JP4112895B2 - Secondary battery charge state detection device - Google Patents

Description

この指数Ｐ（単位：Ａ・ｓｅｃ）は、電極近傍の溶液濃度を電気量で表現したものであり、充放電による電極近傍の溶液濃度変化及び拡散による解消分を考慮している。尚、本明細書中において、この指数ＰがＰ＜０である状態を、放電分極状態と定義し、Ｐ≧０である状態を、充電分極状態と定義する。
【００２１】
ここで、式１において、Ｉは検出電流（Ａ）であり、Ｉ＞０を充電、Ｉ＜０を放電とする。γは二次電池Ｂの充電効率の変動に対する補正項（二次電池Ｂの充電時に０〜１の値となるが、充放電が繰り返される場合は、ほぼ１となる）である。Ｔは時間（秒）である。また、Ｉｄは二次電池Ｂ内の分極に起因する補正項である。そして、Ｐ’をＴ１の１周期前における指数Ｐの値とし、ａ、ｂをそれぞれ定数とすると、Ｐ’＞０のとき、Ｉｄ＝ａ×Ｐ’であり、Ｐ’＝０のとき、Ｉｄ＝０であり、Ｐ’＜０のとき、Ｉｄ＝ｂ×Ｐ’である。ここで定数ａ、ｂを使い分ける理由は、放電後と充電後で分極の影響時間が異なるためである。尚、式１は、マイクロコンピュータ７０のＲＯＭに予め記憶されている。
【００２２】
＜本発明による容量低下判定方法＞
次に、本発明による容量低下判定方法を実現するための制御プログラムの作動について図２を用いて説明する。
【００２３】
自動車のイグニッションスイッチＩＧのオンにより、制御プログラムの実行が開始されると、ステップ１００において、分極状態を表す指数Ｐの値と電池充放電容量の積算値Ｉ_ｓｕｍをゼロにリセットする。
【００２４】
次いで、ステップ１１０から１９０の処理をサンプリング周期ΔＴ毎に実施する。ステップ１１０では、電流センサ４０の検出電流Ｉ、電圧センサ５０の検出電圧Ｖと温度センサ６０の検出温度Ｔが読み込まれる。するとステップ１２０にて、電池充放電容量の積算値Ｉ_ｓｕｍが次式に基づき１周期前の電池充放電容量の積算値Ｉ_ｓｕｍ’とステップ１１０で読み込んだ検出電流Ｉに応じて算出される。
【００２５】
Ｉ_ｓｕｍ＝Ｉ_ｓｕｍ’＋Ｉ×ΔＴ
ここで、検出電流Ｉ＞０を充電、Ｉ＜を放電とする。
【００２６】
さらにステップ１３０において、調整電圧の補正量ΔＶｍをステップ１２０で求めた電池充放電容量の積算値Ｉ_ｓｕｍに応じて、例えば図３に示すマップに基づき算出する。
続くステップ１４０では、調整電圧Ｖｍが次式に基づき、１周期前の調整電圧Ｖｍ’とステップ１３０で算出した調整電圧の補正量ΔＶｍに応じて算出される。
【００２７】
Ｖｍ＝Ｖｍ’＋ΔＶｍ
尚、算出したＶｍが予め設定した上限値以上となった場合は上限値に、予め設定した下限値以下となった場合は下限値に変更する。これら処理により通常は、二次電池Ｂの充放電収支が、ゼロとなるように制御され、電池の過充電によるエネルギ損失が低減できる。
【００２８】
続くステップ１５０では、分極状態を表す指数Ｐが、上記数１の式に基づき、上記ステップ１１０で読み込んだ検出電流Ｉに応じて算出される。
【００２９】
このようにして指数Ｐが算出されると、続くステップ１６０において、指数Ｐが所定値、例えば４００よりも大きいか否か（即ち、充電分極の影響度合いが大きいか否か）、かつ検出電流Ｉがゼロよりも大きいか（即ち、充電中か否か）が判定される。判定が否定された場合は、ステップ１９０に進み、判定が肯定された場合は、ステップ１７０に進む。
【００３０】
ステップ１７０では、検出電流Ｉに対する検出電圧Ｖのプロット点が、例えば図４に示す容量低下判定用の境界線よりも下の領域に属するか否かの判定を行う。この容量低下判定用の境界線は、図４に示すように、電池温度に応じて予め用意されており、この容量低下判定用の境界線は、上記ステップ１１０で読み込んだ検出温度Ｔに応じて選択される。尚、この容量低下判定用の境界線の設定方法については、後に詳説する。ステップ１７０で判定が否定された場合は、ステップ１９０に進み、判定が肯定された場合は、ステップ１８０に進む。
【００３１】
ステップ１８０では、電池容量が低下していると判断し、充電状態の回復性を向上するために、調整電圧を高めに設定して充電を行う通常制御へ移行し、ステップ１９０に進む。尚、このステップ１８０では、判断の確実性を向上すべく、ステップ１７０の条件が連続して成立した場合に、電池容量が低下していると判断するようにしてもよい。
【００３２】
ステップ１９０では、イグニッションスイッチＩＧがオフされたか否かを判定し、判定が肯定された場合は、処理を終了する。一方、判定が否定された場合は、ステップ１１０以後の処理が繰り返される。
【００３３】
＜容量低下判定用の境界線の決定方法＞
次に、図４に示す容量低下判定用の境界線の決定方法について、図５を用いて説明する。図５は、二次電池（電池温度３０℃、定格容量４８Ａｈ）を一定電流で充電した場合における、数１の式で求めた指数Ｐに対する当該二次電池の電圧曲線を示した図である。図５（Ａ）は、電流Ｉａ＝９．６（Ａ）で充電した場合の結果を示し、図５（Ｂ）は、電流Ｉｂ＝２４（Ａ）充電した場合の結果を示している。尚、図５の各図には、電池の充電状態（以下、ＳＯＣという）の異なる二次電池（スタートＳＯＣ：３０％、５０％、７０％、９０％）のそれぞれの電圧曲線が示されている。
【００３４】
図５（Ａ）及び図５（Ｂ）に示すように、充電電流がＩａ＝９．６（Ａ）若しくはＩｂ＝２４（Ａ）のいずれの場合においても、ＳＯＣ５０％以下の状態では、指数Ｐが４００（Ａ・ｓｅｃ）を超える付近から、電圧の上昇率が小さくなることがわかる。他言すると、充電を継続した場合、結果としてＳＯＣが高くなり電圧は上昇していくが、指数Ｐが約４００（Ａ・ｓｅｃ）を超えると、ＳＯＣ５０％以下の二次電池では、ＳＯＣ７０％以上の二次電池に比べて、その電圧上昇が低下していることがわかる。
【００３５】
ここで、電池の容量低下の判断基準をＳＯＣ５０％以下とし、最大ＳＯＣ７０％以下までの充電状態を許容する場合における、具体的な容量低下判定用の境界線の決定方法について言及する。図５（Ａ）に示すように、指数Ｐが４００（Ａ・ｓｅｃ）を超える範囲で、ＳＯＣ７０％に係る電圧曲線とＳＯＣ５０％以下の電圧曲線を電圧Ｖａのラインにより仕切ることができる。同様に、図５（Ｂ）に示すように、指数Ｐが４００（Ａ・ｓｅｃ）を超える範囲で、ＳＯＣ７０％に係る電圧曲線とＳＯＣ５０％以下の電圧曲線を電圧Ｖｂのラインにより仕切ることができる。これらの電圧Ｖａ、Ｖｂは、図５（Ａ）及び図５（Ｂ）に示すように、ＳＯＣ７０％に係る電圧曲線におけるＰ＝４００でのそれぞれの電圧値であってよいが、上記ステップ１６０で例えば４００＜Ｐ＜５００のような範囲で判定する場合には、Ｐ＝４００での電圧値より低い電圧値であってもよい。
【００３６】
このようにして決定された電圧Ｖａ及びＶｂを、それぞれ電流値Ｉａ及びＩｂに対する判定電圧Ｖ_thresholdとして直線で結ぶことにより、図４に示す電池温度３０℃における容量低下判定用の境界線が得られる。尚、電流値Ｉａ及びＩｂ以外の電流値に対する判定電圧Ｖ_thresholdは、この容量低下判定用の境界線上の当該電流値に対する電圧値になる。同様に、電池温度を変更して、図４に示すような各電池温度に対する境界線が得られる。従って、判定電圧Ｖ_thresholdは、電流値Ｉ及び電池温度Ｔを用いて、Ｖ_threshold＝ｆ（Ｉ，Ｔ）で表わされる（上記ステップ１７０参照）。
【００３７】
尚、本例は、２つの電流値ＩａとＩｂに対する各判定電圧に基づいて容量低下判定用の境界線を求めるものであるが、より多くの電流値に対する各判定電圧に基づいて容量低下判定用の境界線を求めるようにしてもよい。また、本例は、ＳＯＣ５０％以下を容量低下の検出目標とし、最大ＳＯＣ７０％以下までを許容するとして、容量低下判定用の境界線を決定したが、検出目標は必要に応じて変更してもよい。
【００３８】
次に、このようにして設定された容量低下判定用の境界線（検出目標をＳＯＣ５０％以下とした境界線）を用いた、上述の制御プログラムによる二次電池の容量低下の検出結果について言及する。
【００３９】
図６は、上述の制御プログラムのステップ１１０（図２参照）により実際の車両走行中の電流と電圧を測定し、測定点をサンプリング周期ΔＴ毎にプロットした図であり、図６（Ａ）は、ＳＯＣ７０％の二次電池を使用した結果を示し、図６（Ｂ）は、ＳＯＣ５０％の二次電池を使用した結果を示している。
【００４０】
図６（Ａ）に示すように、ＳＯＣ７０％でのプロット点の幾つか（小さな○印のプロット点）は、容量低下判定用の境界線よりも下の領域に属したが、電池の分極状態を表す指数Ｐが４００を超えるプロット点（▲印のプロット点）に関しては、当該容量低下判定用の境界線よりも下の領域に属することがなかったので、上記ステップ１８０で容量低下との判断はなされなかった。一方、ＳＯＣ５０％では、指数が４００を超えるプロット点（▲印のプロット点）であっても、図６（Ｂ）に示すように、容量低下判定用の境界線より下の領域に属したため、上記ステップ１８０で容量低下との判断がなされた。この結果から、Ｐ＞４００の範囲で、上述したように設定された容量低下判定用の境界線により、ＳＯＣ５０％以下となる充電状態の低下を確実に検出できることが確認された。
【００４１】
尚、二次電池が劣化した場合、ＳＯＣ７０％以上であっても、ほとんどの場合は、充電分極状態での電圧上昇が低下する（例えば、図５（Ｂ）のＳＯＣ５０％の電圧曲線のようになる）ため、上記ステップ１８０で容量低下との判断が行われることが予測される。しかしながら、この場合には、当該ＳＯＣ７０％の二次電池から実際に取り出せる容量が低下していることになるので、当該ＳＯＣ７０％の二次電池に残っている容量は、例えばＳＯＣ５０％の新品の二次電池と略同一と考えることができ、安全側の判定となる。
【００４２】
以上説明したように、本発明では、容量低下（充電状態が５０％以下）状態では、過電圧が発生する充電分極状態であっても電圧の上昇が抑えられるといった点に着目し、所定値を超える充電分極状態であるにも関わらず、予め定めた容量低下判定用の境界線よりも、検出した充電電流-電圧特性が下回る場合には、容量低下と判断することによって、二次電池が発電機に並列接続されているためにほとんど放電しない状態であっても、当該二次電池の容量低下を検出することが可能となる。
【００４３】
尚、特許請求の範囲に記載した「分極状態検出手段」は、発明の詳細な説明に記載した制御プログラムのステップ１５０をマイクロコンピュータ７０が実行することによって実現されている。
【００４４】
以上、本発明の好ましい実施例について詳説したが、本発明は、上述した実施例に制限されることはなく、本発明の範囲を逸脱することなく、上述した実施例に種々の変形及び置換を加えることができる。例えば、上述した実施例においては、分極状態を判断するために、数１の式で定義された指数を使用していたが、特にこの式に限定されるものではなく、当該式に変更を加えた式、同一の観点から導出された式若しくはその類の式を本発明に適用することもできる。
【００４５】
【発明の効果】
本発明は、以上説明したようなものであるから、以下に記載されるような効果を奏する。請求項１の発明によると、放電がほとんど行われない状態であっても、電池の容量低下を検出することができる。
【００４６】
また、請求項２の発明によると、低コストで電池の充電分極状態を確実に検出できる。また、請求項３、４又は５の発明によると、充電状態が低い二次電池は、所定値を超える分極の影響度合いであっても電圧値が高くならないという特性が利用され、二次電池の充電状態の低下を精度よく検出することができる。
【図面の簡単な説明】
【図１】車両用バッテリを充電制御する充電制御システム９０を示す図である。
【図２】本発明によるマイクロコンピュータ７０の動作を示すフローチャートである。
【図３】調整電圧の補正量ΔＶｍを算出するために予め用意されたマップである。
【図４】容量低下判定用の境界線を示す図である。
【図５】図５は、指数Ｐに対する二次電池の電圧曲線を示した図であり、図５（Ａ）は、電流Ｉａ＝９．６（Ａ）で充電した場合の結果を示し、図５（Ｂ）は、電流Ｉｂ＝２４（Ａ）充電した場合の結果を示す。
【図６】図６は、本発明による制御プログラムよる容量低下の検出結果を示す図であり、図６（Ａ）は、ＳＯＣ７０％の結果を示し、図６（Ｂ）は、ＳＯＣ５０％の結果を示す。
【符号の説明】
１０ 交流発電機
２０ 整流器
３０ レギュレータ
４０ 電流センサ
５０ 電圧センサ
６０ 温度センサ
７０ マイクロコンピュータ
９０ 充電制御システム
Ｂ 二次電池
Ｌ 電気的負荷[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a secondary battery charge state detection device capable of accurately detecting a charge state of a secondary battery even during charging.
[0002]
[Prior art]
In the vehicle battery charging control, the adjustment voltage is set to about 13.5V to 14.5V higher than the rated voltage of the battery 12V in order to efficiently charge the battery. In this case, the battery is always overcharged, the burden on the internal combustion engine is increased, fuel consumption is deteriorated, and liquid leakage of the battery is promoted. Therefore, a current sensor was added to detect the current flowing in and out of the battery, and a system was devised to control the charge / discharge balance of the detected current to zero in a charged state slightly below the over (full) charged state. Has been.
[0003]
In these systems, a minimum voltage guard is generally provided in order to prevent the state of charge from being lowered due to battery self-discharge or current integration error. As a conventional technique for detecting a decrease in the state of charge, current data, voltage data, and battery temperature are measured while the battery is in use, and these data are compared with a discharge current-voltage map stored in advance for each battery temperature. Techniques for detecting the state of charge of a battery are well known. This technique is effective as a state-of-charge detection device for an electric vehicle or the like in which the majority of discharge is generated. Further, as a technique for detecting the current during battery use at a constant sampling period and detecting the polarization state of the battery from the detected current, for example, in Japanese Patent Laid-Open No. 2000-258514, calculation is performed in consideration of the charge / discharge history of the current. A technique for correcting a relationship between an electromotive force measured in advance and a state of charge of a battery by using the polarized electromotive force is disclosed. According to this technique, since the influence of the polarization electromotive force of the battery is appropriately compensated, the state of charge of the battery can be accurately detected.
[0004]
[Problems to be solved by the invention]
However, in vehicles other than electric vehicles, the battery may not be discharged by the minimum voltage guard as described above in a low electric load state such as during daytime driving. Therefore, detecting the state of charge (SOC) of the battery during charging that is performed relatively frequently can detect a decrease in the state of charge even if the state of charge is reduced by self-discharge or dark current discharge. Therefore, it is effective.
[0005]
Further, in a hybrid vehicle that is controlled to be charged so that the charged state is maintained at about 60%, the charged state that is determined to be a decrease in battery capacity is about 40%, which is slightly lower than the fully charged state. In a vehicle that is controlled to be charged in a charged state, the charged state that is determined to be a decrease in battery capacity is about 50%. Therefore, for such a vehicle, the charged state in a relatively high charged state is low. A state-of-charge detection device suitable for detecting a change is useful.
[0006]
Further, in order to accurately detect the state of charge, it is necessary to consider the influence of the polarization of the battery on the current-voltage characteristics, as in the technique described in Japanese Patent Laid-Open No. 2000-2585142. On the other hand, in the charge polarization state, the influence of polarization is particularly large, and the voltage is apparently increased due to hydrogen overvoltage, so that it is difficult to handle the detected current-voltage characteristics.
[0007]
Therefore, the present invention can detect the state of charge of the battery even during charging, and can detect the state of charge with high accuracy even in the charge polarization state, and is suitable for detecting changes in the state of charge in a relatively high state of charge. It aims at provision of the electrical condition detection apparatus for a secondary battery.
[0008]
[Means for Solving the Problems]
The object of the present invention is to provide a state-of-charge detection apparatus for a secondary battery, comprising: voltage detection means for detecting the voltage value of the secondary battery; and current detection means for detecting the current value of the secondary battery. Because
Polarization state detection means for detecting the degree of influence of the current-voltage characteristics of the secondary battery due to the polarization of the secondary battery ;
Charge polarization state detection means for detecting a charge polarization state in which the degree of influence of the polarization is a predetermined value or more;
And a charging state detection means for detecting a state where the secondary battery is being charged ,
By using the voltage state and the current value of the secondary battery in the charge polarization state and the charging state, the state of charge of the secondary battery is determined. Achieved.
[0009]
According to the above-described invention, the state of charge of the secondary battery is determined using the voltage and current of the secondary battery being charged. Therefore, even when the battery is hardly discharged, a decrease in the state of charge of the battery is detected. can do. Therefore, according to the present invention, even when the secondary battery is not discharged in a low electrical load state such as during daytime running, it is possible to detect a decrease in the state of charge due to self-discharge or dark current discharge. it can.
[0010]
Further, as described in claim 2, in the charging state detection device for a secondary battery according to claim 1, the polarization state detection unit is configured to determine the degree of influence of the polarization of the secondary battery from the charge / discharge history of the secondary battery. Is estimated, it is possible to detect the charge polarization state of the battery without using complicated polarization state detection means such as a density meter, a densitometer, and a hydrometer.
[0011]
Further, as described in claim 3, in the charge state detection device for a secondary battery according to claim 1, the voltage value of the secondary battery in the charge polarization state and the charge state, and the current value at this time If the charge state of the secondary battery is determined by comparing with a predetermined threshold value depending on the value, it is possible to accurately detect a decrease in the charge state of the secondary battery. In other words, a secondary battery with a low state of charge can accurately detect a decrease in the state of charge of the secondary battery by utilizing the characteristic that the voltage value does not increase even if the degree of influence of polarization exceeds a predetermined value. it can. Such characteristics are particularly noticeable in a secondary battery having a charge state of 50% or less. Therefore, it is determined that the charge state is 50% or less as a capacity decrease, and the maximum charge state that is not determined as a capacity decrease is approximately 70%. This is particularly effective in a control system. Note that the threshold value depending on the current value is the voltage value of the secondary battery when the degree of influence of polarization is the predetermined value in the maximum charge state that is not determined to be a capacity decrease corresponding to the current value. It's okay. Further, this threshold value may be prepared in advance for each current value in consideration of the degree of influence of polarization and the above characteristics in each state of charge.
[0012]
According to a fourth aspect of the present invention, there is provided a secondary battery that is mounted on a vehicle equipped with an alternator and a regulator that regulates the output voltage of the alternator and is charged and discharged under the regulation of the regulator. Charge state detection device for a secondary battery, including voltage detection means for detecting a voltage value of the battery, current detection means for detecting the current value of the secondary battery, and temperature detection means for detecting the temperature of the secondary battery Because
Polarization state detection means for detecting the degree of influence of the current-voltage characteristics of the secondary battery due to the polarization of the secondary battery ;
Charge polarization state detection means for detecting a charge polarization state in which the degree of influence of the polarization is a predetermined value or more;
And a charging state detection means for detecting a state where the secondary battery is being charged ,
The charging state of the secondary battery is determined by comparing the voltage value of the secondary battery in the charging polarization state and the charging state with a predetermined threshold value depending on the current value and temperature at this time. This is achieved by a charge state detection device for a secondary battery.
[0013]
According to the above-described invention, since the state of charge of the secondary battery is determined using the voltage and current of the secondary battery being charged, it is possible to detect a decrease in the capacity of the battery even in a state where almost no discharge is performed. Can do. In addition, a secondary battery with a low state of charge can accurately detect a decrease in the state of charge of a secondary battery by utilizing the characteristic that the voltage value does not increase even if the degree of influence of polarization exceeds a predetermined value. it can. In addition, since this characteristic appears without depending on the battery temperature, in a general use environment where the battery temperature changes, it is possible to compensate for the change in the battery temperature and accurately detect a decrease in the state of charge of the secondary battery. Can do. Note that the threshold value depending on the battery temperature and current value is a secondary value when the degree of influence of polarization is the predetermined value in the maximum charge state corresponding to the battery temperature and current value and not determined as a capacity decrease. It may be the voltage value of the battery. Further, this threshold value may be prepared in advance for each current value and each battery temperature in consideration of the degree of influence of polarization and the above characteristics in each state of charge.
[0014]
Further, in the secondary battery charge state detection device according to claim 4, when the comparison result is the same continuously for a predetermined number of times, the charge state of the secondary battery is lowered. , It is possible to detect a reduction in the state of charge with high accuracy.
[0015]
Other objects, configurations, and effects of the present invention will become more apparent from the following description of embodiments with reference to the drawings.
[0016]
DETAILED DESCRIPTION OF THE INVENTION
FIG. 1 shows an embodiment of a charging control system 90 for controlling charging of a vehicle battery using the charging state detection method according to the present invention. In addition, this battery is comprised by the secondary battery B like a lead storage battery.
[0017]
As shown in FIG. 1, the charging control system 90 includes an AC generator 10 (hereinafter referred to as a generator 10), a rectifier 20, and a regulator 30. The generator 10 is driven by a vehicle engine to generate an alternating voltage. The rectifier 20 rectifies the AC voltage of the generator 10 to generate a rectified voltage and supplies it to the secondary battery B and the regulator 30. The regulator 30 adjusts the rectified voltage of the rectifier 20 and outputs it to the secondary battery B and the electrical load L under the control of the microcomputer 70 described later.
[0018]
The charging control system 90 includes a current sensor 40, a voltage sensor 50, a temperature sensor 60, and a microcomputer 70. The current sensor 40 detects the charging current or discharging current of the secondary battery B at a predetermined sampling period. Similarly, the voltage sensor 50 detects the terminal voltage of the secondary battery B at a predetermined sampling period. The temperature sensor 60 detects the liquid temperature of the secondary battery B or the temperature of the side surface or the bottom surface of the case (not shown) in which the secondary battery B is stored. The microcomputer 70 executes a control program according to a flowchart described later. During execution of this control program, the microcomputer 70 stores the processing and data required for detecting the charge state of the secondary battery B and controlling the regulator 30 based on the detection values of the current sensor 40, the voltage sensor 50 and the temperature sensor 60. Perform processing. Note that the microcomputer 70 is always in operation by being supplied with power from the secondary battery B, and starts execution of a control program, which will be described later, when an ignition switch IG of the automobile is turned on. This control program is stored in advance in the ROM of the microcomputer 70.
[0019]
<Index indicating polarization state>
The charging state detection method according to the present invention is given by the following equation as an index indicating the degree of influence of the polarization of the secondary battery on the current-voltage characteristics of the secondary battery (hereinafter simply referred to as “polarization state”). The index P is used.
[0020]
[Expression 1]

This index P (unit: A · sec) expresses the solution concentration in the vicinity of the electrode as an electric quantity, and considers the solution concentration change in the vicinity of the electrode due to charge / discharge and the elimination due to diffusion. In the present specification, a state where the index P is P <0 is defined as a discharge polarization state, and a state where P ≧ 0 is defined as a charge polarization state.
[0021]
Here, in Equation 1, I is a detection current (A), where I> 0 is charged and I <0 is discharged. γ is a correction term for a change in charging efficiency of the secondary battery B (a value of 0 to 1 is obtained when the secondary battery B is charged, but is approximately 1 when charging and discharging are repeated). T is time (seconds). Id is a correction term due to polarization in the secondary battery B. If P ′ is the value of the index P one period before T1, and a and b are constants, Id = a × P ′ when P ′> 0, and Id when P ′ = 0. = 0, and when P ′ <0, Id = b × P ′. The reason why the constants a and b are properly used is that the influence time of polarization is different after discharge and after charge. Note that Equation 1 is stored in advance in the ROM of the microcomputer 70.
[0022]
<Method for Determining Capacity Decrease According to the Present Invention>
Next, the operation of the control program for realizing the capacity drop determination method according to the present invention will be described with reference to FIG.
[0023]
When execution of the control program is started by turning on the ignition switch IG of the automobile, the value of the index P indicating the polarization state and the integrated value I _sum of the battery charge / discharge capacity are reset to zero in step 100.
[0024]
Next, the processing of steps 110 to 190 is performed every sampling period ΔT. In step 110, the detection current I of the current sensor 40, the detection voltage V of the voltage sensor 50, and the detection temperature T of the temperature sensor 60 are read. Then, in step 120, the battery charge / discharge capacity integrated value I _sum is calculated according to the battery charge / discharge capacity integrated value I _{sum '} of the previous cycle and the detected current I read in step 110 based on the following equation.
[0025]
I _sum = I _{sum ′} + I × ΔT
Here, the detection current I> 0 is charged and I <is discharged.
[0026]
Further, in step 130, the correction amount ΔVm of the adjustment voltage is calculated based on the integrated value I _sum of the battery charge / discharge capacity obtained in step 120, for example, based on the map shown in FIG.
In the following step 140, the adjustment voltage Vm is calculated according to the adjustment voltage Vm ′ of the previous cycle and the adjustment amount ΔVm of the adjustment voltage calculated in step 130 based on the following equation.
[0027]
Vm = Vm ′ + ΔVm
When the calculated Vm is equal to or higher than a preset upper limit value, the upper limit value is changed. When the calculated Vm is lower than a preset lower limit value, the lower limit value is changed. By these processes, the charge / discharge balance of the secondary battery B is normally controlled to be zero, and energy loss due to overcharge of the battery can be reduced.
[0028]
In the subsequent step 150, the index P representing the polarization state is calculated according to the detected current I read in the step 110 based on the equation (1).
[0029]
When the index P is calculated in this way, in the subsequent step 160, it is determined whether the index P is larger than a predetermined value, for example, 400 (that is, whether the influence degree of the charge polarization is large) and the detected current I. Is greater than zero (ie, whether charging is in progress). If the determination is negative, the process proceeds to step 190, and if the determination is affirmative, the process proceeds to step 170.
[0030]
In step 170, it is determined whether or not the plot point of the detection voltage V with respect to the detection current I belongs to a region below the boundary for determining the capacity decrease shown in FIG. As shown in FIG. 4, the boundary line for determining the capacity reduction is prepared in advance according to the battery temperature, and the boundary line for determining the capacity decrease is determined according to the detected temperature T read in step 110 above. Selected. The method for setting the boundary for determining the capacity decrease will be described in detail later. If the determination in step 170 is negative, the process proceeds to step 190. If the determination is positive, the process proceeds to step 180.
[0031]
In step 180, it is determined that the battery capacity is decreasing, and in order to improve the recoverability of the charged state, the control proceeds to normal control in which charging is performed with the adjustment voltage set high, and the process proceeds to step 190. In this step 180, in order to improve the certainty of determination, it may be determined that the battery capacity is decreasing when the conditions of step 170 are continuously satisfied.
[0032]
In step 190, it is determined whether or not the ignition switch IG is turned off. If the determination is affirmative, the process ends. On the other hand, if the determination is negative, the processing after step 110 is repeated.
[0033]
<Determining the boundary line for capacity reduction judgment>
Next, a method for determining the boundary line for determining the capacity decrease shown in FIG. 4 will be described with reference to FIG. FIG. 5 is a diagram showing a voltage curve of the secondary battery with respect to the index P obtained by the equation 1 when a secondary battery (battery temperature 30 ° C., rated capacity 48 Ah) is charged with a constant current. FIG. 5A shows the result when charging with current Ia = 9.6 (A), and FIG. 5B shows the result when charging with current Ib = 24 (A). In addition, each figure of FIG. 5 shows respective voltage curves of secondary batteries (start SOC: 30%, 50%, 70%, 90%) having different battery charge states (hereinafter referred to as SOC). Yes.
[0034]
As shown in FIG. 5 (A) and FIG. 5 (B), when the charging current is Ia = 9.6 (A) or Ib = 24 (A), the index P It can be seen that the rate of increase in voltage decreases from around 400 (A · sec). In other words, when charging is continued, as a result, the SOC increases and the voltage increases. However, when the index P exceeds about 400 (A · sec), the secondary battery with an SOC of 50% or less has an SOC of 70% or more. It can be seen that the voltage rise is lower than that of the secondary battery.
[0035]
Here, a specific method for determining the boundary line for determining the capacity reduction is described in the case where the criterion for determining the battery capacity reduction is SOC 50% or less and the state of charge up to the maximum SOC 70% or less is allowed. As shown in FIG. 5A, in the range where the index P exceeds 400 (A · sec), the voltage curve related to SOC 70% and the voltage curve of SOC 50% or less can be partitioned by the line of voltage Va. Similarly, as shown in FIG. 5B, in the range where the index P exceeds 400 (A · sec), the voltage curve related to the SOC 70% and the voltage curve below the SOC 50% can be partitioned by the voltage Vb line. . These voltages Va and Vb may be the respective voltage values at P = 400 in the voltage curve relating to SOC 70% as shown in FIG. 5A and FIG. For example, when the determination is made in the range of 400 <P <500, the voltage value may be lower than the voltage value at P = 400.
[0036]
By connecting the voltages Va and Vb determined in this way as straight lines as determination voltages V _threshold for the current values Ia and Ib, respectively, the boundary line for determining the capacity decrease at the battery temperature of 30 ° C. shown in FIG. 4 is obtained. . Note that the determination voltage V _threshold for current values other than the current values Ia and Ib is a voltage value for the current value on the boundary for determining the capacity decrease. Similarly, the boundary line for each battery temperature as shown in FIG. 4 is obtained by changing the battery temperature. Therefore, the determination voltage V _threshold is expressed by V _threshold = f (I, T) using the current value I and the battery temperature T (see step 170 above).
[0037]
In this example, the boundary for determining the capacity decrease is obtained based on the respective determination voltages for the two current values Ia and Ib. However, for determining the capacity decrease based on the respective determination voltages for more current values. The boundary line may be obtained. Further, in this example, the boundary for determining the capacity reduction is determined on the assumption that the SOC is 50% or less and the maximum SOC is 70% or less. However, the detection target may be changed as necessary. Good.
[0038]
Next, reference will be made to the detection result of the capacity decrease of the secondary battery by the above-described control program using the boundary line for determining the capacity decrease set in this way (the boundary line where the detection target is SOC 50% or less). .
[0039]
FIG. 6 is a diagram in which the current and voltage during actual vehicle travel are measured in step 110 (see FIG. 2) of the above-described control program, and the measurement points are plotted for each sampling period ΔT. FIG. FIG. 6B shows the result of using a secondary battery of SOC 50%, and FIG. 6B shows the result of using a secondary battery of SOC 50%.
[0040]
As shown in FIG. 6 (A), some of the plot points at SOC 70% (small plot points marked with ◯) belonged to the region below the boundary for capacity reduction judgment, but the polarization state of the battery Since the plot point (plot point marked with ▲) that has an index P representing 400 does not belong to the region below the boundary for determining the decrease in capacity, it is determined that the capacity is decreased in step 180 above. Was not done. On the other hand, when the SOC is 50%, even plot points with an index exceeding 400 (plot points marked with ▲) belong to the region below the boundary for capacity reduction determination, as shown in FIG. In step 180, it is determined that the capacity has been reduced. From this result, it was confirmed that in the range of P> 400, it is possible to reliably detect a decrease in the state of charge that is 50% or less of the SOC by the boundary line for determining the capacity decrease set as described above.
[0041]
When the secondary battery is deteriorated, even if the SOC is 70% or more, in most cases, the voltage increase in the charge polarization state is reduced (for example, as shown in the voltage curve of SOC 50% in FIG. 5B). Therefore, it is predicted that the determination of capacity reduction is made in step 180 above. However, in this case, the capacity that can be actually taken out from the SOC 70% secondary battery is reduced. Therefore, the capacity remaining in the SOC 70% secondary battery is, for example, a new 50% SOC secondary battery. It can be considered to be substantially the same as the secondary battery, and is a safe determination.
[0042]
As described above, the present invention pays attention to the fact that the increase in voltage is suppressed even in the charge polarization state in which overvoltage occurs in the state of reduced capacity (charge state is 50% or less), and exceeds a predetermined value. If the detected charge current-voltage characteristic falls below the predetermined boundary line for capacity decrease determination in spite of the charge polarization state, the secondary battery can be Therefore, even when the battery is hardly discharged because of being connected in parallel, it is possible to detect a decrease in the capacity of the secondary battery.
[0043]
The “polarization state detecting means” described in the claims is realized by the microcomputer 70 executing step 150 of the control program described in the detailed description of the invention.
[0044]
The preferred embodiments of the present invention have been described in detail above. However, the present invention is not limited to the above-described embodiments, and various modifications and substitutions can be made to the above-described embodiments without departing from the scope of the present invention. Can be added. For example, in the above-described embodiment, the index defined by the formula 1 is used to determine the polarization state. However, the index is not particularly limited to this formula, and the formula is changed. It is also possible to apply to the present invention, a formula derived from the same viewpoint, or a similar formula.
[0045]
【The invention's effect】
Since the present invention is as described above, the following effects can be obtained. According to the first aspect of the present invention, it is possible to detect a decrease in the capacity of the battery even in a state where the discharge is hardly performed.
[0046]
According to the invention of claim 2, the charge polarization state of the battery can be reliably detected at low cost. In addition, according to the invention of claim 3, 4 or 5, the secondary battery having a low state of charge utilizes the characteristic that the voltage value does not increase even when the influence of polarization exceeds a predetermined value. A decrease in the state of charge can be accurately detected.
[Brief description of the drawings]
FIG. 1 is a diagram showing a charging control system 90 for controlling charging of a vehicle battery.
FIG. 2 is a flowchart showing the operation of the microcomputer 70 according to the present invention.
FIG. 3 is a map prepared in advance for calculating an adjustment voltage correction amount ΔVm.
FIG. 4 is a diagram illustrating a boundary line for determining a capacity decrease.
FIG. 5 is a diagram showing a voltage curve of the secondary battery with respect to the index P. FIG. 5 (A) shows a result when charging is performed with a current Ia = 9.6 (A). 5 (B) shows the result when the current Ib = 24 (A) is charged.
FIG. 6 is a diagram showing a detection result of capacity decrease by a control program according to the present invention, FIG. 6 (A) shows a result of SOC 70%, and FIG. 6 (B) shows a result of SOC 50%. Indicates.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 10 AC generator 20 Rectifier 30 Regulator 40 Current sensor 50 Voltage sensor 60 Temperature sensor 70 Microcomputer 90 Charge control system B Secondary battery L Electrical load

Claims (5)

A charging state detection device for a secondary battery, comprising: voltage detection means for detecting a voltage value of the secondary battery; and current detection means for detecting the current value of the secondary battery,
Polarization state detection means for detecting the degree of influence of the current-voltage characteristics of the secondary battery due to the polarization of the secondary battery ;
Charge polarization state detection means for detecting a charge polarization state in which the degree of influence of the polarization is a predetermined value or more;
And a charging state detection means for detecting a state where the secondary battery is being charged ,
A charging state detection device for a secondary battery, wherein the charging state of the secondary battery is determined using a voltage value and a current value of the secondary battery in the charging polarization state and the charging state.   The charge state detection device for a secondary battery according to claim 1, wherein the polarization state detection means estimates an influence degree of polarization of the secondary battery from a charge / discharge history of the secondary battery. The charging state of the secondary battery is determined by comparing the voltage value of the secondary battery in the charging polarization state and the charging state with a predetermined threshold value depending on the current value at this time. Item 3. The secondary battery charge state detection device according to Item 1 or 2. A voltage detection means for detecting a voltage value of a secondary battery mounted on a vehicle equipped with an alternator and a regulator for regulating the output voltage of the alternator, and charged and discharged under the regulation of the regulator; A secondary battery charge state detection device including current detection means for detecting a current value of the secondary battery and temperature detection means for detecting the temperature of the secondary battery,
Polarization state detection means for detecting the degree of influence of the current-voltage characteristics of the secondary battery due to the polarization of the secondary battery ;
Charge polarization state detection means for detecting a charge polarization state in which the degree of influence of the polarization is a predetermined value or more;
And a charging state detection means for detecting a state where the secondary battery is being charged ,
The charging state of the secondary battery is determined by comparing the voltage value of the secondary battery in the charging polarization state and the charging state with a predetermined threshold value depending on the current value and temperature at this time. A charge state detection device for a secondary battery, characterized in that.   The charged state detection device for a secondary battery according to claim 4, wherein when the comparison result is the same continuously for a predetermined number of times, a decrease in the charged state of the secondary battery is detected.

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