JP2005185060A - Lithium-ion battery charging method - Google Patents

Lithium-ion battery charging method Download PDF

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JP2005185060A
JP2005185060A JP2003425419A JP2003425419A JP2005185060A JP 2005185060 A JP2005185060 A JP 2005185060A JP 2003425419 A JP2003425419 A JP 2003425419A JP 2003425419 A JP2003425419 A JP 2003425419A JP 2005185060 A JP2005185060 A JP 2005185060A
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charging
lithium ion
ion battery
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Kazutaka Nishiwaki
一貴 西脇
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DIACELLTEC KK
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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
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    • Y02E60/10—Energy storage using batteries

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Abstract

<P>PROBLEM TO BE SOLVED: To obtain a method of charging a lithium-ion battery in a short period of time while securing durability. <P>SOLUTION: A charging current is started and reduced gradually from a value sufficiently larger than 1CA as shown by a solid line "a". The timing of the reduction is a time when a voltage of a battery pack reaches V<SB>f</SB>+ IR obtained by adding a voltage drop portion IR by a resistor R of a portion other than the inside of the lithium-ion battery body to the voltage V<SB>f</SB>of the lithium-ion battery body. This structure allows a large current to flow in the lithium-ion battery, while suppressing the voltage rise of the body of the lithium-ion battery, so that problem can be solved. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

この発明は、リチウムをドープ又は脱ドープできる炭素質材料を負極活物質としたリチウムイオン電池の充電方法の改良に関し、このリチウムイオン電池の耐久性を確保しつつ、充電時間の短縮を図るものである。   The present invention relates to an improvement in a charging method of a lithium ion battery using a carbonaceous material capable of doping or dedoping lithium as a negative electrode active material, and is intended to shorten the charging time while ensuring the durability of the lithium ion battery. is there.

二次電池であるリチウムイオン電池は、繰り返し使用できてコスト的に有利である等の理由により、カメラ、ＶＴＲ、ヘッドフォンステレオ、ノート型パソコン、携帯電話等の各種ポータブル型の電気機器に使用されている。このリチウムイオン電池の充電方法に就いては、特許文献１〜１２に記載される等により、従来から各種の方法が提案され、その一部は実際に使用されている。又、１乃至複数本のリチウムイオン電池を、保護回路と共にホルダ内に組み込んで電池パックとし、この電池パックを上記電気機器の電源部分に組み込める様にする事も、従来から広く行なわれている。この様な電池パックの構造に就いては、例えば非特許文献１等に記載されている。   Lithium ion batteries, which are secondary batteries, are used in various portable electrical devices such as cameras, VTRs, headphone stereos, notebook computers, mobile phones, etc. because they can be used repeatedly and are advantageous in terms of cost. Yes. As for a method for charging this lithium ion battery, various methods have been proposed in the past, for example, as described in Patent Documents 1 to 12, and some of them are actually used. In addition, it has been widely practiced that one or more lithium ion batteries are assembled in a holder together with a protection circuit to form a battery pack, and this battery pack can be incorporated in the power supply portion of the electric device. Such a battery pack structure is described in, for example, Non-Patent Document 1.

図５は、この非特許文献１に記載された、電池パックの回路図である。リチウムイオン電池１の＋極と正端子２とを第一の電路３により導通させると共に、同じく−極と負端子４とを、第二の電路５により導通させている。そして、この第二の電路５の途中に、スイッチング素子である放電ＦＥＴ６と、第二のスイッチング素子である充電ＦＥＴ７とを、互いに直列に設けている。そして、これら両ＦＥＴ６、７のＯＮ、ＯＦＦ（断接）をＩＣ８により制御する様にしている。即ち、このＩＣ８は、充電時には、これら両ＦＥＴ６、７をＯＮした（閉じた）状態として上記両端子２、３から上記リチウムイオン電池１に電流が流れる様にする。そして、このリチウムイオン電池１の電圧が高位側閾値を越えた場合には上記充電ＦＥＴ７をＯＦＦし（開き）、それ以上の充電を停止する。又、上記ＩＣ８は、使用に伴って上記リチウムイオン電池１の電圧が低位側閾値を下回った場合に上記放電ＦＥＴ６をＯＦＦし（開き）、それ以上の放電を停止する。更に、上記ＩＣ８は、上記両端子２、３同士が短絡されて、これら両端子２、３間に過大な電流が流れた場合にも、上記放電ＦＥＴ６をＯＦＦし、上記リチウムイオン電池１内で急激な反応が生じる事を防止する。   FIG. 5 is a circuit diagram of the battery pack described in Non-Patent Document 1. The positive electrode 2 and the positive terminal 2 of the lithium ion battery 1 are made conductive by the first electric circuit 3, and the negative electrode 4 and the negative terminal 4 are made conductive by the second electric circuit 5. A discharge FET 6 that is a switching element and a charge FET 7 that is a second switching element are provided in series in the middle of the second electric circuit 5. Then, ON and OFF (connection / disconnection) of these FETs 6 and 7 are controlled by the IC 8. That is, when charging, the IC 8 sets the FETs 6 and 7 to ON (closed) so that current flows from the terminals 2 and 3 to the lithium ion battery 1. When the voltage of the lithium ion battery 1 exceeds the high threshold, the charging FET 7 is turned off (opened), and further charging is stopped. Further, the IC 8 turns off (opens) the discharge FET 6 and stops further discharge when the voltage of the lithium ion battery 1 falls below the lower threshold with use. Further, the IC 8 also turns off the discharge FET 6 even when the terminals 2 and 3 are short-circuited and an excessive current flows between the terminals 2 and 3. Prevent sudden reactions from occurring.

近年、上述の様な電池パックとした場合も含め、リチウムイオン電池の充電時間の短縮化に対する要求が大きくなっている。例えば、外出先で消耗した携帯電話用の電池パックを再利用可能にする為、コンビニエンスストアの店頭や駅頭で充電するサービスが行なわれる様になっており、この様な場合には、少しでも充電時間を短くする事が望まれている。一方、リチウムイオン電池を充電する場合に、高い電圧で長時間保持すると、このリチウムイオン電池の劣化が著しくなる事が知られている。従って、充電時間短縮の為に充電電流を大きくすべく、単に電圧を高くする事はできない。この様な事情を考慮した上でリチウムイオン電池の充電時間を短縮する、所謂急速充電方法として、特許文献３に記載されたものが知られている。   In recent years, there has been an increasing demand for shortening the charging time of lithium ion batteries, including the case of battery packs as described above. For example, in order to make it possible to recycle battery packs for mobile phones that have been consumed on the go, charging services are provided at convenience stores and stations. It is desirable to shorten the time. On the other hand, it is known that when a lithium ion battery is charged, if the lithium ion battery is held for a long time at a high voltage, the lithium ion battery is significantly deteriorated. Therefore, the voltage cannot simply be increased in order to increase the charging current in order to shorten the charging time. As a so-called rapid charging method for shortening the charging time of the lithium ion battery in consideration of such circumstances, a method described in Patent Document 3 is known.

図６は、この特許文献３に記載されたリチウムイオン電池の充電方法を示している。この従来方法の場合、充電電流を実線ａに示す様に段階的に変化させ、充電電圧を破線ｂで示す様に変化させる。この従来方法の場合、リチウムイオン電池を、先ず、上記実線ａの左端部に示す様に定電流で充電する事により、このリチウムイオン電池の電圧を鎖線ｂの左端部に示す様に変化させる。そして、この電圧が鎖線ｃで示す規定充電電圧に達したならば、上記実線ａで示した充電電流を低くし、再び上記リチウムイオン電池の電圧が規定充電電圧に達するまで、定電流で充電を行なう。以下、この作業を繰り返し行なう。   FIG. 6 shows a method of charging a lithium ion battery described in Patent Document 3. In the case of this conventional method, the charging current is changed stepwise as shown by a solid line a, and the charging voltage is changed as shown by a broken line b. In the case of this conventional method, the lithium ion battery is first charged with a constant current as shown at the left end of the solid line a, thereby changing the voltage of the lithium ion battery as shown at the left end of the chain line b. If this voltage reaches the specified charging voltage indicated by the chain line c, the charging current indicated by the solid line a is lowered, and charging is performed at a constant current until the voltage of the lithium ion battery reaches the specified charging voltage again. Do. Hereinafter, this operation is repeated.

上述の様な特許文献３に記載されている充電方法の場合、従来から一般に行なわれている充電方法に比べれば、リチウムイオン電池の劣化を抑えつつ、充電時間を短縮できるが、充電時間をより短縮する面からは改良の余地がある。即ち、上記特許文献３に記載された充電方法の場合、図６に鎖線ｃで示した規定充電電圧は、充電開始から充電終了まで全く同じであり、具体的には、４．２０Ｖにする事を想定している（明細書の段落番号［００４３］参照）。この４．２０Ｖなる値は、リチウムイオン電池の本体部分（実際に電気を蓄える部分）の電池電圧（フル充電時の開回路電圧）に一致する。この様な条件で上記リチウムイオン電池の充電を行なうと、上記本体部分の電圧が、この本体部分の劣化を防止する為に必要とされる以上に低く抑えられ、充電時間が長くなる。特に、充電容量を１００％に近付ける為に要する時間が長くなる。この理由に就いて、前述の図５に図７を加えて説明する。   In the case of the charging method described in Patent Document 3 as described above, the charging time can be shortened while suppressing the deterioration of the lithium ion battery as compared with the charging method that has been generally performed. There is room for improvement in terms of shortening. That is, in the case of the charging method described in Patent Document 3, the specified charging voltage indicated by the chain line c in FIG. 6 is exactly the same from the start of charging to the end of charging, specifically, 4.20V. (See paragraph number [0043] of the description). This value of 4.20 V coincides with the battery voltage (open circuit voltage during full charge) of the main body part (the part that actually stores electricity) of the lithium ion battery. When the lithium ion battery is charged under such conditions, the voltage of the main body portion is suppressed to be lower than necessary to prevent the deterioration of the main body portion, and the charging time becomes longer. In particular, the time required to bring the charging capacity close to 100% becomes longer. The reason for this will be described with reference to FIG.

例えば電池パックを構成するリチウムイオン電池１の＋−両極と、充電器の端子が接続される正端子２及び負端子４との間には、第一、第二両電路３、５の他、放電、充電両ＦＥＴ６、７が、互いに直列に接続されている。このうちの放電、充電両ＦＥＴ６、７の抵抗は、例えば２５〜５０ｍΩ程度になる。又、上記リチウムイオン電池１（本体部分）は、図７に示す様に、セル９として上記電池パックに組み込まれるが、このセル９には、上記リチウムイオン電池１自体の抵抗（＝特許請求の範囲に記載した電極抵抗＝例えば５０ｍΩ程度）と直列に、ＰＴＣやタブ部分の抵抗１０（例えば２０ｍΩ程度）が、直列に加わる。このうちのリチウムイオン電池１自体の抵抗は、このリチウムイオン電池１に加わる電圧降下の原因とはならないが、他の部分の抵抗（＝放電、充電両ＦＥＴ６、７の抵抗と抵抗１０との合計＝特許請求の範囲に記載した、電極抵抗を除いた直流抵抗Ｒ）は、上記電圧降下の原因となる。前記特許文献３に記載された充電方法は、この直流抵抗Ｒを考慮せずに規定充電電圧を設定している為、上述の様に上記リチウムイオン電池１の本体部分の電圧が必要以上に低く抑えられ、充電時間が長くなる。   For example, between the positive and negative electrodes of the lithium ion battery 1 constituting the battery pack and the positive terminal 2 and the negative terminal 4 to which the terminal of the charger is connected, in addition to the first and second electric circuits 3 and 5, Both the discharge and charge FETs 6 and 7 are connected in series with each other. Among these, the resistance of both the discharging and charging FETs 6 and 7 is, for example, about 25 to 50 mΩ. Further, as shown in FIG. 7, the lithium ion battery 1 (main body part) is incorporated into the battery pack as a cell 9, and the cell 9 has a resistance (= claim) of the lithium ion battery 1 itself. The resistance 10 (for example, about 20 mΩ) of the PTC and the tab portion is added in series with the electrode resistance described in the range = for example, about 50 mΩ. Of these, the resistance of the lithium ion battery 1 itself does not cause a voltage drop applied to the lithium ion battery 1, but the resistance of other parts (= the sum of the resistances of the discharge and charge FETs 6 and 7 and the resistance 10) = DC resistance R) excluding electrode resistance described in the claims causes the voltage drop. Since the charging method described in Patent Document 3 sets the specified charging voltage without considering this DC resistance R, the voltage of the main body portion of the lithium ion battery 1 is lower than necessary as described above. It is suppressed and the charging time becomes longer.

一方、特許文献８には、リチウムイオン電池の＋−両極と充電器の端子との間に存在する抵抗（抵抗値＝Ｒ）を考慮しつつ、このリチウムイオン電池の充電時間の短縮を図る充電方法に関する発明が記載されている。この従来の充電方法の第２例の場合、図８に実線ａで示す様に、充電すべきリチウムイオン電池の定格容量｛＝１Ｃ＝１Ａｈ（公報の第４欄第１６〜１７行）｝よりも少しだけ大きな充電電流Ｉi （＞１ＣＡ＝１Ａ）で充電を開始する。そして、上記端子間の電圧が、上記リチウムイオン電池の充電完了後の電圧Ｖf （＝４．２Ｖ）に上記抵抗に基づく電圧降下分を足した電圧Ｖi （＝Ｖf ＋ＲＩi ≒４．３Ｖ）に達した後、この充電電流を漸次減少させる。上記端子間の電圧をこの様な電圧Ｖi にまで上昇させる為に、上記充電電流Ｉi を１ＣＡよりも少しだけ大きな値に保持する時間を、図８に破線ｂで示した、上記特許文献８に記載された方法に対する従来方法の場合よりも長くしている。 On the other hand, Patent Document 8 describes charging that shortens the charging time of the lithium ion battery while taking into consideration the resistance (resistance value = R) that exists between the positive and negative electrodes of the lithium ion battery and the terminal of the charger. An invention relating to the method is described. In the case of this second example of the conventional charging method, as indicated by a solid line a in FIG. 8, from the rated capacity of the lithium ion battery to be charged {= 1C = 1 Ah (column 4, lines 16 to 17)} The charging is started with a slightly larger charging current I i (> 1CA = 1A). The voltage between the terminals is a voltage V i (= V f + RI i ≈4.) Obtained by adding a voltage drop based on the resistance to the voltage V f (= 4.2 V) after completion of charging of the lithium ion battery. 3V), the charging current is gradually reduced. In order to raise the voltage between the terminals to such a voltage V i , the time during which the charging current I i is held at a value slightly larger than 1CA is indicated by a broken line b in FIG. 8 is longer than the conventional method.

そして、上記端子間の電圧が上記「Ｖf ＋ＲＩi 」なる値に達した後、上記充電電流Ｉi を漸次減少させて、この端子間の電圧をこの「Ｖf ＋ＲＩi 」なる値に保持する様にしている。従って、上記特許文献８に記載された方法に対する従来方法の場合に上記端子間の電圧が図９の破線ｄで示す様に変化するのに対して、上記特許文献８に記載された充電方法の場合には、同図の実線ｃで示す様に変化する。そして、上記リチウムイオン電池に流れる充電電流を多くして、充電時間の短縮を図るとしている。 Then, after the voltage between the terminals reaches the value of “V f + RI i ”, the charging current I i is gradually decreased to maintain the voltage between the terminals at the value of “V f + RI i ”. I try to do it. Therefore, in the case of the conventional method with respect to the method described in Patent Document 8, the voltage between the terminals changes as indicated by a broken line d in FIG. In this case, it changes as indicated by a solid line c in FIG. And the charging current which flows into the said lithium ion battery is increased, and it aims at shortening of charging time.

この様な特許文献８に記載された従来の充電方法の第２例の場合、単にリチウムイオン電池の＋−両極と充電器の端子との間に存在する抵抗に基づく電圧降下分を考慮しただけであって、それ以上に充電時間を短縮する事を意図してはいない。特に、充電電流を１ＣＡを越えて十分に大きくする事により、充電時間の大幅な短縮を図る事は、全く意図していない。従って、図８の実線ａと破線ｂとの右端部同士を比較すれば明らかな通り、上記特許文献８に記載された充電方法は、この特許文献８に記載された充電方法に対する従来方法に比べても、充電時間の短縮効果は限られたものに過ぎない。充電時間の短縮のみを考慮すれば、上記特許文献８に記載された充電方法で、初期の充電電流を１ＣＡよりも大幅に大きくすれば、短縮化は可能であると考えられる。但し、この場合には、充電中に長い時間に亙ってリチウムイオン電池の電圧が高く維持され、このリチウムイオン電池の耐久性が損なわれる。   In the case of the second example of the conventional charging method described in Patent Document 8 as described above, the voltage drop based on the resistance existing between the positive and negative electrodes of the lithium ion battery and the charger terminal is merely taken into consideration. However, it is not intended to further shorten the charging time. In particular, it is not intended at all to significantly reduce the charging time by increasing the charging current sufficiently to exceed 1CA. Therefore, as is apparent from comparing the right end portions of the solid line a and the broken line b in FIG. 8, the charging method described in Patent Document 8 is more than the conventional method for the charging method described in Patent Document 8. However, the effect of shortening the charging time is only limited. Considering only the shortening of the charging time, it is considered that the shortening is possible if the initial charging current is significantly larger than 1 CA by the charging method described in Patent Document 8. However, in this case, the voltage of the lithium ion battery is maintained high for a long time during charging, and the durability of the lithium ion battery is impaired.

前述の特許文献３に記載された充電方法は、あくまでもリチウムイオン電池の電圧を規定充電電圧以下で変化させる事を意図しており、保護回路やセル内に存在する抵抗に基づく電圧降下を考慮していない。又、特許文献３に記載された充電方法と特許文献８に記載された充電方法とは、充電時間を短縮させる点で共通する点があるとは言え、本来全く別の着眼点でなされたものであり、これら両発明を組み合わせる為の動機づけは存在しない。増して、充電時間の大幅な短縮化の為に、充電作業の初期に１ＣＡを大幅に超える充電電流を流す事に就いては、上記特許文献３、８の何れにも記載されていない。特許文献１１には、充電作業の初期に２〜３．５ＣＡの充電電流を流す事が記載されているが、この特許文献１１に記載された発明は、単に充電電流を大きくする事のみを考慮しており、リチウムイオン電池の耐久性確保が難しいものと考えられる。充電電流を２段階に分けて行なう事も記載されてはいるが、高電流での充電継続を単に時間で規制している（明細書の段落番号［００８５］等）のみであり、そのままでは充電時間の短縮と耐久性確保とを両立させる事は難しいものと考えられる。   The charging method described in Patent Document 3 is intended only to change the voltage of the lithium ion battery below a specified charging voltage, and in consideration of the voltage drop based on the resistance existing in the protection circuit and the cell. Not. Although the charging method described in Patent Document 3 and the charging method described in Patent Document 8 have a common point in shortening the charging time, they were originally made with completely different viewpoints. There is no motivation to combine these two inventions. In addition, there is no description in Patent Documents 3 and 8 regarding the flow of a charging current that greatly exceeds 1 CA in the initial stage of the charging operation in order to significantly shorten the charging time. Patent Document 11 describes that a charging current of 2 to 3.5 CA is allowed to flow at the beginning of the charging operation. However, the invention described in Patent Document 11 only considers increasing the charging current. Therefore, it is considered difficult to ensure the durability of the lithium ion battery. Although it is also described that the charging current is divided into two stages, the continuation of charging at a high current is merely restricted by time (paragraph number [0085] etc. in the specification), and charging is performed as it is. It is considered difficult to achieve both reduction in time and ensuring durability.

特開平６−２９０８１４号公報JP-A-6-290814 特開平６−３０３７２９号公報JP-A-6-303729 特開平７−２９６８５３号公報Japanese Patent Application Laid-Open No. 7-296853 特開平７−２９６８５４号公報JP-A-7-296854 特開平７−３３５２６５号公報JP 7-335265 A 特開平８−３７０３２号公報JP-A-8-37032 特開平８−４５５５０号公報JP-A-8-45550 特開平８−２８７９５７号公報JP-A-8-287957 特開平１１−１９１９３３号公報Japanese Patent Laid-Open No. 11-191933 特開２００２−２０９３３９号公報JP 2002-209339 A 特開２００２−２４６０７０号公報JP 2002-246070 A 特開２００３−１０９６７２号公報JP 2003-109672 A カタログ、「電池関連ＩＣ／オペアンプＩＣ／データブック／’０２〜’０３」、ミツミ電機株式会社、２００２年、ｐ．２４−ｐ．３３Catalog, “Battery-related IC / Op Amp IC / Data Book / '02 to '03", Mitsumi Electric Co., Ltd., 2002, p. 24-p. 33

本発明は、前述の様な事情に鑑みて、リチウムイオン電池の耐久性を確保しつつ、このリチウムイオン電池を充電する為に要する時間を大幅に短縮できる充電方法を実現すべく発明したものである。   In view of the circumstances as described above, the present invention was invented to realize a charging method capable of significantly reducing the time required for charging a lithium ion battery while ensuring the durability of the lithium ion battery. is there.

本発明のリチウムイオン電池の充電方法は、リチウムイオン電池を充電器により充電する為の方法である。
この様な本発明のリチウムイオン電池の充電方法では、先ず、１ＣＡよりも大きな第一の充電電流を設定し、この第一の充電電流により上記リチウムイオン電池を、このリチウムイオン電池側の端子間の電圧（電池パックの正負両端子等、このリチウムイオン電池側に設けられた、充電器の端子を接続する端子部分の電圧）がＶf ＋ＲＩになるまで定電流で充電する。 The method for charging a lithium ion battery of the present invention is a method for charging a lithium ion battery with a charger.
In such a lithium ion battery charging method of the present invention, first, a first charging current larger than 1 CA is set, and the lithium ion battery is connected between the terminals on the lithium ion battery side by the first charging current. Is charged at a constant current until V f + RI is reached (the voltage at the terminal portion of the battery pack, such as both the positive and negative terminals of the battery pack, which is provided on the lithium ion battery side and connected to the charger terminal).

尚、Ｃとは上記リチウムイオン電池の定格容量であり、例えば、このリチウムイオン電池の定格容量が１４００ｍＡｈ（１．４Ａｈ）の場合には、１ＣＡは１４００ｍＡとなる。
又、上記式中、Ｖf とは、充電を完了した状態で達成されるべき、このリチウムイオン電池の開回路電圧（ＰＴＣやタブ部分の抵抗による電圧降下分のない、リチウムイオン本体部分の電圧）である。
又、Ｒとは、上記リチウムイオン電池側の端子間に存在する直流抵抗のうちで、このリチウムイオン電池の電極抵抗（図７で説明した、リチウムイオン電池１自体が有する、例えば５０ｍΩ程度の抵抗）を除いた直流抵抗（図７で説明した、放電、充電両ＦＥＴ６、７が有する、例えば２５〜５０ｍΩ程度の抵抗と、ＰＴＣやタブ部分が有する、例えば２０ｍΩ程度の抵抗１０との合計）である。
更に、上記Ｉとは、上記充電器から上記リチウムイオン電池に送り込む充電電流である。 C is the rated capacity of the lithium ion battery. For example, when the rated capacity of the lithium ion battery is 1400 mAh (1.4 Ah), 1CA is 1400 mA.
In addition, in the above formula, V f is the open circuit voltage of this lithium ion battery (the voltage of the lithium ion main body part without the voltage drop due to the resistance of the PTC and the tab part) that should be achieved in the state where the charging is completed. ).
R is the resistance of the electrode of the lithium ion battery among the DC resistances existing between the terminals on the lithium ion battery side (the resistance of the lithium ion battery 1 itself described in FIG. ) (Excluding the resistance of the discharge and charge FETs 6 and 7, for example, about 25 to 50 mΩ, and the resistance 10 of the PTC and the tab portion, for example, about 20 mΩ, described in FIG. 7) is there.
Further, I is a charging current sent from the charger to the lithium ion battery.

本発明のリチウムイオン電池の充電方法では、前記第一の充電電流で上記リチウムイオン電池の充電を開始し、充電の進行に伴うこのリチウムイオン電池の内部抵抗の変化に対応して、上記充電器側から印加する電圧を調節する事により、定電流（第一の充電電流）で充電を継続する。
そして、上記リチウムイオン電池側の電圧がＶf ＋ＲＩに達した後、上記第一の充電電流よりも小さく、前記１ＣＡよりも大きな第二の充電電流を設定する。そして、この第二の充電電流により上記リチウムイオン電池の定電流充電を継続して行なう。この第二の充電電流による定電流充電は、このリチウムイオン電池側の端子間の電圧がＶf ＋ＲＩになるまで行なう。
以下、同様に定電流で充電する動作を、上記リチウムイオン電池側の端子間の電圧がＶf ＋ＲＩになる毎に充電電流を小さくしつつ複数段階に亙り行なう。この場合に、後段での充電電流を１ＣＡ未満としても良い。但し、上記第二の充電電流は１ＣＡよりも大きくして、充電時間の短縮を図る。
尚、本件の特許請求の範囲及び明細書中で、「電圧がＶf ＋ＲＩになる」とは、完全にＶf ＋ＲＩに一致する状態に限定するものではない事は明らかである。本発明の趣旨である、充電時間の短縮を図る面から、上記電圧がＶf ＋ＲＩに十分に近づいた状態（例えばＶf ＋ＲＩの９５％以上、好ましくは９９％以上、より好ましくは９９．８％以上に達した状態）であれば、電圧がＶf ＋ＲＩになったとする。 In the method for charging a lithium ion battery according to the present invention, charging of the lithium ion battery is started with the first charging current, and the charger is adapted to change in the internal resistance of the lithium ion battery as the charging proceeds. By adjusting the voltage applied from the side, charging is continued at a constant current (first charging current).
Then, after the voltage on the lithium ion battery side reaches V f + RI, a second charging current smaller than the first charging current and larger than the 1CA is set. And the constant current charge of the said lithium ion battery is continuously performed by this 2nd charging current. The constant current charging with the second charging current is performed until the voltage between the terminals on the lithium ion battery side becomes V f + RI.
Hereinafter, similarly, the operation of charging with a constant current is performed over a plurality of stages while reducing the charging current every time the voltage between the terminals on the lithium ion battery side becomes V f + RI. In this case, the charging current at the subsequent stage may be less than 1 CA. However, the second charging current is set to be larger than 1 CA in order to shorten the charging time.
In the claims and specification of the present case, it is clear that “the voltage becomes V f + RI” is not limited to a state that completely matches V f + RI. Is a gist of the present invention, from the surface to shorten the charging time, a state where the voltage is sufficiently close to the V f + RI (e.g. V f + RI 95% or more, preferably 99% or more, more preferably 99.8 %), The voltage is assumed to be V f + RI.

上述の様な本発明のリチウムイオン電池の充電方法によれば、リチウムイオン電池の耐久性を確保しつつ、このリチウムイオン電池を充電する為に要する時間を大幅に短縮できる。
先ず、リチウムイオン電池の耐久性を確保できる理由は、上記リチウムイオン電池側の端子間の電圧が、それまでの充電電流Ｉに基づいて求められるＶf ＋ＲＩになる（Ｖf ＋ＲＩに十分に近づく）毎に、充電電流を段階的に小さくする為である。即ち、この端子間の電圧がＶf ＋ＲＩに達した状態でも、上記リチウムイオン電池の本体部分の電圧は、このリチウムイオン電池の開回路電圧Ｖf （若しくはそれよりも僅かに小さい値）に止まる。そして、上記充電電流Ｉを小さくする毎に、上記端子間の電圧Ｖf ＋ＲＩが（Ｉが小さくなった分だけ）小さくなり、上記開回路電圧もＶf よりも小さくなる。従って、上記リチウムイオン電池の本体部分の電圧が長時間に亙って高いままに保持される事がなく、このリチウムイオン電池の耐久性が損なわれる事はない。 According to the lithium ion battery charging method of the present invention as described above, the time required to charge the lithium ion battery can be greatly shortened while ensuring the durability of the lithium ion battery.
First, the reason why the durability of the lithium ion battery can be ensured is that the voltage between the terminals on the lithium ion battery side becomes V f + RI obtained based on the current charging current I (sufficiently close to V f + RI). This is to reduce the charging current step by step. That is, even when the voltage between the terminals reaches V f + RI, the voltage of the main part of the lithium ion battery remains at the open circuit voltage V f (or a value slightly smaller than that) of the lithium ion battery. . Each time the charging current I is decreased, the voltage V f + RI between the terminals decreases (by the amount I decreases), and the open circuit voltage also decreases below V f . Therefore, the voltage of the main part of the lithium ion battery is not kept high for a long time, and the durability of the lithium ion battery is not impaired.

又、上記リチウムイオン電池を充電する為に要する時間を大幅に低減できる理由は、上記リチウムイオン電池側の端子間に存在する直流抵抗のうち、このリチウムイオン電池の電極抵抗を除いた直流抵抗による電圧降下分を考慮した上で、上記リチウムイオン電池側の端子間の電圧を観察する為である。この為、このリチウムイオン電池の本体部分には、上記電圧降下分が引かれない、この本体部分が耐え得る限界に近い電圧が加わる。言い換えれば、前述の特許文献３に記載された場合の様に、リチウムイオン電池の本体部分の電圧が必要以上に低く抑えられる事はない。この結果、充電時間の大幅な短縮が可能になる。   Also, the reason why the time required for charging the lithium ion battery can be greatly reduced is due to the direct current resistance excluding the electrode resistance of the lithium ion battery among the direct current resistances existing between the terminals on the lithium ion battery side. This is because the voltage between the terminals on the lithium ion battery side is observed in consideration of the voltage drop. For this reason, a voltage close to the limit that the main body portion can withstand is applied to the main body portion of the lithium ion battery so that the voltage drop is not drawn. In other words, unlike the case described in Patent Document 3 described above, the voltage of the main part of the lithium ion battery is not suppressed to an unnecessarily low level. As a result, the charging time can be greatly shortened.

本発明を実施する場合に好ましくは、請求項２に記載した様に、第一の充電電流を１．５ＣＡ以上（より好ましくは２．０ＣＡ以上、更に好ましくは２．５ＣＡ以上）とする。 この様に、第一の充電電流を１ＣＡよりも大幅に（０．５ＣＡ以上、より好ましくは１．０ＣＡ以上、更に好ましくは１．５ＣＡ以上）大きくすれば、充電時間のより大幅な短縮化が可能になる。この様に第一の充電電流を１ＣＡよりも大幅に大きくしても、リチウムイオン電池の本体部分の電圧が開回路電圧Ｖf を越える事はないので、このリチウムイオン電池の耐久性が損なわれる事はない。
又、好ましくは、請求項３に記載した様に、充電電流を凡そ１ＣＡに設定して定電流充電を行なってから、更に充電電流を１ＣＡ未満に設定して定電流充電を行なった後、更に電圧をＶf に設定して定圧充電を行なう。
この様にすれば、リチウムイオン電池の耐久性が損なわれる事を防止しつつ、このリチウムイオン電池の容量率を１００％に近づける事ができる。 When implementing this invention, Preferably, as described in claim 2, the first charging current is set to 1.5 CA or more (more preferably 2.0 CA or more, further preferably 2.5 CA or more). In this way, if the first charging current is significantly larger than 1 CA (0.5 CA or more, more preferably 1.0 CA or more, more preferably 1.5 CA or more), the charging time can be significantly shortened. It becomes possible. Thus, even if the first charging current is significantly larger than 1 CA, the voltage of the main part of the lithium ion battery does not exceed the open circuit voltage Vf , so that the durability of the lithium ion battery is impaired. There is nothing.
Preferably, as described in claim 3, after the constant current charging is performed by setting the charging current to about 1 CA, the constant current charging is further performed by setting the charging current to less than 1 CA, Constant voltage charging is performed with the voltage set to V f .
In this way, it is possible to bring the capacity ratio of the lithium ion battery close to 100% while preventing the durability of the lithium ion battery from being impaired.

更に、好ましくは、請求項４に記載した様に、充電を開始する際に、先ずリチウムイオン電池の開回路電圧を測定する。この測定は、リチウムイオン電池側の端子間の電圧を測定する事で行なう。そして、上記開回路電圧が閾値以上の場合には直ちに第一の充電電流を設定して充電を開始する。これに対して、上記開回路電圧が閾値未満の場合には、１ＣＡよりも小さな充電電流で充電を行ない、この開回路電圧がこの閾値以上に達した後、上記第一の充電電流を設定して充電を開始する。
この様にすれば、何らかの故障が生じているリチウムイオン電池側に、当該リチウムイオン電池にとって過大な電流を流す事を防止して、当該リチウムイオン電池に、過度の発熱等、より重大な故障が発生する事を防止できる。 Further, preferably, when charging is started, first, an open circuit voltage of the lithium ion battery is measured. This measurement is performed by measuring the voltage between the terminals on the lithium ion battery side. When the open circuit voltage is equal to or higher than the threshold, the first charging current is immediately set and charging is started. On the other hand, when the open circuit voltage is less than the threshold value, charging is performed with a charging current smaller than 1 CA, and after the open circuit voltage reaches the threshold value or more, the first charging current is set. Start charging.
In this way, it is possible to prevent excessive current for the lithium ion battery from flowing to the side of the lithium ion battery in which some failure has occurred, and to cause more serious failure such as excessive heat generation in the lithium ion battery. It can be prevented from occurring.

図１〜４は、本発明の実施例を示している。このうちの図１は充電器１１の、図２はリチウムイオン電池１、１を２本備えた電池パック１２の、それぞれ回路図である。上記充電器１１は、商用電源１３から充電器側入力端子１４が受け入れた電力を、電源制御部１５、充電制御部１６を通じて出力端子１７に送る様にしている。この充電制御部１６は、これら電源制御部１５から送り込まれる電源電圧に関する情報信号、並びに、上記出力端子１７側から送り込まれる、上記電池パック１２側の電圧に関する情報信号に基づいて、この出力端子１７から上記電池パック１２に送り出す電流、電圧を制御する。この制御の状態に関しては、図３〜４を用いて後で詳しく説明する。   1 to 4 show an embodiment of the present invention. Among these, FIG. 1 is a circuit diagram of a charger 11 and FIG. 2 is a circuit diagram of a battery pack 12 having two lithium ion batteries 1 and 1. The charger 11 sends the power received by the charger side input terminal 14 from the commercial power supply 13 to the output terminal 17 through the power supply control unit 15 and the charge control unit 16. The charging control unit 16 is based on the information signal regarding the power supply voltage sent from the power supply control unit 15 and the information signal regarding the voltage on the battery pack 12 side sent from the output terminal 17 side. To control the current and voltage sent from the battery pack 12 to the battery pack 12. This control state will be described later in detail with reference to FIGS.

又、上記電池パック１２には、上記リチウムイオン電池１、１の他、保護回路１８と電池側入力端子１９とを設けている。この保護回路１８は、これら各リチウムイオン電池１、１の過充電、過放電、短絡に関する保護を図るもので、前述の図５に示す様に、放電、充電両ＦＥＴ６、７及びこれら両ＦＥＴ６、７のＯＮ、ＯＦＦを制御する為のＩＣ８（何れも図５参照）を備える。又、上記電池側入力端子１９と上記出力端子１７とには、上記充電器１１から上記電池パック１２の側に電力（充電電流）を送る為に必要な電力用端子素子に加えて、この電池パック１２側の電圧を取り出す為の信号用端子素子も備えている。そして、この信号用端子素子を通じて取り出した、上記電池パック１２側の電圧を表す信号を、上記充電制御部１６に制御信号を送る為の信号用制御部２０に送り込む様にしている。この信号用制御部２０は、上記電池パック１２側の電圧を表す信号と、上記商用電源１３側から送り込まれる電力とに応じて、上記出力端子１７から上記電池パック１２に送り出す電流、電圧を制御する。   The battery pack 12 is provided with a protection circuit 18 and a battery side input terminal 19 in addition to the lithium ion batteries 1 and 1. The protection circuit 18 is intended to protect the overcharge, overdischarge, and short circuit of each of these lithium ion batteries 1, 1. As shown in FIG. 5, the discharge and charge FETs 6, 7 and the both FETs 6, 7 is provided with an IC 8 (both see FIG. 5) for controlling ON / OFF of 7. The battery side input terminal 19 and the output terminal 17 are connected to the battery 11 in addition to the power terminal element necessary for sending power (charging current) from the charger 11 to the battery pack 12 side. A signal terminal element for taking out the voltage on the pack 12 side is also provided. A signal representing the voltage on the battery pack 12 side taken out through the signal terminal element is sent to the signal control unit 20 for sending a control signal to the charge control unit 16. The signal control unit 20 controls the current and voltage sent from the output terminal 17 to the battery pack 12 according to the signal representing the voltage on the battery pack 12 side and the power sent from the commercial power supply 13 side. To do.

上述の様な充電器１１と電池パック１２とを使用して、この電池パック１２を構成する上記リチウムイオン電池１、１を充電する際、上記充電制御部１６は、図３に示す様にして、上記電池パック１２の電力用端子素子に送り込む充電電流を制御する。
先ず、充電を開始するに際し、ステップ１で、信号用端子素子により上記電池パック１２の電圧を測定する事で、上記リチウムイオン電池１、１の開回路電圧を測定する。そして、続くステップ２で、各リチウムイオン電池１、１毎の電圧が、上記開回路電圧が閾値である３Ｖ（電池パック１２全体として６Ｖ）以上であると判定された場合には、直ちにステップ５に移り、第一の充電電流を設定して充電を開始する。この場合の充電の手順に就いては後で詳しく説明する。 When charging the lithium ion batteries 1 and 1 constituting the battery pack 12 using the charger 11 and the battery pack 12 as described above, the charge control unit 16 is configured as shown in FIG. The charging current sent to the power terminal element of the battery pack 12 is controlled.
First, when charging is started, the open circuit voltage of the lithium ion batteries 1 and 1 is measured in step 1 by measuring the voltage of the battery pack 12 using a signal terminal element. If it is determined in step 2 that the voltage of each lithium ion battery 1 and 1 is equal to or higher than 3 V (6 V as the whole battery pack 12), which is the threshold value of the open circuit voltage, step 5 is immediately performed. Then, the first charging current is set and charging is started. The charging procedure in this case will be described in detail later.

これに対して、上記ステップ２で、上記リチウムイオン電池１、１毎の開回路電圧が閾値である３Ｖ（電池パック１２全体として６Ｖ）未満であると判定された場合には、上記充電器１１の充電制御部１６は、ステップ３で、１ＣＡよりも小さな充電電流である、（１／１０）ＣＡで充電を行なう。例えば、上記電池パック１２の定格容量が１４００ｍＡｈの場合（以下、定格容量に関して、同じ前提で説明する）には、１４０ｍＡで充電を行なう。この様に低電流での充電を行なう理由は、何らかの故障が生じているリチウムイオン電池１、１側に、当該リチウムイオン電池１、１にとって過大な電流を流す事を防止し、当該リチウムイオン電池１、１に、過度の発熱等、より重大な故障が発生する事を防止する為である。この場合には、低電流での充電を行なう事で充電時間が長くなるが、より重大な損傷の防止を図る為には仕方がない。この様な低電流での充電の結果、ステップ４で、上記リチウムイオン電池１、１毎の開回路電圧が閾値である３Ｖ（電池パック１２全体として６Ｖ）以上に達したと判定されたならば、当該リチウムイオン電池１、１には特に故障がないと考えられるので、上記第一の充電電流を設定して充電を開始する。これに対して、予め設定された所定時間（例えば１０〜３０分）経過しても、上記ステップ４で、上記リチウムイオン電池１、１毎の開回路電圧が閾値である３Ｖ（電池パック１２全体として６Ｖ）以上に達しないと判定された場合には、当該リチウムイオン電池１、１には、充電を行なう事に対して故障が存在すると考えられるので、前記充電器１１に付属させた警告灯を点灯させる等により、使用者に充電不能を知らせる。   On the other hand, when it is determined in step 2 that the open circuit voltage for each of the lithium ion batteries 1 and 1 is less than the threshold value of 3V (6V as the whole battery pack 12), the charger 11 In step 3, the charging control unit 16 performs charging at (1/10) CA, which is a charging current smaller than 1 CA. For example, when the rated capacity of the battery pack 12 is 1400 mAh (hereinafter, the rated capacity will be described under the same assumption), charging is performed at 140 mA. The reason for charging at such a low current is to prevent an excessive current from flowing to the lithium ion battery 1, 1 on the side of the lithium ion battery 1, 1, which has some sort of failure. This is to prevent the occurrence of a more serious failure such as excessive heat generation. In this case, the charging time is increased by charging at a low current, but there is no way to prevent more serious damage. If it is determined in step 4 that the open circuit voltage for each of the lithium ion batteries 1 and 1 has reached the threshold value of 3 V (6 V as the whole battery pack 12) as a result of charging at such a low current, Since the lithium-ion batteries 1 and 1 are considered to have no particular failure, the first charging current is set and charging is started. On the other hand, even if a predetermined time (for example, 10 to 30 minutes) elapses, 3V (the entire battery pack 12) in which the open circuit voltage for each of the lithium ion batteries 1 and 1 is a threshold value in step 4 6V) or more, it is considered that the lithium ion batteries 1 and 1 have a failure for charging. Therefore, a warning lamp attached to the charger 11 is used. Inform the user that charging is not possible, for example by turning on the.

ステップ２或はステップ４で、上記リチウムイオン電池１、１毎の開回路電圧が閾値である３Ｖ（電池パック１２全体として６Ｖ）以上であると判定された場合には、上記充電器１１の充電制御部１６は、ステップ５で、１ＣＡよりも大きな第一の充電電流を設定する。そして、この第一の充電電流により上記リチウムイオン電池１、１の充電を開始する。本実施例の場合、この第一の充電電流を３ＣＡ（４２００ｍＡ）として定電流での充電を開始する。この様な３ＣＡでの定電流充電は、前記信号用端子素子により取り出される、上記電池パック１２側の電圧が、Ｖf ＋ＲＩに達するまで行なう。定電流充電を行なう為に上記充電制御部１６は、充電の進行に伴う上記リチウムイオン電池１、１内部の抵抗の増大に従って、前記電力用端子素子間の電圧を高くする。本実施例の場合、Ｖf が上記リチウムイオン電池１、１毎に４．２Ｖ（電池パック１２全体として８．４Ｖ）であるから、Ｒが凡そ５０ｍΩであると仮定すれば、この抵抗Ｒによる電圧降下分は０．２１Ｖとなる。そこで、ステップ６で、電池パック１２全体としての電圧（上記電力用端子素子間の電圧）が８．６１Ｖに達したと判定されるまで、３ＣＡでの充電を行なう。 If it is determined in step 2 or step 4 that the open circuit voltage for each of the lithium ion batteries 1 and 1 is equal to or higher than the threshold value of 3V (6V for the battery pack 12 as a whole), the charger 11 is charged. In step 5, the control unit 16 sets a first charging current larger than 1CA. Then, charging of the lithium ion batteries 1 and 1 is started by the first charging current. In the case of the present embodiment, the first charging current is set to 3CA (4200 mA), and charging with a constant current is started. Such constant current charging at 3CA is performed until the voltage on the battery pack 12 side taken out by the signal terminal element reaches V f + RI. In order to perform constant current charging, the charging control unit 16 increases the voltage between the power terminal elements as the internal resistance of the lithium ion battery 1 and 1 increases with the progress of charging. In this embodiment, V f is 4.2 V for each lithium ion battery 1 and 1 (8.4 V as the whole battery pack 12). Therefore, assuming that R is about 50 mΩ, this resistance R The voltage drop is 0.21V. Therefore, in step 6, charging at 3CA is performed until it is determined that the voltage of the battery pack 12 as a whole (the voltage between the power terminal elements) has reached 8.61V.

上記ステップ６で、上記電池パック１２側の電圧が、Ｖf ＋ＲＩ（電池パック１２全体として８．６１Ｖ）に達したと判定されたならば、上記充電器１１の充電制御部１６は、ステップ７で、上記第一の充電電流（４２００ｍＡ）よりも小さく、１ＣＡよりも大きな、第二の充電電流を設定する。本実施例の場合、この第二の充電電流を２ＣＡ（２８００ｍＡ）として、上記リチウムイオン電池１、１の定電流での充電を継続する。上記ステップ７で、充電電流が第一の充電電流である３ＣＡから第二の充電電流である２ＣＡにまで、１ＣＡ（１４００ｍＡ）分、瞬間的に減少する事に伴って、上記電池パック１２側の電圧が瞬間的に低下する。この様に電圧が低下する程度は、上記電池パック１２側に設けた１対の電力用端子素子同士の間に存在する抵抗と、充電電流の低減分である１ＣＡとの積となる。この様な２ＣＡでの定電流充電に就いても、上記電池パック１２側の電圧が、Ｖf ＋ＲＩに達するまで行なう。本実施例の場合、上記第二の充電電流での定電流充電を、ステップ８で、上記電池パック１２全体としての電圧が８．５４Ｖに達したと判定されるまで行なう。 If it is determined in step 6 that the voltage on the battery pack 12 side has reached V f + RI (the battery pack 12 as a whole is 8.61 V), the charging control unit 16 of the charger 11 performs step 7. Therefore, a second charging current smaller than the first charging current (4200 mA) and larger than 1 CA is set. In the case of the present embodiment, the second charging current is set to 2CA (2800 mA), and the charging of the lithium ion batteries 1 and 1 at a constant current is continued. In step 7, the charging current is instantaneously decreased by 1 CA (1400 mA) from 3 CA as the first charging current to 2 CA as the second charging current. The voltage drops momentarily. The extent to which the voltage decreases in this way is the product of the resistance existing between the pair of power terminal elements provided on the battery pack 12 side and 1CA, which is a reduction in charging current. Even in such constant current charging at 2CA, the charging is performed until the voltage on the battery pack 12 side reaches V f + RI. In the case of the present embodiment, constant current charging with the second charging current is performed until it is determined in step 8 that the voltage of the battery pack 12 as a whole has reached 8.54V.

上記ステップ８で、上記電池パック１２側の電圧が、Ｖf ＋ＲＩ（電池パック１２全体として８．５４Ｖ）に達したと判定されたならば、上記充電器１１の充電制御部１６は、ステップ９で、第三の充電電流として、１ＣＡ（１４００ｍＡ）を設定し、上記リチウムイオン電池１、１の定電流での充電を継続する。上記ステップ９でも、充電電流が第二の充電電流である２ＣＡから第三の充電電流である１ＣＡにまで、１ＣＡ（１４００ｍＡ）分、瞬間的に減少する事に伴って、上記電池パック１２側の電圧が瞬間的に低下する。この様な１ＣＡでの定電流充電に就いても、上記電池パック１２側の電圧が、Ｖf ＋ＲＩに達するまで行なう。本実施例の場合、ステップ１０で、上記電池パック１２全体としての電圧が８．４７Ｖに達したと判定されるまで行なう。 If it is determined in step 8 that the voltage on the battery pack 12 side has reached V f + RI (8.54 V for the battery pack 12 as a whole), the charging control unit 16 of the charger 11 performs step 9. Thus, 1CA (1400 mA) is set as the third charging current, and the charging of the lithium ion batteries 1 and 1 at a constant current is continued. Even in the above step 9, the charging current is instantaneously decreased by 1 CA (1400 mA) from 2 CA as the second charging current to 1 CA as the third charging current. The voltage drops momentarily. Even in such constant current charging at 1 CA, the charging is performed until the voltage on the battery pack 12 side reaches V f + RI. In the case of the present embodiment, it is performed until it is determined in step 10 that the voltage of the battery pack 12 as a whole has reached 8.47V.

上記ステップ１０で、上記電池パック１２全体としての電圧が８．４７Ｖに達したと判定されたならば、上記充電器１１の充電制御部１６は、ステップ１１で、第四の充電電流として、０．５ＣＡ（７００ｍＡ）を設定し、定電流での充電を継続する。上記ステップ１１でも、充電電流が第三の充電電流である１ＣＡから第四の充電電流である０．５ＣＡにまで、０．５ＣＡ（７００ｍＡ）分、瞬間的に減少する事に伴って、上記電池パック１２側の電圧が瞬間的に低下する。この様な０．５ＣＡでの定電流充電に就いても、上記電池パック１２側の電圧が、Ｖf ＋ＲＩに達するまで行なう。本実施例の場合、ステップ１２で、上記電池パック１２全体としての電圧が８．４３５Ｖに達したと判定されるまで行なう。 If it is determined in step 10 that the voltage of the battery pack 12 as a whole has reached 8.47 V, the charging control unit 16 of the charger 11 determines that the fourth charging current in step 11 is 0. Set 5CA (700mA) and continue charging at constant current. Even in the step 11, the battery is reduced as the charging current instantaneously decreases by 0.5 CA (700 mA) from 1 CA as the third charging current to 0.5 CA as the fourth charging current. The voltage on the pack 12 side instantaneously decreases. Even in such constant current charging at 0.5 CA, the charging is performed until the voltage on the battery pack 12 side reaches V f + RI. In the case of this embodiment, the process is repeated until it is determined in step 12 that the voltage of the battery pack 12 as a whole has reached 8.435V.

そして、上記ステップ１２で、上記電池パック１２側の電圧が、Ｖf ＋ＲＩ（電池パック１２全体として８．４３５Ｖ）に達したと判定されたならば、上記充電器１１の充電制御部１６は、ステップ１３で、電圧をＶf である８．４Ｖ（各リチウムイオン電池毎に４．２Ｖ）に設定して、定圧充電を行なう。この定圧充電の開始直後の状態では、電圧をＶf である８．４Ｖ、充電電流を０．５ＣＡ（７００ｍＡ）に設定する。但し、この充電の進行に伴って上記リチウムイオン電池の内部抵抗が増大すると、前記電力用端子素子間に流れる充電電流が次第に低下する。そこで、ステップ１４でこの充電電流がＣ／１０以下に低減した状態（本実施例の場合、凡そ７０分経過した時点）で、充電を完了する。具体的には、前記保護回路１８中の充電ＦＥＴ７を開き、充電器１１に付属の充電表示用のインジケータを消滅させる。 If it is determined in step 12 that the voltage on the battery pack 12 side has reached V f + RI (8,435 V for the battery pack 12 as a whole), the charge control unit 16 of the charger 11 In step 13, the voltage is set to 8.4 V (4.2 V for each lithium ion battery), which is V f , and constant pressure charging is performed. In the state immediately after the start of the constant pressure charging, the voltage is set to V f 8.4 V and the charging current is set to 0.5 CA (700 mA). However, when the internal resistance of the lithium ion battery increases as the charging progresses, the charging current flowing between the power terminal elements gradually decreases. Therefore, the charging is completed in a state where the charging current is reduced to C / 10 or less in step 14 (in the case of this embodiment, when approximately 70 minutes have passed). Specifically, the charge FET 7 in the protection circuit 18 is opened, and the charge display indicator attached to the charger 11 is extinguished.

尚、上述の説明に使用した図３は、説明が煩雑化するのを防止する為、充電電流を変化させる回数を実際よりも少なく記載している。実際には、図４に示す様に、この充電電流を変化させる回数をより多くする。尚、第一の充電電流は、図３〜４に示す様に、３ＣＡ程度に迄大きくする事ができる。上記図４に示した７本の線のうち、太い実線ａは充電電流を、細い実線ｂは電池パック１２の電圧を、太い破線ｃは各リチウムイオン電池の＋−両極同士の間の電圧を、細い破線ｄは容量を、一点鎖線ｅは容量率を、二点鎖線ｆは上記電池パック１２の温度を、それぞれ表している。尚、図３の線図は、本発明を考察する為のシミュレーションの過程で求めた為、各リチウムイオン電池毎の電圧を求めたが、両電圧を表す線は重なっている。本発明を実施する場合に、各リチウムイオン電池毎に、その電圧を求める必要がある訳ではない。   Note that FIG. 3 used in the above description describes the number of times of changing the charging current less than the actual number in order to prevent the description from becoming complicated. Actually, as shown in FIG. 4, the number of times of changing the charging current is increased. The first charging current can be increased to about 3 CA as shown in FIGS. Of the seven lines shown in FIG. 4, the thick solid line a represents the charging current, the thin solid line b represents the voltage of the battery pack 12, and the thick broken line c represents the voltage between the + and both electrodes of each lithium ion battery. The thin broken line d represents the capacity, the alternate long and short dash line e represents the capacity factor, and the alternate long and two short dashes line f represents the temperature of the battery pack 12. 3 was obtained in the course of simulation for considering the present invention, the voltage for each lithium ion battery was obtained, but the lines representing both voltages overlap. When carrying out the present invention, it is not necessary to obtain the voltage for each lithium ion battery.

又、第一〜第ｎの充電電流の大きさに関しても、前記図３や上記図４に示した値に限らず、各部の抵抗値等、使用する電池パック１２の特性の相違や、要求される充電時間に応じて、適宜設計的に定める。次の表１は、上記第一〜第ｎの充電電流の大きさの別例を示している。尚、この表１には、各セル毎の電圧降下分を考慮したセル電圧と、電圧パックとして、各セルに共通の抵抗となる、保護回路部分に存在する抵抗（基板抵抗）に基づく電圧下降分とを分けて記載している。本発明を実施する場合に、これら両抵抗を分けて考慮する必要がある訳ではない。

Figure 2005185060
In addition, the magnitudes of the first to nth charging currents are not limited to the values shown in FIG. 3 and FIG. Designed appropriately according to the charging time. Table 1 below shows another example of the magnitudes of the first to nth charging currents. This table 1 shows the voltage drop based on the cell voltage taking into account the voltage drop for each cell and the resistance (substrate resistance) present in the protection circuit portion, which is a common resistance for each cell as a voltage pack. The minutes are shown separately. When carrying out the present invention, it is not necessary to consider these two resistances separately.
Figure 2005185060

何れにしても、上述の様に構成する本実施例のリチウムイオン電池の充電方法によれば、前記リチウムイオン電池１、１の耐久性を確保しつつ、このリチウムイオン電池１、１を充電する為に要する時間を大幅に短縮できる。
先ず、上記リチウムイオン電池１、１の耐久性確保は、上記リチウムイオン電池１、１側の端子である電力用端子素子間の電圧を、Ｖf ＋ＲＩになる毎に充電電流を段階的に小さくする事により図られる。即ち、上記電力用端子素子間の電圧がＶf ＋ＲＩに達した状態でも、上記リチウムイオン電池１、１の本体部分の電圧は、図４の細い実線ｂ及び太い破線ｃの頂部から明らかな通り、このリチウムイオン電池１、１の開回路電圧Ｖf に止まる。そして、上記図４の太い実線ａの段差部に対応する位置での上記両線ｂ、ｃから明らかな通り、上記充電電流を小さくする毎に、上記電力用端子素子間の電圧が、それまでの大きな充電電流に基づく、Ｖf ＋ＲＩよりも小さくなり、上記開回路電圧もＶf よりも小さくなる。従って、上記リチウムイオン電池１、１の本体部分の電圧が長時間に亙って高いままに保持される事がなく、このリチウムイオン電池１、１の耐久性が損なわれる事はない。 In any case, according to the lithium ion battery charging method of the present embodiment configured as described above, the lithium ion batteries 1 and 1 are charged while ensuring the durability of the lithium ion batteries 1 and 1. The time required for this can be greatly reduced.
First, to ensure the durability of the lithium ion batteries 1 and 1, the voltage between the power terminal elements which are terminals on the lithium ion battery 1 and 1 side is reduced stepwise for every V f + RI. It is planned by doing. That is, even when the voltage between the power terminal elements reaches V f + RI, the voltage of the main body portion of the lithium ion batteries 1 and 1 is as clearly shown from the tops of the thin solid line b and the thick broken line c in FIG. The open circuit voltage V f of the lithium ion batteries 1 and 1 is stopped. Then, as is apparent from the two lines b and c at the position corresponding to the stepped portion of the thick solid line a in FIG. 4, the voltage between the power terminal elements is increased up to that time each time the charging current is reduced. Based on a large charging current of V f + RI, the open circuit voltage is also smaller than V f . Therefore, the voltage of the main body portion of the lithium ion batteries 1 and 1 is not kept high for a long time, and the durability of the lithium ion batteries 1 and 1 is not impaired.

又、上記リチウムイオン電池１、１を充電する為に要する時間を大幅に短縮できる理由は、上記リチウムイオン電池１、１側の電力用端子素子間に存在する直流抵抗のうちで、このリチウムイオン電池１、１の電極抵抗を除いた直流抵抗による電圧降下分を考慮した上で、上記リチウムイオン電池１、１側の端子間の電圧を観察する為である。この為、このリチウムイオン電池１、１の本体部分には、上記電圧降下分が引かれない、この本体部分が耐え得る限界に近い電圧（≒Ｖf ＝４．２Ｖ）が加わる。言い換えれば、前述の特許文献３に記載された場合の様に、リチウムイオン電池の本体部分の電圧が必要以上に低く抑えられる事はない。この結果、充電時間の大幅な短縮が可能になる。具体的には、図４に示した例で、３０分足らずの間に容量率が９０％を越え、４５分程度で容量率がほぼ１００％に達する。 The reason why the time required for charging the lithium ion batteries 1 and 1 can be greatly shortened is that the lithium ion among the DC resistances existing between the power terminal elements on the lithium ion battery 1 and 1 side. This is because the voltage between the terminals on the lithium ion battery 1 and 1 side is observed in consideration of the voltage drop due to the DC resistance excluding the electrode resistance of the batteries 1 and 1. For this reason, a voltage (≈V f = 4.2 V) that is close to the limit that the main body portion can withstand is applied to the main body portions of the lithium ion batteries 1 and 1. In other words, unlike the case described in Patent Document 3 described above, the voltage of the main part of the lithium ion battery is not suppressed to an unnecessarily low level. As a result, the charging time can be greatly shortened. Specifically, in the example shown in FIG. 4, the capacity ratio exceeds 90% in less than 30 minutes, and the capacity ratio reaches almost 100% in about 45 minutes.

又、本実施例の場合には、第一の充電電流を凡そ３ＣＡと、１ＣＡよりも大幅に（２ＣＡ程度）大きくしているので、充電時間のより大幅な短縮が可能になる。この様に第一の充電電流を１ＣＡよりも大幅に大きくしても、図４の細い実線ｂ及び太い破線ｃの左寄り部分から明らかな通り、上記リチウムイオン電池１、１の本体部分の電圧が開回路電圧Ｖf を越える事はない。従って、このリチウムイオン電池１、１の耐久性が損なわれる事はない。 In the case of the present embodiment, the first charging current is about 3 CA and significantly larger than 1 CA (about 2 CA), so that the charging time can be significantly shortened. In this way, even if the first charging current is significantly larger than 1CA, the voltage of the main body portion of the lithium ion batteries 1 and 1 can be clearly seen from the left side of the thin solid line b and the thick broken line c in FIG. Never exceed the open circuit voltage V f . Therefore, the durability of the lithium ion batteries 1 and 1 is not impaired.

又、本実施例の場合には、充電電流を凡そ１ＣＡに設定して定電流充電を行なってから、更に充電電流を１ＣＡ未満に設定して定電流充電を行なった後、更に電圧をＶf に設定して定圧充電を行なっている為、（例えば４５〜７０分程度と、或る程度充電時間を確保する事により）上記リチウムイオン電池１、１の耐久性が損なわれる事を防止しつつ、このリチウムイオン電池１、１の容量率を１００％に近づける事ができる。 Further, in the case of the embodiment, after set the charging current approximately in 1CA after performing the constant current charging was subjected to constant current charging further sets the charging current to less than 1CA, further voltage V f Since the constant-pressure charging is carried out with the above-described setting, the durability of the lithium ion batteries 1 and 1 is prevented from being impaired (for example, by securing the charging time to some extent, for example, about 45 to 70 minutes). The capacity ratio of the lithium ion batteries 1 and 1 can be brought close to 100%.

更に、本実施例の場合には、図３にステップ１〜４で示した様に、充電を開始する際に、先ずリチウムイオン電池１、１の開回路電圧を測定して、この開回路電圧が閾値以上の場合にのみ第一の充電電流を設定して充電を開始する為、何らかの故障が生じているリチウムイオン電池１、１側に、当該リチウムイオン電池１、１にとって過大な電流を流す事を防止できる。この結果、当該リチウムイオン電池１、１に、過度の発熱等、より重大な故障が発生する事を防止できる。   Further, in the case of this embodiment, as shown in Steps 1 to 4 in FIG. 3, when starting charging, first, the open circuit voltage of the lithium ion batteries 1 and 1 is measured, and this open circuit voltage is measured. Since the first charging current is set and charging is started only when the battery voltage is equal to or greater than the threshold value, an excessive current flows for the lithium ion battery 1 or 1 on the side of the lithium ion battery 1 or 1 where some failure has occurred. You can prevent things. As a result, it is possible to prevent a more serious failure such as excessive heat generation from occurring in the lithium ion batteries 1 and 1.

本発明の実施例を示す、充電器の回路図。The circuit diagram of the charger which shows the Example of this invention. 電池パックの回路図。The circuit diagram of a battery pack. 充電の実施状況を示すフローチャート。The flowchart which shows the implementation condition of charge. 充電の進行に伴う各部の変化を示す線図。The diagram which shows the change of each part accompanying progress of charging. 従来から知られている、保護回路を備えた電池パックの回路図。The circuit diagram of the battery pack provided with the protection circuit known conventionally. 従来の充電方法の第１例を説明する為の、充電の進行に伴う充電電流と両極間の電圧との変化を示す線図。The diagram which shows the change of the charging current accompanying the progress of charge, and the voltage between both poles for demonstrating the 1st example of the conventional charging method. 電池パック内部の抵抗の存在を説明する為の略回路図。The schematic circuit diagram for demonstrating presence of the resistance inside a battery pack. 従来の充電方法の第２例を説明する為の、充電時間の進行に伴う充電電流の変化を示す線図。The diagram which shows the change of the charging current accompanying progress of charging time for demonstrating the 2nd example of the conventional charging method. 同じく、充電時間の進行に伴うリチウムイオン電池の電圧の変化を示す線図。Similarly, the diagram which shows the change of the voltage of a lithium ion battery with progress of charging time.

符号の説明Explanation of symbols

１ リチウムイオン電池
２ 正端子
３ 第一の電路
４ 負端子
５ 第二の電路
６ 放電ＦＥＴ
７ 充電ＦＥＴ
８ ＩＣ
９ セル
１０ 抵抗
１１ 充電器
１２ 電池パック
１３ 商用電源
１４ 充電器側入力端子
１５ 電源制御部
１６ 充電制御部
１７ 出力端子
１８ 保護回路
１９ 電池側入力端子
２０ 信号制御部 DESCRIPTION OF SYMBOLS 1 Lithium ion battery 2 Positive terminal 3 First electric circuit 4 Negative terminal 5 Second electric circuit 6 Discharge FET
7 Charge FET
8 IC
DESCRIPTION OF SYMBOLS 9 Cell 10 Resistance 11 Charger 12 Battery pack 13 Commercial power supply 14 Charger side input terminal 15 Power supply control part 16 Charge control part 17 Output terminal 18 Protection circuit 19 Battery side input terminal 20 Signal control part

Claims (4)

リチウムイオン電池を充電器により充電する為のリチウムイオン電池の充電方法であって、このリチウムイオン電池の定格容量を１Ｃとし、充電を完了した状態で達成されるべき、このリチウムイオン電池の開回路電圧をＶf とし、上記充電器の端子を接続すべきこのリチウムイオン電池側の端子間に存在する直流抵抗のうちで、このリチウムイオン電池の電極抵抗を除いた直流抵抗をＲとし、上記充電器からこのリチウムイオン電池に送り込む充電電流をＩとした場合に、１ＣＡよりも大きな第一の充電電流を設定し、この第一の充電電流により上記リチウムイオン電池を、このリチウムイオン電池側の端子間の電圧がＶf ＋ＲＩになるまで定電流で充電した後、上記第一の充電電流よりも小さく１ＣＡよりも大きな第二の充電電流を設定し、この第二の充電電流により上記リチウムイオン電池を、このリチウムイオン電池側の端子間の電圧がＶf ＋ＲＩになるまで定電流で充電する動作を、充電電流を小さくしつつ複数段階に亙り行なうリチウムイオン電池の充電方法。 A method of charging a lithium ion battery for charging a lithium ion battery with a charger, wherein the rated capacity of the lithium ion battery is set to 1C, and the open circuit of the lithium ion battery is to be achieved in a fully charged state the voltage is V f, among the DC resistance that exists between the charger terminal to be connected to the lithium ion battery side terminal, the DC resistance be R, except for the electrode resistance of the lithium ion battery, the charging When the charging current sent from the battery to the lithium ion battery is I, a first charging current larger than 1 CA is set, and the lithium ion battery is connected to the lithium ion battery side terminal by the first charging current. after the voltage between were charged at a constant current until V f + RI, set a large second charging current than smaller 1CA than the first charging current , Performed over the second the lithium ion battery by the charging current, the operation voltage between the terminals of the lithium ion battery side is charged with a constant current until V f + RI, in a plurality of stages while reducing the charging current How to charge a lithium ion battery. 第一の充電電流を１．５ＣＡ以上とした、請求項１に記載したリチウムイオン電池の充電方法。   The method for charging a lithium ion battery according to claim 1, wherein the first charging current is 1.5 CA or more. 充電電流を凡そ１ＣＡに設定して定電流充電を行なってから、充電電流を１ＣＡ未満に設定して定電流充電を行なった後、更に電圧をＶf に設定して定圧充電を行なう、請求項１〜２の何れかに記載したリチウムイオン電池の充電方法。 The constant current charging is performed by setting the charging current to approximately 1 CA, the constant current charging is performed by setting the charging current to less than 1 CA, and then the constant voltage charging is performed by further setting the voltage to V f. The charging method of the lithium ion battery as described in any one of 1-2. 充電を開始する際に、先ずリチウムイオン電池の開回路電圧を測定し、この開回路電圧が閾値以上の場合には直ちに第一の充電電流を設定して充電を開始し、この開回路電圧が閾値未満の場合には、１ＣＡよりも小さな充電電流で充電を行ない、この開回路電圧がこの閾値以上に達した後、上記第一の充電電流を設定して充電を開始する、請求項１〜３の何れかに記載したリチウムイオン電池の充電方法。   When starting charging, first, the open circuit voltage of the lithium ion battery is measured, and if this open circuit voltage is equal to or higher than the threshold, the first charging current is immediately set and charging is started. When the voltage is less than the threshold, charging is performed with a charging current smaller than 1 CA, and after the open circuit voltage reaches or exceeds the threshold, the first charging current is set and charging is started. 3. The method for charging a lithium ion battery according to any one of 3 above.
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