定値と、前記二次電池が完全放電した後における、前記二次電池が不完全放電状態から充電状態に変化したときの各放電終了時残存容量であって、少なくとも、それ以後の放電終了時残存容量よりも値が小さな放電終了時残存容量と、を記憶する記憶部と、前記電流検出部によって検出された放電電流の積算値に基づき前記二次電池の残存容量を演算する残存容量演算部と、前記残存容量を表示する表示部と、を有し、前記残存容量演算部は放電中に、前記残存容量が前記記憶部に記憶された前記各放電終了時残存容量近傍の値でなく、且つ前記放電電圧の時間微分値が前記記憶部に記憶された第２の所定値になった時、前記残存容量を前記所定残存容量に置き換える、ことを特徴とする二次電池の残存容量演算装置である。
【００１１】
請求項７に記載の発明は、二次電池の放電電圧を検出する電圧検出ステップと、前記二次電池の放電電流を検出する電流検出ステップと、前記二次電池の放電に伴って放電電圧の時間微分値が減少する放電末期における所定残存容量のときの前記放電電圧の時間微分値である第２の所定値と、前記二次電池が完全放電した後における、前記二次電池が不完全放電状態から充電状態に変化したときの各放電終了時残存容量であって、少なくとも、それ以後の放電終了時残存容量よりも値が小さな放電終了時残存容量と、を記憶する記憶ステップと、前記電流検出ステップにおいて検出された放電電流の積算値に基づき前記二次電池の残存容量を演算する残存容量演算ステップと、前記残存容量を表示する表示ステップと、を有し、放電中の前記残存容量演算ステップにおいて、前記残存容量が前記記憶ステップにおいて記憶した前記各放電終了時残存容量近傍の値でなく、且つ前記放電電圧の時間微分値が前記記憶ステップにおいて記憶した第２の所定値になった時、前記残存容量を前記所定残存容量に置き換える、ことを特徴とする二次電池の残存容量演算方法である。
【００１２】
本発明は、放電末期の二次電池の残存容量を正確に演算する二次電池の残存容量演算装置及びその残存容量演算方法を実現するという作用を有する。
本発明は、メモリ効果に起因して残存容量を誤って表示する恐れがなく且つ放電末期の二次電池の残存容量を正確に演算する二次電池の残存容量演算装置及びその残存容量演算方法を実現するという作用を有する。
【００１３】
「残存容量」は、その時点から電池電圧が放電終止電圧に達するまでに放電可能な電気量を表す。「放電電気量」は、放電開始から放電した電気量を表す。
「放電」は、負荷に電力を供給する放電及び負荷に電力を供給しない自己放電を含む。放電開始時の残存容量は任意である（満充電状態から放電を開始しなくても良い）。
例えば放電中、残存容量演算部は、所定の時間間隔で放電電流値をサンプリングし、その積算値（放電電気量）を放電開始時の残存容量から減じ、サンプリングの各タイミングでの残存容量を演算する。
二次電池が連続的に定電流放電する場合、放電曲線（放電開始からの時間に対する電池電圧のグラフ）は単調減少関数であり、放電末期において、急激な電圧降下が発生する。本発明の二次電池の残存容量演算装置及び残存容量演算方法は、放電末期に放電電圧の時間微分値が第２の所定値になったときに、残存容量を予め記憶部に記憶させた残存容量実測値に置き換え、正確な残存容量を表示する。
しかし、二次電池の放電電圧は、放電末期のみならず、メモリ効果の発生点においても、急激に降下する。本発明は、実際の残存容量が十分あるにも関わらず、メモリ効果に起因する放電電圧変動により誤って小さな残存容量を表示することを防止する。
【００１４】
請求項２及び請求項７の発明においては、二次電池が完全放電した後に、１又は複数回の充電及び不完全放電を行った場合に発生するメモリ効果の発生点のうち、メモリ効果を解消されていない点を少なくとも記憶する。即ち、完全放電後の放電終了時残存容量（放電深度）の中で、それ以前の放電深度よりも浅い放電深度の放電終了時残存容量を全て記憶する。
【００１５】
請求項３に記載の発明は、前記残存容量演算部は放電中に、前記の条件で且つ前記残存容量が前記二次電池の放電に伴って放電電圧の時間微分値が増大する放電初期における第１の所定値より小さい場合に、前記残存容量を前記所定残存容量に置き換えることを特徴とする請求項１又は請求項２に記載の二次電池の残存容量演算装置である。
【００１６】
請求項８に記載の発明は、放電中の前記残存容量演算ステップにおいて、前記の条件で且つ前記残存容量が前記二次電池の放電に伴って放電電圧の時間微分値が増大する放電初期における第１の所定値より小さい場合に、前記残存容量を前記所定残存容量に置き換えることを特徴とする請求項６又は請求項７に記載の二次電池の残存容量演算方法である。
二次電池の放電電圧は、放電末期のみならず、放電初期においても、急激に降下する。本発明の二次電池の残存容量演算装置及び残存容量演算方法は、更に放電初期（放電開始後の放電電気量が第１の所定値に達するまで）においても、放電電圧の時間微分値と第２の所定値との比較を行わない。これにより、実際の残存容量が十分あるにも関わらず、放電初期に誤って小さな残存容量を表示することを防止できる。
【００１７】
請求項４に記載の発明は、前記二次電池の温度を検出する温度検出部を更に有し、前記第２の所定値が、前記温度を変数とする値であることを特徴とする請求項１から請求項３のいずれかの請求項に記載の二次電池の残存容量演算装置である。
【００１８】
請求項９に記載の発明は、前記二次電池の温度を検出する温度検出ステップを更に有し、前記第２の所定値が、前記温度を変数とする値であることを特徴とする請求項６から請求項８のいずれかの請求項に記載の二次電池の残存容量演算方法である。
第２の所定値は温度依存性を有する。本発明により、より正確に残存容量を推定する二次電池の残存容量演算装置及び残存容量演算方法を実現できる。
【００２４】
請求項５に記載の発明は、前記二次電池がニッケル−金属水素化物電池であることを特徴とする請求項１から請求項４のいずれかの請求項に記載の二次電池の残存容量演算装置である。
【００２５】
請求項１０に記載の発明は、前記二次電池がニッケル−金属水素化物電池であることを特徴とする請求項６から請求項９のいずれかの請求項に記載の二次電池の残存容量演算方法である。
本発明は、特にメモリ効果を有する二次電池である、ニッケル−金属水素化物電池において、特に有用である。
【００２６】
【発明の実施の形態】
以下本発明の実施をするための最良の形態を具体的に示した実施の形態について、図面とともに記載する。
【００２７】
《実施の形態１》
図１〜図５を用いて、本発明の実施の形態１の残存容量演算装置及びその残存容量演算方法を説明する。
図１は、本発明の実施の形態１の残存容量演算装置を含むバックアップ電源用電池管理装置の構成図である。
【００２８】
図１において、１５０は残存容量演算装置、１０１は二次電池、１０２は電源監視制御部、１０５は放電器、１０６は充電器、１０７は表示部、１０８は商用電源、１０９は整流器、１１０は負荷である。残存容量演算装置１５０は、残存容量演算部１５１、温度検出部１５２、電流検出部１５３、電圧検出部１５４及びタイマ部１５５を有する。
【００２９】
通常、負荷１１０には商用電源１０８が供給されている。商用電源１０８からの交流電流は整流器１０９で直流電流に変換され、負荷１１０に供給される。二次電池１０１は、商用電源１０８が供給されている期間、充電器１０６によって間欠充電され、満充電状態が保持されている。充電器１０６は電源監視制御部１０２によって動作開始及び停止される。二次電池の残存容量がメモリ効果により減少することを防止するため、所定の期間毎に、電源監視制御部１０２は放電器１０５を動作させ、二次電池を完全放電させる。停電時に、電源監視制御部１０２は回路を切り替えて、二次電池１０１に放電させる。二次電池１０１は、負荷１１０へ電力を供給し（放電し）、バックアップ電源として機能する。実施の形態において、二次電池１０１の放電電流値はほぼ一定である。負荷１１０電流の急激な変動はないものとする。商用電源１０８が復旧した後、電源監視制御部１０２は二次電池１０１から負荷１１０への電力供給を中止し（放電を中止し）、商用電源１０８からの供給に切り替える。充電器１０６を動作させ、二次電池１０１を満充電する。なお、二次電池１０１の放電期間及び放電電気量は放電毎に様々である。
【００３０】
二次電池１０１は、互いに直列及び／又は並列に接続されている複数の二次電池セル（図示しない。）、あるいは一つの二次電池セル（図示しない。）から構成されている。それぞれの二次電池セルは、メモリ効果を有する。実施の形態１において二次電池１０１はニッケル−金属水素化物電池である。
【００３１】
温度検出部１５２は、二次電池１０１の内部温度、二次電池１０１の表面温度又は雰囲気温度のいずれかを検出し、残存容量演算部１５１の入出力部１１１に送信する。実施の形態において温度検出部１５２は二次電池１０１の表面温度（以下、「電池温度」と言う。）を検出する。電流検出部１５３は、二次電池１０１の放電電流、満充電電流を検出し、残存容量演算部１５１に送信する。電圧検出部１５４は二次電池１０１の電池電圧を検出し、残存容量演算部１５１に送信する。タイマ部１５５は時刻情報を残存容量演算部１５１に送信する。
【００３２】
残存容量演算部１５１は、二次電池１０１の残存容量を推定し、電源監視制御部１０２に送信する。二次電池１０１の残存容量の情報は、表示部１０７に表示される。表示方法は、定量的な表示（例えばＡｈを単位とする値の表示）であっても良く、定性的な表示（例えば赤色発光ダイオードを点滅させて残存容量が小さいことを示す表示）でも良い。残存容量の情報の出力は、例えば直接ユーザが視覚的又は聴覚的に認識可能なように表示しても良く、ホスト装置等に残存容量の情報を送信しても良い。
【００３３】
図２は、二次電池１０１の放電期間中の放電開始からの時間又は放電電気量に対する電池電圧、電池電圧の時間微分値、残存容量の一例を示すグラフである。図２（ａ）は、電池電圧と放電開始からの時間の関係を表すグラフ（以下、「放電曲線」と言う。）である。二次電池１０１の放電が、満充電状態から完全放電状態まで定電流で連続的に行われるときを想定する。完全放電状態とは、電池電圧が放電終止電圧Ｖｅまで降下した状態を言う。図２（ｂ）は、電池電圧の時間微分値と放電開始からの時間の関係を表すグラフ、図２（ｃ）は、残存容量と放電開始からの時間の関係を表すグラフである。放電電気量は放電開始からの時間に比例し、残存容量は放電開始からの時間をパラメータとし、比例係数が負の値である１次関数で表される。満充電状態での残存容量をＳｆ、完全放電状態での残存容量を０とする。
【００３４】
１０は、二次電池１０１の電池電圧にメモリ効果の影響がない場合の放電曲線である。放電曲線１０は単調減少関数であり、放電初期と放電末期は急激に電圧降下する。１１は、二次電池１０１の電池電圧にメモリ効果の影響がない場合の放電曲線１０の時間に関する１回微分（放電電圧の時間変化率）ｄＶ／ｄｔ（Ｖは電池電圧、ｔは時間）のグラフである。放電電圧の時間変化率ｄＶ／ｄｔのグラフ１１は、常に負の値をとる、上に凸の関数である。
【００３５】
２０は、二次電池１０１の電池電圧にメモリ効果の影響がある場合の放電曲線である。二次電池１０１を完全放電し、満充電した後、残存容量Ｓｍまで（放電開始からの時間Ｔｍまで）不完全放電したときに放電を終了し、満充電し、更に完全放電した場合を想定する。放電曲線２０は、時刻Ｔｍ付近で（残存容量がＳｍになる付近で）その前後より大きな傾きで電圧降下する屈曲部２２を有する。このため、放電曲線２０の１回微分ｄＶ／ｄｔのグラフ２１は、時刻Ｔｍ付近に凹部２３を有する。凹部２３はメモリ効果により発生する。時刻Ｔｍ以降は、放電曲線１０とほぼ同様の形状（傾きがほぼ同じ）の曲線である。図２に示した例の場合、残存容量Ｓｍより下まで二次電池１０１を放電した後（例えば完全放電した後）、充電することにより、二次電池１０１へのメモリ効果の影響（残存容量Ｓｍの近傍で発生するグラフ２１の凹部２３）は消え、放電曲線２０は放電曲線１０に戻る。
【００３６】
二次電池１０１を不完全放電し、残存容量がＳｍの時点から充電すると、次の放電時に、先の放電から充電への変化点で（残存容量がＳｍの時点で）、放電曲線２０の１回微分ｄＶ／ｄｔのグラフ２１に凹部２３が発生する。
二次電池１０１を残存容量がＳｍの時点まで放電すると、残存容量がＳｍよりも大きな時点Ｓｐ（Ｓｐ＞Ｓｍ）においてそれまで発生していた二次電池１０１へのメモリ効果の影響（放電曲線２０の１回微分ｄＶ／ｄｔのグラフ２１の凹部）が消される。残存容量がＳｍよりも小さな時点Ｓｑ（Ｓｑ＜Ｓｍ）においてそれまで発生していた二次電池１０１へのメモリ効果の影響（放電曲線２０の１回微分ｄＶ／ｄｔのグラフ２１の凹部）は消えない。二次電池１０１を完全放電し、その後充電すると、それまでに存在していた全ての二次電池１０１へのメモリ効果の影響（放電曲線２０の１回微分ｄＶ／ｄｔのグラフ２１の凹部）が消される。
以下、二次電池１０１からメモリ効果の影響を取り除くため、完全放電し、その後満充電することを、「リフレッシュ充放電」と言う。電源監視制御部１０２は、所定のタイミングに放電器１０５を動作させて二次電池１０１をリフレッシュ充放電させる。
【００３７】
本発明の実施の形態１の二次電池の残存容量演算方法では、放電電流の積算値（放電電気量の積算値）に基づいて残存容量を推定する。放電電流を長時間積算し続けると電流検出誤差等の誤差が累積していく。そのため、残存容量をより正確に推定する必要がある放電末期ほど残存容量の推定精度が悪い。一方、放電末期には二次電池１０１の電圧は大きく変化する（図２（ａ）及び図２（ｂ）参照）。放電末期に、二次電池１０１の電圧が大きく変化して完全放電状態（電池電圧が放電終止電圧Ｖｅまで降下した状態）になるまでの時間変化は、完全放電状態の時点から時間をさかのぼって見ると、メモリ効果の有無によらずほぼ一定である。そこで、残存容量が所定値Ｓａのとき（放電可能時間がＴａのとき）の電圧の時間変化率Ｇｃ（第２の所定値）を予め求め、残存容量演算装置に記憶しておき、放電末期に電圧の時間変化率が第２の所定値Ｇｃになったときに残存容量をＳａに置き換える。
【００３８】
図３を用いて、本発明の実施の形態１の二次電池の残存容量演算方法を具体的に説明する。図３は、本発明の実施の形態１の二次電池の残存容量演算方法を示すフローチャートである。ステップ３０１で二次電池１０１は、放電を開始する。以下、残存容量演算部１５１は二次電池１０１の残存容量を連続的に推定し、電源監視制御部１０２に送信する。ステップ３０２で、リフレッシュ充放電後１回目の放電か否か判断する。該当しない場合は、ステップ３０４に進む。該当する場合はステップ３０３で最小放電終了時残存容量Ｓｍｉｎを満充電状態での残存容量Ｓｆに初期化する。最小放電終了時残存容量Ｓｍｉｎは、リフレッシュ充放電後（二次電池が完全放電した後）における、二次電池が不完全放電状態から充電状態に変化したとき（放電終了時）の各放電終了時残存容量の最小値である。ステップ３０４に進む。
【００３９】
ステップ３０４で残存容量演算部１５１は、電流検出部１５３から受信した放電電流値の積算値に基づき、現在の残存容量Ｓを計算する。典型的には、次の式による。
新しい残存容量Ｓ＝古い残存容量Ｓ−放電電流値の積算値
ステップ３０５で残存容量Ｓが第１の所定値（Ｓｆ−ΔＳｉ）より小さいか否か判断する。二次電池の放電電圧は、放電初期において急激に降下する。ΔＳｉは、放電初期の電池電圧が急激に低下する期間に二次電池１０１が放電する電気量である（図２（ａ）及び図２（ｃ）参照。）。ステップ３０６で、残存容量Ｓが最小放電終了時残存容量Ｓｍｉｎより小さいか否か判断する。Ｓ＜（Ｓｆ−ΔＳｉ）でなく（ステップ３０５）、又はＳ＜Ｓｍｉｎでない（ステップ３０６）場合、ステップ３０４に戻り、引き続き残存容量Ｓの計算を行う。Ｓ＜（Ｓｆ−ΔＳｉ）であって（ステップ３０５）且つＳ＜Ｓｍｉｎである（ステップ３０６）場合、ステップ３０７に進む。ステップ３０７で、最小放電終了時残存容量Ｓｍｉｎを現在の残存容量Ｓに更新する。
【００４０】
リフレッシュ充放電後（二次電池が完全放電した後）における、二次電池が不完全放電状態から充電状態に変化したとき（放電終了時）に、放電終了時残存容量と最小放電終了時残存容量Ｓｍｉｎとを比較し、放電終了時残存容量の方が小さければ（最小値であれば）、放電終了時残存容量を新たな最小放電終了時残存容量Ｓｍｉｎとして記憶しても良い。
【００４１】
ステップ３０８で、残存容量演算部１５１は電圧検出部１５４から受信した電圧値及びタイマ部１５５から受信した時刻情報から、電圧の時間変化率ｄＶ／ｄｔを計算する。ステップ３０９で、電圧の時間変化率ｄＶ／ｄｔが閾値Ｇｃ（第２の所定値）以下か否か判断する。電圧の時間変化率ｄＶ／ｄｔが閾値Ｇｃ（第２の所定値）より大きい場合ステップ３１０に進み、引き続き放電電流の積算値から、現在の残存容量Ｓを計算する（ステップ３０４と同じ）。ステップ３０７に戻る。ステップ３０９で、初めて電圧の時間変化率ｄＶ／ｄｔが閾値Ｇｃ（第２の所定値）以下になった場合、ステップ３１１に進み、残存容量ＳをＳａにリセットする。ステップ３１２で表示部１０７は、「バッテリーが残りわずか（Ｓａ）です。バッテリーの残り時間はあとＴａです」という警告メッセージを表示し、ブザーを鳴らす。処理を終了する。
【００４２】
なお、二次電池１０１の放電が中断された場合、図３のフローチャートを直ちに終了する。二次電池１０１を満充電し、次の放電開始に備える。
ステップ３１２の後、完全放電するまで、図２（ａ）若しくは（ｂ）並びに（ｃ）のグラフに従い（典型的にはグラフを表又は関数の形式で記憶する。）、残存容量演算部１５１は、放電電圧又はその時間微分値をパラメータとして、残存容量Ｓを算出し、表示しても良い。
又は、ステップ３１２の後、完全放電するまで、残存容量Ｓａを初期値として、放電電流の積算値から、現在の残存容量Ｓを計算しても良い（ステップ３０４と同じ）。
【００４３】
放電開始時には電池電圧が急激に低下し、電圧の時間変化率ｄＶ／ｄｔが第２の所定値Ｇｃを下回る（絶対値においては、電圧の時間変化率ｄＶ／ｄｔが第２の所定値Ｇｃより大きい。）。実施の形態１では、放電開始後電圧の時間変化率ｄＶ／ｄｔが第２の所定値Ｇｃを上回るまでの（絶対値において、電圧の時間変化率ｄＶ／ｄｔが第２の所定値Ｇｃより小さくなるまでの）期間の放電電気量ΔＳｉを予め求めておく。残存容量ＳがＳｉ（＝Ｓｆ−ΔＳｉ）を下回るまでは、ｄＶ／ｄｔ≦Ｇｃに初めてなったことに基づく残存容量Ｓのリセット（Ｓａへの置き換え）（ステップ３１１）を行わない。
放電曲線にメモリ効果による電圧降下が見られる場合、電圧降下が起きる残存容量近傍で電圧の時間変化率ｄＶ／ｄｔが第２の所定値Ｇｃを下回る（図２（ｂ）参照）。実施の形態１では、リフレッシュ充放電後に行った放電での放電終了時の残存容量の最小値（最小放電終了時残存容量Ｓｍｉｎ）を求め、放電時に残存容量が最小放電終了時残存容量Ｓｍｉｎを下回るまでは、ｄＶ／ｄｔ≦Ｇｃに初めてなったことに基づく残存容量Ｓのリセット（Ｓａへの置き換え）（ステップ３１１）を行わない。
【００４４】
次に、二次電池１０１の充放電サイクルの例を示し、実施の形態１の二次電池の残存容量演算方法を更に説明する。放電中に、電圧の時間変化率ｄＶ／ｄｔと第２の所定値Ｇｃとの比較を行い（図３のステップ３０９）、残存容量ＳをＳａにリセット（ステップ３１１）すべきか否か判定する期間に着目する。
【００４５】
図４は、二次電池１０１の充放電サイクルの一例を示す図である。時刻と残存容量の関係を示す。１枚の図に全てを表示する都合上、図４において、満充電終了直後に放電を開始する（時刻Ｔ１、時刻Ｔ４及び時刻Ｔ９）ように表示している。二次電池１０１を時刻０から時刻Ｔ０にリフレッシュ充放電する。時刻Ｔ０から時刻Ｔ１に、満充電し（残存容量Ｓｆ）、期間Ｃ１（時刻Ｔ１から時刻Ｔ３）に放電する。時刻Ｔ３から時刻Ｔ４に、満充電し、期間Ｃ２（時刻Ｔ４から時刻Ｔ８）に放電する。時刻Ｔ８から時刻Ｔ９に、満充電し、期間Ｃ３（時刻Ｔ９から時刻Ｔ１７）に放電する。放電期間Ｃ１、Ｃ２及びＣ３での放電終了時の残存容量（放電終了時残存容量）は、それぞれＳ１、Ｓ２及びＳ３（Ｓ１＞Ｓ２＞Ｓａ＞Ｓ３）である。
【００４６】
放電期間Ｃ１での放電は、リフレッシュ充放電後１回目の放電であるため、放電曲線にはメモリ効果による電圧降下は生じない。放電期間Ｃ２での放電曲線には、放電期間Ｃ１での放電によるメモリ効果により、残存容量Ｓ１の時点で急激な電圧降下が生じる。放電期間Ｃ３での放電曲線には、放電期間Ｃ２での放電によるメモリ効果により、残存容量Ｓ２の時点で急激な電圧降下が生じる。放電期間Ｃ１での放電によるメモリ効果（残存容量Ｓ１の時点での急激な電圧降下）は、放電期間Ｃ２に消去される。
【００４７】
放電期間Ｃ１では、放電初期の時刻Ｔ１から時刻Ｔ２には、電圧が急激に低下するため、電圧の時間変化率ｄＶ／ｄｔと第２の所定値Ｇｃとの比較を行わない。時刻Ｔ２から時刻Ｔ３、時刻Ｔ７から時刻Ｔ８及び時刻Ｔ１４から時刻Ｔ１６に電圧の時間変化率ｄＶ／ｄｔと第２の所定値Ｇｃとの比較を行う。
【００４８】
図５は、二次電池１０１の充放電サイクルの別の一例を示す図である。時刻と残存容量の関係を示す。１枚の図に全てを表示する都合上、図５において、満充電終了直後に放電を開始する（時刻Ｔ１、時刻Ｔ４及び時刻Ｔ７）ように表示している。二次電池１０１を時刻０から時刻Ｔ０にリフレッシュ充放電する。時刻Ｔ０から時刻Ｔ１に、満充電し（残存容量Ｓｆ）、期間Ｃ１（時刻Ｔ１から時刻Ｔ３）に放電する。時刻Ｔ３から時刻Ｔ４に、満充電し、期間Ｃ２（時刻Ｔ４から時刻Ｔ６）に放電する。時刻Ｔ６から時刻Ｔ７に、満充電し、期間Ｃ３（時刻Ｔ７から時刻Ｔ１４）に放電する。放電期間Ｃ１、Ｃ２及びＣ３での放電終了時の残存容量（放電終了時残存容量）は、それぞれＳ１、Ｓ２及びＳ３（Ｓ２＞Ｓ１＞Ｓａ＞Ｓ３）である。
【００４９】
放電期間Ｃ１での放電は、リフレッシュ充放電後１回目の放電であるため、放電曲線にはメモリ効果による電圧降下は生じない。放電期間Ｃ２終了時（時刻Ｔ６）の残存容量Ｓ２は、放電期間Ｃ１終了時（時刻Ｔ３）の残存容量Ｓ１に比べて十分大きく、放電曲線にはメモリ効果による電圧降下が生じない。放電期間Ｃ３での放電では、放電期間Ｃ１及び放電期間Ｃ２での放電によるメモリ効果が重畳し、放電曲線にはメモリ効果による急激な電圧降下が２回（残存容量Ｓ１の時点及びＳ２）生じる。
【００５０】
放電期間Ｃ１では、放電初期の時刻Ｔ１から時刻Ｔ２には、電圧が急激に低下するため、電圧の時間変化率ｄＶ／ｄｔと第２の所定値Ｇｃとの比較を行わない。時刻Ｔ２から時刻Ｔ３及び時刻Ｔ１２から時刻Ｔ１３に電圧の時間変化率ｄＶ／ｄｔと第２の所定値Ｇｃとの比較を行う。
【００５１】
発明者は、放電末期に電圧の時間変化率ｄＶ／ｄｔが第２の所定値Ｇｃを下回った後、電圧が放電終止電圧に達するまでの時間（Ｔａ）は、メモリ効果による電圧降下の有無に関わらず、ほぼ一定であることを見いだした（図２参照）。本発明の実施の形態１の二次電池の残存容量演算装置及びその残存容量演算方法によれば、放電時に電圧の時間変化率を連続的に測定し、放電末期に残存容量をリセットするので、放電末期の残存容量演算を正確に行うことができる。
なお、各電池温度毎に、二次電池１０１の残存容量がＳａのときの電圧の時間変化率Ｇｃ（第２の所定値）を求めておけば、より正確に残存容量を推定できる。
【００５２】
本発明の実施の形態１の二次電池の残存容量演算方法のフローチャートは、図３に示したフローチャートに限られない。
なお、実施の形態１では放電は満充電状態（残存容量がＳｆ）から始めるとして説明したが、満充電していない状態から放電を開始する構成としても良い。
実施の形態では、放電中には二次電池１０１から負荷１１０に電力を供給した。放電中に二次電池から負荷に電力を供給しない、自己放電の場合についても本発明の二次電池の残存容量演算方法によって、二次電池の残存容量を正確に推定できる。
【００５３】
《実施の形態２》
図１、図２、図６〜図８を用いて、本発明の実施の形態２の残存容量演算装置及びその残存容量演算方法を説明する。図１は、本発明の実施の形態２の残存容量演算装置を含むバックアップ電源用電池管理装置の構成図であり、実施の形態１と同じであるので説明を省略する。図２は、既に説明したので説明を省略する。
【００５４】
本発明の実施の形態２の二次電池の残存容量演算方法では、放電電流の積算値に基づいて残存容量を推定する。放電電流を長時間積算し続けると電流検出誤差が累積していく。そのため、残存容量をより正確に推定する必要がある放電末期ほど残存容量の推定精度が悪い。一方、放電末期には二次電池１０１の電圧は大きく変化する（図２（ａ）及び図２（ｂ）参照）。そこで、残存容量がＳａのとき（放電可能時間がＴａのとき）の電圧の時間変化率Ｇｃ（第２の所定値）を予め求め、残存容量演算装置に記憶しておき、放電末期に電圧の時間変化率がＧｃ（第２の所定値）になったときに残存容量をＳａに置き換える。
【００５５】
図６を用いて、本発明の実施の形態２の二次電池の残存容量演算方法を具体的に説明する。図６は、本発明の実施の形態２の二次電池の残存容量演算方法を示すフローチャートである。ステップ６０１で二次電池１０１は、放電を開始する。以下、残存容量演算部１５１は二次電池１０１の残存容量を連続的に推定し、電源監視制御部１０２に送信する。ステップ６０２で、ｎに１を加算する。ｎはリフレッシュ充放電後の放電の回数であり、リフレッシュ充放電終了時に０に初期化されている。ステップ６０３で残存容量演算部１５１は、電流検出部１５３から受信した放電電流の積算値に基づき、現在の残存容量Ｓを計算する（計算方法は実施の形態１と同じ）。ステップ６０４で、ｎ回目の放電での残存容量ＳｎにＳを代入する。ステップ６０５で、残存容量Ｓが第１の所定値（Ｓｆ−ΔＳｉ）より小さいか否か判断する。ΔＳｉは、放電初期の電池電圧が急激に低下する期間に二次電池１０１が放電する電気量である（図２（ｃ）参照）。Ｓ＜（Ｓｆ−ΔＳｉ）でない場合（放電初期）、ステップ６０３に戻る。Ｓ＜（Ｓｆ−ΔＳｉ）である場合（放電初期を過ぎた場合）、ステップ６０６に進む。
【００５６】
ステップ６０６からステップ６０９では、残存容量Ｓがリフレッシュ充放電後の各放電終了時の残存容量Ｓｋ（ｋ＝１〜ｎ−１）近傍の値であるか否か判定する。ステップ６０６でｋを０に初期化する。ステップ６０７でｋに１を加算する。ステップ６０８でｋがｎより小さいか否か判断する。ｋがｎより小さい場合ステップ６０９で、残存容量がｋ回目の放電終了時の残存容量Ｓｋ以上Ｓｋ＋ΔＳｍ以下か否か判断する。ΔＳｍは、メモリ効果によって電池電圧が急激に低下する期間に二次電池１０１が放電する電気量である（図２（ｃ）参照）。以下、残存容量Ｓｋ以上Ｓｋ＋ΔＳｍ以下の範囲を、「ｋ回目の放電による残存容量のマスク範囲」と言う。ステップ６０９で、残存容量Ｓがｋ回目の放電による残存容量のマスク範囲に含まれる場合は、ステップ６０３に戻る。含まれない場合はステップ６０７に戻る。ステップ６０８でｋがｎ以上の場合、残存容量Ｓはリフレッシュ充放電後のｎ−１回の放電による残存容量のマスク範囲に含まれず、ステップ６１０に進む。
【００５７】
ステップ６１０で、残存容量演算部１５１は電圧検出部１５４から入力した電圧値及びタイマ部１５５から入力した時刻情報から、電圧の時間変化率ｄＶ／ｄｔを計算する。ステップ６１１で、電圧の時間変化率ｄＶ／ｄｔが閾値Ｇｃ（第２の所定値）以下か否か判断する。電圧の時間変化率ｄＶ／ｄｔが閾値Ｇｃ（第２の所定値）より大きい場合（絶対値において、ｄＶ／ｄｔがＧｃより小さい場合）ステップ６０３に戻り、引き続き放電電流の積算値から、現在の残存容量Ｓを計算する。ステップ６１１で、初めて電圧の時間変化率ｄＶ／ｄｔが閾値Ｇｃ（第２の所定値）以下になった場合（絶対値において、ｄＶ／ｄｔがＧｃ以上になった場合）、ステップ６１２に進み、残存容量ＳをＳａにリセットする。ステップ６１３で表示部１０７は、「バッテリーが残りわずか（Ｓａ）です。バッテリーの残り時間はあとＴａです」という警告メッセージを表示し、ブザーを鳴らす。処理を終了する。
【００５８】
なお、二次電池１０１の放電が中断された場合、図６のフローチャートを直ちに終了する。二次電池１０１を満充電し、次の放電開始に備える。
ステップ６１３の後、完全放電するまで、図２（ａ）若しくは（ｂ）並びに（ｃ）のグラフに従い（典型的にはグラフを表又は関数の形式で記憶する。）、残存容量演算部１５１は、放電電圧又はその時間微分値をパラメータとして、残存容量Ｓを算出し、表示しても良い。
又は、ステップ６１３の後、完全放電するまで、残存容量Ｓａを初期値として、放電電流の積算値から、現在の残存容量Ｓを計算しても良い（ステップ６０３と同じ）。
【００５９】
放電開始時には電池電圧が急激に低下し、電圧の時間変化率ｄＶ／ｄｔが第２の所定値Ｇｃを下回る。実施の形態１では、電圧の時間変化率ｄＶ／ｄｔが第２の所定値Ｇｃを上回るまでの放電電気量ΔＳｉを予め求めておき、残存容量がＳｉ（＝Ｓｆ−ΔＳｉ）を下回るまでは、電圧の時間変化率ｄＶ／ｄｔによる残存容量のリセット（ステップ６１２）を行わない。
放電曲線にメモリ効果による電圧降下が見られる場合、電圧降下が起きる残存容量近傍で電圧の時間変化率ｄＶ／ｄｔが第２の所定値Ｇｃを下回る。実施の形態２では、リフレッシュ充放電後に行った全ての放電終了時の残存容量近傍で、電圧の時間変化率ｄＶ／ｄｔによる残存容量のリセット（ステップ６１２）を行わない。二次電池１０１の放電時に、メモリ効果によって、電圧の時間変化率ｄＶ／ｄｔが第２の所定値Ｇｃを下回っている間に放電する電気量ΔＳｍを予め求めておく（図２参照）。
【００６０】
次に、二次電池１０１の充放電サイクルの例を示し、実施の形態１の二次電池の残存容量演算方法を更に説明する。放電中に、電圧の時間変化率ｄＶ／ｄｔと第２の所定値Ｇｃとの比較を行い（図６のステップ６１１）、残存容量をＳａにリセット（ステップ６１２）すべきか否か判定する期間に着目する。
【００６１】
図７は、二次電池１０１の充放電サイクルの一例を示す図である。充放電サイクルでの充電量及び放電量は図４と同じであるので、説明を省略する。各放電サイクルで、放電初期（時刻Ｔ１〜時刻Ｔ２、時刻Ｔ４〜時刻Ｔ５及び時刻Ｔ９〜時刻Ｔ１０）、及びメモリ効果により放電電圧の急激な低下が発生する期間（時刻Ｔ６〜時刻Ｔ７、時刻Ｔ１１〜時刻Ｔ１２、時刻Ｔ１３〜時刻Ｔ１４）は、電圧の時間変化率ｄＶ／ｄｔと第２の所定値Ｇｃとの比較を行わない。時刻Ｔ２〜時刻Ｔ３、時刻Ｔ５〜時刻Ｔ６、時刻Ｔ７〜時刻Ｔ８、時刻Ｔ１０〜時刻Ｔ１１、時刻Ｔ１２〜時刻Ｔ１３及び時刻Ｔ１４〜時刻Ｔ１６に電圧の時間変化率ｄＶ／ｄｔと第２の所定値Ｇｃとの比較を行う。
【００６２】
図８は、二次電池１０１の充放電サイクルの別の一例を示す図である。充放電サイクルでの充電量及び放電量は図５と同じであるので、説明を省略する。各放電サイクルで、放電初期（時刻Ｔ１〜時刻Ｔ２、時刻Ｔ４〜時刻Ｔ５及び時刻Ｔ７〜時刻Ｔ８）及びメモリ効果により放電電圧の急激な低下が発生する期間（時刻Ｔ９〜時刻Ｔ１０、時刻Ｔ１１〜時刻Ｔ１２）は、電圧の時間変化率ｄＶ／ｄｔと第２の所定値Ｇｃとの比較を行わない。時刻Ｔ２〜時刻Ｔ３、時刻Ｔ５〜時刻Ｔ６、時刻Ｔ８〜時刻Ｔ９、時刻Ｔ１０〜時刻Ｔ１１及び時刻Ｔ１２〜時刻Ｔ１３に電圧の時間変化率ｄＶ／ｄｔと第２の所定値Ｇｃとの比較を行う。
【００６３】
実施の形態２の二次電池の残存容量演算装置及びその残存容量演算方法は、実施の形態１のそれと同様の効果を奏する。
なお、各電池温度毎に、二次電池１０１の残存容量がＳａのときの電圧の時間変化率Ｇｃ（第２の所定値）を求めておけば、より正確に残存容量を推定できる。
実施の形態では、放電中には二次電池１０１から負荷１１０に電力を供給した。放電中に二次電池から負荷に電力を供給しない、自己放電の場合についても本発明の二次電池の残存容量演算方法によって、二次電池の残存容量を正確に推定できる。
【００６４】
なお、実施の形態１では放電は満充電状態（残存容量がＳｆ）から始めるとして説明したが、満充電していない状態から放電を開始する構成としても良い。
本発明の実施の形態２の二次電池の残存容量演算方法のフローチャートは、図６に示したフローチャートに限られない。
実施の形態２において、残存容量演算部１５１（記憶部を含む。）は、二次電池が完全放電した後における、二次電池が不完全放電状態から充電状態に変化したときの各放電終了時残存容量を全て記憶し、全ての放電終了時残存容量についてステップ６０６〜６０９の処理を行った。これに代えて、残存容量演算部１５１（記憶部を含む。）が、二次電池が完全放電した後における、二次電池が不完全放電状態から充電状態に変化したときの各放電終了時残存容量のうち、それ以後の放電終了時残存容量よりも値が小さな放電終了時残存容量のみを記憶し、記憶した放電終了時残存容量についてステップ６０６〜６０９の処理を行っても良い。
【００６５】
【発明の効果】
本発明によれば、放電末期の二次電池の残存容量を正確に演算する二次電池の残存容量演算装置及びその残存容量演算方法を実現できるという有利な効果が得られる。
本発明によれば、メモリ効果に起因して残存容量を誤って表示する恐れがなく、且つ放電末期の二次電池の残存容量を正確に演算する二次電池の残存容量演算装置及びその残存容量演算方法を実現できるという有利な効果が得られる。
本発明によれば、二次電池の電圧がほとんど変化しない区間においても、放電末期においても、二次電池の残存容量を正確に演算する二次電池の残存容量演算装置及びその残存容量演算方法を実現できるという有利な効果が得られる。
本発明の二次電池の残存容量演算装置は、携帯電話基地局のバックアップ電源用電池管理装置として有用である。
【図面の簡単な説明】
【図１】本発明の実施の形態１及び実施の形態２の残存容量演算装置を含むバックアップ電源用電池管理装置の構成図
【図２】二次電池の放電期間中の放電開始からの時間又は放電電気量に対する電池電圧、電池電圧の時間微分値（ｄＶ／ｄｔ）、残存容量の一例を示すグラフ。図２（ａ）は、電池電圧と放電開始からの時間の関係を表すグラフ、図２（ｂ）は、電池電圧の時間微分値（ｄＶ／ｄｔ）と放電開始からの時間の関係を表すグラフ、図２（ｃ）は、残存容量と放電開始からの時間の関係を表すグラフ
【図３】本発明の実施の形態１の二次電池の残存容量演算方法を示すフローチャート
【図４】二次電池の充放電サイクルの一例を示す図
【図５】二次電池の充放電サイクルの別の一例を示す図
【図６】本発明の実施の形態２の二次電池の残存容量演算方法を示すフローチャート
【図７】二次電池の充放電サイクルの一例を示す図
【図８】二次電池の充放電サイクルの別の一例を示す図
【符号の説明】
１０１二次電池
１０２電源監視制御部
１０５放電器
１０６充電器
１０７表示部
１０８商用電源
１０９整流器
１１０負荷
１５０残存容量演算装置
１５１残存容量演算部
１５２温度検出部
１５３電流検出部
１５４電圧検出部
１５５タイマ部[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a secondary battery remaining capacity calculation device and a remaining capacity calculation method thereof.
[0002]
[Prior art]
Conventionally, lead-acid batteries have been widely used as backup power sources for electronic and electrical equipment used in equipment such as mobile phone base stations. Recently, however, demand for nickel-metal hydride batteries has increased. The reason is that nickel-metal hydride batteries have a higher energy density than lead-acid batteries, and can be reduced in weight and size.
A nickel-metal hydride battery used as a power source for backup is normally intermittently charged without supplying power to a load. Power is supplied to the load (discharges) during a power failure. In the event of a power failure, the user must perform power recovery work while the backup power supply can be discharged, so the remaining capacity or usable time of the backup power supply is calculated and displayed accurately, especially at the end of the discharge. There is a need to. Hereinafter, “remaining capacity” represents “amount of electricity that can be discharged from that point in time”.
[0003]
A battery capacity remaining amount detection device disclosed in Patent Document 1 (Japanese Patent Application Laid-Open No. 9-17827) measures a voltage value change amount within a predetermined time during battery discharge, and determines a predetermined time value and a voltage value change amount. The remaining time corresponding to the remaining battery capacity (remaining capacity) is calculated and displayed.
[0004]
[Patent Document 1]
JP-A-9-178827
[0005]
[Problems to be solved by the invention]
In general, when a secondary battery is discharged at a substantially constant current, the battery voltage monotonously decreases with respect to the amount of discharge electricity (or time from the start of discharge). At the end of discharge, the discharge voltage of the secondary battery rapidly decreases. The secondary battery remaining capacity calculation device disclosed in Patent Document 1 detects that the discharge voltage has dropped abruptly and displays that it has entered the end of discharge (remaining capacity at the end of discharge). However, in the case of a secondary battery having a memory effect, the discharge voltage may drop rapidly even outside the end of discharge. Therefore, the secondary battery remaining capacity calculation device disclosed in Patent Document 1 may display a small remaining capacity even though the remaining capacity is actually sufficient.
[0006]
When the remaining capacity of the secondary battery is within a predetermined range, the voltage of the secondary battery hardly changes. The secondary battery remaining capacity calculation device (Patent Document 1) that calculates the remaining capacity based on the discharge voltage is difficult to accurately calculate the remaining capacity in a section where the voltage of the secondary battery hardly changes. .
There is a secondary battery remaining capacity calculation device that calculates a new remaining capacity by accumulating the amount of discharged electricity based on the discharge current and subtracting the amount of discharged electricity from the remaining capacity. However, according to this apparatus, a slight error occurs between the calculated remaining capacity and the actual remaining capacity due to various factors that are not considered in the calculation. The error accumulates at the end of discharge. At the end of discharge, although the remaining capacity calculation device indicates that the remaining capacity is still present, the secondary battery may actually suddenly fall into a fully discharged state.
[0007]
SUMMARY OF THE INVENTION The present invention solves the above-described conventional problems, and an object thereof is to provide a secondary battery remaining capacity calculation device and a remaining capacity calculation method for accurately calculating the remaining capacity of a secondary battery at the end of discharge.
The present invention relates to a secondary battery remaining capacity calculation device and a remaining capacity calculation method for accurately calculating the remaining capacity of a secondary battery at the end of discharge without causing a risk of erroneous display of the remaining capacity due to the memory effect. The purpose is to provide.
The present invention provides a secondary battery remaining capacity calculating device and a remaining capacity calculating method for accurately calculating the remaining capacity of a secondary battery even in a section where the voltage of the secondary battery hardly changes or in the end of discharge. For the purpose.
[0008]
[Means for Solving the Problems]
In order to solve the above problems, the present invention has the following configuration. The invention according to claim 1 is a voltage detector that detects a discharge voltage of a secondary battery, a current detector that detects a discharge current of the secondary battery, When the secondary battery has a predetermined remaining capacity at the end of discharge in which the time differential value of the discharge voltage decreases with the discharge of the secondary battery. Time derivative of the discharge voltage Is Second predetermined value When And a minimum remaining capacity at the end of discharge, which is the minimum value of the remaining capacity at the end of each discharge when the secondary battery changes from an incompletely discharged state to a charged state after the secondary battery has been completely discharged. A storage unit; Integrated value of discharge current detected by the current detector And a display unit for displaying the remaining capacity, the remaining capacity calculating unit is configured to display the remaining capacity during discharge. Stored in the storage unit It is smaller than the remaining capacity at the end of the minimum discharge, and the time differential value of the discharge voltage is Stored in the storage unit When the second predetermined value is reached, the remaining capacity is The predetermined remaining capacity This is a secondary battery remaining capacity calculation device.
[0009]
Claim 6 The invention described in the above, a voltage detection step of detecting the discharge voltage of the secondary battery, a current detection step of detecting the discharge current of the secondary battery, A second predetermined value that is a time differential value of the discharge voltage at a predetermined remaining capacity at the end of discharge in which the time differential value of the discharge voltage decreases with the discharge of the secondary battery; The minimum remaining capacity at the end of discharge, which is the minimum value of the remaining capacity at the end of each discharge when the secondary battery changes from an incompletely discharged state to a charged state after the secondary battery has been completely discharged. When, A memory step for storing In the integrated value of the discharge current detected in the current detection step A remaining capacity calculating step for calculating the remaining capacity of the secondary battery, and a display step for displaying the remaining capacity. In the remaining capacity calculating step during discharging, Stored in the storing step It is smaller than the remaining capacity at the end of the minimum discharge, and the time differential value of the discharge voltage is Stored in the storing step When the second predetermined value is reached, the remaining capacity is Predetermined remaining capacity The remaining battery capacity calculating method of the secondary battery, characterized in that
[0010]
The invention according to claim 2 is a voltage detector that detects a discharge voltage of the secondary battery, a current detector that detects a discharge current of the secondary battery, When the secondary battery has a predetermined remaining capacity at the end of discharge in which the time differential value of the discharge voltage decreases with the discharge of the secondary battery. Time derivative of the discharge voltage Is Second predetermined value When A remaining capacity at the end of each discharge when the secondary battery changes from an incompletely discharged state to a charged state after the secondary battery is completely discharged, and at least from the remaining capacity at the end of subsequent discharge A storage unit for storing the remaining capacity at the end of discharge with a small value; In the integrated value of the discharge current detected by the current detector And a display unit for displaying the remaining capacity, and the remaining capacity calculating unit stores the remaining capacity in the storage unit during discharging. Is not the value near the remaining capacity at the end of each discharge, and the time differential value of the discharge voltage is Stored in the storage unit When the second predetermined value is reached, the remaining capacity is The predetermined remaining capacity This is a secondary battery remaining capacity calculation device.
[0011]
Claim 7 The invention described in the above, a voltage detection step of detecting the discharge voltage of the secondary battery, a current detection step of detecting the discharge current of the secondary battery, A second predetermined value that is a time differential value of the discharge voltage at a predetermined remaining capacity at the end of discharge in which the time differential value of the discharge voltage decreases with the discharge of the secondary battery; After the secondary battery is fully discharged, the remaining capacity at the end of each discharge when the secondary battery changes from an incompletely discharged state to a charged state, at least more than the remaining capacity at the end of subsequent discharge Low capacity at the end of discharge When, A memory step for storing Integrated value of discharge current detected in the current detection step A remaining capacity calculating step for calculating the remaining capacity of the secondary battery on the basis of, and a display step for displaying the remaining capacity. In the remaining capacity calculating step during discharging, the remaining capacity is determined in the storing step. Memory did Not the value near the remaining capacity at the end of each discharge, and the time differential value of the discharge voltage is Stored in the storing step When the second predetermined value is reached, the remaining capacity is The predetermined remaining capacity The remaining battery capacity calculating method of the secondary battery, characterized in that
[0012]
The present invention has an effect of realizing a secondary battery remaining capacity computing device and a remaining capacity computing method for accurately computing the remaining capacity of a secondary battery at the end of discharge.
The present invention relates to a secondary battery remaining capacity calculating device and a remaining capacity calculating method for accurately calculating the remaining capacity of a secondary battery at the end of discharge without erroneously displaying the remaining capacity due to the memory effect. It has the effect of realizing.
[0013]
“Remaining capacity” represents the amount of electricity that can be discharged from the time point until the battery voltage reaches the end-of-discharge voltage. “Discharge electricity amount” represents the amount of electricity discharged from the start of discharge.
“Discharge” includes discharge that supplies power to the load and self-discharge that does not supply power to the load. The remaining capacity at the start of discharging is arbitrary (it is not necessary to start discharging from the fully charged state).
For example, during discharge, the remaining capacity calculation unit samples the discharge current value at predetermined time intervals, subtracts the integrated value (discharged electric energy) from the remaining capacity at the start of discharge, and calculates the remaining capacity at each sampling timing. To do.
When the secondary battery continuously discharges at a constant current, the discharge curve (battery voltage graph with respect to time from the start of discharge) is a monotonically decreasing function, and a rapid voltage drop occurs at the end of discharge. The remaining capacity calculating device and the remaining capacity calculating method of the secondary battery according to the present invention include a remaining capacity in which the remaining capacity is stored in advance in the storage unit when the time differential value of the discharge voltage reaches the second predetermined value at the end of discharging. Replace with the actual measured value and display the correct remaining capacity.
However, the discharge voltage of the secondary battery rapidly drops not only at the end of discharge but also at the memory effect occurrence point. The present invention prevents erroneous display of a small remaining capacity due to discharge voltage fluctuations caused by the memory effect, even though the actual remaining capacity is sufficient.
[0014]
Claim 2 and claim 7 In the invention of the invention, at least a point where the memory effect is not eliminated among the occurrence points of the memory effect that occurs when one or more times of charging and incomplete discharging are performed after the secondary battery is completely discharged is stored. To do. That is, all the remaining capacity at the end of discharge at the discharge depth shallower than the previous discharge depth is stored in the remaining capacity at the end of discharge (discharge depth) after complete discharge.
[0015]
According to a third aspect of the present invention, the remaining capacity calculation unit is in the above condition during discharge and In the initial stage of discharge, the remaining capacity increases with time in the discharge voltage as the secondary battery discharges. First predetermined value Less than If the remaining capacity is The predetermined remaining capacity 3. The secondary battery remaining capacity computing device according to claim 1, wherein the remaining capacity computing device is replaced with.
[0016]
Claim 8 According to the present invention, in the remaining capacity calculation step during discharge, In the initial stage of discharge, the remaining capacity increases with time in the discharge voltage as the secondary battery discharges. First predetermined value Less than If the remaining capacity is The predetermined remaining capacity Claims replaced by 6 Or claim 7 The method for calculating the remaining capacity of the secondary battery as described in 1).
The discharge voltage of the secondary battery drops rapidly not only at the end of discharge but also at the beginning of discharge. The secondary battery remaining capacity calculation apparatus and remaining capacity calculation method according to the present invention further includes the time differential value of the discharge voltage and the first value even in the initial stage of discharge (until the amount of discharged electricity after the start of discharge reaches the first predetermined value). No comparison with a predetermined value of 2 is performed. As a result, it is possible to prevent a small remaining capacity from being displayed erroneously in the early stage of discharge even though the actual remaining capacity is sufficient.
[0017]
The invention described in claim 4 further includes a temperature detection unit that detects a temperature of the secondary battery, and the second predetermined value is a value having the temperature as a variable. The secondary battery remaining capacity calculation device according to any one of claims 1 to 3.
[0018]
Claim 9 The invention according to claim 2, further comprising a temperature detection step of detecting a temperature of the secondary battery, wherein the second predetermined value is a value having the temperature as a variable. 6 Claims from 8 The method for calculating the remaining capacity of the secondary battery according to any one of the claims.
The second predetermined value has temperature dependency. According to the present invention, it is possible to realize a secondary battery remaining capacity calculation device and a remaining capacity calculation method that more accurately estimate the remaining capacity.
[0024]
Claim 5 The invention according to claim 1, wherein the secondary battery is a nickel-metal hydride battery. 4 A remaining capacity calculation device for a secondary battery according to any one of the claims.
[0025]
Claim 10 The invention described in claim 2 is characterized in that the secondary battery is a nickel-metal hydride battery. 6 Claims from 9 The method for calculating the remaining capacity of the secondary battery according to any one of the claims.
The present invention is particularly useful in a nickel-metal hydride battery, which is a secondary battery having a memory effect.
[0026]
DETAILED DESCRIPTION OF THE INVENTION
DESCRIPTION OF THE PREFERRED EMBODIMENTS Embodiments that specifically show the best mode for carrying out the present invention will be described below with reference to the drawings.
[0027]
Embodiment 1
The remaining capacity calculation device and the remaining capacity calculation method according to the first embodiment of the present invention will be described with reference to FIGS.
FIG. 1 is a configuration diagram of a backup power supply battery management apparatus including the remaining capacity calculation apparatus according to the first embodiment of the present invention.
[0028]
In FIG. 1, 150 is a remaining capacity calculation device, 101 is a secondary battery, 102 is a power supply monitoring control unit, 105 is a discharger, 106 is a charger, 107 is a display unit, 108 is a commercial power supply, 109 is a rectifier, and 110 is It is a load. The remaining capacity calculation device 150 includes a remaining capacity calculation unit 151, a temperature detection unit 152, a current detection unit 153, a voltage detection unit 154, and a timer unit 155.
[0029]
Usually, a commercial power supply 108 is supplied to the load 110. The alternating current from the commercial power supply 108 is converted into a direct current by the rectifier 109 and supplied to the load 110. The secondary battery 101 is intermittently charged by the charger 106 while the commercial power supply 108 is supplied, and the fully charged state is maintained. The charger 106 is started and stopped by the power supply monitoring control unit 102. In order to prevent the remaining capacity of the secondary battery from decreasing due to the memory effect, the power supply monitoring control unit 102 operates the discharger 105 every predetermined period to completely discharge the secondary battery. At the time of a power failure, the power monitoring control unit 102 switches the circuit and causes the secondary battery 101 to discharge. The secondary battery 101 supplies (discharges) power to the load 110 and functions as a backup power source. In the embodiment, the discharge current value of the secondary battery 101 is substantially constant. It is assumed that there is no sudden change in the load 110 current. After the commercial power supply 108 is restored, the power supply monitoring control unit 102 stops the power supply from the secondary battery 101 to the load 110 (stops discharging) and switches to the supply from the commercial power supply 108. The charger 106 is operated to fully charge the secondary battery 101. Note that the discharge period and the amount of discharge electricity of the secondary battery 101 vary for each discharge.
[0030]
The secondary battery 101 includes a plurality of secondary battery cells (not shown) connected in series and / or in parallel to each other, or one secondary battery cell (not shown). Each secondary battery cell has a memory effect. In Embodiment 1, secondary battery 101 is a nickel-metal hydride battery.
[0031]
The temperature detection unit 152 detects any of the internal temperature of the secondary battery 101, the surface temperature of the secondary battery 101, and the ambient temperature, and transmits the detected temperature to the input / output unit 111 of the remaining capacity calculation unit 151. In the embodiment, the temperature detection unit 152 detects the surface temperature of the secondary battery 101 (hereinafter referred to as “battery temperature”). The current detection unit 153 detects the discharge current and the full charge current of the secondary battery 101 and transmits them to the remaining capacity calculation unit 151. The voltage detection unit 154 detects the battery voltage of the secondary battery 101 and transmits it to the remaining capacity calculation unit 151. The timer unit 155 transmits time information to the remaining capacity calculation unit 151.
[0032]
The remaining capacity calculation unit 151 estimates the remaining capacity of the secondary battery 101 and transmits it to the power supply monitoring control unit 102. Information on the remaining capacity of the secondary battery 101 is displayed on the display unit 107. The display method may be a quantitative display (for example, display of a value in units of Ah) or a qualitative display (for example, a display indicating that the remaining capacity is small by blinking a red light emitting diode). The output of the remaining capacity information may be displayed so that the user can visually or audibly recognize it directly, or the remaining capacity information may be transmitted to the host device or the like.
[0033]
FIG. 2 is a graph showing an example of the battery voltage, the time differential value of the battery voltage, and the remaining capacity with respect to the time from the start of discharge during the discharge period of the secondary battery 101 or the amount of discharge electricity. FIG. 2A is a graph showing the relationship between the battery voltage and the time from the start of discharge (hereinafter referred to as “discharge curve”). Assume that the secondary battery 101 is continuously discharged at a constant current from a fully charged state to a fully discharged state. The fully discharged state means a state where the battery voltage has dropped to the discharge end voltage Ve. FIG. 2B is a graph showing the relationship between the time differential value of the battery voltage and the time from the start of discharge, and FIG. 2C is a graph showing the relationship between the remaining capacity and the time from the start of discharge. The amount of electric discharge is proportional to the time from the start of discharge, and the remaining capacity is expressed by a linear function with the time from the start of discharge as a parameter and the proportionality coefficient is a negative value. The remaining capacity in the fully charged state is Sf, and the remaining capacity in the fully discharged state is 0.
[0034]
10 is a discharge curve when the battery voltage of the secondary battery 101 is not affected by the memory effect. The discharge curve 10 is a monotonically decreasing function, and the voltage drops sharply at the beginning and end of discharge. 11 is a one-time derivative (time change rate of discharge voltage) dV / dt (V is battery voltage, t is time) with respect to the time of the discharge curve 10 when the battery voltage of the secondary battery 101 is not affected by the memory effect. It is a graph. The graph 11 of the discharge voltage time change rate dV / dt is an upwardly convex function that always takes a negative value.
[0035]
20 is a discharge curve when the battery voltage of the secondary battery 101 is affected by the memory effect. Assume a case where the secondary battery 101 is fully discharged and fully charged and then discharged to the remaining capacity Sm (until time Tm from the start of discharge) when the discharge is terminated, fully charged, and further fully discharged. . The discharge curve 20 has a bent portion 22 in which the voltage drops near the time Tm (in the vicinity of the remaining capacity becomes Sm) with a greater slope than before and after that. For this reason, the graph 21 of the first derivative dV / dt of the discharge curve 20 has a recess 23 near the time Tm. The recess 23 is generated due to the memory effect. After the time Tm, the curve has substantially the same shape (same inclination) as the discharge curve 10. In the case of the example shown in FIG. 2, after the secondary battery 101 is discharged to a level lower than the remaining capacity Sm (for example, after being completely discharged), charging is performed to thereby influence the memory effect on the secondary battery 101 (remaining capacity Sm The concave portion 23) of the graph 21 generated in the vicinity of disappears, and the discharge curve 20 returns to the discharge curve 10.
[0036]
When the secondary battery 101 is incompletely discharged and charged from the point of time when the remaining capacity is Sm, 1 of the discharge curve 20 at the point of change from the previous discharge to charge (at the time when the remaining capacity is Sm) at the next discharge. A concave portion 23 is generated in the graph 21 of the time differential dV / dt.
When the secondary battery 101 is discharged to the point where the remaining capacity is Sm, the influence of the memory effect on the secondary battery 101 that has been generated at the point Sp (Sp> Sm) where the remaining capacity is larger than Sm (discharge curve 20). In the graph 21 of the first derivative dV / dt of FIG. The influence of the memory effect on the secondary battery 101 that has occurred up to that point Sq (Sq <Sm) when the remaining capacity is smaller than Sm (the concave portion of the graph 21 of the first derivative dV / dt of the discharge curve 20) disappears. Absent. When the secondary battery 101 is completely discharged and then charged, the influence of the memory effect on all the secondary batteries 101 that existed so far (the concave portion of the graph 21 of the first derivative dV / dt of the discharge curve 20) is Be erased.
Hereinafter, in order to remove the influence of the memory effect from the secondary battery 101, complete discharge and then full charge will be referred to as “refresh charge / discharge”. The power monitoring control unit 102 operates the discharger 105 at a predetermined timing to refresh and discharge the secondary battery 101.
[0037]
In the method for calculating the remaining capacity of the secondary battery according to the first embodiment of the present invention, the remaining capacity is estimated based on the integrated value of the discharge current (the integrated value of the discharge electricity amount). If the discharge current is accumulated for a long time, errors such as current detection errors accumulate. For this reason, the estimation accuracy of the remaining capacity is worse in the end stage of discharge where the remaining capacity needs to be estimated more accurately. On the other hand, the voltage of the secondary battery 101 changes greatly at the end of discharge (see FIGS. 2A and 2B). The change in time until the voltage of the secondary battery 101 changes greatly at the end of discharge until it reaches a fully discharged state (a state where the battery voltage has dropped to the discharge end voltage Ve) is viewed from the time of the complete discharge state. It is almost constant regardless of the presence or absence of the memory effect. Therefore, the time change rate Gc (second predetermined value) of the voltage when the remaining capacity is the predetermined value Sa (when the dischargeable time is Ta) is obtained in advance and stored in the remaining capacity calculation device, and at the end of discharge. When the voltage change rate with time reaches the second predetermined value Gc, the remaining capacity is replaced with Sa.
[0038]
The method for calculating the remaining capacity of the secondary battery according to the first embodiment of the present invention will be specifically described with reference to FIG. FIG. 3 is a flowchart showing a method for calculating the remaining capacity of the secondary battery according to the first embodiment of the present invention. In step 301, the secondary battery 101 starts discharging. Thereafter, the remaining capacity calculation unit 151 continuously estimates the remaining capacity of the secondary battery 101 and transmits it to the power supply monitoring control unit 102. In step 302, it is determined whether or not the first discharge after the refresh charge / discharge. If not, go to step 304. If this is the case, in step 303, the remaining capacity Smin at the end of the minimum discharge is initialized to the remaining capacity Sf in the fully charged state. The remaining capacity Smin at the end of the minimum discharge is the value at the end of each discharge after the refresh charge / discharge (after the secondary battery is completely discharged) and when the secondary battery is changed from the incomplete discharge state to the charged state (at the end of discharge). This is the minimum remaining capacity. Proceed to step 304.
[0039]
In step 304, the remaining capacity calculation unit 151 calculates the current remaining capacity S based on the integrated value of the discharge current value received from the current detection unit 153. Typically, according to the following formula:
New remaining capacity S = old remaining capacity S−integrated value of discharge current value
In step 305, it is determined whether or not the remaining capacity S is smaller than a first predetermined value (Sf−ΔSi). The discharge voltage of the secondary battery drops sharply at the beginning of discharge. ΔSi is the amount of electricity that the secondary battery 101 discharges during a period in which the battery voltage at the initial stage of discharge suddenly decreases (see FIGS. 2A and 2C). In step 306, it is determined whether or not the remaining capacity S is smaller than the remaining capacity Smin at the end of the minimum discharge. If S <(Sf−ΔSi) is not satisfied (step 305), or if S <Smin is not satisfied (step 306), the process returns to step 304 and the remaining capacity S is continuously calculated. If S <(Sf−ΔSi) (step 305) and S <Smin (step 306), the process proceeds to step 307. In step 307, the remaining capacity Smin at the end of the minimum discharge is updated to the current remaining capacity S.
[0040]
After the refresh charge / discharge (after the secondary battery is fully discharged), when the secondary battery changes from an incompletely discharged state to a charged state (at the end of discharge), the remaining capacity at the end of discharge and the remaining capacity at the end of minimum discharge Compared with Smin, if the remaining capacity at the end of discharge is smaller (if it is a minimum value), the remaining capacity at the end of discharge may be stored as a new remaining capacity Smin at the end of discharge.
[0041]
In step 308, the remaining capacity calculation unit 151 calculates a time change rate dV / dt of the voltage from the voltage value received from the voltage detection unit 154 and the time information received from the timer unit 155. In step 309, it is determined whether or not the voltage temporal change rate dV / dt is equal to or less than a threshold value Gc (second predetermined value). If the voltage time change rate dV / dt is larger than the threshold value Gc (second predetermined value), the process proceeds to step 310, and the current remaining capacity S is calculated from the integrated value of the discharge current (same as step 304). Return to step 307. In step 309, when the time rate of change dV / dt of the voltage becomes equal to or lower than the threshold value Gc (second predetermined value) for the first time, the process proceeds to step 311 and the remaining capacity S is reset to Sa. In step 312, the display unit 107 displays a warning message “The battery is very low (Sa). The remaining battery time is about Ta”, and sounds a buzzer. End the process.
[0042]
If the discharge of the secondary battery 101 is interrupted, the flowchart of FIG. 3 is immediately terminated. The secondary battery 101 is fully charged to prepare for the start of the next discharge.
After step 312, until the battery is fully discharged, the remaining capacity calculation unit 151 follows the graph of FIG. 2 (a) or (b) and (c) (typically stores the graph in the form of a table or function). The remaining capacity S may be calculated and displayed using the discharge voltage or its time derivative as a parameter.
Alternatively, after step 312, until the battery is completely discharged, the current remaining capacity S may be calculated from the integrated value of the discharge current with the remaining capacity Sa as an initial value (same as step 304).
[0043]
At the start of discharging, the battery voltage rapidly decreases, and the voltage time change rate dV / dt falls below the second predetermined value Gc (in the absolute value, the voltage time change rate dV / dt is lower than the second predetermined value Gc. large.). In the first embodiment, until the time change rate dV / dt of the voltage after the start of discharge exceeds the second predetermined value Gc (in absolute value, the time change rate dV / dt of the voltage is smaller than the second predetermined value Gc. The amount of discharge electricity ΔSi during the period until the above is obtained in advance. Until the remaining capacity S falls below Si (= Sf−ΔSi), the remaining capacity S is not reset (replaced with Sa) (step 311) based on the fact that dV / dt ≦ Gc is first reached.
When a voltage drop due to the memory effect is observed in the discharge curve, the time change rate dV / dt of the voltage is below the second predetermined value Gc in the vicinity of the remaining capacity where the voltage drop occurs (see FIG. 2B). In the first embodiment, the minimum value of the remaining capacity at the end of discharge (remaining capacity Smin at the end of minimum discharge) in the discharge performed after refresh charge / discharge is obtained, and the remaining capacity at the time of discharge is lower than the remaining capacity Smin at the end of minimum discharge. Until then, the resetting of the remaining capacity S (replacement with Sa) based on the fact that dV / dt ≦ Gc is first performed (step 311) is not performed.
[0044]
Next, an example of the charge / discharge cycle of the secondary battery 101 will be shown, and the secondary battery remaining capacity calculation method of the first embodiment will be further described. During discharge, a period of time for determining whether or not the remaining capacity S should be reset to Sa (step 311) by comparing the voltage temporal change rate dV / dt with the second predetermined value Gc (step 309 in FIG. 3). Pay attention to.
[0045]
FIG. 4 is a diagram illustrating an example of a charge / discharge cycle of the secondary battery 101. Shows the relationship between time and remaining capacity. For the convenience of displaying all in one figure, in FIG. 4, the discharge is started immediately after the end of full charge (time T1, time T4 and time T9). The secondary battery 101 is refreshed and discharged from time 0 to time T0. From time T0 to time T1, the battery is fully charged (remaining capacity Sf) and discharged during period C1 (time T1 to time T3). From time T3 to time T4, the battery is fully charged and discharged during period C2 (time T4 to time T8). The battery is fully charged from time T8 to time T9, and discharged in period C3 (time T9 to time T17). The remaining capacities at the end of discharge in the discharge periods C1, C2 and C3 (remaining capacities at the end of discharge) are S1, S2 and S3 (S1>S2>Sa> S3), respectively.
[0046]
Since the discharge in the discharge period C1 is the first discharge after the refresh charge / discharge, the voltage drop due to the memory effect does not occur in the discharge curve. In the discharge curve in the discharge period C2, a sudden voltage drop occurs at the time of the remaining capacity S1 due to the memory effect due to the discharge in the discharge period C1. In the discharge curve in the discharge period C3, a sudden voltage drop occurs at the time of the remaining capacity S2 due to the memory effect due to the discharge in the discharge period C2. The memory effect (abrupt voltage drop at the time of the remaining capacity S1) due to the discharge in the discharge period C1 is erased in the discharge period C2.
[0047]
In the discharge period C1, since the voltage rapidly decreases from the time T1 to the time T2 at the initial stage of discharge, the time change rate dV / dt of the voltage is not compared with the second predetermined value Gc. From time T2 to time T3, from time T7 to time T8, and from time T14 to time T16, the voltage time change rate dV / dt is compared with the second predetermined value Gc.
[0048]
FIG. 5 is a diagram illustrating another example of the charge / discharge cycle of the secondary battery 101. Shows the relationship between time and remaining capacity. For the convenience of displaying all in one figure, in FIG. 5, the discharge is started immediately after the end of full charge (time T1, time T4 and time T7). The secondary battery 101 is refreshed and discharged from time 0 to time T0. From time T0 to time T1, the battery is fully charged (remaining capacity Sf) and discharged during period C1 (time T1 to time T3). From time T3 to time T4, the battery is fully charged and discharged during period C2 (time T4 to time T6). From time T6 to time T7, the battery is fully charged and discharged during period C3 (time T7 to time T14). Remaining capacities at the end of discharge in the discharge periods C1, C2, and C3 (remaining capacities at the end of discharge) are S1, S2, and S3 (S2>S1>Sa> S3), respectively.
[0049]
Since the discharge in the discharge period C1 is the first discharge after the refresh charge / discharge, the voltage drop due to the memory effect does not occur in the discharge curve. The remaining capacity S2 at the end of the discharge period C2 (time T6) is sufficiently larger than the remaining capacity S1 at the end of the discharge period C1 (time T3), and a voltage drop due to the memory effect does not occur in the discharge curve. In the discharge in the discharge period C3, the memory effect due to the discharge in the discharge period C1 and the discharge period C2 is superimposed, and a rapid voltage drop due to the memory effect occurs twice in the discharge curve (at the time of the remaining capacity S1 and S2).
[0050]
In the discharge period C1, since the voltage rapidly decreases from the time T1 to the time T2 at the initial stage of discharge, the time change rate dV / dt of the voltage is not compared with the second predetermined value Gc. From time T2 to time T3 and from time T12 to time T13, the voltage temporal change rate dV / dt is compared with the second predetermined value Gc.
[0051]
The inventor determines that the time (Ta) until the voltage reaches the discharge end voltage after the time change rate dV / dt of the voltage falls below the second predetermined value Gc at the end of the discharge depends on whether there is a voltage drop due to the memory effect. Nevertheless, it was found to be almost constant (see FIG. 2). According to the secondary battery remaining capacity calculating apparatus and the remaining capacity calculating method of the first embodiment of the present invention, the time change rate of the voltage is continuously measured at the time of discharging, and the remaining capacity is reset at the end of discharging. The remaining capacity at the end of discharge can be calculated accurately.
If the time change rate Gc (second predetermined value) of the voltage when the remaining capacity of the secondary battery 101 is Sa is obtained for each battery temperature, the remaining capacity can be estimated more accurately.
[0052]
The flowchart of the secondary battery remaining capacity calculation method of Embodiment 1 of the present invention is not limited to the flowchart shown in FIG.
In the first embodiment, the discharge is described as starting from the fully charged state (remaining capacity is Sf). However, the discharge may be started from the state where the full charge is not performed.
In the embodiment, power is supplied from the secondary battery 101 to the load 110 during discharging. Even in the case of self-discharge in which power is not supplied from the secondary battery to the load during discharge, the remaining capacity of the secondary battery can be accurately estimated by the remaining battery capacity calculation method of the present invention.
[0053]
<< Embodiment 2 >>
The remaining capacity calculation apparatus and the remaining capacity calculation method according to the second embodiment of the present invention will be described with reference to FIGS. 1, 2, and 6 to 8. FIG. 1 is a configuration diagram of a backup power supply battery management apparatus including the remaining capacity calculation apparatus according to the second embodiment of the present invention, and since it is the same as that of the first embodiment, the description thereof is omitted. Since FIG. 2 has already been described, a description thereof will be omitted.
[0054]
In the secondary battery remaining capacity calculation method according to the second embodiment of the present invention, the remaining capacity is estimated based on the integrated value of the discharge current. If the discharge current is accumulated for a long time, current detection errors accumulate. For this reason, the estimation accuracy of the remaining capacity is worse in the end stage of discharge where the remaining capacity needs to be estimated more accurately. On the other hand, the voltage of the secondary battery 101 changes greatly at the end of discharge (see FIGS. 2A and 2B). Therefore, the time change rate Gc (second predetermined value) of the voltage when the remaining capacity is Sa (when the dischargeable time is Ta) is obtained in advance and stored in the remaining capacity calculation device. When the time change rate reaches Gc (second predetermined value), the remaining capacity is replaced with Sa.
[0055]
The method for calculating the remaining capacity of the secondary battery according to the second embodiment of the present invention will be specifically described with reference to FIG. FIG. 6 is a flowchart showing a method for calculating the remaining capacity of the secondary battery according to the second embodiment of the present invention. In step 601, the secondary battery 101 starts discharging. Thereafter, the remaining capacity calculation unit 151 continuously estimates the remaining capacity of the secondary battery 101 and transmits it to the power supply monitoring control unit 102. In step 602, 1 is added to n. n is the number of discharges after refresh charge / discharge, and is initialized to 0 at the end of refresh charge / discharge. In step 603, the remaining capacity calculation unit 151 calculates the current remaining capacity S based on the integrated value of the discharge current received from the current detection unit 153 (the calculation method is the same as in the first embodiment). In step 604, S is substituted for the remaining capacity Sn in the n-th discharge. In step 605, it is determined whether the remaining capacity S is smaller than a first predetermined value (Sf−ΔSi). ΔSi is the amount of electricity that the secondary battery 101 discharges during a period when the battery voltage at the initial stage of discharge suddenly decreases (see FIG. 2C). If S <(Sf−ΔSi) is not satisfied (initial stage of discharge), the process returns to step 603. When S <(Sf−ΔSi) (when the initial stage of discharge has passed), the process proceeds to step 606.
[0056]
In steps 606 to 609, it is determined whether or not the remaining capacity S is a value in the vicinity of the remaining capacity Sk (k = 1 to n−1) at the end of each discharge after the refresh charge / discharge. In step 606, k is initialized to 0. In step 607, 1 is added to k. In step 608, it is determined whether k is smaller than n. If k is smaller than n, it is determined in step 609 whether the remaining capacity is not less than the remaining capacity Sk at the end of the k-th discharge and not more than Sk + ΔSm. ΔSm is the amount of electricity that the secondary battery 101 discharges during a period when the battery voltage rapidly decreases due to the memory effect (see FIG. 2C). Hereinafter, the range from the remaining capacity Sk to the Sk + ΔSm is referred to as the “mask range of the remaining capacity due to the k-th discharge”. If it is determined in step 609 that the remaining capacity S is included in the mask range of the remaining capacity due to the k-th discharge, the process returns to step 603. If not included, the process returns to step 607. If k is greater than or equal to n in step 608, the remaining capacity S is not included in the mask range of the remaining capacity due to n−1 discharges after the refresh charge / discharge, and the process proceeds to step 610.
[0057]
In step 610, the remaining capacity calculation unit 151 calculates a time change rate dV / dt of the voltage from the voltage value input from the voltage detection unit 154 and the time information input from the timer unit 155. In step 611, it is determined whether the time rate of change dV / dt of the voltage is equal to or less than a threshold value Gc (second predetermined value). When the voltage time change rate dV / dt is larger than the threshold value Gc (second predetermined value) (in the absolute value, dV / dt is smaller than Gc), the process returns to step 603, and from the integrated value of the discharge current, The remaining capacity S is calculated. In step 611, when the voltage time change rate dV / dt is equal to or lower than the threshold value Gc (second predetermined value) for the first time (in the absolute value, dV / dt is equal to or higher than Gc), the process proceeds to step 612. The remaining capacity S is reset to Sa. In step 613, the display unit 107 displays a warning message “Battery is very low (Sa). Battery remaining time is about Ta” and sounds a buzzer. End the process.
[0058]
If the discharge of the secondary battery 101 is interrupted, the flowchart of FIG. 6 is immediately terminated. The secondary battery 101 is fully charged to prepare for the start of the next discharge.
After step 613, until the battery is completely discharged, the remaining capacity calculation unit 151 follows the graph of FIG. 2A, 2B, and 2C (typically stores the graph in the form of a table or a function). The remaining capacity S may be calculated and displayed using the discharge voltage or its time derivative as a parameter.
Alternatively, after the step 613, the current remaining capacity S may be calculated from the integrated value of the discharge current using the remaining capacity Sa as an initial value until complete discharge (same as step 603).
[0059]
At the start of discharge, the battery voltage rapidly decreases, and the time change rate dV / dt of the voltage falls below the second predetermined value Gc. In the first embodiment, the amount of discharge electricity ΔSi until the time change rate dV / dt of the voltage exceeds the second predetermined value Gc is obtained in advance, and until the remaining capacity falls below Si (= Sf−ΔSi), The remaining capacity is not reset (step 612) according to the time change rate dV / dt of the voltage.
When a voltage drop due to the memory effect is seen in the discharge curve, the voltage temporal change rate dV / dt is below the second predetermined value Gc in the vicinity of the remaining capacity where the voltage drop occurs. In the second embodiment, the remaining capacity is not reset (step 612) based on the time rate of change dV / dt of the voltage in the vicinity of the remaining capacity at the end of all discharges performed after the refresh charge / discharge. When the secondary battery 101 is discharged, the amount of electricity ΔSm that is discharged while the time change rate dV / dt of the voltage is below the second predetermined value Gc is obtained in advance by the memory effect (see FIG. 2).
[0060]
Next, an example of the charge / discharge cycle of the secondary battery 101 will be shown, and the secondary battery remaining capacity calculation method of the first embodiment will be further described. During the discharge, a comparison is made between the voltage temporal change rate dV / dt and the second predetermined value Gc (step 611 in FIG. 6) to determine whether the remaining capacity should be reset to Sa (step 612). Pay attention.
[0061]
FIG. 7 is a diagram illustrating an example of a charge / discharge cycle of the secondary battery 101. The amount of charge and the amount of discharge in the charge / discharge cycle are the same as in FIG. In each discharge cycle, the initial period of discharge (time T1 to time T2, time T4 to time T5 and time T9 to time T10), and the period in which the discharge voltage rapidly decreases due to the memory effect (time T6 to time T7, time T11). ~ Time T12, Time T13 ~ Time T14), the voltage temporal change rate dV / dt is not compared with the second predetermined value Gc. From time T2 to time T3, from time T5 to time T6, from time T7 to time T8, from time T10 to time T11, from time T12 to time T13, and from time T14 to time T16, the time change rate dV / dt of the voltage and the second predetermined value Comparison with Gc is performed.
[0062]
FIG. 8 is a diagram illustrating another example of the charge / discharge cycle of the secondary battery 101. The amount of charge and the amount of discharge in the charge / discharge cycle are the same as in FIG. In each discharge cycle, the initial period of discharge (time T1 to time T2, time T4 to time T5 and time T7 to time T8) and the period in which the discharge voltage rapidly decreases due to the memory effect (time T9 to time T10, time T11 to time T1) At time T12), the voltage temporal change rate dV / dt is not compared with the second predetermined value Gc. The time change rate dV / dt of the voltage is compared with the second predetermined value Gc at time T2 to time T3, time T5 to time T6, time T8 to time T9, time T10 to time T11, and time T12 to time T13. .
[0063]
The secondary battery remaining capacity calculation apparatus and the remaining capacity calculation method according to the second embodiment have the same effects as those of the first embodiment.
If the time change rate Gc (second predetermined value) of the voltage when the remaining capacity of the secondary battery 101 is Sa is obtained for each battery temperature, the remaining capacity can be estimated more accurately.
In the embodiment, power is supplied from the secondary battery 101 to the load 110 during discharging. Even in the case of self-discharge in which power is not supplied from the secondary battery to the load during discharge, the remaining capacity of the secondary battery can be accurately estimated by the remaining battery capacity calculation method of the present invention.
[0064]
In the first embodiment, the discharge is described as starting from the fully charged state (remaining capacity is Sf). However, the discharge may be started from the state where the full charge is not performed.
The flowchart of the secondary battery remaining capacity calculation method according to the second embodiment of the present invention is not limited to the flowchart shown in FIG.
In the second embodiment, the remaining capacity calculation unit 151 (including the storage unit) is at the end of each discharge when the secondary battery changes from the incompletely discharged state to the charged state after the secondary battery is completely discharged. All remaining capacities were stored, and the processes of steps 606 to 609 were performed for all remaining capacities at the end of discharge. Instead, the remaining capacity calculation unit 151 (including the storage unit) remains at the end of each discharge when the secondary battery changes from the incompletely discharged state to the charged state after the secondary battery is completely discharged. Of the capacities, only the remaining capacity at the end of discharge that is smaller than the remaining capacity at the end of discharge thereafter may be stored, and the processing at steps 606 to 609 may be performed on the stored remaining capacity at the end of discharge.
[0065]
【The invention's effect】
According to the present invention, it is possible to obtain an advantageous effect of realizing a secondary battery remaining capacity calculation device and a remaining capacity calculation method for accurately calculating the remaining capacity of a secondary battery at the end of discharge.
According to the present invention, there is no possibility of erroneously displaying the remaining capacity due to the memory effect, and the remaining capacity calculating device of the secondary battery that accurately calculates the remaining capacity of the secondary battery at the end of discharge, and the remaining capacity thereof An advantageous effect that the calculation method can be realized is obtained.
According to the present invention, there is provided a secondary battery remaining capacity calculating device and a remaining capacity calculating method for accurately calculating a remaining capacity of a secondary battery, even in a section where the voltage of the secondary battery hardly changes, or at the end of discharge. An advantageous effect that it can be realized is obtained.
The secondary battery remaining capacity computing device of the present invention is useful as a battery management device for a backup power source of a mobile phone base station.
[Brief description of the drawings]
FIG. 1 is a configuration diagram of a backup power supply battery management device including a remaining capacity calculation device according to a first embodiment and a second embodiment of the present invention.
FIG. 2 is a graph showing an example of a battery voltage, a time differential value (dV / dt) of the battery voltage, and a remaining capacity with respect to a time from the start of discharge during a discharge period of the secondary battery or a discharge electric quantity. 2A is a graph showing the relationship between the battery voltage and the time from the start of discharge, and FIG. 2B is a graph showing the relationship between the time differential value (dV / dt) of the battery voltage and the time from the start of discharge. FIG. 2 (c) is a graph showing the relationship between the remaining capacity and the time from the start of discharge.
FIG. 3 is a flowchart showing a method for calculating the remaining capacity of the secondary battery according to the first embodiment of the present invention.
FIG. 4 is a diagram showing an example of a charge / discharge cycle of a secondary battery.
FIG. 5 is a diagram showing another example of the charge / discharge cycle of the secondary battery.
FIG. 6 is a flowchart showing a method for calculating the remaining capacity of the secondary battery according to the second embodiment of the present invention.
FIG. 7 shows an example of a charge / discharge cycle of a secondary battery.
FIG. 8 is a diagram showing another example of the charge / discharge cycle of the secondary battery.
[Explanation of symbols]
101 Secondary battery
102 Power supply monitoring control unit
105 Discharger
106 charger
107 Display
108 Commercial power supply
109 Rectifier
110 load
150 Remaining capacity calculator
151 Remaining capacity calculator
152 Temperature detector
153 Current detector
154 Voltage detector
155 Timer part

Claims

A voltage detector for detecting a discharge voltage of the secondary battery;
A current detection unit for detecting a discharge current of the secondary battery;
A second predetermined value which is a time differential value of the discharge voltage at a predetermined remaining capacity at the end of discharge in which the time differential value of the discharge voltage decreases with the discharge of the secondary battery, and the secondary battery is completely discharged. A storage unit for storing a minimum remaining capacity at the end of discharge, which is a minimum value of the remaining capacity at the end of each discharge when the secondary battery is changed from an incompletely discharged state to a charged state later,
A remaining capacity calculation unit that calculates a remaining capacity of the secondary battery based on an integrated value of the discharge current detected by the current detection unit ;
A display unit for displaying the remaining capacity,
The remaining capacity calculation unit is configured such that during discharge, the remaining capacity is smaller than the remaining capacity at the end of the minimum discharge stored in the storage unit , and a time differential value of the discharge voltage is stored in the storage unit . When the predetermined value is reached, the remaining capacity is replaced with the predetermined remaining capacity .
A rechargeable battery remaining capacity computing device.

A voltage detector for detecting a discharge voltage of the secondary battery;
A current detection unit for detecting a discharge current of the secondary battery;
A second predetermined value which is a time differential value of the discharge voltage at a predetermined remaining capacity at the end of discharge in which the time differential value of the discharge voltage decreases with the discharge of the secondary battery, and the secondary battery is completely discharged The remaining capacity at the end of each discharge when the secondary battery changes from an incompletely discharged state to a charged state, at least at the end of discharge, which is smaller than the remaining capacity at the end of subsequent discharge. A storage unit for storing the capacity;
A remaining capacity calculation unit that calculates a remaining capacity of the secondary battery based on an integrated value of the discharge current detected by the current detection unit ;
A display unit for displaying the remaining capacity,
During the discharge, the remaining capacity calculation unit stores the remaining capacity not the value near the remaining capacity at the end of each discharge stored in the storage unit, and the time differential value of the discharge voltage stored in the storage unit. When the second predetermined value is reached, the remaining capacity is replaced with the predetermined remaining capacity ;
A rechargeable battery remaining capacity computing device.

When the remaining capacity calculation unit is less than a first predetermined value in the initial stage of discharge in which the time differential value of the discharge voltage increases with the discharge of the secondary battery under the above conditions during discharge . 3. The secondary battery remaining capacity calculation apparatus according to claim 1, wherein the remaining capacity is replaced with the predetermined remaining capacity .

4. The apparatus according to claim 1, further comprising a temperature detection unit that detects a temperature of the secondary battery, wherein the second predetermined value is a value having the temperature as a variable. The remaining capacity calculating device of the secondary battery according to claim.

5. The secondary battery remaining capacity calculation device according to claim 1, wherein the secondary battery is a nickel-metal hydride battery .

A voltage detection step for detecting a discharge voltage of the secondary battery;
A current detection step of detecting a discharge current of the secondary battery;
A second predetermined value which is a time differential value of the discharge voltage at a predetermined remaining capacity at the end of discharge in which the time differential value of the discharge voltage decreases with the discharge of the secondary battery, and the secondary battery is completely discharged A storage step for storing a minimum discharge end remaining capacity that is a minimum value of each discharge end remaining capacity when the secondary battery changes from an incomplete discharge state to a charged state after
A remaining capacity calculating step of calculating a remaining capacity of the secondary battery based on an integrated value of the discharge current detected in the current detecting step;
Displaying the remaining capacity, and
In the remaining capacity calculating step during discharge, the remaining capacity is smaller than the remaining capacity at the end of the minimum discharge stored in the storing step, and a time differential value of the discharge voltage is stored in the storing step. The remaining capacity is replaced with the predetermined remaining capacity.
Residual capacity calculation method of the secondary battery you wherein a.

A voltage detection step for detecting a discharge voltage of the secondary battery;
A current detection step of detecting a discharge current of the secondary battery;
A second predetermined value which is a time differential value of the discharge voltage at a predetermined remaining capacity at the end of discharge in which the time differential value of the discharge voltage decreases with the discharge of the secondary battery, and the secondary battery is completely discharged The remaining capacity at the end of each discharge when the secondary battery changes from an incompletely discharged state to a charged state, at least at the end of discharge, which is smaller than the remaining capacity at the end of subsequent discharge. A storage step for storing the capacity;
A remaining capacity calculating step of calculating a remaining capacity of the secondary battery based on an integrated value of the discharge current detected in the current detecting step;
Displaying the remaining capacity, and
In the remaining capacity calculation step during discharge, the remaining capacity is not the value in the vicinity of the remaining capacity at the end of each discharge stored in the storage step, and the time differential value of the discharge voltage is stored in the storage step. When the predetermined value is reached, the remaining capacity is replaced with the predetermined remaining capacity.
Residual capacity calculation method of the secondary battery you wherein a.

In the remaining capacity calculation step during discharge, when the remaining capacity is smaller than a first predetermined value in the initial stage of discharge in which the time differential value of the discharge voltage increases with the discharge of the secondary battery under the above conditions, 8. The method for calculating a remaining capacity of a secondary battery according to claim 6 , wherein the remaining capacity is replaced with the predetermined remaining capacity .

9. The method according to claim 6 , further comprising a temperature detection step of detecting a temperature of the secondary battery, wherein the second predetermined value is a value having the temperature as a variable . The method for calculating the remaining capacity of the secondary battery according to claim .

The secondary battery remaining capacity calculation method according to any one of claims 6 to 9, wherein the secondary battery is a nickel-metal hydride battery .