從再(zai)(zai)生(sheng)能(neng)源（如光電(dian)(dian)(dian)池(chi)面板或(huo)風力發電(dian)(dian)(dian)機）接收能(neng)量的(de)(de)(de)(de)系統一般(ban)會將能(neng)量保(bao)存在可充電(dian)(dian)(dian)電(dian)(dian)(dian)池(chi)中,再(zai)(zai)提(ti)供給(gei)負載。通常情況下(xia),兩個(ge)過程是(shi)同時發生(sheng)的(de)(de)(de)(de)。對電(dian)(dian)(dian)池(chi)剩余(yu)電(dian)(dian)(dian)量的(de)(de)(de)(de)周期性評估可以保(bao)證(zheng)延長(chang)電(dian)(dian)(dian)池(chi)的(de)(de)(de)(de)性能(neng)和壽命,同時控(kong)制電(dian)(dian)(dian)池(chi)供給(gei)負載的(de)(de)(de)(de)電(dian)(dian)(dian)流。電(dian)(dian)(dian)池(chi)的(de)(de)(de)(de)剩余(yu)電(dian)(dian)(dian)量包括前次計(ji)算的(de)(de)(de)(de)充電(dian)(dian)(dian)量,加上新增電(dian)(dian)(dian)量,或(huo)者減去消耗的(de)(de)(de)(de)電(dian)(dian)(dian)量。根(gen)據Coulomb定律,可以用下(xia)式計(ji)算出累積充電(dian)(dian)(dian)量：

　　其(qi)中(zhong)QACC是電池最新(xin)的(de)累(lei)積電量,i表示在時(shi)間(jian)(jian)間(jian)(jian)隔Δt期(qi)間(jian)(jian)累(lei)積的(de)電流量。

　　在不連續的(de)情(qing)況下(xia),該(gai)式變(bian)成

　　其(qi)中n表示在時(shi)(shi)間間隔(ge)Δt內電(dian)流Ik的(de)(de)測量次數。雖然Δt值(zhi)可(ke)以任意選(xuan)擇(ze),但選(xuan)等于一小時(shi)(shi)的(de)(de)值(zhi)比較方(fang)便,因為電(dian)池制造商標定容量的(de)(de)單位是(shi)安培小時(shi)(shi)。

　　為了簡(jian)化微控制器(qi)的(de)硬件,降(jiang)低算(suan)術運算(suan)所(suo)需內存(cun)數量,可以將1小時劃(hua)分為128個(ge)測量周期,并用(yong)(yong)寄存(cun)器(qi)移位方法完成(cheng)公式(shi)中(zhong)所(suo)需的(de)分割(ge)。可以從32個(ge)電(dian)(dian)流(liu)(liu)采(cai)(cai)樣取平均(jun)值(zhi)作(zuo)為每次(ci)充電(dian)(dian)測量值(zhi),采(cai)(cai)樣值(zhi)經(jing)微處理器(qi)內部ADC轉換(huan)。一個(ge)ADC的(de)輸入(ru)通(tong)道用(yong)(yong)于轉換(huan)充電(dian)(dian)電(dian)(dian)流(liu)(liu),另一個(ge)ADC用(yong)(yong)于轉換(huan)放電(dian)(dian)電(dian)(dian)流(liu)(liu)。因此,剩(sheng)余電(dian)(dian)池(chi)充電(dian)(dian)量的(de)公式(shi)就簡(jian)化為 QREM=QPREV±QACC,其中(zhong)QREM 是(shi)剩(sheng)余電(dian)(dian)池(chi)充電(dian)(dian)量,QPREV是(shi)前次(ci)計算(suan)的(de)充電(dian)(dian)量,加號(hao)表明(ming)是(shi)凈(jing)充電(dian)(dian),而(er)減號(hao)則表明(ming)是(shi)凈(jing)放電(dian)(dian)。

　　如圖1所(suo)示,電(dian)(dian)(dian)(dian)路包括一個8腳的(de)(de)飛思卡爾(Freescale)公司低成本MC68HC908QT2微(wei)控制(zhi)(zhi)器IC3。電(dian)(dian)(dian)(dian)流(liu)(liu)采(cai)(cai)樣電(dian)(dian)(dian)(dian)阻(zu)R1兩(liang)端(duan)的(de)(de)電(dian)(dian)(dian)(dian)壓會根(gen)據電(dian)(dian)(dian)(dian)池充(chong)電(dian)(dian)(dian)(dian)還是放(fang)(fang)(fang)電(dian)(dian)(dian)(dian)而(er)(er)轉(zhuan)換極性。IC2A和(he)(he)IC2B分別接成相(xiang)同(tong)增(zeng)益(yi)的(de)(de)非(fei)反(fan)相(xiang)和(he)(he)反(fan)相(xiang)放(fang)(fang)(fang)大器,用于檢測R1兩(liang)端(duan)的(de)(de)電(dian)(dian)(dian)(dian)壓。非(fei)反(fan)相(xiang)放(fang)(fang)(fang)大器IC2A只響應(ying)充(chong)電(dian)(dian)(dian)(dian)電(dian)(dian)(dian)(dian)流(liu)(liu)產生(sheng)的(de)(de)正向電(dian)(dian)(dian)(dian)壓,而(er)(er)對放(fang)(fang)(fang)電(dian)(dian)(dian)(dian)電(dian)(dian)(dian)(dian)流(liu)(liu)產生(sheng)的(de)(de)負輸入(ru)(ru)電(dian)(dian)(dian)(dian)壓則(ze)提(ti)供零輸出。反(fan)相(xiang)放(fang)(fang)(fang)大器IC2B則(ze)只響應(ying)負輸入(ru)(ru),而(er)(er)對正充(chong)電(dian)(dian)(dian)(dian)電(dian)(dian)(dian)(dian)流(liu)(liu)提(ti)供0V。兩(liang)個運放(fang)(fang)(fang)的(de)(de)輸出都是正的(de)(de),范圍從0 V至約5V,從而(er)(er)簡化了與ADC多路輸入(ru)(ru)的(de)(de)接口設計。IC2采(cai)(cai)用德(de)州(zhou)儀器(Texas Instruments)公司的(de)(de)TLC277,它的(de)(de)優點(dian)是占用印制(zhi)(zhi)電(dian)(dian)(dian)(dian)路板面(mian)積小,并有低的(de)(de)輸入(ru)(ru)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的值和放大器增益G,公(gong)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,必須修改電池最大可充能量值,該(gai)值保(bao)存(cun)在(zai)一個專(zhuan)用(yong)的硬(ying)件(jian)寄存(cun)器內。