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電(dian)(dian)一樣，熟悉(xi)了(le)解(jie)鋰電(dian)(dian)池(chi)容量(liang)的(de)學(xue)問(wen)，也許(xu)對使用和設計鋰電(dian)(dian)池(chi)供電(dian)(dian)包括設計電(dian)(dian)池(chi)充電(dian)(dian)器來說，很(hen)有必要(yao)。

現(xian)在好多關(guan)注(zhu)鋰(li)電(dian)(dian)(dian)池(chi)放(fang)(fang)(fang)電(dian)(dian)(dian)的人，都有這樣(yang)的體(ti)會(hui)，就是當(dang)鋰(li)電(dian)(dian)(dian)池(chi)從充滿電(dian)(dian)(dian)壓4.2V放(fang)(fang)(fang)電(dian)(dian)(dian)到(dao)3.7V時(shi)，時(shi)間很長，但(dan)一(yi)旦過了(le)3.7V就放(fang)(fang)(fang)電(dian)(dian)(dian)很快(kuai)了(le)，沒(mei)錯，確實這樣(yang)。

下面(mian)翻(fan)閱一些鋰電池的一些資(zi)料(liao)，給大家做一個總結。

先說一下電(dian)池(chi)(chi)的(de)放電(dian)平臺(tai)，就是指充滿(man)電(dian)的(de)鋰(li)電(dian)池(chi)(chi)在放電(dian)時，電(dian)池(chi)(chi)的(de)電(dian)壓變化狀態。

電(dian)池(chi)恒(heng)流放(fang)電(dian)，電(dian)池(chi)電(dian)壓(ya)要(yao)經歷三(san)個(ge)過程(cheng)，即下降(jiang)、穩定(ding)、再下降(jiang)，在這三(san)個(ge)過程(cheng)中，穩定(ding)期是最長的。穩定(ding)時間越長，說明電(dian)池(chi)的放(fang)電(dian)平(ping)臺(tai)越高(gao)。放(fang)電(dian)平(ping)臺(tai)的高(gao)低，與電(dian)池(chi)制(zhi)造工(gong)藝息息相(xiang)關。就(jiu)是因為各個(ge)鋰電(dian)池(chi)廠家的市場(chang)定(ding)位不一樣(yang)，技術工(gong)藝手段不同(tong)，其控制(zhi)的放(fang)電(dian)平(ping)臺(tai)就(jiu)不一樣(yang)，質量也就(jiu)有(you)很大差別。

一般地，一節18650的鋰電(dian)池(chi)(chi)滿(man)電(dian)壓(ya)4.2V，當用(yong)1C的電(dian)流(liu)放(fang)電(dian)放(fang)到(dao)3.7V，放(fang)了(le)60分鐘(zhong)，那(nei)么我們就說電(dian)池(chi)(chi)的使用(yong)容量是2200mAh，在這段時間里 根(gen)據充電(dian)電(dian)池(chi)(chi)特性，做出一個圖(tu)如下，可(ke)以更好理解(jie)電(dian)池(chi)(chi)容量和電(dian)壓(ya)電(dian)流(liu)時間與放(fang)電(dian)平臺關系：

鋰電池(chi)電池(chi)容量與放電平臺理解示(shi)意圖

容量(liang)（C）=放電(dian)電(dian)流×電(dian)池放電(dian)平臺時間

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

容量（C）=2200mA×1小時(shi)=2200mAh

那么問題(ti)就(jiu)來(lai)了，對(dui)于好一點的鋰電(dian)池，一般在(zai)我們做產(chan)品測試時(shi)(shi)會在(zai)3.7V以后(hou)電(dian)壓下(xia)降的很快，那么在(zai)短(duan)時(shi)(shi)間內放的電(dian)量就(jiu)很少(shao)。

相反不好(hao)的(de)(de)(de)電(dian)池在4.2V到3.7V放電(dian)的(de)(de)(de)時候，電(dian)壓下降(jiang)的(de)(de)(de)很快，而在3.7V以后電(dian)壓又(you)下降(jiang)的(de)(de)(de)有很慢，這(zhe)種電(dian)池是(shi)性能不好(hao)的(de)(de)(de)一般(ban)容量也(ye)非常低。那么(me)好(hao)的(de)(de)(de)鋰電(dian)池的(de)(de)(de)放電(dian)平(ping)臺就是(shi)3.7V。

就(jiu)一(yi)般而言，在恒壓條件下，充到電(dian)壓為4.2V，電(dian)流小于0.01C時(shi)停充電(dian)，然后擱(ge)置(zhi)10分鐘，在任何倍率(lv)的放電(dian)電(dian)流下，放電(dian)至(zhi)3.7V時(shi)，電(dian)池(chi)放電(dian)所經歷(li)的一(yi)個(ge)時(shi)間(jian)長度，是衡量電(dian)池(chi)好壞(huai)的重(zhong)要(yao)指標(biao)。

不(bu)過，不(bu)要一味地追求高平臺(tai)，有時(shi)候平臺(tai)電(dian)壓高，容量(liang)卻下降了(le)，因為，不(bu)同(tong)倍(bei)率(lv)條(tiao)件下，平臺(tai)電(dian)壓是不(bu)同(tong)的，因此(ci)，平臺(tai)的問(wen)題應從(cong)多(duo)方(fang)考(kao)慮。既要容量(liang)高，又(you)要在指定電(dian)壓持續時(shi)間長，才算真(zhen)正(zheng)的好電(dian)池。

什么又是放電率(lv)的呢？

放電率F：[1/時(shi)]，意思是 "N小(xiao)時(shi)充(chong)（放）電率，常常只(zhi)說"數",而不說單位;F也稱做(zuo) "N小(xiao)時(shi)充(chong)（放）電率", F =1/(N小(xiao)時(shi))， 一般可以這樣(yang)計算(suan)：I=0.1 X [1/(N小(xiao)時(shi))] X C

舉例,電(dian)(dian)池容量時2200mAh,以(yi) 0.1C 的(de)電(dian)(dian)流(liu)充(chong)電(dian)(dian),相當于明確: 對(dui)電(dian)(dian)池的(de)充(chong)電(dian)(dian)電(dian)(dian)流(liu) I=0.1[1/時]X2200[毫安(an)時]=220[毫安(an)]

借助上面的鋰電池電池容量與放電(dian)(dian)(dian)(dian)(dian)(dian)平(ping)(ping)臺理解(jie)示意圖(tu)，能比較好的(de)(de)理解(jie)充電(dian)(dian)(dian)(dian)(dian)(dian)電(dian)(dian)(dian)(dian)(dian)(dian)池(chi)(chi)(chi)容量和電(dian)(dian)(dian)(dian)(dian)(dian)池(chi)(chi)(chi)的(de)(de)放電(dian)(dian)(dian)(dian)(dian)(dian)平(ping)(ping)臺的(de)(de)道理，也可以說是(shi)衡量電(dian)(dian)(dian)(dian)(dian)(dian)池(chi)(chi)(chi)高功率的(de)(de)工作時(shi)(shi)(shi)間(jian)(jian),同(tong)(tong)(tong)樣兩(liang)(liang)個(ge)電(dian)(dian)(dian)(dian)(dian)(dian)池(chi)(chi)(chi)容量是(shi)相同(tong)(tong)(tong)的(de)(de),充滿電(dian)(dian)(dian)(dian)(dian)(dian)后假設同(tong)(tong)(tong)時(shi)(shi)(shi)從4.2V放到3.7V,但是(shi)一(yi)(yi)個(ge)時(shi)(shi)(shi)間(jian)(jian)長(chang),一(yi)(yi)個(ge)時(shi)(shi)(shi)間(jian)(jian)短(duan)(duan),就(jiu)是(shi)時(shi)(shi)(shi)間(jian)(jian)長(chang)的(de)(de)電(dian)(dian)(dian)(dian)(dian)(dian)池(chi)(chi)(chi)平(ping)(ping)臺高,就(jiu)是(shi)高電(dian)(dian)(dian)(dian)(dian)(dian)壓的(de)(de)時(shi)(shi)(shi)間(jian)(jian)工作時(shi)(shi)(shi)間(jian)(jian)長(chang),比如這兩(liang)(liang)個(ge)電(dian)(dian)(dian)(dian)(dian)(dian)池(chi)(chi)(chi)用在手機上,待機時(shi)(shi)(shi)間(jian)(jian)是(shi)相同(tong)(tong)(tong)的(de)(de),但兩(liang)(liang)個(ge)手機一(yi)(yi)起(qi)打(da)電(dian)(dian)(dian)(dian)(dian)(dian)話(hua),平(ping)(ping)臺時(shi)(shi)(shi)間(jian)(jian)長(chang)的(de)(de)電(dian)(dian)(dian)(dian)(dian)(dian)池(chi)(chi)(chi)通知時(shi)(shi)(shi)間(jian)(jian)會(hui)長(chang),平(ping)(ping)臺時(shi)(shi)(shi)間(jian)(jian)短(duan)(duan)的(de)(de)電(dian)(dian)(dian)(dian)(dian)(dian)池(chi)(chi)(chi)通話(hua)時(shi)(shi)(shi)間(jian)(jian)會(hui)短(duan)(duan) 二，對于這個(ge)圖(tu)，另一(yi)(yi)個(ge)含義，對理解(jie)鋰電(dian)(dian)(dian)(dian)(dian)(dian)池(chi)(chi)(chi)的(de)(de)電(dian)(dian)(dian)(dian)(dian)(dian)量管理監測也很有意義。

比如，目(mu)前，對(dui)充電(dian)電(dian)池進行電(dian)量監(jian)控方法，一般有兩種。

測量電池電壓方法。當充電器在(zai)充電(dian)(dian)(dian)(dian)(dian)時檢(jian)測電(dian)(dian)(dian)(dian)(dian)池電(dian)(dian)(dian)(dian)(dian)壓(ya)(ya)，當(dang)電(dian)(dian)(dian)(dian)(dian)壓(ya)(ya)達(da)到(dao)(dao)規(gui)定電(dian)(dian)(dian)(dian)(dian)壓(ya)(ya)值時就(jiu)(jiu)認(ren)為充滿。如(ru)鋰電(dian)(dian)(dian)(dian)(dian)池的(de)電(dian)(dian)(dian)(dian)(dian)壓(ya)(ya)充到(dao)(dao)4.2V時就(jiu)(jiu)認(ren)為充滿。檢(jian)測電(dian)(dian)(dian)(dian)(dian)壓(ya)(ya)的(de)電(dian)(dian)(dian)(dian)(dian)壓(ya)(ya)表精度(du)(du)要達(da)到(dao)(dao)正負(fu)1%的(de)精度(du)(du)。因鋰電(dian)(dian)(dian)(dian)(dian)池過(guo)充電(dian)(dian)(dian)(dian)(dian)要損壞。如(ru)果想監視電(dian)(dian)(dian)(dian)(dian)池充放電(dian)(dian)(dian)(dian)(dian)的(de)話，書(shu)上(shang)有很成熟的(de)電(dian)(dian)(dian)(dian)(dian)路可以參考，如(ru)果只是測量一下的(de)話那就(jiu)(jiu)好辦(ban)了(le)，根據容量計算(suan)一下負(fu)載電(dian)(dian)(dian)(dian)(dian)阻，用標準放電(dian)(dian)(dian)(dian)(dian)電(dian)(dian)(dian)(dian)(dian)流放電(dian)(dian)(dian)(dian)(dian)，這(zhe)時再檢(jian)測電(dian)(dian)(dian)(dian)(dian)壓(ya)(ya)，只要能達(da)到(dao)(dao)或接近(jin)標稱的(de)放電(dian)(dian)(dian)(dian)(dian)時間(jian)就(jiu)(jiu)行(xing)。

測(ce)量(liang)電池電壓這(zhe)種(zhong)方法，有(you)很多不足。例如對(dui)于(yu)不同(tong)廠商生(sheng)產的電池，其開路電壓與容量(liang)之間的關系各(ge)不相同(tong)等。優點是設計成本(ben)比較(jiao)低。

還有一個常用(yong)的(de)(de)監測剩(sheng)(sheng)余(yu)電量(liang)(liang)的(de)(de)方法是(shi)，在一些要求(qiu)比較(jiao)精(jing)確電池(chi)容量(liang)(liang)的(de)(de)地(di)方， 了解電池(chi)剩(sheng)(sheng)余(yu)容量(liang)(liang)用(yong)估算(suan)電池(chi)使用(yong)時(shi)間，通過測量(liang)(liang)流(liu)入/流(liu)出電池(chi)的(de)(de)凈電荷來(lai)估算(suan)電池(chi)剩(sheng)(sheng)余(yu)容量(liang)(liang)。對流(liu)入/流(liu)出電池(chi)的(de)(de)總電流(liu)進行積(ji)分，也就是(shi)求(qiu)圖(tu)中曲線(xian)下的(de)(de)面積(ji)，得到(dao)的(de)(de)凈電荷數即為剩(sheng)(sheng)余(yu)容量(liang)(liang)。

這就電(dian)(dian)(dian)池容量計算(suan)的方法(fa)是(shi)(shi)目前認為(wei)是(shi)(shi)比較精(jing)確的計算(suan)電(dian)(dian)(dian)池電(dian)(dian)(dian)量的方法(fa)。當然(ran)設(she)計成(cheng)本也(ye)是(shi)(shi)比較高的。