從再(zai)(zai)生能(neng)源（如(ru)光電(dian)(dian)(dian)池(chi)面板或(huo)風力發(fa)電(dian)(dian)(dian)機）接收能(neng)量(liang)(liang)(liang)的(de)系(xi)統一般會將(jiang)能(neng)量(liang)(liang)(liang)保(bao)存在(zai)可(ke)充(chong)電(dian)(dian)(dian)電(dian)(dian)(dian)池(chi)中,再(zai)(zai)提(ti)供給負載(zai)。通(tong)常情況下(xia),兩個(ge)過程是同時(shi)發(fa)生的(de)。對電(dian)(dian)(dian)池(chi)剩余(yu)電(dian)(dian)(dian)量(liang)(liang)(liang)的(de)周期(qi)性(xing)評(ping)估可(ke)以保(bao)證延長電(dian)(dian)(dian)池(chi)的(de)性(xing)能(neng)和壽命,同時(shi)控制(zhi)電(dian)(dian)(dian)池(chi)供給負載(zai)的(de)電(dian)(dian)(dian)流。電(dian)(dian)(dian)池(chi)的(de)剩余(yu)電(dian)(dian)(dian)量(liang)(liang)(liang)包括前次計(ji)算(suan)的(de)充(chong)電(dian)(dian)(dian)量(liang)(liang)(liang),加上新(xin)增(zeng)電(dian)(dian)(dian)量(liang)(liang)(liang),或(huo)者(zhe)減去(qu)消耗的(de)電(dian)(dian)(dian)量(liang)(liang)(liang)。根(gen)據Coulomb定律,可(ke)以用下(xia)式(shi)計(ji)算(suan)出(chu)累積充(chong)電(dian)(dian)(dian)量(liang)(liang)(liang)：

　　其中QACC是(shi)電(dian)池最新的(de)累(lei)積電(dian)量(liang),i表示在時間(jian)間(jian)隔Δt期間(jian)累(lei)積的(de)電(dian)流量(liang)。

　　在不(bu)連續的情況下(xia),該式變成

　　其(qi)中n表示在時間間隔Δt內(nei)電(dian)流Ik的(de)測量(liang)次數。雖然(ran)Δt值可以任意選擇,但選等于一小時的(de)值比較方便,因為電(dian)池制造商標定容量(liang)的(de)單(dan)位是安培小時。

　　為(wei)了簡化微控制器(qi)(qi)的硬件,降低算術運(yun)算所需(xu)(xu)內存數量(liang)(liang),可(ke)以(yi)將1小時劃分為(wei)128個測量(liang)(liang)周期(qi),并用寄(ji)存器(qi)(qi)移位(wei)方(fang)法完(wan)成公(gong)式(shi)中(zhong)(zhong)所需(xu)(xu)的分割。可(ke)以(yi)從(cong)32個電(dian)流采樣取平均值作為(wei)每次(ci)充(chong)電(dian)測量(liang)(liang)值,采樣值經微處理器(qi)(qi)內部ADC轉換(huan)。一個ADC的輸入(ru)通道用于轉換(huan)充(chong)電(dian)電(dian)流,另一個ADC用于轉換(huan)放(fang)電(dian)電(dian)流。因(yin)此,剩(sheng)余電(dian)池充(chong)電(dian)量(liang)(liang)的公(gong)式(shi)就簡化為(wei) QREM=QPREV±QACC,其中(zhong)(zhong)QREM 是剩(sheng)余電(dian)池充(chong)電(dian)量(liang)(liang),QPREV是前次(ci)計算的充(chong)電(dian)量(liang)(liang),加(jia)號(hao)表明是凈(jing)充(chong)電(dian),而減號(hao)則(ze)表明是凈(jing)放(fang)電(dian)。

　　如圖1所示,電(dian)(dian)(dian)(dian)路包括一個8腳的(de)(de)(de)(de)(de)飛思卡(ka)爾(er)(Freescale)公(gong)司低(di)成本(ben)MC68HC908QT2微(wei)控制(zhi)器(qi)IC3。電(dian)(dian)(dian)(dian)流采(cai)樣電(dian)(dian)(dian)(dian)阻R1兩(liang)(liang)(liang)端的(de)(de)(de)(de)(de)電(dian)(dian)(dian)(dian)壓會根據(ju)電(dian)(dian)(dian)(dian)池充(chong)電(dian)(dian)(dian)(dian)還是放電(dian)(dian)(dian)(dian)而轉換極(ji)性。IC2A和IC2B分別接成相(xiang)同增益的(de)(de)(de)(de)(de)非反(fan)(fan)相(xiang)和反(fan)(fan)相(xiang)放大器(qi),用于(yu)檢測R1兩(liang)(liang)(liang)端的(de)(de)(de)(de)(de)電(dian)(dian)(dian)(dian)壓。非反(fan)(fan)相(xiang)放大器(qi)IC2A只(zhi)響應充(chong)電(dian)(dian)(dian)(dian)電(dian)(dian)(dian)(dian)流產(chan)生的(de)(de)(de)(de)(de)正向(xiang)電(dian)(dian)(dian)(dian)壓,而對放電(dian)(dian)(dian)(dian)電(dian)(dian)(dian)(dian)流產(chan)生的(de)(de)(de)(de)(de)負輸(shu)(shu)(shu)入電(dian)(dian)(dian)(dian)壓則提供零輸(shu)(shu)(shu)出。反(fan)(fan)相(xiang)放大器(qi)IC2B則只(zhi)響應負輸(shu)(shu)(shu)入,而對正充(chong)電(dian)(dian)(dian)(dian)電(dian)(dian)(dian)(dian)流提供0V。兩(liang)(liang)(liang)個運放的(de)(de)(de)(de)(de)輸(shu)(shu)(shu)出都是正的(de)(de)(de)(de)(de),范圍從(cong)0 V至約5V,從(cong)而簡(jian)化了(le)與ADC多路輸(shu)(shu)(shu)入的(de)(de)(de)(de)(de)接口(kou)設計。IC2采(cai)用德州(zhou)儀器(qi)(Texas Instruments)公(gong)司的(de)(de)(de)(de)(de)TLC277,它(ta)的(de)(de)(de)(de)(de)優(you)點是占用印制(zhi)電(dian)(dian)(dian)(dian)路板面積小,并有低(di)的(de)(de)(de)(de)(de)輸(shu)(shu)(shu)入失調電(dian)(dian)(dian)(dian)壓。

　　確定了最低、最高期望的充、放電電流后,就可以計算出檢測電阻R₁的(de)值和放大器(qi)增(zeng)益G,公式如下：

　　其中I_MAX是最大放電電流,V_IN(MAX)是最大ADC輸入。在本例中,最大充、放電電流均約為1A。

　　因此,對1A充電或放電電流和最大ADC輸入為5V時,可以選擇0.5Ω的R₁,增益為10或100。一旦計算出了電池的充電能力,就可以通過單線接口SIP、I²C、CAN（控制器局域網絡）或其它工業標準方法,將數據發送給主控處理器或其它目標（參考文獻1）。為使電池壽命最長,可以用微處理器的輸出來控制外部負載吸入的電流。

　　制造商一般交付充滿電的鉛酸電池,這是為了防止出現硫酸鉛沉淀問題,本設計假定一塊電池開始時處于滿充電狀態。如要將此電路用于鉛酸電池以外的其它化學性質電池,必須修改電池最(zui)大可充能量值,該值保存在一個專用的硬件寄存器(qi)內。