鋰電池的電池容量

我們現在設計電子產品，很多時候也用鋰電池供電，同手機或者平板電腦用鋰電池供(gong)電(dian)(dian)一(yi)樣，熟(shu)悉了解鋰(li)電(dian)(dian)池(chi)容(rong)量的學問，也(ye)許對使用和設計(ji)鋰(li)電(dian)(dian)池(chi)供(gong)電(dian)(dian)包(bao)括設計(ji)電(dian)(dian)池(chi)充電(dian)(dian)器(qi)來說，很有必要(yao)。

現在好多關(guan)注鋰電(dian)池放電(dian)的人(ren)，都(dou)有這樣的體(ti)會(hui)，就(jiu)是當鋰電(dian)池從充滿(man)電(dian)壓4.2V放電(dian)到3.7V時，時間(jian)很(hen)長，但一旦過了3.7V就(jiu)放電(dian)很(hen)快了，沒錯(cuo)，確實這樣。

下面翻(fan)閱一(yi)些鋰電池的一(yi)些資料(liao)，給(gei)大(da)家做一(yi)個總(zong)結。

先說一下電(dian)(dian)池的放(fang)電(dian)(dian)平臺，就是指充滿電(dian)(dian)的鋰電(dian)(dian)池在放(fang)電(dian)(dian)時，電(dian)(dian)池的電(dian)(dian)壓(ya)變(bian)化(hua)狀態。

電(dian)池(chi)(chi)恒流放(fang)電(dian)，電(dian)池(chi)(chi)電(dian)壓(ya)要經歷三(san)個(ge)過(guo)程(cheng)，即下降(jiang)、穩定、再下降(jiang)，在這三(san)個(ge)過(guo)程(cheng)中，穩定期(qi)是(shi)最長(chang)的(de)(de)(de)。穩定時間越長(chang)，說(shuo)明(ming)電(dian)池(chi)(chi)的(de)(de)(de)放(fang)電(dian)平臺(tai)越高。放(fang)電(dian)平臺(tai)的(de)(de)(de)高低，與電(dian)池(chi)(chi)制(zhi)造工(gong)藝息(xi)息(xi)相(xiang)關。就是(shi)因(yin)為各個(ge)鋰電(dian)池(chi)(chi)廠家的(de)(de)(de)市場定位不(bu)一樣，技術工(gong)藝手段不(bu)同，其控制(zhi)的(de)(de)(de)放(fang)電(dian)平臺(tai)就不(bu)一樣，質量也就有很大差別。

一(yi)般地，一(yi)節(jie)18650的鋰電(dian)(dian)(dian)(dian)(dian)(dian)(dian)池(chi)滿電(dian)(dian)(dian)(dian)(dian)(dian)(dian)壓4.2V，當(dang)用1C的電(dian)(dian)(dian)(dian)(dian)(dian)(dian)流放(fang)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)放(fang)到(dao)3.7V，放(fang)了60分鐘，那么(me)我們就說電(dian)(dian)(dian)(dian)(dian)(dian)(dian)池(chi)的使(shi)用容量是2200mAh，在(zai)這段時間(jian)(jian)里 根據充電(dian)(dian)(dian)(dian)(dian)(dian)(dian)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)池(chi)特性(xing)，做出一(yi)個圖(tu)如下，可(ke)以更好理解電(dian)(dian)(dian)(dian)(dian)(dian)(dian)池(chi)容量和電(dian)(dian)(dian)(dian)(dian)(dian)(dian)壓電(dian)(dian)(dian)(dian)(dian)(dian)(dian)流時間(jian)(jian)與放(fang)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)平臺關系：

鋰電池(chi)電池(chi)容(rong)量與放電平臺理(li)解示意圖

容量(liang)（C）=放電(dian)電(dian)流×電(dian)池放電(dian)平(ping)臺(tai)時間(jian)

對于1節容量為2200mAh的18650鋰電(dian)(dian)池來說，1C放電(dian)(dian)到3.7V用時1小時，

容(rong)量(liang)（C）=2200mA×1小時(shi)=2200mAh

那(nei)么(me)問(wen)題就(jiu)來了，對(dui)于好一(yi)點的(de)鋰電池，一(yi)般(ban)在我們做產(chan)品測(ce)試時會在3.7V以后電壓下(xia)降的(de)很快，那(nei)么(me)在短時間內放的(de)電量就(jiu)很少(shao)。

相反不(bu)好的(de)電(dian)(dian)池(chi)在(zai)4.2V到3.7V放電(dian)(dian)的(de)時候，電(dian)(dian)壓下降的(de)很快，而在(zai)3.7V以后(hou)電(dian)(dian)壓又下降的(de)有很慢，這種電(dian)(dian)池(chi)是(shi)性能不(bu)好的(de)一般容(rong)量(liang)也非常低。那么好的(de)鋰電(dian)(dian)池(chi)的(de)放電(dian)(dian)平臺就是(shi)3.7V。

就一(yi)般而(er)言，在恒壓(ya)條件下，充(chong)到電(dian)(dian)壓(ya)為4.2V，電(dian)(dian)流小于0.01C時停充(chong)電(dian)(dian)，然后擱(ge)置(zhi)10分鐘，在任何倍率的放(fang)(fang)電(dian)(dian)電(dian)(dian)流下，放(fang)(fang)電(dian)(dian)至3.7V時，電(dian)(dian)池(chi)放(fang)(fang)電(dian)(dian)所經歷的一(yi)個時間(jian)長度，是(shi)衡量(liang)電(dian)(dian)池(chi)好(hao)壞的重要指標。

不過，不要一味地追求高平臺(tai)，有(you)時候平臺(tai)電壓高，容(rong)量(liang)卻下(xia)降了，因(yin)為，不同(tong)倍率條件下(xia)，平臺(tai)電壓是不同(tong)的，因(yin)此，平臺(tai)的問題應從多方考(kao)慮。既要容(rong)量(liang)高，又要在指定電壓持續時間長，才算真正的好電池。

什么(me)又是(shi)放(fang)電率(lv)的呢？

放電(dian)率F：[1/時(shi)]，意思是 "N小時(shi)充（放）電(dian)率，常常只說(shuo)"數",而不說(shuo)單位;F也稱做 "N小時(shi)充（放）電(dian)率", F =1/(N小時(shi))， 一(yi)般可以這(zhe)樣計算：I=0.1 X [1/(N小時(shi))] X C

舉(ju)例,電(dian)(dian)池(chi)容(rong)量時(shi)(shi)2200mAh,以(yi) 0.1C 的電(dian)(dian)流充電(dian)(dian),相當于明確: 對電(dian)(dian)池(chi)的充電(dian)(dian)電(dian)(dian)流 I=0.1[1/時(shi)(shi)]X2200[毫安(an)時(shi)(shi)]=220[毫安(an)]

借助上面的鋰電池電池容(rong)量(liang)與放(fang)電(dian)(dian)(dian)(dian)平(ping)(ping)臺(tai)(tai)理解示(shi)意(yi)圖，能比(bi)較(jiao)好的(de)理解充(chong)電(dian)(dian)(dian)(dian)電(dian)(dian)(dian)(dian)池(chi)(chi)容(rong)量(liang)和(he)電(dian)(dian)(dian)(dian)池(chi)(chi)的(de)放(fang)電(dian)(dian)(dian)(dian)平(ping)(ping)臺(tai)(tai)的(de)道理，也(ye)可以說是(shi)(shi)衡量(liang)電(dian)(dian)(dian)(dian)池(chi)(chi)高功率(lv)的(de)工作時(shi)間(jian)(jian),同樣兩個(ge)(ge)(ge)電(dian)(dian)(dian)(dian)池(chi)(chi)容(rong)量(liang)是(shi)(shi)相(xiang)同的(de),充(chong)滿電(dian)(dian)(dian)(dian)后(hou)假(jia)設同時(shi)從4.2V放(fang)到3.7V,但(dan)是(shi)(shi)一(yi)(yi)個(ge)(ge)(ge)時(shi)間(jian)(jian)長,一(yi)(yi)個(ge)(ge)(ge)時(shi)間(jian)(jian)短(duan),就是(shi)(shi)時(shi)間(jian)(jian)長的(de)電(dian)(dian)(dian)(dian)池(chi)(chi)平(ping)(ping)臺(tai)(tai)高,就是(shi)(shi)高電(dian)(dian)(dian)(dian)壓(ya)的(de)時(shi)間(jian)(jian)工作時(shi)間(jian)(jian)長,比(bi)如(ru)這兩個(ge)(ge)(ge)電(dian)(dian)(dian)(dian)池(chi)(chi)用在手(shou)機上,待機時(shi)間(jian)(jian)是(shi)(shi)相(xiang)同的(de),但(dan)兩個(ge)(ge)(ge)手(shou)機一(yi)(yi)起打電(dian)(dian)(dian)(dian)話,平(ping)(ping)臺(tai)(tai)時(shi)間(jian)(jian)長的(de)電(dian)(dian)(dian)(dian)池(chi)(chi)通知(zhi)時(shi)間(jian)(jian)會(hui)長,平(ping)(ping)臺(tai)(tai)時(shi)間(jian)(jian)短(duan)的(de)電(dian)(dian)(dian)(dian)池(chi)(chi)通話時(shi)間(jian)(jian)會(hui)短(duan) 二，對(dui)(dui)于這個(ge)(ge)(ge)圖，另一(yi)(yi)個(ge)(ge)(ge)含義，對(dui)(dui)理解鋰電(dian)(dian)(dian)(dian)池(chi)(chi)的(de)電(dian)(dian)(dian)(dian)量(liang)管理監測(ce)也(ye)很(hen)有意(yi)義。

比(bi)如，目(mu)前，對(dui)充電電池進行電量監控方(fang)法，一般有(you)兩種(zhong)。

測量電池電壓方法。當充電器在充(chong)電(dian)(dian)(dian)(dian)時(shi)檢(jian)測電(dian)(dian)(dian)(dian)池(chi)(chi)電(dian)(dian)(dian)(dian)壓(ya)(ya)(ya)，當(dang)電(dian)(dian)(dian)(dian)壓(ya)(ya)(ya)達(da)到規定電(dian)(dian)(dian)(dian)壓(ya)(ya)(ya)值時(shi)就認為(wei)充(chong)滿(man)。如(ru)鋰(li)電(dian)(dian)(dian)(dian)池(chi)(chi)的(de)(de)電(dian)(dian)(dian)(dian)壓(ya)(ya)(ya)充(chong)到4.2V時(shi)就認為(wei)充(chong)滿(man)。檢(jian)測電(dian)(dian)(dian)(dian)壓(ya)(ya)(ya)的(de)(de)電(dian)(dian)(dian)(dian)壓(ya)(ya)(ya)表精(jing)(jing)度要(yao)達(da)到正負1%的(de)(de)精(jing)(jing)度。因鋰(li)電(dian)(dian)(dian)(dian)池(chi)(chi)過充(chong)電(dian)(dian)(dian)(dian)要(yao)損壞。如(ru)果(guo)想(xiang)監視電(dian)(dian)(dian)(dian)池(chi)(chi)充(chong)放(fang)電(dian)(dian)(dian)(dian)的(de)(de)話(hua)，書上有很成熟的(de)(de)電(dian)(dian)(dian)(dian)路(lu)可以參考，如(ru)果(guo)只是測量一下(xia)的(de)(de)話(hua)那(nei)就好辦了，根據容量計(ji)算一下(xia)負載電(dian)(dian)(dian)(dian)阻，用標準放(fang)電(dian)(dian)(dian)(dian)電(dian)(dian)(dian)(dian)流放(fang)電(dian)(dian)(dian)(dian)，這時(shi)再檢(jian)測電(dian)(dian)(dian)(dian)壓(ya)(ya)(ya)，只要(yao)能達(da)到或接近標稱的(de)(de)放(fang)電(dian)(dian)(dian)(dian)時(shi)間(jian)就行(xing)。

測量電池(chi)電壓這種方法(fa)，有很多(duo)不足。例如對于不同廠商生(sheng)產(chan)的(de)電池(chi)，其開路(lu)電壓與(yu)容量之間的(de)關系各不相同等。優點是(shi)設計成本比較低。

還有(you)一個常用(yong)的(de)監測(ce)剩(sheng)(sheng)余(yu)(yu)電量的(de)方法是(shi)，在一些(xie)要求比較精確電池(chi)容(rong)量的(de)地方， 了(le)解電池(chi)剩(sheng)(sheng)余(yu)(yu)容(rong)量用(yong)估算(suan)電池(chi)使用(yong)時間(jian)，通過測(ce)量流(liu)(liu)入/流(liu)(liu)出(chu)電池(chi)的(de)凈電荷來(lai)估算(suan)電池(chi)剩(sheng)(sheng)余(yu)(yu)容(rong)量。對流(liu)(liu)入/流(liu)(liu)出(chu)電池(chi)的(de)總電流(liu)(liu)進行積分(fen)，也就是(shi)求圖中曲線下(xia)的(de)面積，得到(dao)的(de)凈電荷數即為剩(sheng)(sheng)余(yu)(yu)容(rong)量。

這就電(dian)池(chi)容(rong)量(liang)計算的(de)(de)方法是目(mu)前認(ren)為是比(bi)較(jiao)精確(que)的(de)(de)計算電(dian)池(chi)電(dian)量(liang)的(de)(de)方法。當然設計成本也(ye)是比(bi)較(jiao)高的(de)(de)。