從再(zai)生能(neng)(neng)源(yuan)（如光電(dian)(dian)池(chi)面(mian)板或風力發電(dian)(dian)機）接收能(neng)(neng)量(liang)(liang)(liang)的(de)(de)(de)系統一般(ban)會將能(neng)(neng)量(liang)(liang)(liang)保存在可充電(dian)(dian)電(dian)(dian)池(chi)中,再(zai)提(ti)供給負載。通常情況下,兩個(ge)過(guo)程是同時發生的(de)(de)(de)。對電(dian)(dian)池(chi)剩(sheng)余電(dian)(dian)量(liang)(liang)(liang)的(de)(de)(de)周期性評估可以保證延長電(dian)(dian)池(chi)的(de)(de)(de)性能(neng)(neng)和壽命,同時控制電(dian)(dian)池(chi)供給負載的(de)(de)(de)電(dian)(dian)流。電(dian)(dian)池(chi)的(de)(de)(de)剩(sheng)余電(dian)(dian)量(liang)(liang)(liang)包括前次計(ji)算的(de)(de)(de)充電(dian)(dian)量(liang)(liang)(liang),加上新增電(dian)(dian)量(liang)(liang)(liang),或者減去(qu)消耗(hao)的(de)(de)(de)電(dian)(dian)量(liang)(liang)(liang)。根(gen)據(ju)Coulomb定律,可以用下式計(ji)算出累(lei)積充電(dian)(dian)量(liang)(liang)(liang)：

　　其中QACC是電池最新的(de)累積電量(liang),i表示在時(shi)間(jian)(jian)間(jian)(jian)隔Δt期間(jian)(jian)累積的(de)電流(liu)量(liang)。

　　在不連續(xu)的情況下,該式變(bian)成(cheng)

　　其中n表示在時(shi)間(jian)間(jian)隔Δt內電流Ik的(de)(de)測量次數。雖然Δt值可以(yi)任意選擇,但(dan)選等(deng)于一小時(shi)的(de)(de)值比較方便,因為電池制造(zao)商標定容(rong)量的(de)(de)單位是安培小時(shi)。

　　為了簡(jian)化微控(kong)制器的硬件,降(jiang)低(di)算術運算所(suo)需內存數量,可以將1小時劃分(fen)為128個測量周期,并用(yong)(yong)(yong)寄(ji)存器移位方法(fa)完成公(gong)式(shi)中所(suo)需的分(fen)割。可以從32個電(dian)(dian)(dian)流(liu)采(cai)樣(yang)(yang)取平均值作為每次(ci)充電(dian)(dian)(dian)測量值,采(cai)樣(yang)(yang)值經微處理器內部ADC轉(zhuan)換(huan)。一個ADC的輸入通(tong)道用(yong)(yong)(yong)于轉(zhuan)換(huan)充電(dian)(dian)(dian)電(dian)(dian)(dian)流(liu),另一個ADC用(yong)(yong)(yong)于轉(zhuan)換(huan)放(fang)電(dian)(dian)(dian)電(dian)(dian)(dian)流(liu)。因此,剩余電(dian)(dian)(dian)池充電(dian)(dian)(dian)量的公(gong)式(shi)就簡(jian)化為 QREM=QPREV±QACC,其中QREM 是(shi)剩余電(dian)(dian)(dian)池充電(dian)(dian)(dian)量,QPREV是(shi)前次(ci)計算的充電(dian)(dian)(dian)量,加號表(biao)明(ming)是(shi)凈充電(dian)(dian)(dian),而減號則(ze)表(biao)明(ming)是(shi)凈放(fang)電(dian)(dian)(dian)。

　　如圖(tu)1所示(shi),電(dian)(dian)(dian)(dian)路(lu)(lu)包括一個8腳的(de)飛思卡(ka)爾(Freescale)公司低成本MC68HC908QT2微控制器(qi)(qi)IC3。電(dian)(dian)(dian)(dian)流(liu)采樣(yang)電(dian)(dian)(dian)(dian)阻R1兩(liang)端(duan)的(de)電(dian)(dian)(dian)(dian)壓(ya)會(hui)根據電(dian)(dian)(dian)(dian)池(chi)充電(dian)(dian)(dian)(dian)還是放電(dian)(dian)(dian)(dian)而(er)(er)轉(zhuan)換極性。IC2A和IC2B分別(bie)接成相(xiang)(xiang)同(tong)增益的(de)非反(fan)相(xiang)(xiang)和反(fan)相(xiang)(xiang)放大(da)器(qi)(qi),用于檢測R1兩(liang)端(duan)的(de)電(dian)(dian)(dian)(dian)壓(ya)。非反(fan)相(xiang)(xiang)放大(da)器(qi)(qi)IC2A只響應充電(dian)(dian)(dian)(dian)電(dian)(dian)(dian)(dian)流(liu)產(chan)生的(de)正向電(dian)(dian)(dian)(dian)壓(ya),而(er)(er)對放電(dian)(dian)(dian)(dian)電(dian)(dian)(dian)(dian)流(liu)產(chan)生的(de)負(fu)輸(shu)(shu)入(ru)電(dian)(dian)(dian)(dian)壓(ya)則(ze)提(ti)供(gong)零(ling)輸(shu)(shu)出。反(fan)相(xiang)(xiang)放大(da)器(qi)(qi)IC2B則(ze)只響應負(fu)輸(shu)(shu)入(ru),而(er)(er)對正充電(dian)(dian)(dian)(dian)電(dian)(dian)(dian)(dian)流(liu)提(ti)供(gong)0V。兩(liang)個運放的(de)輸(shu)(shu)出都是正的(de),范圍從0 V至(zhi)約5V,從而(er)(er)簡化了與ADC多路(lu)(lu)輸(shu)(shu)入(ru)的(de)接口設計。IC2采用德州儀(yi)器(qi)(qi)(Texas Instruments)公司的(de)TLC277,它的(de)優點(dian)是占用印制電(dian)(dian)(dian)(dian)路(lu)(lu)板面積小,并有(you)低的(de)輸(shu)(shu)入(ru)失(shi)調電(dian)(dian)(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(de)值和放大(da)器增(zeng)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,必須修改電池最大可充能量(liang)值(zhi),該值(zhi)保(bao)存(cun)在一(yi)個(ge)專(zhuan)用的硬件寄存(cun)器內。