電池均衡是指對串聯電池包中不同的電池（或電(dian)(dian)(dian)(dian)(dian)(dian)池(chi)(chi)(chi)組(zu)）采(cai)用差(cha)分(fen)電(dian)(dian)(dian)(dian)(dian)(dian)流。串(chuan)聯電(dian)(dian)(dian)(dian)(dian)(dian)池(chi)(chi)(chi)包(bao)(bao)中(zhong)每個(ge)電(dian)(dian)(dian)(dian)(dian)(dian)池(chi)(chi)(chi)的(de)電(dian)(dian)(dian)(dian)(dian)(dian)流通常是一(yi)樣的(de)，因此(ci)必須給電(dian)(dian)(dian)(dian)(dian)(dian)池(chi)(chi)(chi)包(bao)(bao)增加額外的(de)元件和(he)電(dian)(dian)(dian)(dian)(dian)(dian)路來實現(xian)電(dian)(dian)(dian)(dian)(dian)(dian)池(chi)(chi)(chi)均(jun)衡(heng)。只有當電(dian)(dian)(dian)(dian)(dian)(dian)池(chi)(chi)(chi)包(bao)(bao)中(zhong)的(de)電(dian)(dian)(dian)(dian)(dian)(dian)池(chi)(chi)(chi)是串(chuan)聯的(de)，同時串(chuan)聯電(dian)(dian)(dian)(dian)(dian)(dian)池(chi)(chi)(chi)等于(yu)或大于(yu)三級時才會考慮電(dian)(dian)(dian)(dian)(dian)(dian)池(chi)(chi)(chi)均(jun)衡(heng)問題。

當電(dian)池包中所有電(dian)池都(dou)滿足下面兩個條件時(shi)，便(bian)實現了(le)電(dian)池均衡：

1.如果所(suo)(suo)有電(dian)(dian)(dian)(dian)(dian)池的(de)(de)容(rong)(rong)量相同(tong)，那么當(dang)(dang)它(ta)們的(de)(de)相對(dui)(dui)充(chong)電(dian)(dian)(dian)(dian)(dian)狀態(tai)一樣(yang)時(shi)便實(shi)現了電(dian)(dian)(dian)(dian)(dian)池均衡。SOC通(tong)常以當(dang)(dang)前容(rong)(rong)量與(yu)額定(ding)容(rong)(rong)量的(de)(de)百分(fen)比來表示(shi)，因此，開(kai)路電(dian)(dian)(dian)(dian)(dian)壓（OCV）可(ke)作為SOC的(de)(de)一個衡量標準。如果一個不均衡電(dian)(dian)(dian)(dian)(dian)池包中的(de)(de)所(suo)(suo)有電(dian)(dian)(dian)(dian)(dian)池可(ke)以通(tong)過差分(fen)充(chong)電(dian)(dian)(dian)(dian)(dian)達到滿(man)容(rong)(rong)量（均衡點），它(ta)們便可(ke)以進行正常的(de)(de)充(chong)放電(dian)(dian)(dian)(dian)(dian)而無需任(ren)何額外(wai)的(de)(de)調(diao)整，通(tong)常這種(zhong)調(diao)整是一次(ci)性的(de)(de)。用(yong)戶(hu)在使用(yong)新電(dian)(dian)(dian)(dian)(dian)池時(shi)，通(tong)常需要求(qiu)對(dui)(dui)電(dian)(dian)(dian)(dian)(dian)池進行長時(shi)間充(chong)電(dian)(dian)(dian)(dian)(dian)，這個過程(cheng)實(shi)際上包括一次(ci)完整的(de)(de)放-充(chong)電(dian)(dian)(dian)(dian)(dian)。該過程(cheng)使負載(zai)最(zui)小化，并使電(dian)(dian)(dian)(dian)(dian)池充(chong)電(dian)(dian)(dian)(dian)(dian)時(shi)間最(zui)長，降(jiang)低對(dui)(dui)電(dian)(dian)(dian)(dian)(dian)池均衡電(dian)(dian)(dian)(dian)(dian)路的(de)(de)要求(qiu)。

2.如果電池(chi)的(de)(de)(de)容量不(bu)同(tong)(tong)，當SOC相同(tong)(tong)時(shi)(shi)也認為它(ta)們(men)是(shi)均衡的(de)(de)(de)。但SOC 只是(shi)一個(ge)(ge)相對值，每個(ge)(ge)電池(chi)容量的(de)(de)(de)絕(jue)對值是(shi)不(bu)同(tong)(tong)的(de)(de)(de)。為了使容量不(bu)同(tong)(tong)的(de)(de)(de)電池(chi)的(de)(de)(de)SOC相同(tong)(tong)，每次對串(chuan)聯電池(chi)進行充(chong)(chong)(chong)放(fang)(fang)電時(shi)(shi)都必須使用(yong)差分電流。正常充(chong)(chong)(chong)放(fang)(fang)電的(de)(de)(de)時(shi)(shi)間比(bi)初次充(chong)(chong)(chong)放(fang)(fang)電更短，并需(xu)要更大的(de)(de)(de)電流。

當電(dian)池(chi)(chi)包(bao)中(zhong)的電(dian)池(chi)(chi)不均(jun)衡時，它的可用容量將(jiang)減少，串聯電(dian)池(chi)(chi)包(bao)中(zhong)容量最(zui)低(di)的電(dian)池(chi)(chi)將(jiang)決定(ding)電(dian)池(chi)(chi)包(bao)的總容量。在(zai)(zai)不均(jun)衡電(dian)池(chi)(chi)包(bao)中(zhong)，一個(ge)或幾個(ge)電(dian)池(chi)(chi)會(hui)在(zai)(zai)其它電(dian)池(chi)(chi)尚需充(chong)電(dian)時便已達到最(zui)大容量。而在(zai)(zai)放(fang)電(dian)時，未完全(quan)充(chong)電(dian)的電(dian)池(chi)(chi)又會(hui)比其它電(dian)池(chi)(chi)先放(fang)完電(dian)，使電(dian)池(chi)(chi)包(bao)因(yin)電(dian)壓不足而提前停止供電(dian)。