從再(zai)生能源（如光電(dian)(dian)(dian)(dian)(dian)(dian)(dian)池面板(ban)或(huo)風力發電(dian)(dian)(dian)(dian)(dian)(dian)(dian)機(ji)）接收能量(liang)的系統一般會(hui)將能量(liang)保(bao)存在(zai)可(ke)充(chong)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)池中,再(zai)提供給負(fu)載。通常情況下,兩(liang)個過程是同時發生的。對電(dian)(dian)(dian)(dian)(dian)(dian)(dian)池剩余電(dian)(dian)(dian)(dian)(dian)(dian)(dian)量(liang)的周(zhou)期性(xing)評估可(ke)以保(bao)證延長電(dian)(dian)(dian)(dian)(dian)(dian)(dian)池的性(xing)能和壽命,同時控制電(dian)(dian)(dian)(dian)(dian)(dian)(dian)池供給負(fu)載的電(dian)(dian)(dian)(dian)(dian)(dian)(dian)流。電(dian)(dian)(dian)(dian)(dian)(dian)(dian)池的剩余電(dian)(dian)(dian)(dian)(dian)(dian)(dian)量(liang)包括(kuo)前次計算(suan)(suan)的充(chong)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)量(liang),加上新增電(dian)(dian)(dian)(dian)(dian)(dian)(dian)量(liang),或(huo)者(zhe)減去消(xiao)耗的電(dian)(dian)(dian)(dian)(dian)(dian)(dian)量(liang)。根(gen)據Coulomb定律,可(ke)以用(yong)下式計算(suan)(suan)出累積充(chong)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)量(liang)：

　　其(qi)中QACC是電池最新的累積電量,i表示(shi)在時間間隔Δt期間累積的電流(liu)量。

　　在不連續(xu)的情況下,該式變成

　　其(qi)中n表(biao)示在時(shi)間(jian)間(jian)隔Δt內電流Ik的測量次數(shu)。雖然Δt值可以任意選擇,但(dan)選等于一小時(shi)的值比較方便(bian),因為(wei)電池(chi)制(zhi)造(zao)商標定容量的單位是安培小時(shi)。

　　為(wei)了(le)簡(jian)(jian)化微控制器的(de)硬(ying)件,降(jiang)低(di)算(suan)術運算(suan)所需內(nei)存數量(liang),可(ke)以(yi)將1小時劃分(fen)為(wei)128個(ge)(ge)(ge)測量(liang)周期(qi),并用(yong)寄存器移(yi)位方法(fa)完成公式(shi)中所需的(de)分(fen)割。可(ke)以(yi)從32個(ge)(ge)(ge)電(dian)(dian)流(liu)(liu)采樣取平(ping)均(jun)值作為(wei)每次充電(dian)(dian)測量(liang)值,采樣值經(jing)微處理器內(nei)部ADC轉換(huan)。一個(ge)(ge)(ge)ADC的(de)輸入(ru)通(tong)道用(yong)于轉換(huan)充電(dian)(dian)電(dian)(dian)流(liu)(liu),另一個(ge)(ge)(ge)ADC用(yong)于轉換(huan)放電(dian)(dian)電(dian)(dian)流(liu)(liu)。因此,剩余電(dian)(dian)池充電(dian)(dian)量(liang)的(de)公式(shi)就簡(jian)(jian)化為(wei) QREM=QPREV±QACC,其中QREM 是(shi)剩余電(dian)(dian)池充電(dian)(dian)量(liang),QPREV是(shi)前次計算(suan)的(de)充電(dian)(dian)量(liang),加號(hao)表(biao)明(ming)是(shi)凈充電(dian)(dian),而減號(hao)則表(biao)明(ming)是(shi)凈放電(dian)(dian)。

　　如圖1所(suo)示(shi),電(dian)(dian)路(lu)包括一個8腳的(de)飛思(si)卡爾(Freescale)公(gong)司低成本(ben)MC68HC908QT2微控制(zhi)器IC3。電(dian)(dian)流(liu)采(cai)樣電(dian)(dian)阻R1兩端的(de)電(dian)(dian)壓(ya)會根據電(dian)(dian)池充電(dian)(dian)還是放(fang)(fang)電(dian)(dian)而(er)轉換極性。IC2A和IC2B分(fen)別接(jie)(jie)成相(xiang)同(tong)增益(yi)的(de)非(fei)反(fan)相(xiang)和反(fan)相(xiang)放(fang)(fang)大(da)器,用于檢測R1兩端的(de)電(dian)(dian)壓(ya)。非(fei)反(fan)相(xiang)放(fang)(fang)大(da)器IC2A只響應充電(dian)(dian)電(dian)(dian)流(liu)產生(sheng)的(de)正向(xiang)電(dian)(dian)壓(ya),而(er)對(dui)放(fang)(fang)電(dian)(dian)電(dian)(dian)流(liu)產生(sheng)的(de)負輸入電(dian)(dian)壓(ya)則提供零輸出(chu)(chu)。反(fan)相(xiang)放(fang)(fang)大(da)器IC2B則只響應負輸入,而(er)對(dui)正充電(dian)(dian)電(dian)(dian)流(liu)提供0V。兩個運放(fang)(fang)的(de)輸出(chu)(chu)都是正的(de),范圍從(cong)(cong)0 V至約5V,從(cong)(cong)而(er)簡化了與ADC多路(lu)輸入的(de)接(jie)(jie)口設(she)計(ji)。IC2采(cai)用德州(zhou)儀器(Texas Instruments)公(gong)司的(de)TLC277,它的(de)優(you)點(dian)是占用印(yin)制(zhi)電(dian)(dian)路(lu)板面(mian)積小,并有低的(de)輸入失調電(dian)(dian)壓(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(he)放(fang)大器(qi)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,必須修改電池最大可充(chong)能量值,該值保存在(zai)一(yi)個專用的硬(ying)件寄存器內。