充電時,鉛酸蓄電池充電器的參數指標
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電動車鉛酸蓄電池組充電時，有幾個關鍵參數：最高充電電壓、浮充電壓、浮充轉換電流、最大充電電流。它們應該是多少？如何制定？其中最主要的是最高充電電壓，多少為好？與析氣量、充入電容量和環境溫度又是什么關系？對此眾說不一，各電池生產廠家的要求也不一樣。最高充電電壓值相對誤差范圍是多少？我們不能脫離實際的工作對象，盲目制定出超常規的精度要求。我們接到某電動車售后服務部通知：充電器比(bi)規定電壓高(gao)0.1V，電池因此熱(re)失控而充(chong)(chong)脹(zhang)了；也接到通知說：電壓比(bi)規定定低0.1V，電池欠充(chong)(chong)，提(ti)前報廢。一個(ge)千分之(zhi)(zhi)幾的誤(wu)差造成如此嚴重(zhong)后果(guo)，真是失之(zhi)(zhi)毫厘，謬之(zhi)(zhi)千里之(zhi)(zhi)外，鉛酸蓄(xu)電池果(guo)真有(you)這么神秘(mi)嗎？為了解開困(kun)擾電動車(che)充(chong)(chong)電中的這個(ge)謎團(tuan)，做如下(xia)實驗。
用(yong)一個水(shui)槽盛(sheng)滿水(shui)，電池放在(zai)(zai)水(shui)中，在(zai)(zai)電池上方有一個收(shou)集(ji)氣體(ti)用(yong)的(de)倒扣的(de)漏斗，漏斗頂(ding)端(duan)裝有可以(yi)計量(liang)氣體(ti)容量(liang)的(de)注(zhu)射針筒(tong)。充電用(yong)可調穩壓(ya)電源，用(yong)兩只四位半數字萬用(yong)表(biao)測量(liang)充電電流和充電電壓(ya)。
試(shi)驗時(shi)間(jian)(jian)是(shi)在冬季(ji)，水溫(wen)5℃。實驗條件是(shi)統一用2A電(dian)(dian)(dian)流(liu)充電(dian)(dian)(dian)，最(zui)充電(dian)(dian)(dian)電(dian)(dian)(dian)壓分別用43V、44V、45V輪(lun)循環依次進行，浮充轉換電(dian)(dian)(dian)流(liu)一律400mA，記(ji)錄下每次的(de)(de)充電(dian)(dian)(dian)時(shi)間(jian)(jian)，包括充電(dian)(dian)(dian)末期隨(sui)時(shi)間(jian)(jian)電(dian)(dian)(dian)流(liu)下降各點數(shu)據、開始析(xi)氣電(dian)(dian)(dian)壓，按時(shi)間(jian)(jian)記(ji)錄析(xi)氣量(liang)(liang)(liang)。電(dian)(dian)(dian)池充完后，用萬分之(zhi)幾精度的(de)(de)電(dian)(dian)(dian)量(liang)(liang)(liang)臺(tai)記(ji)錄放電(dian)(dian)(dian)容量(liang)(liang)(liang)。充入電(dian)(dian)(dian)量(liang)(liang)(liang)是(shi)在計算紙(zhi)上讀出時(shi)間(jian)(jian)電(dian)(dian)(dian)流(liu)曲線(xian)與坐標之(zhi)間(jian)(jian)的(de)(de)面積（電(dian)(dian)(dian)容量(liang)(liang)(liang)就是(shi)充電(dian)(dian)(dian)電(dian)(dian)(dian)流(liu)對時(shi)間(jian)(jian)的(de)(de)定積分）。數(shu)據見下表：
充號(hao)
最高電壓
V
充(chong)電(dian)電(dian)流
A
浮充電壓V
切換電流A
充入電量Ah
放出(chu)電量
Ah
析氣電壓
V
析氣量(liang)
mL
溫度℃
1
43
2
41.5
0.4
6.35
6.30
42.6
10
5
2
44
2
41.5
0.4
6.41
6.38
43.0
22
3
45
2
41.5
0.4
6.33
6.31
43.5
160
4
43
2
41.5
0.4
6.52
6.37
42.5
10
5
44
2
41.5
0.4
6.57
6.38
42.5
18
6
45
2
41.5
0.4
6.43
6.39
43
135
備注：該電池組30℃時，放電(dian)容量為10Ah。
得(de)到試(shi)驗數據后，最(zui)感(gan)到驚異的(de)(de)(de)(de)是(shi)(shi)：充(chong)(chong)(chong)(chong)(chong)入(ru)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)量(liang)的(de)(de)(de)(de)多(duo)少幾(ji)乎與充(chong)(chong)(chong)(chong)(chong)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)壓(ya)(ya)(ya)無(wu)關。很(hen)多(duo)人認(ren)為充(chong)(chong)(chong)(chong)(chong)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)壓(ya)(ya)(ya)低電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)池(chi)(chi)(chi)(chi)會(hui)充(chong)(chong)(chong)(chong)(chong)不滿，電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)池(chi)(chi)(chi)(chi)會(hui)提(ti)前鹽(yan)化(hua)報(bao)廢，特別是(shi)(shi)在(zai)冬季(ji)氣溫較低的(de)(de)(de)(de)時(shi)候。而這(zhe)次試(shi)驗正好是(shi)(shi)在(zai)冬季(ji)，水溫只有5℃，試(shi)驗的(de)(de)(de)(de)中心電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)壓(ya)(ya)(ya)值是(shi)(shi)44V，上下偏(pian)差(cha)1V，相(xiang)對誤差(cha)是(shi)(shi)2.3%。在(zai)用(yong)43V和45V充(chong)(chong)(chong)(chong)(chong)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)的(de)(de)(de)(de)情況下，充(chong)(chong)(chong)(chong)(chong)入(ru)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)量(liang)和放(fang)出(chu)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)量(liang)相(xiang)差(cha)無(wu)幾(ji)，與大家公認(ren)的(de)(de)(de)(de)看(kan)法大相(xiang)徑庭，試(shi)驗是(shi)(shi)用(yong)的(de)(de)(de)(de)同一(yi)組電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)池(chi)(chi)(chi)(chi)，同樣的(de)(de)(de)(de)充(chong)(chong)(chong)(chong)(chong)、放(fang)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)條件，輪番做同樣的(de)(de)(de)(de)測試(shi)，實驗數據重復同樣的(de)(de)(de)(de)規律(lv)，可排(pai)除偶然因素(su)干擾，試(shi)驗數據是(shi)(shi)準(zhun)確可信的(de)(de)(de)(de)。從(cong)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)池(chi)(chi)(chi)(chi)充(chong)(chong)(chong)(chong)(chong)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)原理上看(kan)，只要充(chong)(chong)(chong)(chong)(chong)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)源電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)壓(ya)(ya)(ya)高于電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)池(chi)(chi)(chi)(chi)端電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)壓(ya)(ya)(ya)，都(dou)會(hui)給電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)池(chi)(chi)(chi)(chi)充(chong)(chong)(chong)(chong)(chong)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)，一(yi)直到電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)池(chi)(chi)(chi)(chi)中的(de)(de)(de)(de)活性物質轉換(huan)完成。充(chong)(chong)(chong)(chong)(chong)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)最(zui)高電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)壓(ya)(ya)(ya)，也就是(shi)(shi)充(chong)(chong)(chong)(chong)(chong)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)源開(kai)始由恒(heng)流區轉變(bian)到恒(heng)壓(ya)(ya)(ya)區，這(zhe)種轉變(bian)是(shi)(shi)由電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)池(chi)(chi)(chi)(chi)自身充(chong)(chong)(chong)(chong)(chong)入(ru)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)量(liang)多(duo)少、活性物質反應了多(duo)少決定的(de)(de)(de)(de)，充(chong)(chong)(chong)(chong)(chong)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)壓(ya)(ya)(ya)的(de)(de)(de)(de)高低，僅(jin)是(shi)(shi)能進行(xing)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)化(hua)學(xue)反應的(de)(de)(de)(de)條件，只要高于電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)池(chi)(chi)(chi)(chi)開(kai)路電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)壓(ya)(ya)(ya)就會(hui)給電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)池(chi)(chi)(chi)(chi)充(chong)(chong)(chong)(chong)(chong)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)，多(duo)少物質能參與反應由電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)池(chi)(chi)(chi)(chi)自身決定。從(cong)這(zhe)個思路理解，就不難得(de)出(chu)，充(chong)(chong)(chong)(chong)(chong)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)壓(ya)(ya)(ya)高低對電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)池(chi)(chi)(chi)(chi)容量(liang)沒有多(duo)大影響。
電(dian)(dian)(dian)池在42.5V～43.5V時(shi)(shi)(shi)開始析氣(qi),而(er)析氣(qi)的速度與充(chong)電(dian)(dian)(dian)電(dian)(dian)(dian)壓有關。到充(chong)電(dian)(dian)(dian)結(jie)束時(shi)(shi)(shi)，總析氣(qi)量與充(chong)電(dian)(dian)(dian)最高電(dian)(dian)(dian)壓有關，43V與45V總析氣(qi)量相差10位(wei)（注：以單(dan)格(ge)允許極限(xian)失水10克，18格(ge)相當240公升氣(qi)體，該電(dian)(dian)(dian)池45V時(shi)(shi)(shi)失水并不大）。 在充(chong)電(dian)(dian)(dian)末期電(dian)(dian)(dian)流下降區時(shi)(shi)(shi)，只(zhi)要降低電(dian)(dian)(dian)壓到42.5V時(shi)(shi)(shi)，析氣(qi)立即停止，這時(shi)(shi)(shi)充(chong)電(dian)(dian)(dian)電(dian)(dian)(dian)流稍小一點，還會(hui)依著原來的規(gui)律下降。
這里對浮充電壓、浮充電流討論一下。對于長期處于浮充狀態下的鉛酸電池組，如后備電源上用的等，對浮充電壓要求是嚴格的。據國處文獻，浮充電壓有-0.2%溫度系數，浮充電壓偏差太大會造成電池鹽化。而電動車用的電池屬循環使用，不是處于這種狀態，不應該用套用浮充狀態使用的條件，充電器設定(ding)浮(fu)充的(de)目的(de)僅是免(mian)于充電(dian)(dian)(dian)(dian)末(mo)期大量析氣失水，只(zhi)要把(ba)電(dian)(dian)(dian)(dian)壓降到析氣點(dian)電(dian)(dian)(dian)(dian)壓以(yi)下(xia)，但(dan)也不(bu)能(neng)低(di)于電(dian)(dian)(dian)(dian)池端(duan)電(dian)(dian)(dian)(dian)壓而停止向(xiang)電(dian)(dian)(dian)(dian)池充電(dian)(dian)(dian)(dian)。前面說(shuo)過，在浮(fu)充電(dian)(dian)(dian)(dian)壓下(xia)，充電(dian)(dian)(dian)(dian)電(dian)(dian)(dian)(dian)流的(de)走勢基本還是依著原曲(qu)線下(xia)降，一般還補足(zu)5%的(de)容量。所以(yi)浮(fu)充電(dian)(dian)(dian)(dian)壓應(ying)在的(de)范圍是低(di)于析氣電(dian)(dian)(dian)(dian)壓（42.5V），高于電(dian)(dian)(dian)(dian)池充足(zu)電(dian)(dian)(dian)(dian)以(yi)后的(de)開路(lu)端(duan)電(dian)(dian)(dian)(dian)壓（約40V）。
浮(fu)充(chong)(chong)(chong)(chong)轉(zhuan)(zhuan)換(huan)(huan)電(dian)(dian)(dian)(dian)(dian)(dian)流(liu)(liu)(liu)，只不過(guo)是(shi)(shi)(shi)選擇在充(chong)(chong)(chong)(chong)電(dian)(dian)(dian)(dian)(dian)(dian)末(mo)期(qi)電(dian)(dian)(dian)(dian)(dian)(dian)池(chi)活性物質反(fan)應接近(jin)尾聲(sheng)，充(chong)(chong)(chong)(chong)電(dian)(dian)(dian)(dian)(dian)(dian)電(dian)(dian)(dian)(dian)(dian)(dian)流(liu)(liu)(liu)自動下(xia)降到某一(yi)(yi)點(dian)(dian)時，切換(huan)(huan)浮(fu)充(chong)(chong)(chong)(chong)電(dian)(dian)(dian)(dian)(dian)(dian)壓(ya)的(de)(de)(de)記號，不少人(ren)以為(wei)浮(fu)充(chong)(chong)(chong)(chong)電(dian)(dian)(dian)(dian)(dian)(dian)流(liu)(liu)(liu)高(gao)了(le)(le)電(dian)(dian)(dian)(dian)(dian)(dian)池(chi)會(hui)充(chong)(chong)(chong)(chong)不滿是(shi)(shi)(shi)概念不清，充(chong)(chong)(chong)(chong)電(dian)(dian)(dian)(dian)(dian)(dian)電(dian)(dian)(dian)(dian)(dian)(dian)壓(ya)只要(yao)高(gao)于電(dian)(dian)(dian)(dian)(dian)(dian)池(chi)端電(dian)(dian)(dian)(dian)(dian)(dian)壓(ya)，都會(hui)對電(dian)(dian)(dian)(dian)(dian)(dian)池(chi)充(chong)(chong)(chong)(chong)電(dian)(dian)(dian)(dian)(dian)(dian)，只不過(guo)有用戶看到指示燈紅(hong)轉(zhuan)(zhuan)綠后(hou)提前(qian)去(qu)用電(dian)(dian)(dian)(dian)(dian)(dian)池(chi)，這種情況(kuang)是(shi)(shi)(shi)不多的(de)(de)(de)，一(yi)(yi)般(ban)都是(shi)(shi)(shi)夜間充(chong)(chong)(chong)(chong)電(dian)(dian)(dian)(dian)(dian)(dian)，到早晨綠燈已亮了(le)(le)多時。有的(de)(de)(de)廠(chang)家使用說明書上提醒用戶，在轉(zhuan)(zhuan)綠燈后(hou)繼續充(chong)(chong)(chong)(chong)電(dian)(dian)(dian)(dian)(dian)(dian)2小時，是(shi)(shi)(shi)很好(hao)很正確的(de)(de)(de)。所以沒有必要(yao)刻意去(qu)追求浮(fu)充(chong)(chong)(chong)(chong)轉(zhuan)(zhuan)換(huan)(huan)點(dian)(dian)的(de)(de)(de)高(gao)低，一(yi)(yi)般(ban)新電(dian)(dian)(dian)(dian)(dian)(dian)池(chi)末(mo)期(qi)電(dian)(dian)(dian)(dian)(dian)(dian)流(liu)(liu)(liu)約為(wei)50mA，失水以后(hou)，酸比(bi)增高(gao)，那(nei)時可(ke)達500 mA以上。從析氣速率(lv)與電(dian)(dian)(dian)(dian)(dian)(dian)壓(ya)的(de)(de)(de)關系上來看（上圖），早點(dian)(dian)脫離(li)析氣區為(wei)好(hao)，一(yi)(yi)方面(mian)，一(yi)(yi)方面(mian)可(ke)以減少析氣量(liang)(liang)，另一(yi)(yi)方面(mian)，電(dian)(dian)(dian)(dian)(dian)(dian)池(chi)用了(le)(le)一(yi)(yi)段時間，末(mo)期(qi)電(dian)(dian)(dian)(dian)(dian)(dian)流(liu)(liu)(liu)增高(gao)，但還能(neng)低于我們設定的(de)(de)(de)轉(zhuan)(zhuan)換(huan)(huan)點(dian)(dian)電(dian)(dian)(dian)(dian)(dian)(dian)流(liu)(liu)(liu)，否則電(dian)(dian)(dian)(dian)(dian)(dian)池(chi)一(yi)(yi)直(zhi)在最高(gao)電(dian)(dian)(dian)(dian)(dian)(dian)壓(ya)充(chong)(chong)(chong)(chong)電(dian)(dian)(dian)(dian)(dian)(dian)下(xia)，大量(liang)(liang)失水，引發(fa)熱(re)控(kong)，充(chong)(chong)(chong)(chong)脹充(chong)(chong)(chong)(chong)壞(huai)電(dian)(dian)(dian)(dian)(dian)(dian)池(chi)。有人(ren)固(gu)執(zhi)地強(qiang)調，浮(fu)充(chong)(chong)(chong)(chong)轉(zhuan)(zhuan)換(huan)(huan)點(dian)(dian)高(gao)電(dian)(dian)(dian)(dian)(dian)(dian)池(chi)會(hui)欠(qian)充(chong)(chong)(chong)(chong)，前(qian)面(mian)已討論過(guo)，切換(huan)(huan)到浮(fu)充(chong)(chong)(chong)(chong)電(dian)(dian)(dian)(dian)(dian)(dian)壓(ya)后(hou)，不是(shi)(shi)(shi)停(ting)止充(chong)(chong)(chong)(chong)電(dian)(dian)(dian)(dian)(dian)(dian)了(le)(le)，還會(hui)繼續對電(dian)(dian)(dian)(dian)(dian)(dian)池(chi)充(chong)(chong)(chong)(chong)電(dian)(dian)(dian)(dian)(dian)(dian)的(de)(de)(de)，轉(zhuan)(zhuan)換(huan)(huan)電(dian)(dian)(dian)(dian)(dian)(dian)流(liu)(liu)(liu)適(shi)當高(gao)一(yi)(yi)點(dian)(dian)有利于避(bi)免過(guo)分失水和熱(re)失控(kong)。
至于充電電流的大小設定，先看一下電池制造廠家對10Ah（12Ah）吸附式小型密封電池對充電時的技術要求，通常規定充電速率不要大于0.3C，相當于4A電流，而充電器充(chong)電電流在2A左右，遠離(li)極(ji)限充(chong)電電流。