從再生(sheng)能(neng)源（如光電(dian)(dian)(dian)(dian)(dian)池(chi)(chi)面板(ban)或(huo)風(feng)力發電(dian)(dian)(dian)(dian)(dian)機）接收能(neng)量(liang)(liang)的(de)(de)系(xi)統(tong)一般會將能(neng)量(liang)(liang)保存在可充電(dian)(dian)(dian)(dian)(dian)電(dian)(dian)(dian)(dian)(dian)池(chi)(chi)中,再提供(gong)給負(fu)載(zai)。通常(chang)情況下(xia),兩個過程(cheng)是(shi)同時發生(sheng)的(de)(de)。對電(dian)(dian)(dian)(dian)(dian)池(chi)(chi)剩余電(dian)(dian)(dian)(dian)(dian)量(liang)(liang)的(de)(de)周期性(xing)評估可以保證延(yan)長電(dian)(dian)(dian)(dian)(dian)池(chi)(chi)的(de)(de)性(xing)能(neng)和(he)壽命(ming),同時控制電(dian)(dian)(dian)(dian)(dian)池(chi)(chi)供(gong)給負(fu)載(zai)的(de)(de)電(dian)(dian)(dian)(dian)(dian)流。電(dian)(dian)(dian)(dian)(dian)池(chi)(chi)的(de)(de)剩余電(dian)(dian)(dian)(dian)(dian)量(liang)(liang)包(bao)括前次計(ji)算的(de)(de)充電(dian)(dian)(dian)(dian)(dian)量(liang)(liang),加上新(xin)增電(dian)(dian)(dian)(dian)(dian)量(liang)(liang),或(huo)者減去(qu)消耗的(de)(de)電(dian)(dian)(dian)(dian)(dian)量(liang)(liang)。根據(ju)Coulomb定律,可以用下(xia)式計(ji)算出累積充電(dian)(dian)(dian)(dian)(dian)量(liang)(liang)：

　　其中QACC是電(dian)池最新的累積(ji)電(dian)量(liang),i表示在時間(jian)(jian)間(jian)(jian)隔Δt期(qi)間(jian)(jian)累積(ji)的電(dian)流量(liang)。

　　在不(bu)連續的情況下,該式(shi)變成

　　其中n表(biao)示在時(shi)間間隔(ge)Δt內電流Ik的(de)測(ce)量(liang)次數(shu)。雖然Δt值可以任意(yi)選(xuan)擇,但選(xuan)等于一小時(shi)的(de)值比較方便,因為電池(chi)制造商(shang)標定容量(liang)的(de)單(dan)位(wei)是安培(pei)小時(shi)。

　　為了(le)簡(jian)化(hua)微控制(zhi)器(qi)的(de)(de)(de)(de)硬件(jian),降低算(suan)(suan)術運算(suan)(suan)所(suo)需內(nei)存(cun)數(shu)量(liang)(liang),可以(yi)將1小時(shi)劃分(fen)為128個(ge)測量(liang)(liang)周期(qi),并用寄存(cun)器(qi)移位方(fang)法完成公(gong)式(shi)中所(suo)需的(de)(de)(de)(de)分(fen)割。可以(yi)從32個(ge)電(dian)流采樣(yang)取平均(jun)值(zhi)(zhi)作為每(mei)次充(chong)(chong)(chong)電(dian)測量(liang)(liang)值(zhi)(zhi),采樣(yang)值(zhi)(zhi)經(jing)微處理器(qi)內(nei)部(bu)ADC轉(zhuan)換。一個(ge)ADC的(de)(de)(de)(de)輸入通道用于(yu)(yu)轉(zhuan)換充(chong)(chong)(chong)電(dian)電(dian)流,另(ling)一個(ge)ADC用于(yu)(yu)轉(zhuan)換放(fang)電(dian)電(dian)流。因此(ci),剩(sheng)余(yu)電(dian)池(chi)充(chong)(chong)(chong)電(dian)量(liang)(liang)的(de)(de)(de)(de)公(gong)式(shi)就簡(jian)化(hua)為 QREM=QPREV±QACC,其中QREM 是剩(sheng)余(yu)電(dian)池(chi)充(chong)(chong)(chong)電(dian)量(liang)(liang),QPREV是前次計算(suan)(suan)的(de)(de)(de)(de)充(chong)(chong)(chong)電(dian)量(liang)(liang),加號表(biao)明(ming)是凈(jing)充(chong)(chong)(chong)電(dian),而減號則表(biao)明(ming)是凈(jing)放(fang)電(dian)。

　　如圖1所示(shi),電(dian)(dian)(dian)路(lu)包括(kuo)一個(ge)8腳的(de)飛思卡爾(Freescale)公(gong)(gong)司低成本MC68HC908QT2微控制器(qi)IC3。電(dian)(dian)(dian)流(liu)采樣電(dian)(dian)(dian)阻R1兩(liang)端(duan)的(de)電(dian)(dian)(dian)壓(ya)(ya)會根據電(dian)(dian)(dian)池(chi)充(chong)(chong)電(dian)(dian)(dian)還是(shi)(shi)放(fang)(fang)電(dian)(dian)(dian)而(er)轉(zhuan)換(huan)極性(xing)。IC2A和(he)(he)IC2B分別(bie)接(jie)成相(xiang)同增益(yi)的(de)非反相(xiang)和(he)(he)反相(xiang)放(fang)(fang)大器(qi),用于檢測R1兩(liang)端(duan)的(de)電(dian)(dian)(dian)壓(ya)(ya)。非反相(xiang)放(fang)(fang)大器(qi)IC2A只響(xiang)應(ying)充(chong)(chong)電(dian)(dian)(dian)電(dian)(dian)(dian)流(liu)產生(sheng)的(de)正向電(dian)(dian)(dian)壓(ya)(ya),而(er)對(dui)放(fang)(fang)電(dian)(dian)(dian)電(dian)(dian)(dian)流(liu)產生(sheng)的(de)負輸(shu)入(ru)電(dian)(dian)(dian)壓(ya)(ya)則提供零輸(shu)出。反相(xiang)放(fang)(fang)大器(qi)IC2B則只響(xiang)應(ying)負輸(shu)入(ru),而(er)對(dui)正充(chong)(chong)電(dian)(dian)(dian)電(dian)(dian)(dian)流(liu)提供0V。兩(liang)個(ge)運放(fang)(fang)的(de)輸(shu)出都是(shi)(shi)正的(de),范圍(wei)從(cong)0 V至約5V,從(cong)而(er)簡化了與ADC多(duo)路(lu)輸(shu)入(ru)的(de)接(jie)口設計。IC2采用德州(zhou)儀器(qi)(Texas Instruments)公(gong)(gong)司的(de)TLC277,它的(de)優點是(shi)(shi)占用印制電(dian)(dian)(dian)路(lu)板(ban)面積小,并有低的(de)輸(shu)入(ru)失(shi)調電(dian)(dian)(dian)壓(ya)(ya)。

　　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(zhi)和放大器增益G,公式如(ru)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(da)可充能量(liang)值,該值保存在一個專用的硬件寄存器(qi)內。