JP3539123B2 - Method and apparatus for determining deterioration of secondary battery - Google Patents

Method and apparatus for determining deterioration of secondary battery Download PDF

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JP3539123B2
JP3539123B2 JP08886697A JP8886697A JP3539123B2 JP 3539123 B2 JP3539123 B2 JP 3539123B2 JP 08886697 A JP08886697 A JP 08886697A JP 8886697 A JP8886697 A JP 8886697A JP 3539123 B2 JP3539123 B2 JP 3539123B2
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secondary battery
voltage
charging
open circuit
state
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JPH10270092A (en
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和彦 竹野
幹夫 山崎
亨 鈴木
誠一 室山
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Nippon Telegraph and Telephone Corp
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    • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
    • Y02E—REDUCTION OF GREENHOUSE GAS [GHG] EMISSIONS, RELATED TO ENERGY GENERATION, TRANSMISSION OR DISTRIBUTION
    • Y02E60/00—Enabling technologies; Technologies with a potential or indirect contribution to GHG emissions mitigation
    • Y02E60/10—Energy storage using batteries

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  • Charge And Discharge Circuits For Batteries Or The Like (AREA)
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Description

【０００１】
【発明の属する技術分野】
本発明は、無停電電源に関するものであり、ニッケルカドミニウム電池、ニッケル水素電池、リチウムイオン電池等の二次電池を予備電力源とする装置において、上記二次電池の容量低下に伴う劣化を検出する方法および装置に関するものである。
【０００２】
【従来の技術】
従来、バックアップ電源に用いられているニッケルカドミニウム電池等の二次電池は、常時微少電流を流して充電を行うトリクル充電が行われている。
【０００３】
しかし、このトリクル充電は、電池に常時電流を流しているので、電池にとっては過充電状態が長時間続くことになり、電池の電解液や電極板の劣化を進行し、電池寿命が短くなるという問題がある。このために、トリクル充電によっては劣化しにくいトリクル充電用電池を使用する必要があるが、このトリクル充電用電池は、充電電荷が全て放電された後に充電するサイクル用電池よりも高価であるという問題がある。
【０００４】
また、ニッケルカドミニウム電池よりも高エネルギー密度である二次電池としては、ニッケル水素電池が知られているが、このニッケル水素電池は、トリクル充電方式を採用することができないという問題がある。
【０００５】
これらの問題を解決するには、安価なサイクル用電池を二次電池として使用し、この二次電池を間欠的に充電すればよい。
【０００６】
つまり、定電流回路から二次電池を充電し、二次電池の電圧が最大閾値電圧に達したときに、充電用スイッチをオフにして充電を止めるとともに二次電池を開回路状態にし、二次電池の電圧が自己放電によって最低閾値電圧まで低下したときに二次電池の充電を開始し、上記充電状態と上記開回路状態とを繰り返す間欠充電を行えばよい。そして、この間欠充電において、二次電池の劣化を判定するには、二次電池を負荷から切り離し、二次電池の放電を実際に行い、二次電池の容量を測定することによって、二次電池の劣化を判定する方法、または、二次電池を負荷から切り離した状態で、二次電池の内部抵抗を測定することによって、二次電池の劣化を判定する方法を実行する。
【０００７】
【発明が解決しようとする課題】
しかし、上記従来例においては、二次電池に間欠充電を行いながら、その二次電池の劣化を判定しようとすると、その二次電池を負荷から切り離す必要があるので、二次電池を負荷から切り離している間、バックアップできないという問題がある。
【０００８】
本発明は、間欠充電によって二次電池を充電する場合、二次電池を負荷から切り離さずに、二次電池の劣化を判定することができる二次電池の劣化判定方法およびその装置を提供することを目的とするものである。
【０００９】
【課題を解決するための手段】
本発明は、定電流回路から二次電池を充電し、二次電池の電圧が最大閾値電圧に達したときに、充電用スイッチをオフにして充電を止めるとともに二次電池を開回路状態にし、二次電池の電圧が自己放電によって最低閾値電圧まで低下したときに二次電池の充電を開始し、上記充電状態と上記開回路状態とを繰り返す二次電池の間欠充電において、充電状態から開回路状態に切り替えてから所定時間以内に、開回路状態における二次電池の電圧である開回路電圧を測定し、最大閾値電圧から開回路電圧を差し引いた差電圧と所定の閾値とを比較し、差電圧が所定の閾値に達したときに、二次電池が劣化したと判定するものである。
【００１０】
【発明の実施の形態および実施例】
図１は、本発明の第１の実施例である二次電池の劣化判定回路ＤＣ１を示す図である。
【００１１】
二次電池の劣化判定回路ＤＣ１は、二次電池１と、二次電池１を充電する定電流回路２と、充電状態を制御する充電用スイッチであるＭＯＳＦＥＴ３と、基準電圧源４と、コンパレータ５と、抵抗Ｒ１、Ｒ２と、電圧判定回路を実現するシュミット・トリガ回路８と、直流電源回路９と、コンパレータ１１と、アナログスイッチ１２と、インバータ回路１３と、矩形波発生回路１４と、シュミット・トリガ回路の最大閾値電圧Ｖ１を発生する基準電圧源１５と、基準電圧ΔＶｑを発生する基準電圧源１６と、抵抗１９と、減算器２１とを有する。減算器２１は、オペアンプ１０、抵抗１７、１８、２０で構成されている。
【００１２】
二次電池１は、ニッケルカドミニウム電池、ニッケル水素電池、リチウムイオン電池等である。
【００１３】
なお、ＡＣ電源３１のＡＣ電圧がＡＣ−ＤＣコンバータ３２によって直流電圧に変換され、この直流電圧が負荷３３に印加されている。また、二次電池１の＋電極がダイオード３４のアノード側に接続され、このダイオード３４のカソード側が負荷３３の入力端子に接続されている。そして、常時はＡＣ電源から負荷３３に電力が供給されるが、ＡＣ電源が停電した場合には、ダイオード３４を介して、二次電池１に充電された電荷が負荷３３に供給される。
【００１４】
次に、二次電池の劣化判定回路ＤＣ１の動作について説明する。
【００１５】
図２は、二次電池の劣化判定回路ＤＣ１の動作波形を示す図である。
【００１６】
図２において、縦軸に電圧、横軸に時間が示されている。Ｖａは、二次電池１の端子電圧波形であり、Ｖｂはシュミット・トリガ回路８の出力電圧であり、Ｖｃはインバータ１３の出力電圧波形であり、Ｖｄは矩形波発生回路１４の出力電圧波形であり、Ｖｅはアナログスイッチ１２の出力波形信号であり、Ｖｆはコンパレータ１１の出力電圧波形である。
【００１７】
二次電池１は、ＭＯＳＦＥＴ３がオンしている場合、すなわち、Ｖｂがオン信号レベルである場合、定電流回路２から電流が流れ込み充電が行われる（充電状態）。この充電状態において、抵抗Ｒ１、Ｒ２、基準電圧源４が出力する最大閾値電圧（充電終止電圧）Ｖ１と最小閾値電圧（充電開始電圧）Ｖ２において、シュミット・トリガ回路８の最大閾値電圧（充電終止電圧）Ｖ１まで、二次電池１の電圧が上昇した時点でコンパレータ５の出力はオフ信号を発生し、充電用スイッチ３がオフ状態になり、定電流回路２と二次電池１との間が開回路になる（開回路状態）。この開回路状態において、定電流回路２からの充電電流が停止し、二次電池１への充電が停止される。
【００１８】
開回路状態になった二次電池は自己放電によって、蓄えられた電気容量が徐々に低下し、この自己放電とともに開回路電圧Ｖ３（開回路状態における二次電池１の電圧）も低下する。そして、開回路電圧が、シュミット・トリガ回路８の最小閾値電圧（充電開始電圧）Ｖ２まで低下した時点で、コンパレータ５の出力信号がオン信号になる。これによって、充電用スイッチ３がオン状態になり、定電流回路２からの充電電流が二次電池１に流れ込み、二次電池１への充電が開始される。上記開回路状態と充電状態とを繰り返すことによって、間欠充電が行われ、二次電池１の容量が、所定の容量以上に常時保持される。
【００１９】
図３は、二次電池としてのニッケル水素電池を間欠充電したときにおける電圧波形を拡大して示す図である。
【００２０】
充電停止直後に測定する電圧Ｖ３は、時間が経つに従って、自己放電によって低下していく。この現象は劣化とは無関係の現象であり、その影響を軽減する必要がある。一般に、充電停止直後に測定する電圧Ｖ３の時間的変化は、充電停止後１分以内では緩やかな変化であるが、１分を越えると、自己放電によって、大きく変化する。したがって、充電停止直後に電圧Ｖ３を測定する場合、充電停止から１分以内に測定を行うことを条件とし、これによって自己放電の影響を軽減する。
つまり、上記開回路電圧Ｖ３は、充電状態から開回路状態に切り替えてから所定時間内に測定された開回路状態における二次電池の電圧である。
【００２１】
図４は、二次電池としてのニッケル水素電池の劣化に伴って低下する二次電池の容量Ｑと、差電圧ΔＶとの関係を示す図である。
【００２２】
二次電池１を間欠充電する場合、充電状態から開回路状態へ移行する瞬間、二次電池１の端子電圧Ｖａは急激に降下する。この急激な電圧降下による差電圧ΔＶ（＝Ｖ１−Ｖ３）は、図４に示してあるように、差電圧ΔＶと二次電池１の容量Ｑとに相関があるので、二次電池１の劣化と、判定する容量Ｑｑに対応する差電圧の閾値ΔＶｑを決定し、差電圧ΔＶが閾値ΔＶｑに達した時点で劣化と判定する。
【００２３】
すなわち、基準電圧源１５が出力する充電終止電圧Ｖ１から、開回路電圧Ｖ３を引いた差電圧Ｖ１−Ｖ３を、減算器２１が出力する。一方、充電状態から開回路状態に移行するときに、シュミット・トリガ回路８の出力電圧Ｖｂの値がオフ信号状態になり、電圧Ｖｂを入力したインバータ１３の出力電圧Ｖｃはオン信号状態になる。矩形波発生回路１４は、立ち上がり信号が入力された場合、パルス時間Ｔ０の矩形波信号Ｖｄを出力するので、電圧Ｖｃがオン信号に立ち上がったことを検出して、パルス時間Ｔ０の矩形波信号Ｖｄが出力される。
【００２４】
そして、アナログスイッチ１２のゲートに、矩形波発生回路１４からオン信号が入力されると、アナログスイッチ１２の切り替え接片がＡ側に切り替わり、アナログスイッチ１２のゲートにオフ信号が入力されると、その切り替え接片がＢ側に切り替わる。パルス時間Ｔ０の矩形波信号Ｖｄがアナログスイッチ１２のゲートに入力されると、アナログスイッチ１２がＢ側からＡ側に切り替わる。これによって、減算器２１からの信号Ｖｅが、コンパレータ１１の＋入力端子に入力される。コンパレータ１１は、減算器２１からの信号Ｖｅ（＝Ｖ１−Ｖ３）と閾値ΔＶｑの値とを比較して、信号Ｖｅの値が閾値ΔＶｑよりも大きくなったときに、出力電圧波形Ｖｆの信号がオンレベルになり、二次電池１が劣化したことを知らせる。
【００２５】
なお、差電圧ΔＶは、充電停止から短い時間Ｔ０が経過したときにおける電圧Ｖ３を、間欠充電における充電終止電圧Ｖ１から差し引いた差の電圧である。つまり、差電圧ΔＶ＝Ｖ１−Ｖ３である。そして、充電状態から開回路状態に移行してから、１分以内においては、二次電池１の電圧波形はほぼ一定であることが図３に示されている。したがって、充電停止直後に電圧Ｖ３を測定する時間（パルス時間Ｔ０）を１分以内に設定することによって、自己放電の影響を排除し、差電圧ΔＶを精度よく測定することができる。
【００２６】
上記実施例は、図４に示すように、二次電池１の容量Ｑの低下に伴って、差電圧ΔＶが大きくなり、この特性を利用して、二次電池１が劣化していると判断される容量Ｑｑに対応する差電圧の閾値ΔＶｑを設定し、間欠充電中に、差電圧ΔＶを監視し、差電圧ΔＶが、閾値Ｖｑになったときに、その二次電池１が劣化していると判定する。
【００２７】
なお、上記劣化判定動作が実行されているときに、二次電池１が負荷から切り離されないので、停電時（ＡＣ電源３１の故障時）に、上記劣化判定動作が実行されたとしても、バックアップが停止されることはない。
【００２８】
図５は、本発明の第２の実施例である二次電池の劣化判定回路ＤＣ２を示す図である。
【００２９】
二次電池の劣化判定回路ＤＣ２は、基本的には二次電池の劣化判定回路ＤＣ１と同じであり、二次電池の劣化判定回路ＤＣ１において、基準電圧源１６と直列に、抵抗２２とサーミスタ２３との直列回路が接続され、サーミスタ２３が二次電池１の温度を検出するようになっている点が、二次電池の劣化判定回路ＤＣ１とは異なる。
【００３０】
つまり、二次電池の劣化判定回路ＤＣ２において、サーミスタ２３が、劣化判定電圧における差電圧の閾値ΔＶｑを温度補正している。
【００３１】
具体的には、二次電池１にサーミスタ２３を接触させ、このサーミスタ２３によって二次電池１の温度を測定し、このときに、二次電池１の温度変化に応じてサーミスタ２３の抵抗値が変化し、抵抗２２とサーミスタ２３とによって電圧分割された閾値ΔＶｑが、温度によって変化される。
【００３２】
図６は、劣化に伴って低下するニッケル水素電池の容量Ｑと、差電圧ΔＶとの関係が、温度依存性を有することを示す特性図である。
【００３３】
図６に示す特性図によれば、容量ＱとΔＶとの関係が、温度の変化に対して変化している。この特性から、劣化と判断する容量Ｑｑに対応する閾値ΔＶｑの値を、温度変化とともに変化させて、温度補正を行う。
【００３４】
【発明の効果】
本発明によれば、間欠充電によって二次電池を充電する場合に、二次電池を負荷から切り離さずに、二次電池の劣化を判定することができるという効果を奏する。
【図面の簡単な説明】
【図１】本発明の第１の実施例である二次電池の劣化判定回路ＤＣ１の図である。
【図２】二次電池の劣化判定回路ＤＣ１の動作波形を示す図である。
【図３】二次電池としてのニッケル水素電池を間欠充電したときにおける電圧波形を拡大して示す図である。
【図４】二次電池としてのニッケル水素電池の劣化に伴って低下する二次電池の容量Ｑと、差電圧ΔＶとの関係を示す図である。
【図５】本発明の第２の実施例である二次電池の劣化判定回路ＤＣ２の図である。
【図６】劣化に伴って低下するニッケル水素電池の容量Ｑと、差電圧ΔＶとの関係が、温度依存性を有することを示す特性図である。
【符号の説明】
ＤＣ１、ＤＣ２…二次電池の劣化判定回路、
１…二次電池、
２…定電流回路、
３…ＭＯＳＦＥＴ、
４…基準電圧源、
８…シュミット・トリガ回路、
９…直流電源回路、
１１…コンパレータ１１、
１２…アナログスイッチ、
１４…矩形波発生回路、
２１…減算器、
２３…サーミスタ、
３１…ＡＣ電源、
３３…負荷、
３４…ダイオード。[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to an uninterruptible power supply, and in a device using a secondary battery such as a nickel-cadmium battery, a nickel-metal hydride battery, and a lithium-ion battery as a standby power source, detects deterioration due to a decrease in the capacity of the secondary battery. The present invention relates to a method and an apparatus.
[0002]
[Prior art]
2. Description of the Related Art Conventionally, a trickle charge, in which a secondary battery such as a nickel cadmium battery used as a backup power supply is charged by passing a small current at all times, is performed.
[0003]
However, in trickle charging, current always flows through the battery, so that the battery is overcharged for a long time, and the battery electrolyte and electrode plates are deteriorated, and the battery life is shortened. There's a problem. For this reason, it is necessary to use a trickle charging battery that is not easily deteriorated by trickle charging. However, this trickle charging battery is more expensive than a cycle battery that is charged after all the charge has been discharged. There is.
[0004]
As a secondary battery having a higher energy density than a nickel-cadmium battery, a nickel-metal hydride battery is known. However, this nickel-metal hydride battery has a problem that a trickle charging method cannot be adopted.
[0005]
To solve these problems, an inexpensive cycle battery may be used as a secondary battery, and the secondary battery may be intermittently charged.
[0006]
That is, the secondary battery is charged from the constant current circuit, and when the voltage of the secondary battery reaches the maximum threshold voltage, the charging switch is turned off to stop charging, and the secondary battery is opened, and the secondary battery is opened. The charging of the secondary battery may be started when the voltage of the battery drops to the minimum threshold voltage due to self-discharge, and the intermittent charging may be performed by repeating the above-described charging state and the above-described open circuit state. Then, in this intermittent charging, to determine the deterioration of the secondary battery, the secondary battery is disconnected from the load, the secondary battery is actually discharged, and the capacity of the secondary battery is measured. Of the deterioration of the secondary battery or a method of determining the deterioration of the secondary battery by measuring the internal resistance of the secondary battery with the secondary battery disconnected from the load.
[0007]
[Problems to be solved by the invention]
However, in the above conventional example, while performing intermittent charging of the secondary battery and trying to determine the deterioration of the secondary battery, it is necessary to disconnect the secondary battery from the load. While backup is not possible.
[0008]
An object of the present invention is to provide a secondary battery deterioration determination method and device capable of determining secondary battery deterioration without disconnecting the secondary battery from a load when the secondary battery is charged by intermittent charging. The purpose is.
[0009]
[Means for Solving the Problems]
The present invention charges a rechargeable battery from a constant current circuit, and when the voltage of the rechargeable battery reaches a maximum threshold voltage, turns off a charging switch to stop charging and puts the rechargeable battery into an open circuit state, When the voltage of the secondary battery is reduced to the minimum threshold voltage by self-discharge, charging of the secondary battery is started, and in the intermittent charging of the secondary battery that repeats the above-mentioned charged state and the above-mentioned open circuit state, the open circuit from the charged state Within a predetermined time after switching to the state, the open circuit voltage, which is the voltage of the secondary battery in the open circuit state, is measured, and a difference voltage obtained by subtracting the open circuit voltage from the maximum threshold voltage is compared with a predetermined threshold value. When the voltage reaches a predetermined threshold value, it is determined that the secondary battery has deteriorated.
[0010]
Embodiments and Examples of the Invention
FIG. 1 is a diagram illustrating a deterioration determination circuit DC1 of a secondary battery according to a first embodiment of the present invention.
[0011]
The secondary battery deterioration determination circuit DC1 includes a secondary battery 1, a constant current circuit 2 for charging the secondary battery 1, a MOSFET 3 serving as a charging switch for controlling the state of charge, a reference voltage source 4, and a comparator 5 , Resistors R1 and R2, a Schmitt trigger circuit 8 for realizing a voltage determination circuit, a DC power supply circuit 9, a comparator 11, an analog switch 12, an inverter circuit 13, a rectangular wave generation circuit 14, a Schmitt The trigger circuit includes a reference voltage source 15 that generates a maximum threshold voltage V 1, a reference voltage source 16 that generates a reference voltage ΔVq, a resistor 19, and a subtractor 21. The subtracter 21 includes the operational amplifier 10 and the resistors 17, 18, and 20.
[0012]
The secondary battery 1 is a nickel cadmium battery, a nickel hydrogen battery, a lithium ion battery, or the like.
[0013]
The AC voltage of the AC power supply 31 is converted into a DC voltage by the AC-DC converter 32, and the DC voltage is applied to the load 33. The positive electrode of the secondary battery 1 is connected to the anode of the diode 34, and the cathode of the diode 34 is connected to the input terminal of the load 33. Then, power is always supplied from the AC power supply to the load 33. However, when the AC power supply is interrupted, the charge charged in the secondary battery 1 is supplied to the load 33 via the diode 34.
[0014]
Next, the operation of the secondary battery deterioration determination circuit DC1 will be described.
[0015]
FIG. 2 is a diagram showing operation waveforms of the secondary battery deterioration determination circuit DC1.
[0016]
In FIG. 2, the vertical axis represents voltage and the horizontal axis represents time. Va is the terminal voltage waveform of the secondary battery 1, Vb is the output voltage of the Schmitt trigger circuit 8, Vc is the output voltage waveform of the inverter 13, and Vd is the output voltage waveform of the rectangular wave generation circuit 14. Ve is an output waveform signal of the analog switch 12, and Vf is an output voltage waveform of the comparator 11.
[0017]
When the MOSFET 3 is on, that is, when Vb is at the ON signal level, the secondary battery 1 is charged by flowing current from the constant current circuit 2 (charge state). In this charging state, the maximum threshold voltage (charging end voltage) of the Schmitt trigger circuit 8 is determined by the maximum threshold voltage (charging end voltage) V1 and the minimum threshold voltage (charging start voltage) V2 output from the resistors R1 and R2 and the reference voltage source 4. When the voltage of the secondary battery 1 rises to the voltage of V1), the output of the comparator 5 generates an off signal, the charging switch 3 is turned off, and the connection between the constant current circuit 2 and the secondary battery 1 is established. Open circuit (open circuit state). In this open circuit state, the charging current from the constant current circuit 2 stops, and the charging of the secondary battery 1 stops.
[0018]
The stored electric capacity of the secondary battery in the open circuit state gradually decreases due to self-discharge, and the open circuit voltage V3 (the voltage of the secondary battery 1 in the open circuit state) also decreases along with the self-discharge. Then, when the open circuit voltage decreases to the minimum threshold voltage (charging start voltage) V2 of the Schmitt trigger circuit 8, the output signal of the comparator 5 becomes an ON signal. As a result, the charging switch 3 is turned on, the charging current from the constant current circuit 2 flows into the secondary battery 1, and the charging of the secondary battery 1 is started. By repeating the open circuit state and the charging state, intermittent charging is performed, and the capacity of the secondary battery 1 is constantly maintained at a predetermined capacity or more.
[0019]
FIG. 3 is an enlarged diagram showing a voltage waveform when a nickel-metal hydride battery as a secondary battery is intermittently charged.
[0020]
The voltage V3 measured immediately after the stop of charging gradually decreases due to self-discharge over time. This phenomenon is irrelevant to deterioration, and its effects need to be reduced. In general, the temporal change of the voltage V3 measured immediately after the stop of charging is a gradual change within one minute after the stop of charging, but greatly changes after 1 minute due to self-discharge. Therefore, when the voltage V3 is measured immediately after the charging is stopped, the measurement is performed within one minute after the charging is stopped, thereby reducing the influence of self-discharge.
That is, the open circuit voltage V3 is the voltage of the secondary battery in the open circuit state measured within a predetermined time after switching from the charging state to the open circuit state.
[0021]
FIG. 4 is a diagram showing the relationship between the capacity Q of the secondary battery, which decreases with the deterioration of the nickel-metal hydride battery as the secondary battery, and the difference voltage ΔV.
[0022]
In the case where the secondary battery 1 is intermittently charged, the terminal voltage Va of the secondary battery 1 sharply drops at the moment of transition from the charging state to the open circuit state. The difference voltage ΔV (= V1−V3) due to the sudden voltage drop is correlated with the difference voltage ΔV and the capacity Q of the secondary battery 1 as shown in FIG. Is determined, the threshold value ΔVq of the difference voltage corresponding to the capacity Qq to be determined is determined.
[0023]
That is, the subtractor 21 outputs a difference voltage V1−V3 obtained by subtracting the open circuit voltage V3 from the charge termination voltage V1 output by the reference voltage source 15. On the other hand, when the state changes from the charging state to the open circuit state, the value of the output voltage Vb of the Schmitt trigger circuit 8 becomes an off signal state, and the output voltage Vc of the inverter 13 to which the voltage Vb is input becomes an on signal state. When the rising signal is input, the rectangular wave generating circuit 14 outputs the rectangular wave signal Vd of the pulse time T0. Therefore, the rectangular wave generating circuit 14 detects that the voltage Vc has risen to the ON signal, and detects the rectangular wave signal Vd of the pulse time T0. Is output.
[0024]
When an ON signal is input to the gate of the analog switch 12 from the rectangular wave generation circuit 14, the switching contact of the analog switch 12 switches to the A side, and when an OFF signal is input to the gate of the analog switch 12, The switching contact switches to the B side. When the rectangular wave signal Vd of the pulse time T0 is input to the gate of the analog switch 12, the analog switch 12 switches from the B side to the A side. As a result, the signal Ve from the subtractor 21 is input to the + input terminal of the comparator 11. The comparator 11 compares the signal Ve (= V1−V3) from the subtractor 21 with the value of the threshold value ΔVq, and when the value of the signal Ve becomes larger than the threshold value ΔVq, the signal of the output voltage waveform Vf It goes to the on level, and notifies that the secondary battery 1 has deteriorated.
[0025]
Note that the difference voltage ΔV is a voltage obtained by subtracting the voltage V3 when a short time T0 has elapsed from the stop of charging from the charge end voltage V1 in intermittent charging. That is, the difference voltage ΔV = V1−V3. FIG. 3 shows that the voltage waveform of the secondary battery 1 is substantially constant within one minute from the transition from the charging state to the open circuit state. Therefore, by setting the time (pulse time T0) for measuring the voltage V3 immediately after the charging is stopped to within 1 minute, the influence of self-discharge can be eliminated, and the difference voltage ΔV can be measured accurately.
[0026]
In the above embodiment, as shown in FIG. 4, as the capacity Q of the secondary battery 1 decreases, the difference voltage ΔV increases, and by utilizing this characteristic, it is determined that the secondary battery 1 has deteriorated. The threshold value ΔVq of the difference voltage corresponding to the capacity Qq to be performed is set, the difference voltage ΔV is monitored during the intermittent charging, and when the difference voltage ΔV becomes the threshold value Vq, the secondary battery 1 is deteriorated. It is determined that there is.
[0027]
Since the secondary battery 1 is not disconnected from the load when the above-described deterioration determination operation is being performed, even if the above-described deterioration determination operation is performed at the time of a power failure (when the AC power supply 31 fails), a backup is performed. Will not be stopped.
[0028]
FIG. 5 is a diagram showing a secondary battery deterioration determination circuit DC2 according to a second embodiment of the present invention.
[0029]
The deterioration judgment circuit DC2 of the secondary battery is basically the same as the deterioration judgment circuit DC1 of the secondary battery. In the deterioration judgment circuit DC1 of the secondary battery, the resistor 22 and the thermistor 23 are connected in series with the reference voltage source 16. Is different from the secondary battery deterioration determination circuit DC1 in that the series circuit is connected and the thermistor 23 detects the temperature of the secondary battery 1.
[0030]
That is, in the deterioration determination circuit DC2 of the secondary battery, the thermistor 23 corrects the temperature difference ΔVq of the difference voltage in the deterioration determination voltage.
[0031]
Specifically, the thermistor 23 is brought into contact with the secondary battery 1, and the temperature of the secondary battery 1 is measured by the thermistor 23. At this time, the resistance of the thermistor 23 is changed according to the temperature change of the secondary battery 1. The threshold value ΔVq that changes and is voltage-divided by the resistor 22 and the thermistor 23 is changed by the temperature.
[0032]
FIG. 6 is a characteristic diagram showing that the relationship between the capacity Q of the nickel-metal hydride battery that decreases with deterioration and the difference voltage ΔV has temperature dependency.
[0033]
According to the characteristic diagram shown in FIG. 6, the relationship between the capacitance Q and ΔV changes with a change in temperature. From this characteristic, the temperature correction is performed by changing the value of the threshold value ΔVq corresponding to the capacity Qq determined to be deteriorated with the temperature change.
[0034]
【The invention's effect】
Advantageous Effects of Invention According to the present invention, when a secondary battery is charged by intermittent charging, it is possible to determine the deterioration of the secondary battery without disconnecting the secondary battery from a load.
[Brief description of the drawings]
FIG. 1 is a diagram of a secondary battery deterioration determination circuit DC1 according to a first embodiment of the present invention.
FIG. 2 is a diagram showing operation waveforms of a secondary battery deterioration determination circuit DC1.
FIG. 3 is an enlarged view showing a voltage waveform when a nickel-metal hydride battery as a secondary battery is intermittently charged.
FIG. 4 is a diagram showing a relationship between the capacity Q of the secondary battery, which decreases with the deterioration of a nickel-metal hydride battery as a secondary battery, and a difference voltage ΔV.
FIG. 5 is a diagram of a secondary battery deterioration determination circuit DC2 according to a second embodiment of the present invention.
FIG. 6 is a characteristic diagram showing that the relationship between the capacity Q of the nickel-metal hydride battery, which decreases with deterioration, and the difference voltage ΔV has temperature dependency.
[Explanation of symbols]
DC1, DC2 ... rechargeable battery deterioration determination circuit,
1 ... secondary battery,
2. Constant current circuit
3 ... MOSFET,
4: Reference voltage source,
8 ... Schmitt trigger circuit
9 DC power supply circuit,
11 ... Comparator 11,
12. Analog switch,
14 ... Square wave generation circuit,
21 ... Subtractor,
23 ... Thermistor,
31 ... AC power supply,
33 ... load,
34 ... Diode.

Claims (6)

定電流回路から二次電池を充電し、上記二次電池の電圧が最大閾値電圧に達したときに、充電用スイッチをオフにして充電を停止するとともに上記二次電池を上記定電流回路から切り離して開回路状態にし、上記二次電池の電圧が自己放電によって最低閾値電圧まで低下したときに上記二次電池の充電を開始し、上記充電状態と上記開回路状態とを繰り返す二次電池の間欠充電において、
上記充電状態から上記開回路状態に切り替えてから所定時間以内に、上記開回路状態における上記二次電池の電圧である開回路電圧を測定する開回路電圧測定段階と；
上記最大閾値電圧から上記開回路電圧を差し引いた差電圧を演算する差電圧演算段階と；
上記差電圧と所定の閾値とを比較する比較段階と；
上記差電圧が上記所定の閾値に達したときに、上記二次電池が劣化したと判定する劣化判定段階と；
を有することを特徴とする二次電池の劣化判定方法。The secondary battery is charged from the constant current circuit, and when the voltage of the secondary battery reaches the maximum threshold voltage, the charging switch is turned off to stop charging and the secondary battery is disconnected from the constant current circuit. To open the circuit, and when the voltage of the secondary battery drops to the minimum threshold voltage due to self-discharge, charging of the secondary battery is started, and the intermittent operation of the secondary battery is repeated between the charging state and the open circuit state. In charging,
An open circuit voltage measuring step of measuring an open circuit voltage that is a voltage of the secondary battery in the open circuit state within a predetermined time after switching from the charge state to the open circuit state;
Calculating a difference voltage obtained by subtracting the open circuit voltage from the maximum threshold voltage;
A comparing step of comparing the difference voltage with a predetermined threshold;
A deterioration determining step of determining that the secondary battery has deteriorated when the difference voltage has reached the predetermined threshold;
A method for judging deterioration of a secondary battery, comprising: 請求項１において、
上記所定の閾値に、上記二次電池の使用温度の依存性を持たせることを特徴とする二次電池の劣化判定方法。In claim 1,
A method for determining deterioration of a secondary battery, wherein the predetermined threshold value has a dependency on a use temperature of the secondary battery. 請求項１または請求項２において
上記充電状態から上記開回路状態に切り替えてからの上記所定時間は、１分間であることを特徴とする二次電池の劣化判定方法。3. The method according to claim 1, wherein the predetermined time after switching from the charging state to the open circuit state is one minute. 定電流回路から二次電池を充電し、上記二次電池の電圧が最大閾値電圧に達したときに、充電用スイッチをオフにして充電を停止するとともに上記二次電池を上記定電流回路から切り離して開回路状態にし、上記二次電池の電圧が自己放電によって最低閾値電圧まで低下したときに上記二次電池の充電を開始し、上記充電状態と上記開回路状態とを繰り返す二次電池の間欠充電回路において、
上記最大閾値電圧から、上記充電状態から上記開回路状態に切り替えてから所定時間内に測定された上記開回路状態における上記二次電池の電圧である開回路電圧を差し引いた差電圧を演算する差電圧演算手段と；
上記差電圧と所定の閾値とを比較し、上記差電圧が上記所定の閾値に達したときに、上記二次電池が劣化したと判定する劣化判定手段と；
を有することを特徴とする二次電池の劣化判定装置。The secondary battery is charged from the constant current circuit, and when the voltage of the secondary battery reaches the maximum threshold voltage, the charging switch is turned off to stop charging and the secondary battery is disconnected from the constant current circuit. To open the circuit, and when the voltage of the secondary battery drops to the minimum threshold voltage due to self-discharge, charging of the secondary battery is started, and the intermittent operation of the secondary battery is repeated between the charging state and the open circuit state. In the charging circuit,
A difference for calculating a difference voltage obtained by subtracting an open circuit voltage that is a voltage of the secondary battery in the open circuit state measured within a predetermined time after switching from the charge state to the open circuit state from the maximum threshold voltage. Voltage calculation means;
Degradation determination means for comparing the difference voltage with a predetermined threshold value, and determining that the secondary battery has deteriorated when the difference voltage has reached the predetermined threshold value;
A degradation determination device for a secondary battery, comprising: 請求項４において、
上記劣化判定手段は、上記差電圧演算手段が出力した差電圧と上記所定の閾値とを比較するコンパレータによって構成され、
上記二次電池の電圧が上記最大閾値電圧に達したときにパルスを発生するパルス発生手段と；
上記パルス発生手段が上記パルスを発生したときにのみ、上記差電圧演算手段が出力した差電圧を、上記コンパレータへ供給するスイッチ手段と；
を有することを特徴とする二次電池の劣化判定装置。In claim 4,
The deterioration determination unit is configured by a comparator that compares the difference voltage output by the difference voltage calculation unit with the predetermined threshold,
Pulse generation means for generating a pulse when the voltage of the secondary battery reaches the maximum threshold voltage;
Switch means for supplying the difference voltage output by the difference voltage calculation means to the comparator only when the pulse generation means generates the pulse;
A degradation determination device for a secondary battery, comprising: 請求項４または請求項５において、
上記劣化判定手段は、上記二次電池の使用温度を保証する温度補償手段を有する回路であることを特徴とする二次電池の劣化判定装置。In claim 4 or claim 5,
The said deterioration judgment means is a circuit which has a temperature compensation means which guarantees the use temperature of the said secondary battery, The deterioration judgment apparatus of the secondary battery characterized by the above-mentioned.
JP08886697A 1997-03-24 1997-03-24 Method and apparatus for determining deterioration of secondary battery Expired - Fee Related JP3539123B2 (en)

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