從(cong)再生能源（如(ru)光電(dian)(dian)(dian)池(chi)面板或風力發電(dian)(dian)(dian)機）接(jie)收能量的(de)系統一般會(hui)將能量保存在可充電(dian)(dian)(dian)電(dian)(dian)(dian)池(chi)中,再提供(gong)給負載。通常情況下,兩個過程是同(tong)時發生的(de)。對(dui)電(dian)(dian)(dian)池(chi)剩(sheng)余(yu)(yu)電(dian)(dian)(dian)量的(de)周期性(xing)評估可以(yi)保證延長電(dian)(dian)(dian)池(chi)的(de)性(xing)能和壽(shou)命(ming),同(tong)時控制電(dian)(dian)(dian)池(chi)供(gong)給負載的(de)電(dian)(dian)(dian)流(liu)。電(dian)(dian)(dian)池(chi)的(de)剩(sheng)余(yu)(yu)電(dian)(dian)(dian)量包括前次計(ji)算的(de)充電(dian)(dian)(dian)量,加上新(xin)增電(dian)(dian)(dian)量,或者減去消耗(hao)的(de)電(dian)(dian)(dian)量。根據Coulomb定律,可以(yi)用下式計(ji)算出累積充電(dian)(dian)(dian)量：

　　其(qi)中QACC是電(dian)(dian)池最新的累(lei)積電(dian)(dian)量,i表示在時間間隔(ge)Δt期(qi)間累(lei)積的電(dian)(dian)流量。

　　在不連續的情況(kuang)下(xia),該式變成(cheng)

　　其中(zhong)n表示在時間間隔Δt內(nei)電流Ik的(de)(de)測(ce)量次數。雖然(ran)Δt值可以任意(yi)選擇,但選等于一小時的(de)(de)值比較方便,因為電池(chi)制造商標定(ding)容量的(de)(de)單(dan)位是安培小時。

　　為了(le)簡化微控制器(qi)的(de)(de)硬件,降低算術運算所需內存(cun)數量(liang),可(ke)以(yi)(yi)將1小時劃分(fen)為128個測量(liang)周期,并用(yong)寄(ji)存(cun)器(qi)移位方法完成公式中所需的(de)(de)分(fen)割。可(ke)以(yi)(yi)從32個電(dian)(dian)(dian)(dian)流采樣(yang)取平均值作為每次(ci)充(chong)電(dian)(dian)(dian)(dian)測量(liang)值,采樣(yang)值經微處(chu)理器(qi)內部ADC轉換(huan)(huan)。一(yi)個ADC的(de)(de)輸入通(tong)道用(yong)于轉換(huan)(huan)充(chong)電(dian)(dian)(dian)(dian)電(dian)(dian)(dian)(dian)流,另一(yi)個ADC用(yong)于轉換(huan)(huan)放電(dian)(dian)(dian)(dian)電(dian)(dian)(dian)(dian)流。因此,剩(sheng)余電(dian)(dian)(dian)(dian)池(chi)充(chong)電(dian)(dian)(dian)(dian)量(liang)的(de)(de)公式就簡化為 QREM=QPREV±QACC,其中QREM 是剩(sheng)余電(dian)(dian)(dian)(dian)池(chi)充(chong)電(dian)(dian)(dian)(dian)量(liang),QPREV是前次(ci)計算的(de)(de)充(chong)電(dian)(dian)(dian)(dian)量(liang),加號表明是凈充(chong)電(dian)(dian)(dian)(dian),而減號則表明是凈放電(dian)(dian)(dian)(dian)。

　　如圖1所示,電(dian)(dian)路(lu)包(bao)括一個8腳的(de)(de)(de)飛思卡爾(Freescale)公司低(di)成(cheng)本MC68HC908QT2微控制(zhi)器(qi)(qi)IC3。電(dian)(dian)流(liu)采樣電(dian)(dian)阻(zu)R1兩(liang)端(duan)的(de)(de)(de)電(dian)(dian)壓(ya)(ya)會根(gen)據(ju)電(dian)(dian)池充電(dian)(dian)還(huan)是(shi)放(fang)電(dian)(dian)而(er)轉(zhuan)換(huan)極性(xing)。IC2A和IC2B分別接成(cheng)相(xiang)(xiang)同增(zeng)益的(de)(de)(de)非(fei)反(fan)相(xiang)(xiang)和反(fan)相(xiang)(xiang)放(fang)大(da)器(qi)(qi),用于檢測R1兩(liang)端(duan)的(de)(de)(de)電(dian)(dian)壓(ya)(ya)。非(fei)反(fan)相(xiang)(xiang)放(fang)大(da)器(qi)(qi)IC2A只響應(ying)充電(dian)(dian)電(dian)(dian)流(liu)產生的(de)(de)(de)正向(xiang)電(dian)(dian)壓(ya)(ya),而(er)對放(fang)電(dian)(dian)電(dian)(dian)流(liu)產生的(de)(de)(de)負輸(shu)(shu)入電(dian)(dian)壓(ya)(ya)則(ze)提供零輸(shu)(shu)出。反(fan)相(xiang)(xiang)放(fang)大(da)器(qi)(qi)IC2B則(ze)只響應(ying)負輸(shu)(shu)入,而(er)對正充電(dian)(dian)電(dian)(dian)流(liu)提供0V。兩(liang)個運放(fang)的(de)(de)(de)輸(shu)(shu)出都是(shi)正的(de)(de)(de),范(fan)圍從(cong)0 V至約5V,從(cong)而(er)簡化了與ADC多(duo)路(lu)輸(shu)(shu)入的(de)(de)(de)接口(kou)設(she)計。IC2采用德州儀器(qi)(qi)(Texas Instruments)公司的(de)(de)(de)TLC277,它的(de)(de)(de)優點是(shi)占用印制(zhi)電(dian)(dian)路(lu)板(ban)面積(ji)小,并有低(di)的(de)(de)(de)輸(shu)(shu)入失調電(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的值和放(fang)大器增益(yi)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,必須修改電池最大(da)可(ke)充能(neng)量值,該(gai)值保存在一個(ge)專用的硬件寄存器內。