鋰離子電池材料的(de)(de)化學(xue)屬性本身并不(bu)會造成(cheng)電(dian)池(chi)(chi)不(bu)均(jun)衡(heng)問題(ti)，也不(bu)具有(you)可(ke)逆(ni)自放電(dian)機理(li)。但是，鋰離子(zi)電(dian)池(chi)(chi)還必須經過一(yi)個過程才能使性能穩定，并將產生(sheng)不(bu)可(ke)逆(ni)損(sun)耗(hao)，多(duo)數此(ci)(ci)類(lei)損(sun)耗(hao)都(dou)出現(xian)(xian)在(zai)電(dian)池(chi)(chi)出廠之前。高溫(wen)(wen)放電(dian)以(yi)及在(zai)室(shi)溫(wen)(wen)下放置過久(jiu)也會出現(xian)(xian)少量(liang)此(ci)(ci)類(lei)不(bu)可(ke)逆(ni)損(sun)耗(hao)，這種(zhong)損(sun)耗(hao)的(de)(de)最大比(bi)例在(zai)10%以(yi)內(nei)。所有(you)同(tong)時(shi)入庫或(huo)同(tong)時(shi)使用的(de)(de)電(dian)池(chi)(chi)發生(sheng)這種(zhong)損(sun)耗(hao)的(de)(de)機率一(yi)樣，因(yin)此(ci)(ci)這種(zhong)情況不(bu)會引起(qi)電(dian)池(chi)(chi)不(bu)均(jun)衡(heng)問題(ti)。在(zai)出現(xian)(xian)不(bu)可(ke)逆(ni)損(sun)耗(hao)時(shi)還伴隨著少量(liang)可(ke)逆(ni)損(sun)耗(hao)，二者之間存在(zai)著某種(zhong)比(bi)例關(guan)系。大部分(fen)在(zai)工廠中出現(xian)(xian)的(de)(de)可(ke)逆(ni)損(sun)耗(hao)在(zai)進行電(dian)池(chi)(chi)容量(liang)分(fen)類(lei)前已(yi)經被再(zai)次(ci)充(chong)電(dian)，因(yin)此(ci)(ci)這類(lei)損(sun)耗(hao)非常小，而且(qie)每個電(dian)池(chi)(chi)都(dou)一(yi)樣，不(bu)會引起(qi)電(dian)池(chi)(chi)不(bu)均(jun)衡(heng)問題(ti)。

引起電(dian)(dian)池(chi)(chi)(chi)(chi)不(bu)均衡(heng)的(de)(de)另一(yi)(yi)個原因是電(dian)(dian)池(chi)(chi)(chi)(chi)在裝(zhuang)配前(qian)被閑置過久，而如果(guo)將若干批生(sheng)產時間(jian)不(bu)同的(de)(de)電(dian)(dian)池(chi)(chi)(chi)(chi)放到(dao)同一(yi)(yi)個電(dian)(dian)池(chi)(chi)(chi)(chi)包(bao)(bao)中(zhong)將會加重這種(zhong)不(bu)均衡(heng)。在這種(zhong)情(qing)況下，通過容(rong)量分類但尚未(wei)裝(zhuang)配的(de)(de)具有不(bu)同可(ke)逆損耗(hao)的(de)(de)電(dian)(dian)池(chi)(chi)(chi)(chi)將隨(sui)著時間(jian)的(de)(de)推移累計更大的(de)(de)差異。即使在裝(zhuang)配成電(dian)(dian)池(chi)(chi)(chi)(chi)包(bao)(bao)后，如果(guo)包(bao)(bao)中(zhong)的(de)(de)電(dian)(dian)池(chi)(chi)(chi)(chi)變化很大（尤其是當電(dian)(dian)池(chi)(chi)(chi)(chi)包(bao)(bao)放置過久），隨(sui)著時間(jian)推移，電(dian)(dian)池(chi)(chi)(chi)(chi)包(bao)(bao)內的(de)(de)電(dian)(dian)池(chi)(chi)(chi)(chi)不(bu)均衡(heng)也(ye)會加重。

軟短路

軟短路（soft short是引起某些(xie)電(dian)(dian)池(chi)不均(jun)衡(heng)的(de)主要原因。在(zai)電(dian)(dian)池(chi)生(sheng)產(chan)時的(de)細微瑕疵(ci)可(ke)能使電(dian)(dian)池(chi)出現40KQ以上的(de)短路電(dian)(dian)阻(zu)，由(you)這(zhe)種高阻(zu)抗(kang)引起的(de)自放電(dian)(dian)速率可(ke)達(da)0.1mA或每月3%。一些(xie)出廠時合格(ge)的(de)電(dian)(dian)池(chi)也可(ke)能產(chan)生(sheng)軟短路問題，但(dan)多(duo)數電(dian)(dian)池(chi)不會出現這(zhe)種情況，因而(er)可(ke)將容(rong)(rong)(rong)量(liang)(liang)保持若干年。嚴(yan)格(ge)來說，軟短路是一種機電(dian)(dian)變化，如果電(dian)(dian)池(chi)包僅由(you)單(dan)個電(dian)(dian)池(chi)構成(cheng)，那么這(zhe)個電(dian)(dian)池(chi)可(ke)以反(fan)復充(chong)電(dian)(dian)而(er)不會出現容(rong)(rong)(rong)量(liang)(liang)損耗。然(ran)而(er)，在(zai)串聯電(dian)(dian)池(chi)包中出現軟短路的(de)電(dian)(dian)池(chi)每月會損耗3%的(de)容(rong)(rong)(rong)量(liang)(liang)，而(er)其它電(dian)(dian)池(chi)則毫(hao)無損耗。

電(dian)(dian)池(chi)(chi)包中電(dian)(dian)池(chi)(chi)的(de)(de)SOC不一樣時會降(jiang)低總容量。在未出現相應的(de)(de)容量降(jiang)低之前，電(dian)(dian)池(chi)(chi)包使(shi)用時需(xu)要(yao)進行一次調整(zheng)(zheng)，入庫保存后再經常不定期調整(zheng)(zheng)，這(zhe)(zhe)樣便(bian)可恢復(fu)最(zui)初的(de)(de)容量損耗(hao)。同時，在每次充電(dian)(dian)過程中只需(xu)要(yao)進行較為簡單的(de)(de)均(jun)(jun)衡，以(yi)(yi)避免重新產生失配(pei)。這(zhe)(zhe)些連續(xu)調整(zheng)(zheng)通常用戶是(shi)根本不能覺察到。初次使(shi)用后，以(yi)(yi)后的(de)(de)放電(dian)(dian)過程便(bian)不再需(xu)要(yao)均(jun)(jun)衡處(chu)理。

例如，假設(she)一個(ge)(ge)電(dian)池包(bao)中有兩個(ge)(ge)串(chuan)聯電(dian)池C1和C2，C1每個(ge)(ge)月放(fang)(fang)電(dian)3%，三個(ge)(ge)月后(hou)起(qi)SOC值從40%下降到(dao)31%。C2沒(mei)有軟(ruan)短路，因此SOC保持為40%。充電(dian)時，C2的SOC恢復(fu)到(dao)100%，而C1只能恢復(fu)到(dao)91%。放(fang)(fang)電(dian)時，C1的SOC到(dao)達0%時C2還剩余9%。因此電(dian)池包(bao)產生了9%的損耗。

如果對C1施(shi)加一個(ge)(ge)差分電(dian)(dian)流進(jin)行均衡，則兩個(ge)(ge)電(dian)(dian)池以及整個(ge)(ge)電(dian)(dian)池包都將恢復滿容量(liang)。C1的(de)損耗沒(mei)有使電(dian)(dian)池包的(de)容量(liang)降低(di)，如圖1a和1b所示。

電池容量退化

容量(liang)(liang)退化是(shi)由于生(sheng)(sheng)產或(huo)工藝(yi)差異(yi)而導(dao)致的電(dian)(dian)(dian)池(chi)(chi)(chi)容量(liang)(liang)降低，通(tong)常(chang)在(zai)生(sheng)(sheng)產過(guo)(guo)程中(zhong)出現(xian)這種情(qing)況的可(ke)能(neng)性極小。此外，同(tong)批生(sheng)(sheng)產的電(dian)(dian)(dian)池(chi)(chi)(chi)性能(neng)通(tong)常(chang)一樣，因此，大(da)多(duo)(duo)數電(dian)(dian)(dian)池(chi)(chi)(chi)包(bao)(bao)(bao)中(zhong)的電(dian)(dian)(dian)池(chi)(chi)(chi)不(bu)會出現(xian)不(bu)均衡問(wen)題。然而，電(dian)(dian)(dian)池(chi)(chi)(chi)可(ke)能(neng)會偶然出現(xian)很(hen)小的缺陷，如(ru)果在(zai)這種情(qing)況下電(dian)(dian)(dian)池(chi)(chi)(chi)包(bao)(bao)(bao)工作的溫(wen)度變化較大(da)，那么某些電(dian)(dian)(dian)池(chi)(chi)(chi)就會比(bi)其它(ta)電(dian)(dian)(dian)池(chi)(chi)(chi)性能(neng)降低得更(geng)快(kuai)。例如(ru)，用于電(dian)(dian)(dian)腦的電(dian)(dian)(dian)池(chi)(chi)(chi)包(bao)(bao)(bao)的面積(ji)很(hen)大(da)，因此電(dian)(dian)(dian)池(chi)(chi)(chi)包(bao)(bao)(bao)的某部(bu)分會靠近電(dian)(dian)(dian)源或(huo)CPU，這部(bu)分電(dian)(dian)(dian)池(chi)(chi)(chi)比(bi)其它(ta)電(dian)(dian)(dian)池(chi)(chi)(chi)受熱更(geng)多(duo)(duo)。此類問(wen)題可(ke)通(tong)過(guo)(guo)電(dian)(dian)(dian)池(chi)(chi)(chi)均衡來彌補，這種均衡處理(li)必須在(zai)充電(dian)(dian)(dian)和(he)放電(dian)(dian)(dian)過(guo)(guo)程中(zhong)實現(xian)，該過(guo)(guo)程稱為容量(liang)(liang)/能(neng)量(liang)(liang)最(zui)大(da)化。然而，這在(zai)實際(ji)應用中(zhong)很(hen)難實現(xian)，同(tong)時不(bu)夠直觀，容量(liang)(liang)/能(neng)量(liang)(liang)最(zui)大(da)化問(wen)題還有待進一步深入研究。保持電(dian)(dian)(dian)池(chi)(chi)(chi)均衡

監測電(dian)(dian)(dian)池的電(dian)(dian)(dian)壓和溫度可追蹤(zong)電(dian)(dian)(dian)池的電(dian)(dian)(dian)壓變化(hua)，當電(dian)(dian)(dian)池電(dian)(dian)(dian)壓變化(hua)超(chao)過10mV時(shi)，電(dian)(dian)(dian)路便啟動均(jun)衡處(chu)理來對(dui)電(dian)(dian)(dian)池包中不同的電(dian)(dian)(dian)池電(dian)(dian)(dian)壓進行匹配。

這種均(jun)衡(heng)(heng)是通(tong)過(guo)“分流(liu)(liu)”需要均(jun)衡(heng)(heng)的(de)電(dian)(dian)池(chi)(chi)(chi)(chi)（電(dian)(dian)壓(ya)最(zui)高的(de)電(dian)(dian)池(chi)(chi)(chi)(chi)）電(dian)(dian)流(liu)(liu)來實現(xian)的(de)。通(tong)常(chang)，將一個(ge)功(gong)率晶(jing)體管和限流(liu)(liu)電(dian)(dian)阻串(chuan)聯后(hou)，再(zai)與電(dian)(dian)池(chi)(chi)(chi)(chi)包(bao)中的(de)每個(ge)電(dian)(dian)池(chi)(chi)(chi)(chi)并聯來控(kong)制(zhi)均(jun)衡(heng)(heng)過(guo)程(cheng)(cheng)。在(zai)充(chong)(chong)電(dian)(dian)過(guo)程(cheng)(cheng)中導通(tong)功(gong)率晶(jing)體管，將該電(dian)(dian)池(chi)(chi)(chi)(chi)的(de)電(dian)(dian)流(liu)(liu)部分分流(liu)(liu)，從而使(shi)它的(de)充(chong)(chong)電(dian)(dian)速(su)度(du)比其(qi)(qi)它電(dian)(dian)池(chi)(chi)(chi)(chi)慢。在(zai)放電(dian)(dian)過(guo)程(cheng)(cheng)中導通(tong)功(gong)率晶(jing)體管，增加該電(dian)(dian)池(chi)(chi)(chi)(chi)的(de)有效(xiao)負(fu)載，使(shi)它的(de)放電(dian)(dian)速(su)度(du)比其(qi)(qi)它電(dian)(dian)池(chi)(chi)(chi)(chi)快，從而在(zai)充(chong)(chong)/放電(dian)(dian)模式下對(dui)電(dian)(dian)池(chi)(chi)(chi)(chi)進行均(jun)衡(heng)(heng)。

外部晶體管的功耗

均衡電(dian)路設計時必須注意(yi)(yi)功率(lv)晶(jing)體(ti)管和限流(liu)電(dian)阻(zu)的選擇，以(yi)使電(dian)流(liu)保(bao)持在合理的范(fan)圍內(nei)。如果(guo)均衡電(dian)流(liu)過高(gao)，功耗會很大，引(yin)起電(dian)池包升溫(wen)或(huo)增加元件負擔；相反，如果(guo)均衡電(dian)流(liu)過低，就(jiu)需要較(jiao)長的時間或(huo)多個周期才能(neng)起到均衡作(zuo)用，從而降低電(dian)池均衡效(xiao)率(lv)，甚(shen)至失(shi)去(qu)意(yi)(yi)義(yi)。

在決(jue)定電流大小時要注意不(bu)均衡程(cheng)度、可用時間以及電池容量三項：

1.將合理的(de)電池均(jun)衡(heng)量(liang)定為10-20%的(de)電池容(rong)量(liang)。對于(yu)軟短路情況(kuang)，這相當于(yu)以(yi)每月3%的(de)放電速(su)率持續3-6個月；對于(yu)周期時間不(bu)均(jun)衡(heng)，這相當于(yu)100個周期的(de)16%容(rong)量(liang)損耗。

2.電(dian)(dian)池均衡(heng)(heng)所需(xu)(xu)的合理時間可(ke)短至(zhi)(zhi)僅1個(ge)充(chong)(chong)(chong)/放(fang)電(dian)(dian)周期(qi)。SOC不均衡(heng)(heng)需(xu)(xu)要較長(chang)的時間，最多(duo)可(ke)達18個(ge)小時（這18個(ge)小時并非完全用于充(chong)(chong)(chong)電(dian)(dian)，而(er)是(shi)一個(ge)至(zhi)(zhi)少包(bao)括一次充(chong)(chong)(chong)、放(fang)電(dian)(dian)的調(diao)整過程。也(ye)可(ke)能(neng)是(shi)多(duo)個(ge)充(chong)(chong)(chong)/放(fang)電(dian)(dian)周期(qi)）。容量不均衡(heng)(heng)通常(chang)需(xu)(xu)要充(chong)(chong)(chong)電(dian)(dian)1小時，并且至(zhi)(zhi)少放(fang)電(dian)(dian)2.5小時。

3.18650具有(you)最(zui)高的(de)容量(liang)(liang)，為2，000mAh，通常最(zui)多(duo)采用3個(ge)電(dian)池并(bing)聯。因此，修(xiu)正20%容量(liang)(liang)不均(jun)(jun)(jun)衡(heng)(heng)所需的(de)最(zui)大均(jun)(jun)(jun)衡(heng)(heng)電(dian)流(liu)(liu)為IBALANCE=（20%×2000mAh×3）/1.0hr=1200mA為了實現這(zhe)一程(cheng)度的(de)均(jun)(jun)(jun)衡(heng)(heng)，電(dian)池包的(de)調整必須經過(guo)較長時間(jian)。假(jia)設充(chong)電(dian)時間(jian)為1小時，放電(dian)時間(jian)為3小時，則經過(guo)兩個(ge)充(chong)/放電(dian)周(zhou)(zhou)期便(bian)可獲(huo)得(de)8小時的(de)均(jun)(jun)(jun)衡(heng)(heng)處(chu)理(li)，這(zhe)要求均(jun)(jun)(jun)衡(heng)(heng)電(dian)流(liu)(liu)為150mA，這(zhe)個(ge)電(dian)流(liu)(liu)相當高。例如(ru)，如(ru)果電(dian)池為4V，均(jun)(jun)(jun)衡(heng)(heng)電(dian)源為150mA時的(de)功耗可達0.6W。最(zui)好的(de)折衷方法是將電(dian)池均(jun)(jun)(jun)衡(heng)(heng)電(dian)流(liu)(liu)控(kong)制(zhi)在50mA-150mA之間(jian)，同時將初始均(jun)(jun)(jun)衡(heng)(heng)持續多(duo)個(ge)周(zhou)(zhou)期。