JP3634077B2 - Battery fuel gauge - Google Patents

Description

【００２５】
ステップ１０９ではｔをｎ_ｅｎｄ と比較し、ｔがｎ_ｅｎｄ に達していなければステップ１０８に戻りステップ１０８〜１０９を繰り返す。しかしてｔがｎ_ｅｎｄ に達すると、評価値Ｉ_ａｖは現時点を遡るｎ_ｅｎｄ 秒間における充放電電流Ｉ（ｎ−ｔ_ｐ ） を、その検出時からの経過時間で重みを付けて平均した重み付き平均値となる。
【００２６】
ｎ_ｅｎｄ は車両に搭載される電池１と同一仕様の電池について予め以下の手順で実験を行い設定する。まず電池を２ＣＡの電流で５分以上放電せしめた後、放電電流を０．２ＣＡに変更する。そして放電電流を変更してから端子電圧がほぼ一定値に収束するまでの時間を測定し、この収束時間を所定時間ｎ_ｅｎｄ として設定する。図５はかかる実験における充放電電流と端子電圧の経時変化を示すもので、端子電圧は、電流が２ＣＡから０．２ＣＡに変更された後収束するまでに、６０秒要している。このようにＮｉ系電池では数十秒前の充放電状態が現在の電池状態に影響を与え、その影響の程度が直前の充放電状態ほど大きいことを発明者らは確認したので、所定時間における充放電電流の重み付き平均値を電池状態を判ずる評価値として用い本発明の完成に到ったのである。
【００２７】
ステップ１１０では評価値Ｉ_ａｖにより電池１の状態を判定する。すなわち０．４＜Ｉ_ａｖ＜０．６のとき電池状態は普通放電状態と判じ、０．９＜Ｉ_ａｖ＜１．１のとき高放電状態と判じる。
【００２８】
電池状態が普通放電状態もしくは高放電状態と判じられた場合にはＶ_ｎ ，Ｉ_ｎ よりなる検出データを第２の記憶手段たるメモリ３ｂ内の配列に格納し一時記憶する。配列は２種類用意され、電池状態の分類結果により検出データが振り分けられる。すなわち普通放電状態の場合、ステップ１１１に進み、カウント数ｓ_ｌｏｗ を１増加させる。そして配列Ｖ_ｌｏｗ （ ｓ_ｌｏｗ ） にＶ_ｎ を格納し、配列Ｉ_ｌｏｗ （ ｓ_ｌｏｗ ） にＩ_ｎ を格納する。高放電状態の場合、ステップ１１２に進み、カウント数ｓ_ｈｉを１増加させる。そして配列Ｖ_ｈｉ（ ｓ_ｈｉ） にＶ_ｎ を格納し、配列Ｉ_ｈｉ （ｓ_ｈｉ） にＩ_ｎ を格納する。なおステップ１１０において電池状態が普通放電状態、高放電状態のいずれとも判じられなかった場合にはＶ_ｎ ，Ｉ_ｎ は記憶されない。
【００２９】
またステップ１１１もしくは１１２では、ステップ１０３に続く平均放電量演算手段としての後半の作動もしている。すなわち満充電からの放電量Ｑ_ｎ を、普通放電状態の場合にはＱ_{ｌｏｗ−ａｖ}に加算し（ステップ１１１）、高放電状態の場合にはＱ_{ｈｉ−ａｖ} に加算する。このようにＱ_ｎ をＱ_{ｌｏｗ−ａｖ}，Ｑ_{ｈｉ−ａｖ} に加算するのは後で電池状態ごとに平均化するためである。
【００３０】
そしてステップ１１１もしくは１１２からステップ１１３に進む。なおステップ１１０において電池状態が普通放電状態、高放電状態いずれにも分類されなかった場合もステップ１１３に進む。ステップ１１３ではＱ_ｎ を基準放電量Ｑ_ｂ と比較する。Ｑ_ｎ がＱ_ｂ を越えていなければ図４のステップ１３２に進み走行継続であれば再びステップ１０１（図２）に戻る。したがって放電量Ｑ_ｎ がＱ_ｂ を越えるまでは１秒ごとに評価値Ｉ_ａｖが求められ、その大きさによって電池状態が分類され、普通放電状態、高放電状態の場合にはその電池状態ごとに検出データが配列Ｖ_ｌｏｗ （ ｓ_ｌｏｗ ） ，Ｉ_ｌｏｗ （ ｓ_ｌｏｗ ） ，Ｖ_ｈｉ（ ｓ_ｈｉ） ，Ｉ_ｈｉ（ ｓ_ｈｉ） に順次格納される。基準放電量Ｑ_ｂ は２Ａｈの初期値から後述するステップ１３０において２Ａｈずつすなわち公称容量の２％ずつ増加する放電量の標準値である。したがって配列Ｖ_ｌｏｗ （ ｓ_ｌｏｗ ） ，Ｉ_ｌｏｗ （ ｓ_ｌｏｗ ） ，Ｖ_ｈｉ（ ｓ_ｈｉ） ，Ｉ_ｈｉ（ ｓ_ｈｉ） に格納されるデータは、各データに対応する放電量Ｑ_ｎ のばらつきが２パーセント以内したがって放電量Ｑ_ｎ が略等しいとみなせる放電状態におけるデータである。
【００３１】
Ｑ_ｎ がＱ_ｂ を越えると（ステップ１１３）、Ｑ_{ｌｏｗ−ａｖ}およびＱ_{ｈｉ−ａｖ} をそれぞれｓ_ｌｏｗ およびｓ_ｈｉで除し、あらためてＱ_{ｌｏｗ−ａｖ}およびＱ_{ｈｉ−ａｖ} とする（ステップ１１４）。すなわち電池状態ごとに、配列Ｖ_ｌｏｗ （ ｓ_ｌｏｗ ） ，Ｉ_ｌｏｗ （ ｓ_ｌｏｗ ） ，Ｖ_ｈｉ（ ｓ_ｈｉ） ，Ｉ_ｈｉ（ ｓ_ｈｉ） に格納されたデータの検出時点における放電量の平均値Ｑ_{ｌｏｗ−ａｖ}およびＱ_{ｈｉ−ａｖ} が求められる。
【００３２】
続く図４のステップ１１５以降の手順は回帰手段としての作動で、配列Ｖ_ｌｏｗ （ ｓ_ｌｏｗ ） ，Ｉ_ｌｏｗ （ ｓ_ｌｏｗ ） およびＶ_ｈｉ（ ｓ_ｈｉ） ，Ｉ_ｈｉ（ ｓ_ｈｉ） に格納された検出データＶ_ｎ ，Ｉ_ｎ を一次関数に回帰せしめて一次関数を得、基準の放電電流１（ＣＡ）における基準放電電圧Ｖ_ｃ を求めるようになっており、以下に詳説する。
【００３３】
まずｓ_ｌｏｗ を２０と比較し（ステップ１１５）、ｓ_ｌｏｗ が２０よりも大きければＱ_{ｌｏｗ−ａｖ}をＱ_ａｖとする（ステップ１１７）。次いでＶ_ｌｏｗ （ ｓ_ｌｏｗ ） ，Ｉ_ｌｏｗ （ ｓ_ｌｏｗ ） に格納されたＶ_ｎ ，Ｉ_ｎ すなわち普通放電状態として分類されたＶ_ｎ ，Ｉ_ｎ より最小自乗法を用いて一次関数たる回帰直線Ｖ＝ａ_ｌｏｗ ×Ｉ＋ｂ_ｌｏｗ （Ｖ：端子電圧、Ｉ：充放電電流）の傾きａ_ｌｏｗ 、切片ｂ_ｌｏｗ を算出する（ステップ１１８）。次いでこの回帰直線に基づいてＩ＝１（ＣＡ）における端子電圧Ｖを算出し、算出した端子電圧Ｖを基準放電電圧Ｖ_ｃ とする（ステップ１１９）。そしてステップ１２０に進む。なおステップ１１５でｓ_ｌｏｗ が２０よりも小さければ普通放電状態と分類された電池状態のＶ_ｎ ，Ｉ_ｎ による回帰演算は行わない。回帰直線の確度が充分ではないからである。この場合はｆｌａｇを１にして（ステップ１１６）、ステップ１２０に進む。
【００３４】
ステップ１２０ではｓ_ｈｉを２０と比較し、ｓ_ｈｉが２０よりも大きければＶ_ｈｉ（ ｓ_ｈｉ） ，Ｉ_ｈｉ（ ｓ_ｈｉ） に格納されたＶ_ｎ ，Ｉ_ｎ すなわち高放電状態と分類された電池状態のＶ_ｎ ，Ｉ_ｎ により、ステップ１１８，１１９と同様の手順により回帰直線Ｖ＝ａ_ｈｉ×Ｉ＋ｂ_ｈｉの傾きａ_ｈｉ、切片ｂ_ｈｉを算出し（ステップ１２２）、この回帰直線に基づいてＶ_ｃ−ｈｉ（Ｉ＝１（ＣＡ））を算出する（ステップ１２３）。なおステップ１２０でｓ_ｈｉが２０よりも小さければ上記ステップ１１６と同様の趣旨により高放電状態と分類された電池状態のＶ_ｎ ，Ｉ_ｎ による回帰演算は行わない。
【００３５】
Ｖ_ｃ−ｈｉ算出（ステップ１２３）に続くステップ１２４〜１２９は残量演算手段としての作動で、ステップ１２４ではｆｌａｇが０かどうかを判定する。ｆｌａｇが１の場合すなわち高放電状態と分類された電池状態のＶ_ｎ ，Ｉ_ｎ による回帰演算のみが行われた場合は、Ｑ_{ｈｉ−ａｖ} をＱ_ａｖとし（ステップ１２５）、Ｖ_ｃ−ｈｉに電圧補正値ΔＶを加算して、これを基準放電電圧Ｖ_ｃ とする（ステップ１２６）。放電電流が４ＣＡ以下の連続放電では、横軸をＳＯＣとした放電特性が電圧方向に平行移動したプロファイルを示す特徴がある。したがって普通放電状態における放電特性と高放電状態における放電特性間の電圧差ΔＶを電圧補正値ΔＶとしてＶ_ｃ を算出することにより、メモリ３ｂには一つの電池状態における放電特性のマップを記憶しておくだけで異なる電池状態に対応できる。なお電圧補正値ΔＶについては後述するステップ１２８において算出する。
【００３６】
ｆｌａｇが０の場合（ステップ１２４）すなわち普通放電状態と分類された電池状態のＶ_ｎ ，Ｉ_ｎ による回帰演算および高放電状態として分類されたＶ_ｎ ，Ｉ_ｎ による回帰演算が行われた場合は、ステップ１２７に進む。ステップ１２７，１２８は電圧差演算手段としての作動で、普通放電状態と分類された電池状態における平均放電量Ｑ_ａｖと高放電状態と分類された電池状態における平均放電量Ｑ_{ｈｉ−ａｖ} の差を１Ａｈと比較する（ステップ１２７）。Ｑ_ａｖとＱ_{ｈｉ−ａｖ} の差が１Ａｈよりも小さい場合はＱ_ａｖとＱ_{ｈｉ−ａｖ} とが略等しいと判断し、式（３）により基準放電電圧Ｖ_ｃ とＶ_ｃ−ｈｉの差を算出し、その電圧差をシフト量たる電圧補正値ΔＶとする（ステップ１２８）。ここで得られた電圧補正値ΔＶは以降の作動フローにおけるステップ１２６で用いられる。このように電圧補正値ΔＶを更新することにより電池１が経時劣化等により放電特性が変化しても、それに基準放電電圧が追随していくから電池残量ＳＯＣの精度が高く保たれる。
ΔＶ＝Ｖ_ｃ −Ｖ_ｃ−ｈｉ・・・・（３）
【００３７】
次いでステップ１２９に進む。なおステップ１２７でＱ_ａｖとＱ_{ｈｉ−ａｖ} の差が１Ａｈよりも大きい場合はステップ１２８は実行せずにステップ１２９に進む。
【００３８】
なおステップ１２０でｓ_ｈｉが２０に達していなければステップ１２１に進み、ｆｌａｇが０すなわち普通放電状態と分類された電池状態のＶ_ｎ ，Ｉ_ｎ による回帰演算のみが行われた場合はステップ１２９に進む。
【００３９】
しかして普通放電状態と分類された電池状態のＶ_ｎ ，Ｉ_ｎ による回帰演算と高放電状態と分類された電池状態のＶ_ｎ ，Ｉ_ｎ による回帰演算の少なくとも一方が行われた場合は、ステップ１２９で放電量補正値βを更新する。更新は現行のβにｋ×（Ｖ_ｍａｐ −Ｖ_ｃ ）を加算した値に更新する。ここでｋは定数である。Ｖ_ｍａｐ はメモリ３ｂに格納された、現在の電池表面温度Ｔ_ｎ におけるマップを検索して電池の残存量に対応する基準の放電電圧として読みだされるデータである。なお電池の残存量は現時点での放電量Ｑ_ｎ より求められる。
【００４０】
次いでステップ１３０に進む。なおステップ１２１でｆｌａｇが１の場合、すなわち普通放電状態と分類された電池状態のＶ_ｎ ，Ｉ_ｎ による回帰演算と高放電状態と分類された電池状態のＶ_ｎ ，Ｉ_ｎ による回帰演算のいずれも行われなかった場合もステップ１３０に進む。
【００４１】
ステップ１３０では基準放電量Ｑ_ｂ を２（Ａｈ）増加せしめ、ｆｌａｇ，配列Ｖ_ｌｏｗ （ ｓ_ｌｏｗ ） ，Ｉ_ｌｏｗ （ ｓ_ｌｏｗ ） ，Ｖ_ｈｉ（ ｓ_ｈｉ） ，Ｉ_ｈｉ（ ｓ_ｈｉ） ，ｓ_ｌｏｗ ，ｓ_ｈｉ，Ｑ_ａｖ，Ｑ_{ｌｏｗ−ａｖ}，Ｑ_{ｈｉ−ａｖ} の初期設定を行ってステップ１３２に進む。走行継続であれば再びステップ１０１（図２）に戻って以上の手順が繰り返される。このようにＮｉ系電池に適用しても所定時間（ｎ_ｅｎｄ ）内の充放電状態を示す評価値により電池状態が分類されて基準放電電圧が演算されるから精度よく電池残量が測定できる。しかも電池状態ごとに基準放電電圧Ｖ_ｃ が算出されるから測定の機会が失われることがない。走行終了であれば本作動フローも終了する。なお本作動フローが終了する場合、現行のＱ_ｎ ，β，ΔＶはメモリ３ｂに保持される。
【００４２】
本発明の電池残量計を従来の、予め記憶した放電特性（理想値）との比較により電池残量を検出する電池残量計と比較するため次の試験を行った。電池を満充電状態とした電気自動車を、端子電圧が放電終止電圧となるまで市街地を走行させ、その間の充放電電流、端子電圧、電池表面温度を検出してそのデータを０．１秒ごとにパーソナルコンピュータに記録した。次いで記録したデータを、実走行の場合と同様に本発明の電池残量計および従来の電池残量計のマイクロコンピュータに入力し、基準放電電流１Ｃ放電時の基準放電電圧を得た。
【００４３】
図６はその試験結果を示すもので、横軸は試験終了後に電池の放電量から算出した電池残量ＳＯＣである。縦軸は所定電流１Ｃ放電時の基準放電電圧である。図中、○は本発明の電池残量計の場合を示し、●は従来の電池残量計の場合を示す。なお実線は理想値を示している。図より本発明の電池残量計で得られた基準放電電圧は、電池残量によらず理想値との誤差が従来の電池残量計で得られた基準放電電圧に比して小さく、理想値とよく一致しており、予め記憶した放電特性（理想値）との比較により電池残量を検出する電池残量計において、本発明の電池残量計が極めて精度のよいものであることがわかる。
【００４４】
なお上記実施形態では、電池残量ＳＯＣを式（１）により算出したが、メモリ３ｂに格納した基準の放電特性から、走行中に算出された基準放電電圧に対応する電池残量を読み出すようにしてもよい。
【００４５】
電圧補正値ΔＶ、放電量補正値βはＣＰＵ３ａが満充電完了信号を受け取るとリセットするようにしたが、電池を充電する前、最後に設定された値を保持しておき、これを使用してもよい。
【００４６】
ステップ１１３を設けて２Ａｈ（公称容量の２％）放電ごとに回帰演算を実行したが、放電量の略等しいとみなせる範囲（例えば上記実施形態のごとく公称容量の２％）で、検出データが配列Ｖ_ｌｏｗ （ ｓ_ｌｏｗ ） ，Ｉ_ｌｏｗ （ ｓ_ｌｏｗ ） ，Ｖ_ｈｉ（ ｓ_ｈｉ） ，Ｉ_ｈｉ（ ｓ_ｈｉ） に回帰演算に必要な数（例えば２０）が格納され次第、回帰演算を実行するようにしてもよい。
【００４７】
基準放電電圧は所定放電電流における端子電圧としたが、所定の放電電力における端子電圧とし得る。また基準放電電圧を電圧補正値により補正することにより異なる電池状態に対応するようにしたが、電池状態ごとの基準の放電特性をメモリに記憶しておいてもよい。電圧補正値ΔＶは更新されていくようにしたが要求される精度によっては一定値としてもよい。
【００４８】
Ｖ_ｍａｐ を読みだすマップは、現在の電池表面温度Ｔ_ｎ のマップとしたが、電池表面温度の変動の大きさによっては所定時間内における平均温度のマップとするのがよい。またマップの数を間引きしてメモリに記憶されるデータ量を減らす場合は、相隣れる温度のマップを直線補間して所望の温度のマップとし得る。
【００４９】
所定時間ｎ_ｅｎｄ についても車両の諸元により設定する必要があり、実施形態で説明した試験により個々に設定するのが望ましい。
【００５０】
評価値Ｉ_ａｖによる電池状態の判定基準は普通放電状態と高放電状態の区別が明確なように車両の諸元により個々に設定する必要がある。なお検出データの回帰演算が多く行われるように普通放電状態および高放電状態と分類される頻度が高いのが望ましい。上記実施形態記載の基準の設定にあたっては、発明者らは実走行を模擬した数種のランダム充放電試験データを用いて分類ができることを確認した。また電池状態は普通放電状態と高放電状態の２種類としたがそれ以上としてもよい。
【００５１】
評価値Ｉ_ａｖは検出データの検出時からの経過時間に応じて直線的に減少する重み係数で重みを付けて平均したものとしたが、他の単調減少する重み係数で重みを付けて重み付き平均したものとし得る。この場合の重み係数は、例えば図５の電圧が収束するときのごときプロファイルを示す指数関数でもよい。また重み平均手段に代えて所定時間ｎ_ｅｎｄ 秒内の充放電電流Ｉ_ｎ を平均し評価値を充放電電流Ｉ_ｎ の平均値とする平均手段とし得る。この場合、上記実施形態のものに比し精度の点でやや劣るが評価値の計算時間を短縮することができる。
【図面の簡単な説明】
【図１】本発明の電池残量計のブロック図である。
【図２】本発明の電池残量計の作動を説明する第１のフローチャートである。
【図３】本発明の電池残量計の作動を説明する第２のフローチャートである。
【図４】本発明の電池残量計の作動を説明する第３のフローチャートである。
【図５】本発明の電池残量計の作動を説明するグラフである。
【図６】本発明の電池残量計を従来の一つの電池残量計と比較するグラフである。
【符号の説明】
１ 電池
３ａ マイクロコンピュータ（分類手段、重み平均手段、回帰手段、基準放電電圧演算手段、残量演算手段、平均放電量演算手段、電圧差演算手段）
３ｂ メモリ（第１の記憶手段、第２の記憶手段）
５ 電流検出器（電流検出手段）
６ 電圧検出器（電圧検出手段）[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a battery fuel gauge, and more particularly to a battery fuel gauge of an electric vehicle or the like.
[0002]
[Prior art]
The battery fuel gauge measures the amount of electricity remaining in the battery (hereinafter referred to as the battery remaining capacity). In an electric vehicle, an important device for knowing the travel distance of an electric vehicle, such as a fuel gauge in a gasoline vehicle. It is. A general method of such a battery fuel gauge stores a standard discharge characteristic in a memory as a map, detects a terminal voltage and a discharge current of the battery, and estimates a voltage under a predetermined discharge current from this. Thus, the remaining battery level is obtained based on the estimated voltage and the map. As a battery fuel gauge of this type, for example, Japanese Patent Laid-Open No. 6-34727 discloses a relationship between the terminal voltage and the discharge current and the remaining battery level when the discharge current is greater than a predetermined value and the discharge current is increasing. Therefore, the remaining battery level is calculated only when the battery is in a state where the discharge current is greater than or equal to the predetermined value and the discharge current is increasing. An improved battery capacity meter is disclosed.
[0003]
By the way, although the said battery remaining capacity meter is applied to the lead acid battery, in recent years, Ni system batteries, such as a Ni-MH battery whose discharge amount from a full charge is larger than a lead acid battery, have begun to be adopted as a power source for electric vehicles. It is conceivable to apply the battery remaining capacity meter to a Ni-based battery.
[0004]
[Problems to be solved by the invention]
However, when the remaining capacity meter described in Japanese Patent Laid-Open No. 6-34727 is used for Ni-based batteries, the charge / discharge history of the battery before the measurement changes variously, such as charging pause, high current discharge, low current discharge, regenerative charge, etc. Therefore, there is a problem that the measurement accuracy of the remaining battery level is lowered.
[0005]
Further, in the battery remaining capacity meter, since the battery state that can be measured is limited, there is a possibility that the battery remaining capacity may not be obtained when the battery capacity is large or when traveling on a highway at a constant speed.
[0006]
SUMMARY OF THE INVENTION Accordingly, an object of the present invention is to provide a battery fuel gauge that has good measurement accuracy of the remaining battery level even when applied to a Ni-based battery and that does not limit the measurable battery state.
[0007]
[Means for Solving the Problems]
The present invention is based on the knowledge of the inventors that the charge / discharge state several tens of seconds ago affects the current battery state in Ni-based batteries and the like, and the degree of the influence is greater as the previous charge / discharge state. In the invention according to item 1, the battery fuel gauge is stored in the storage means, the first storage means for storing the charge / discharge currents detected by the current detection means at a plurality of time points within a predetermined time set in advance. And a classifying unit that sequentially calculates an evaluation value indicating a charge / discharge state within the predetermined time by the charge / discharge current and classifies the current battery state into a plurality according to the magnitude of the evaluation value. And for each battery state classified by the classification means, the same as the second storage means for storing detection data comprising the charge / discharge current detected by the current detection means and the voltage detected by the voltage detection means Regression means for regressing a plurality of charge / discharge currents and voltages classified and stored by the second storage means in a discharge state that can be regarded as a discharge state into a linear function for each classification, and a reference in a reference discharge current from the linear function A reference discharge voltage calculating means for obtaining a discharge voltage; a remaining charge calculating means for calculating a battery remaining amount based on a reference discharge voltage and a reference discharge characteristic of the battery under a preset discharge power or discharge current; It has.
[0008]
Accordingly, since the reference discharge voltage is obtained by the regression unit and the reference discharge voltage calculation unit for each battery state classified by the evaluation value reflecting the past charge / discharge state, the influence of the past charge / discharge state is affected by the current battery. The reference discharge voltage obtained is accurate even when used in Ni-based batteries that reach the state. Since the remaining battery level is calculated based on the reference discharge voltage, the measurement accuracy of the remaining battery level is improved. Moreover, since the reference discharge voltage can be obtained for a plurality of battery states, the measurement opportunities are not limited.
[0009]
According to a second aspect of the present invention, the battery fuel gauge is a weight by which the classification means weights and averages the charging / discharging current within a predetermined time with a weighting factor that monotonously decreases in accordance with the elapsed time from the detection time. It comprises an averaging means. Since the degree of influence on the battery state at the end point of the predetermined time monotonously decreases according to the elapsed time from the detection time, the battery state can be accurately determined by setting the evaluation value as the weighted average value of the charge / discharge current. be able to. This weighting factor can be a weighting factor proportional to the time from the start point of the predetermined time to the time of detection of the charge / discharge current as in the invention described in claim 3.
[0010]
In the invention according to claim 4, the classification means comprises an averaging means for averaging the charge / discharge current within a predetermined time, and the evaluation value is made the average value of the charge / discharge current, thereby shortening the calculation time of the evaluation value. Can do.
[0011]
In the invention according to claim 5, the remaining amount calculating means sets the reference discharge characteristic for each battery state, so that the remaining amount can be accurately maintained even when the battery is continuously discharged in a biased discharge state, for example, high current discharge. A quantity is calculated.
[0012]
According to a sixth aspect of the present invention, the remaining amount calculating means stores only a reference discharge characteristic in one battery state, and a voltage direction shift between the reference discharge characteristic and a reference discharge characteristic in another battery state It is characterized by setting an amount. Since the reference discharge characteristics with different battery states are substantially the same when the profile is uniform and translated in the voltage direction, it is not necessary to store the reference discharge characteristics for each battery state, and the storage capacity can be reduced.
[0013]
In the invention according to claim 7, the reference discharge voltage calculation means calculates the discharge amount from full charge by integrating the charge / discharge current, and is used to calculate a linear function of the charge / discharge current and voltage in the regression means. The average discharge amount calculating means for calculating the average value of the discharge amount at the time of detection of the detection data, and comparing the average discharge amount calculated for each battery state, the average discharge amount in one battery state and the other battery state Are provided with voltage difference calculation means for calculating a difference between the reference discharge voltages of one battery state and another battery state, and the amount of shift is the difference between the reference discharge voltages. Even if the characteristics change due to deterioration over time or the like, the amount of shift in the voltage direction between the reference discharge characteristics is self-learned so that the measurement error of the remaining battery level can be suppressed.
[0014]
DETAILED DESCRIPTION OF THE INVENTION
FIG. 1 shows an overall block diagram of a battery fuel gauge of the present invention. The battery 1 is a battery in which, for example, 24 Ni-MH batteries having a nominal capacity of 100 (Ah) (in the following description, appropriately represented by the symbol Q for convenience) are connected in series in a total of 240 cells. Is connected to a load 2 such as an inverter for driving an electric vehicle motor. The detector unit 4 attached to the battery 1 includes a current detector 5 as current detection means, a voltage detector 6 as voltage detection means, and a temperature detector 7. The current detector 5 is provided in the middle of the power supply line connecting the battery 1 and the load 2, and detects the charge / discharge current of the battery 1. The voltage detector 6 is connected between both terminals of the battery and detects the terminal voltage of the battery 1. In the temperature detector 7, a thermocouple 7a is bonded to the surface of the case of the battery 1, and a temperature detection signal from the thermocouple 7a is input.
[0015]
A microcomputer 3 is provided with the detection signals of the charge / discharge current, terminal voltage, and battery surface temperature from the detector unit 4 as inputs. The microcomputer 3 includes a CPU 3a and a memory 3b, and calculates the remaining amount of the battery 1 based on charge / discharge current and the like. The memory 3b stores a map in which the standard discharge characteristics of the battery 1, that is, the remaining battery level and the standard discharge voltage have a one-to-one correspondence. Here, the map stored in the memory 3b is a battery that has the same specifications as the battery 1 mounted on the vehicle, and is continuously charged by a power command simulating urban driving such as 15-mode driving from full charge to full discharge. A discharge test was carried out and obtained from the remaining battery level and discharge voltage at that time. In addition, maps are stored for different battery surface temperatures by performing the continuous charge / discharge test by changing the test atmosphere temperature.
[0016]
A display device 8 is provided with the remaining amount of the battery 1 calculated by the microcomputer 3 as an input. The display device 8 is arranged in front of the driver together with a speedometer and the like, and displays the remaining amount of the battery 1 calculated by the microcomputer 3 to the driver.
[0017]
2, 3 and 4 show the processing flow of the microcomputer 3, and the operation of the battery fuel gauge will be described. When the full charge of the battery 1 is completed and a full charge completion signal is input to the CPU 3a from a not-shown charger, the value of the timer n in the CPU 3a is 0, the reference discharge amount Q _b Is set to 2 (Ah) and the discharge amount Q from full charge _n The discharge amount correction value β (Ah), the voltage correction value ΔV (V / cell), etc. are reset. Then, this flowchart starts when the ignition key of the vehicle is turned on.
[0018]
In step 101, the timer n is incremented by one. The timer n is a predetermined time n described later. _end The time until (second) is counted, and one count corresponds to one second.
[0019]
In step 102, the current detector 5, the voltage detector 6, and the temperature detector 7 detect the charging / discharging current, the terminal voltage, and the battery surface temperature of the battery 1 every 0.1 second, and output them to the CPU 3a. The terminal voltage of the battery 1 is converted into a value per cell in the CPU 3a and used for the calculation. The CPU 3a uses the average value I per second for these detected values. _n (CA), V _n (V / cell), T _n (° C) is calculated.
[0020]
In step 103, the discharge amount Q is calculated by integrating the charge / discharge current. _n Is calculated. That is, the discharge amount per second is I _n Since it is represented by × Q / 3600 (Ah), this is the discharge amount Q _n Discharge amount Q in addition to _n Update. Step 103 is also a part of operation as an average discharge amount calculation means. The remaining operation as the average discharge amount calculating means is executed in steps 111 (or 112) and 114 described later.
[0021]
Next, the percentage of the remaining amount with respect to the full charge amount of the battery 1 is calculated as a remaining battery SOC (%) by the equation (1). The calculated battery remaining amount SOC is output to the display device 8, and the display device 8 displays the remaining battery amount SOC (step 104).
SOC = (Q−β−Q _n ) / (Q-β) × 100 (%) (1)
[0022]
Then I _n (CA) is stored in the array I (n) in the memory 3b as the first storage means and temporarily stored (step 105). n is n _end And n is n _end If not, the process proceeds to step 132 in FIG. If traveling is continued (step 132), the process returns to step 101 in FIG. Therefore, timer n is n _end Steps 101 to 106 are repeated until the battery level SOC is reached, and the remaining battery charge SOC displayed on the display device 8 is updated every second. And timer n is n _end (Step 106), the memory 3b stores n in the array I (n), which is the first predetermined time after starting the device. _end I for seconds _n (CA) is temporarily stored. Thereafter, after steps 101 to 106 are executed in step 107 of FIG. 3, the process proceeds every second.
[0023]
Steps 107 to 110 in FIG. 3 are operations as classification means, and steps 107 to 109 are operations as weight average means. First, count variable t, evaluation value I _av Is reset (step 107). The count variable t is a predetermined time (n _end 1 count corresponds to 1 second. Next, the count variable t is incremented by 1 and I _av I (nt _p ) Evaluation value I by adding xσ _av Is updated (step 108). σ is a weighting coefficient expressed by the equation (2), and I (nt−t _p ) Elapsed time t from the time of detection _p Decreases monotonically depending on Where t _p = N _end -T, and σ is n _end It is proportional to the time t from the start point.
[0024]
[Expression 1]

[0025]
In step 109, t is changed to n _end And t is n _end If not, the process returns to step 108 and steps 108 to 109 are repeated. T is n _end The evaluation value I _av N goes back to the present _end Charge / discharge current I (nt) _p ) Is a weighted average value obtained by weighting and averaging with the elapsed time from the detection.
[0026]
n _end Is set by conducting an experiment in advance with respect to a battery having the same specifications as the battery 1 mounted on the vehicle. First, the battery is discharged at a current of 2 CA for 5 minutes or more, and then the discharge current is changed to 0.2 CA. Then, the time from when the discharge current is changed until the terminal voltage converges to a substantially constant value is measured. _end Set as. FIG. 5 shows the change over time of the charge / discharge current and the terminal voltage in such an experiment. It takes 60 seconds for the terminal voltage to converge after the current is changed from 2CA to 0.2CA. As described above, in the Ni-based battery, the inventors confirmed that the charge / discharge state several tens of seconds ago affects the current battery state, and the degree of the influence is larger as the previous charge / discharge state. The weighted average value of the charge / discharge current was used as an evaluation value for determining the battery state, and the present invention was completed.
[0027]
In step 110, the evaluation value I _av To determine the state of the battery 1. That is, 0.4 <I _av When <0.6, the battery state is determined to be a normal discharge state, and 0.9 <I _av When <1.1, it is determined that the discharge state is high.
[0028]
If the battery status is determined to be normal discharge or high discharge, V _n , I _n The detected data is stored in an array in the memory 3b as the second storage means and temporarily stored. Two types of arrays are prepared, and the detection data is distributed according to the classification result of the battery state. That is, in the normal discharge state, the process proceeds to step 111 and the count number s. _low Increase by one. And array V _low (S _low ) To V _n And the array I _low (S _low ) I _n Is stored. In the case of a high discharge state, the process proceeds to step 112 and the count number s _hi Increase by one. And array V _hi (S _hi ) To V _n And the array I _hi (S _hi ) I _n Is stored. In step 110, if the battery state is not determined to be a normal discharge state or a high discharge state, V _n , I _n Is not remembered.
[0029]
In step 111 or 112, the second half operation as the average discharge amount calculation means following step 103 is also performed. That is, the amount of discharge Q from full charge _n For normal discharge, Q _low-av (Step 111), and in the case of a high discharge state, Q _hi-av Add to. Q _n Q _low-av , Q _hi-av Is added for the purpose of averaging for each battery state later.
[0030]
Then, the process proceeds from step 111 or 112 to step 113. Note that if the battery state is not classified into either the normal discharge state or the high discharge state in step 110, the process proceeds to step 113. In step 113 Q _n The reference discharge amount Q _b Compare with Q _n Is Q _b If not, the routine proceeds to step 132 in FIG. 4 and if the running is continued, the routine returns to step 101 (FIG. 2) again. Therefore, discharge amount Q _n Is Q _b Evaluation value I every second until it exceeds _av The battery state is classified according to the size, and in the normal discharge state and the high discharge state, the detection data is arranged for each battery state. _low (S _low ), I _low (S _low ), V _hi (S _hi ), I _hi (S _hi ) Are stored sequentially. Reference discharge amount Q _b Is a standard value of the discharge amount that is increased by 2 Ah from the initial value of 2 Ah by 2 Ah, that is, by 2% of the nominal capacity, in step 130 described later. Thus the array V _low (S _low ), I _low (S _low ), V _hi (S _hi ), I _hi (S _hi ) Is stored in the discharge amount Q corresponding to each data. _n Variation within 2% _n Are data in a discharge state that can be regarded as substantially equal.
[0031]
Q _n Is Q _b Exceeds Q (step 113), Q _low-av And Q _hi-av Each _low And s _hi Divide by, and again Q _low-av And Q _hi-av (Step 114). That is, for each battery state, the array V _low (S _low ), I _low (S _low ), V _hi (S _hi ), I _hi (S _hi ) Average discharge amount Q at the time of detection of data stored in _low-av And Q _hi-av Is required.
[0032]
The procedure after step 115 in FIG. 4 is an operation as a regression means. _low (S _low ), I _low (S _low ) And V _hi (S _hi ), I _hi (S _hi ) Detection data V stored in _n , I _n To a linear function to obtain a linear function, and a reference discharge voltage V at a reference discharge current 1 (CA) _c Is described in detail below.
[0033]
First s _low Is compared to 20 (step 115) and s _low Q is greater than 20 _low-av Q _av (Step 117). Then V _low (S _low ), I _low (S _low V stored in) _n , I _n That is, V classified as a normal discharge state _n , I _n A regression line V = a which is a linear function using the least square method _low × I + b _low (V: terminal voltage, I: charge / discharge current) slope a _low , Intercept b _low Is calculated (step 118). Next, the terminal voltage V at I = 1 (CA) is calculated based on this regression line, and the calculated terminal voltage V is used as the reference discharge voltage V. _c (Step 119). Then, the process proceeds to step 120. In step 115, s _low Is less than 20, the battery state V classified as a normal discharge state _n , I _n The regression calculation by is not performed. This is because the accuracy of the regression line is not sufficient. In this case, the flag is set to 1 (step 116), and the process proceeds to step 120.
[0034]
In step 120, s _hi To 20 and s _hi If V is greater than 20, V _hi (S _hi ), I _hi (S _hi V stored in) _n , I _n That is, V of the battery state classified as a high discharge state _n , I _n Thus, the regression line V = a by the same procedure as steps 118 and 119. _hi × I + b _hi Slope a _hi , Intercept b _hi Is calculated (step 122), and V is calculated based on the regression line. _c-hi (I = 1 (CA)) is calculated (step 123). In step 120, s _hi Is less than 20, the V of the battery state classified as the high discharge state for the same purpose as step 116 above. _n , I _n The regression calculation by is not performed.
[0035]
V _c-hi Steps 124 to 129 following the calculation (step 123) are operations as remaining amount calculation means. In step 124, it is determined whether or not flag is zero. When the flag is 1, that is, the battery state V classified as the high discharge state _n , I _n When only regression calculation is performed by Q _hi-av Q _av (Step 125), V _c-hi Voltage correction value ΔV is added to the reference discharge voltage V _c (Step 126). In continuous discharge with a discharge current of 4 CA or less, there is a characteristic that the discharge characteristic with the horizontal axis as SOC shows a profile translated in the voltage direction. Therefore, the voltage difference ΔV between the discharge characteristics in the normal discharge state and the discharge characteristics in the high discharge state is defined as a voltage correction value ΔV. _c Thus, the memory 3b can cope with different battery states only by storing a map of discharge characteristics in one battery state. The voltage correction value ΔV is calculated in step 128 described later.
[0036]
When the flag is 0 (step 124), that is, the battery state V classified as the normal discharge state _n , I _n Regression by V and V classified as high discharge state _n , I _n When the regression calculation is performed, the process proceeds to step 127. Steps 127 and 128 are operations as voltage difference calculation means, and the average discharge amount Q in the battery state classified as the normal discharge state. _av And average discharge amount Q in battery states classified as high discharge states _hi-av Is compared with 1Ah (step 127). Q _av And Q _hi-av Q is less than 1Ah _av And Q _hi-av Are substantially equal to each other, and the reference discharge voltage V _c And V _c-hi And the voltage difference is set as a voltage correction value ΔV as a shift amount (step 128). The voltage correction value ΔV obtained here is used in step 126 in the subsequent operation flow. By updating the voltage correction value ΔV in this way, even if the discharge characteristics of the battery 1 change due to deterioration over time or the like, the reference discharge voltage follows the battery 1 so that the accuracy of the remaining battery charge SOC is kept high.
ΔV = V _c -V _c-hi .... (3)
[0037]
Next, the routine proceeds to step 129. In step 127, Q _av And Q _hi-av If the difference is larger than 1 Ah, step 128 is not executed and the routine proceeds to step 129.
[0038]
In step 120, s _hi If it has not reached 20, the process proceeds to step 121, where the flag is 0, that is, the V of the battery state classified as the normal discharge state. _n , I _n If only the regression calculation is performed, the process proceeds to step 129.
[0039]
Thus, the V of the battery state classified as the normal discharge state _n , I _n Of battery state classified as regression and high discharge state _n , I _n When at least one of the regression calculations is performed, the discharge amount correction value β is updated at step 129. Update the current β to k × (V _map -V _c ) Is added to the added value. Here, k is a constant. V _map Is the current battery surface temperature T stored in the memory 3b. _n Is a data read out as a reference discharge voltage corresponding to the remaining amount of the battery by searching the map in FIG. The remaining amount of the battery is the current discharge amount Q _n More demanded.
[0040]
Next, the routine proceeds to step 130. In addition, when flag is 1 in step 121, that is, V of the battery state classified as the normal discharge state. _n , I _n Of battery state classified as regression and high discharge state _n , I _n If neither of the regression calculations is performed, the process proceeds to step 130.
[0041]
In step 130, the reference discharge amount Q _b Is increased by 2 (Ah), flag, sequence V _low (S _low ), I _low (S _low ), V _hi (S _hi ), I _hi (S _hi ), S _low , S _hi , Q _av , Q _low-av , Q _hi-av The initial setting is performed, and the process proceeds to step 132. If the running is continued, the process returns to step 101 (FIG. 2) and the above procedure is repeated. Thus, even when applied to a Ni-based battery, a predetermined time (n _end Since the battery state is classified by the evaluation value indicating the charge / discharge state in () and the reference discharge voltage is calculated, the remaining battery level can be measured with high accuracy. Moreover, the reference discharge voltage V for each battery state _c Since the value is calculated, the opportunity for measurement is not lost. If the traveling is finished, this operation flow is also finished. When this operation flow ends, the current Q _n , Β, ΔV are held in the memory 3b.
[0042]
The following test was conducted to compare the battery fuel gauge of the present invention with a conventional battery fuel gauge that detects the remaining battery capacity by comparing with a previously stored discharge characteristic (ideal value). An electric vehicle with a fully charged battery is run in a city area until the terminal voltage reaches the end-of-discharge voltage, and the charge / discharge current, terminal voltage, and battery surface temperature are detected during that period, and the data is obtained every 0.1 seconds. Recorded on a personal computer. Next, the recorded data was input to the microcomputer of the battery fuel gauge of the present invention and the conventional battery fuel gauge in the same manner as in actual driving, and the reference discharge voltage at the time of discharging the reference discharge current 1C was obtained.
[0043]
FIG. 6 shows the test results. The horizontal axis represents the remaining battery charge SOC calculated from the battery discharge after the test. The vertical axis represents the reference discharge voltage when discharging at a predetermined current of 1C. In the figure, ◯ indicates the case of the battery fuel gauge of the present invention, and ● indicates the case of the conventional battery fuel gauge. The solid line represents the ideal value. From the figure, the reference discharge voltage obtained with the battery fuel gauge of the present invention is less than the reference discharge voltage obtained with the conventional battery fuel gauge, and the difference from the ideal value is small regardless of the battery remaining power. The battery fuel gauge of the present invention is very accurate in the battery fuel gauge that detects the remaining battery capacity by comparing with the discharge characteristic (ideal value) stored in advance. Understand.
[0044]
In the above embodiment, the battery remaining amount SOC is calculated by the equation (1). However, the battery remaining amount corresponding to the reference discharge voltage calculated during traveling is read from the reference discharge characteristics stored in the memory 3b. May be.
[0045]
The voltage correction value ΔV and the discharge amount correction value β are reset when the CPU 3a receives the full charge completion signal. However, before the battery is charged, the last set values are held and used. Also good.
[0046]
Step 113 is provided, and the regression calculation is performed for each discharge of 2 Ah (2% of the nominal capacity). V _low (S _low ), I _low (S _low ), V _hi (S _hi ), I _hi (S _hi ), The regression calculation may be executed as soon as the number necessary for the regression calculation (for example, 20) is stored.
[0047]
The reference discharge voltage is a terminal voltage at a predetermined discharge current, but may be a terminal voltage at a predetermined discharge power. Further, the reference discharge voltage is corrected by the voltage correction value to cope with different battery states. However, the reference discharge characteristics for each battery state may be stored in the memory. The voltage correction value ΔV is updated, but may be a constant value depending on the required accuracy.
[0048]
V _map Is the current battery surface temperature T _n However, depending on the magnitude of the fluctuation of the battery surface temperature, a map of the average temperature within a predetermined time may be used. When the number of maps is thinned to reduce the amount of data stored in the memory, adjacent temperature maps can be linearly interpolated to obtain a desired temperature map.
[0049]
Predetermined time n _end Also, it is necessary to set according to the specifications of the vehicle, and it is desirable to set individually by the test described in the embodiment.
[0050]
Evaluation value I _av It is necessary to individually set the criteria for determining the battery state according to the vehicle specifications so that the distinction between the normal discharge state and the high discharge state is clear. In addition, it is desirable that the frequency of classification into the normal discharge state and the high discharge state is high so that many regression operations of the detection data are performed. In setting the standards described in the above embodiments, the inventors have confirmed that classification can be performed using several types of random charge / discharge test data simulating actual driving. In addition, although there are two types of battery states, a normal discharge state and a high discharge state, it may be more than that.
[0051]
Evaluation value I _av Is weighted with a weighting factor that decreases linearly according to the elapsed time from detection of detection data, but is weighted with another monotonically decreasing weighting factor and weighted average. obtain. The weighting factor in this case may be an exponential function indicating a profile such as when the voltage in FIG. 5 converges. Also, instead of the weighted average means, a predetermined time n _end Charge / discharge current I in seconds I _n Is the charge / discharge current I _n It is possible to use an average means for obtaining an average value of In this case, the calculation time of the evaluation value can be shortened although the accuracy is slightly inferior to that of the above embodiment.
[Brief description of the drawings]
FIG. 1 is a block diagram of a battery fuel gauge of the present invention.
FIG. 2 is a first flowchart for explaining the operation of the battery fuel gauge of the present invention.
FIG. 3 is a second flowchart for explaining the operation of the battery fuel gauge of the present invention.
FIG. 4 is a third flowchart for explaining the operation of the battery fuel gauge of the present invention.
FIG. 5 is a graph illustrating the operation of the battery fuel gauge of the present invention.
FIG. 6 is a graph comparing the battery fuel gauge of the present invention with one conventional battery fuel gauge.
[Explanation of symbols]
1 battery
3a Microcomputer (classification means, weighted average means, regression means, reference discharge voltage calculation means, remaining amount calculation means, average discharge amount calculation means, voltage difference calculation means)
3b memory (first storage means, second storage means)
5 Current detector (current detection means)
6 Voltage detector (voltage detection means)

Claims (7)

Current detecting means for detecting charging / discharging current of the battery, voltage detecting means for detecting voltage between the terminals of the battery, and charging / discharging detected by the current detecting means at a plurality of time points within a predetermined time set in advance A first storage means for storing current; and an evaluation value indicating a charge / discharge state within the predetermined time based on the charge / discharge current stored in the storage means, and a current battery state determined by the magnitude of the evaluation value A first classifying unit configured to classify the data into a plurality of classification units, and to store detection data including a charge / discharge current detected by the current detection unit and a voltage detected by the voltage detection unit for each battery state classified by the classification unit; Two storage means, a regression means for regressing a plurality of charge / discharge currents and voltages classified and stored by the second storage means in a discharge state that can be regarded as the same discharge state into a linear function for each classification, and the regression By means A reference discharge power or a reference discharge current is calculated from a linear function, a reference discharge voltage calculation means using this as a reference discharge voltage, a reference discharge voltage calculated by the reference discharge voltage calculation means, and a reference discharge power or A battery fuel gauge comprising: a remaining capacity calculating means for calculating a remaining battery capacity based on a reference discharge characteristic of the battery under a reference discharge current. 2. The battery fuel gauge according to claim 1, wherein the classification means weights and averages the charge / discharge current within the predetermined time by weighting with a weighting factor that monotonously decreases in accordance with the elapsed time from the detection time. A battery fuel gauge with the evaluation value as a weighted average value of charge / discharge current. 3. The battery fuel gauge according to claim 2, wherein the classification means uses the weighting factor as a weighting factor proportional to a time from the start point of a predetermined time to the time when the charge / discharge current is detected. 2. The battery fuel gauge according to claim 1, wherein the classification unit includes an averaging unit that averages charge / discharge currents within the predetermined time, and the evaluation value is an average value of charge / discharge currents. 5. The battery fuel gauge according to claim 1, wherein the remaining capacity calculator is configured to set the reference discharge characteristics for each battery state. 6. 6. The battery fuel gauge according to claim 5, wherein the remaining amount calculating means stores reference discharge characteristics in one battery state among reference discharge characteristics having different battery states, and the reference discharge characteristics and others. A battery fuel gauge in which the amount of shift in the voltage direction between the reference discharge characteristics in the battery state is set. 7. The battery fuel gauge according to claim 6, wherein the remaining amount calculating means calculates a discharge amount from full charge by integrating charge / discharge currents, and is used for calculating a linear function of the charge / discharge current and voltage in the regression means. The average discharge amount calculating means for calculating the average value of the discharge amount at the time of detection of the detected detection data, and comparing the average discharge amount calculated for each battery state to discharge in one battery state and another battery state Voltage difference calculating means for calculating a difference between reference discharge voltages of one battery state and another battery state when the amounts are substantially equal, and the shift amount of the reference discharge voltage calculated by the voltage difference calculating means. Battery fuel gauge with difference.

Images