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(gui)定(ding)電(dian)壓(ya)高0.1V，電(dian)池(chi)因此(ci)熱失控而充(chong)脹了(le)；也(ye)接到通知說(shuo)：電(dian)壓(ya)比(bi)規(gui)定(ding)定(ding)低0.1V，電(dian)池(chi)欠充(chong)，提前報廢。一個千(qian)分之(zhi)(zhi)幾的(de)誤(wu)差造成如(ru)此(ci)嚴重后(hou)果，真是(shi)失之(zhi)(zhi)毫厘，謬之(zhi)(zhi)千(qian)里之(zhi)(zhi)外，鉛酸蓄電(dian)池(chi)果真有(you)這(zhe)么神秘嗎(ma)？為了(le)解(jie)開困擾電(dian)動車充(chong)電(dian)中的(de)這(zhe)個謎團，做(zuo)如(ru)下(xia)實驗。
用(yong)一(yi)個(ge)水(shui)槽(cao)盛滿水(shui)，電(dian)(dian)池放在水(shui)中，在電(dian)(dian)池上方有一(yi)個(ge)收集氣體(ti)用(yong)的倒扣(kou)的漏(lou)(lou)斗，漏(lou)(lou)斗頂端裝有可(ke)以計量氣體(ti)容量的注射(she)針筒(tong)。充電(dian)(dian)用(yong)可(ke)調穩壓(ya)電(dian)(dian)源，用(yong)兩只四(si)位半數字萬用(yong)表測量充電(dian)(dian)電(dian)(dian)流和充電(dian)(dian)電(dian)(dian)壓(ya)。
試驗時間是(shi)在冬季(ji)，水(shui)溫5℃。實驗條(tiao)件(jian)是(shi)統一用2A電(dian)(dian)(dian)(dian)(dian)流充電(dian)(dian)(dian)(dian)(dian)，最充電(dian)(dian)(dian)(dian)(dian)電(dian)(dian)(dian)(dian)(dian)壓(ya)分(fen)別用43V、44V、45V輪循環依次進行，浮(fu)充轉換電(dian)(dian)(dian)(dian)(dian)流一律400mA，記(ji)(ji)錄下(xia)(xia)每(mei)次的(de)(de)充電(dian)(dian)(dian)(dian)(dian)時間，包括充電(dian)(dian)(dian)(dian)(dian)末期隨(sui)時間電(dian)(dian)(dian)(dian)(dian)流下(xia)(xia)降(jiang)各點數據、開始析氣(qi)電(dian)(dian)(dian)(dian)(dian)壓(ya)，按(an)時間記(ji)(ji)錄析氣(qi)量。電(dian)(dian)(dian)(dian)(dian)池充完后，用萬分(fen)之幾精度(du)的(de)(de)電(dian)(dian)(dian)(dian)(dian)量臺記(ji)(ji)錄放(fang)電(dian)(dian)(dian)(dian)(dian)容量。充入電(dian)(dian)(dian)(dian)(dian)量是(shi)在計(ji)算紙上讀出(chu)時間電(dian)(dian)(dian)(dian)(dian)流曲線(xian)與坐標之間的(de)(de)面積(ji)（電(dian)(dian)(dian)(dian)(dian)容量就是(shi)充電(dian)(dian)(dian)(dian)(dian)電(dian)(dian)(dian)(dian)(dian)流對時間的(de)(de)定積(ji)分(fen)）。數據見下(xia)(xia)表：
充號
最高電壓(ya)
V
充(chong)電電流
A
浮充電壓V
切換電流A
充入電量Ah
放(fang)出電量
Ah
析氣電壓
V
析氣(qi)量
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，放電容(rong)量為10Ah。
得到試(shi)驗(yan)數(shu)據(ju)后(hou)，最感到驚(jing)異的(de)是(shi)(shi)(shi)：充(chong)(chong)(chong)入(ru)(ru)電(dian)(dian)(dian)(dian)(dian)量(liang)的(de)多少(shao)幾(ji)乎與(yu)(yu)充(chong)(chong)(chong)電(dian)(dian)(dian)(dian)(dian)電(dian)(dian)(dian)(dian)(dian)壓(ya)(ya)(ya)無(wu)關。很多人認為充(chong)(chong)(chong)電(dian)(dian)(dian)(dian)(dian)電(dian)(dian)(dian)(dian)(dian)壓(ya)(ya)(ya)低電(dian)(dian)(dian)(dian)(dian)池(chi)會(hui)充(chong)(chong)(chong)不滿(man)，電(dian)(dian)(dian)(dian)(dian)池(chi)會(hui)提前(qian)鹽(yan)化(hua)報(bao)廢(fei)，特別是(shi)(shi)(shi)在(zai)冬(dong)季氣溫(wen)(wen)較低的(de)時(shi)候。而這(zhe)次(ci)試(shi)驗(yan)正好(hao)是(shi)(shi)(shi)在(zai)冬(dong)季，水溫(wen)(wen)只有(you)5℃，試(shi)驗(yan)的(de)中心電(dian)(dian)(dian)(dian)(dian)壓(ya)(ya)(ya)值是(shi)(shi)(shi)44V，上下偏(pian)差1V，相(xiang)對誤差是(shi)(shi)(shi)2.3%。在(zai)用43V和(he)45V充(chong)(chong)(chong)電(dian)(dian)(dian)(dian)(dian)的(de)情況(kuang)下，充(chong)(chong)(chong)入(ru)(ru)電(dian)(dian)(dian)(dian)(dian)量(liang)和(he)放出(chu)電(dian)(dian)(dian)(dian)(dian)量(liang)相(xiang)差無(wu)幾(ji)，與(yu)(yu)大家公(gong)認的(de)看法大相(xiang)徑庭，試(shi)驗(yan)是(shi)(shi)(shi)用的(de)同(tong)(tong)一(yi)組電(dian)(dian)(dian)(dian)(dian)池(chi)，同(tong)(tong)樣的(de)充(chong)(chong)(chong)、放電(dian)(dian)(dian)(dian)(dian)條(tiao)件(jian)，輪番做同(tong)(tong)樣的(de)測試(shi)，實驗(yan)數(shu)據(ju)重復同(tong)(tong)樣的(de)規律，可排除偶然因素干擾，試(shi)驗(yan)數(shu)據(ju)是(shi)(shi)(shi)準確可信的(de)。從電(dian)(dian)(dian)(dian)(dian)池(chi)充(chong)(chong)(chong)電(dian)(dian)(dian)(dian)(dian)原理(li)上看，只要(yao)充(chong)(chong)(chong)電(dian)(dian)(dian)(dian)(dian)源(yuan)(yuan)電(dian)(dian)(dian)(dian)(dian)壓(ya)(ya)(ya)高(gao)(gao)(gao)(gao)(gao)于(yu)電(dian)(dian)(dian)(dian)(dian)池(chi)端電(dian)(dian)(dian)(dian)(dian)壓(ya)(ya)(ya)，都會(hui)給電(dian)(dian)(dian)(dian)(dian)池(chi)充(chong)(chong)(chong)電(dian)(dian)(dian)(dian)(dian)，一(yi)直到電(dian)(dian)(dian)(dian)(dian)池(chi)中的(de)活(huo)性物(wu)質(zhi)(zhi)轉換完成。充(chong)(chong)(chong)電(dian)(dian)(dian)(dian)(dian)最高(gao)(gao)(gao)(gao)(gao)電(dian)(dian)(dian)(dian)(dian)壓(ya)(ya)(ya)，也就是(shi)(shi)(shi)充(chong)(chong)(chong)電(dian)(dian)(dian)(dian)(dian)電(dian)(dian)(dian)(dian)(dian)源(yuan)(yuan)開(kai)始由恒流區轉變(bian)到恒壓(ya)(ya)(ya)區，這(zhe)種(zhong)轉變(bian)是(shi)(shi)(shi)由電(dian)(dian)(dian)(dian)(dian)池(chi)自(zi)身充(chong)(chong)(chong)入(ru)(ru)電(dian)(dian)(dian)(dian)(dian)量(liang)多少(shao)、活(huo)性物(wu)質(zhi)(zhi)反應了多少(shao)決定的(de)，充(chong)(chong)(chong)電(dian)(dian)(dian)(dian)(dian)電(dian)(dian)(dian)(dian)(dian)壓(ya)(ya)(ya)的(de)高(gao)(gao)(gao)(gao)(gao)低，僅是(shi)(shi)(shi)能(neng)(neng)進行電(dian)(dian)(dian)(dian)(dian)化(hua)學反應的(de)條(tiao)件(jian)，只要(yao)高(gao)(gao)(gao)(gao)(gao)于(yu)電(dian)(dian)(dian)(dian)(dian)池(chi)開(kai)路電(dian)(dian)(dian)(dian)(dian)壓(ya)(ya)(ya)就會(hui)給電(dian)(dian)(dian)(dian)(dian)池(chi)充(chong)(chong)(chong)電(dian)(dian)(dian)(dian)(dian)，多少(shao)物(wu)質(zhi)(zhi)能(neng)(neng)參與(yu)(yu)反應由電(dian)(dian)(dian)(dian)(dian)池(chi)自(zi)身決定。從這(zhe)個思路理(li)解，就不難(nan)得出(chu)，充(chong)(chong)(chong)電(dian)(dian)(dian)(dian)(dian)電(dian)(dian)(dian)(dian)(dian)壓(ya)(ya)(ya)高(gao)(gao)(gao)(gao)(gao)低對電(dian)(dian)(dian)(dian)(dian)池(chi)容量(liang)沒有(you)多大影響。
電(dian)池(chi)在42.5V～43.5V時(shi)開始(shi)析(xi)氣(qi),而(er)析(xi)氣(qi)的(de)速(su)度(du)與充(chong)(chong)電(dian)電(dian)壓(ya)有(you)關(guan)。到(dao)充(chong)(chong)電(dian)結(jie)束時(shi)，總析(xi)氣(qi)量(liang)與充(chong)(chong)電(dian)最高(gao)電(dian)壓(ya)有(you)關(guan)，43V與45V總析(xi)氣(qi)量(liang)相差10位（注：以(yi)單格允(yun)許極限失水10克，18格相當(dang)240公升氣(qi)體，該電(dian)池(chi)45V時(shi)失水并不大）。 在充(chong)(chong)電(dian)末期(qi)電(dian)流下降區時(shi)，只要降低電(dian)壓(ya)到(dao)42.5V時(shi)，析(xi)氣(qi)立即停止，這時(shi)充(chong)(chong)電(dian)電(dian)流稍小一點，還會(hui)依著(zhu)原來的(de)規律下降。
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，充電器設定浮充的(de)目的(de)僅是免于(yu)充電(dian)(dian)(dian)末期大量(liang)(liang)析氣(qi)失水，只要把(ba)電(dian)(dian)(dian)壓(ya)(ya)(ya)降(jiang)到析氣(qi)點電(dian)(dian)(dian)壓(ya)(ya)(ya)以下，但也不能低(di)于(yu)電(dian)(dian)(dian)池端電(dian)(dian)(dian)壓(ya)(ya)(ya)而停止向電(dian)(dian)(dian)池充電(dian)(dian)(dian)。前面說過，在浮充電(dian)(dian)(dian)壓(ya)(ya)(ya)下，充電(dian)(dian)(dian)電(dian)(dian)(dian)流(liu)的(de)走勢(shi)基本(ben)還是依著(zhu)原曲線(xian)下降(jiang)，一般(ban)還補足5%的(de)容量(liang)(liang)。所以浮充電(dian)(dian)(dian)壓(ya)(ya)(ya)應在的(de)范圍是低(di)于(yu)析氣(qi)電(dian)(dian)(dian)壓(ya)(ya)(ya)（42.5V），高(gao)于(yu)電(dian)(dian)(dian)池充足電(dian)(dian)(dian)以后的(de)開路端電(dian)(dian)(dian)壓(ya)(ya)(ya)（約40V）。
浮(fu)充(chong)(chong)(chong)轉(zhuan)換(huan)(huan)電(dian)(dian)(dian)(dian)(dian)流(liu)，只(zhi)不(bu)過是(shi)(shi)選擇在(zai)(zai)充(chong)(chong)(chong)電(dian)(dian)(dian)(dian)(dian)末(mo)(mo)(mo)期電(dian)(dian)(dian)(dian)(dian)池(chi)活性物質反應接近(jin)尾聲，充(chong)(chong)(chong)電(dian)(dian)(dian)(dian)(dian)電(dian)(dian)(dian)(dian)(dian)流(liu)自動(dong)下(xia)降(jiang)到某一(yi)(yi)點時(shi)，切換(huan)(huan)浮(fu)充(chong)(chong)(chong)電(dian)(dian)(dian)(dian)(dian)壓的(de)(de)記號，不(bu)少(shao)人以為(wei)浮(fu)充(chong)(chong)(chong)電(dian)(dian)(dian)(dian)(dian)流(liu)高了電(dian)(dian)(dian)(dian)(dian)池(chi)會充(chong)(chong)(chong)不(bu)滿是(shi)(shi)概念不(bu)清，充(chong)(chong)(chong)電(dian)(dian)(dian)(dian)(dian)電(dian)(dian)(dian)(dian)(dian)壓只(zhi)要高于(yu)電(dian)(dian)(dian)(dian)(dian)池(chi)端電(dian)(dian)(dian)(dian)(dian)壓，都會對(dui)電(dian)(dian)(dian)(dian)(dian)池(chi)充(chong)(chong)(chong)電(dian)(dian)(dian)(dian)(dian)，只(zhi)不(bu)過有用(yong)(yong)戶看(kan)到指示燈紅轉(zhuan)綠后(hou)提前(qian)去用(yong)(yong)電(dian)(dian)(dian)(dian)(dian)池(chi)，這種(zhong)情況是(shi)(shi)不(bu)多的(de)(de)，一(yi)(yi)般都是(shi)(shi)夜(ye)間充(chong)(chong)(chong)電(dian)(dian)(dian)(dian)(dian)，到早晨綠燈已亮了多時(shi)。有的(de)(de)廠家(jia)使(shi)用(yong)(yong)說明書上(shang)(shang)提醒用(yong)(yong)戶，在(zai)(zai)轉(zhuan)綠燈后(hou)繼續充(chong)(chong)(chong)電(dian)(dian)(dian)(dian)(dian)2小時(shi)，是(shi)(shi)很(hen)好很(hen)正(zheng)確的(de)(de)。所以沒有必要刻意去追求浮(fu)充(chong)(chong)(chong)轉(zhuan)換(huan)(huan)點的(de)(de)高低(di)，一(yi)(yi)般新電(dian)(dian)(dian)(dian)(dian)池(chi)末(mo)(mo)(mo)期電(dian)(dian)(dian)(dian)(dian)流(liu)約為(wei)50mA，失水以后(hou)，酸比增(zeng)高，那時(shi)可(ke)達(da)500 mA以上(shang)(shang)。從析(xi)氣速率與電(dian)(dian)(dian)(dian)(dian)壓的(de)(de)關系上(shang)(shang)來看(kan)（上(shang)(shang)圖），早點脫(tuo)離析(xi)氣區為(wei)好，一(yi)(yi)方(fang)面，一(yi)(yi)方(fang)面可(ke)以減少(shao)析(xi)氣量，另一(yi)(yi)方(fang)面，電(dian)(dian)(dian)(dian)(dian)池(chi)用(yong)(yong)了一(yi)(yi)段時(shi)間，末(mo)(mo)(mo)期電(dian)(dian)(dian)(dian)(dian)流(liu)增(zeng)高，但還(huan)能低(di)于(yu)我們設定的(de)(de)轉(zhuan)換(huan)(huan)點電(dian)(dian)(dian)(dian)(dian)流(liu)，否則(ze)電(dian)(dian)(dian)(dian)(dian)池(chi)一(yi)(yi)直在(zai)(zai)最高電(dian)(dian)(dian)(dian)(dian)壓充(chong)(chong)(chong)電(dian)(dian)(dian)(dian)(dian)下(xia)，大量失水，引(yin)發熱控，充(chong)(chong)(chong)脹充(chong)(chong)(chong)壞電(dian)(dian)(dian)(dian)(dian)池(chi)。有人固執地強調，浮(fu)充(chong)(chong)(chong)轉(zhuan)換(huan)(huan)點高電(dian)(dian)(dian)(dian)(dian)池(chi)會欠充(chong)(chong)(chong)，前(qian)面已討論過，切換(huan)(huan)到浮(fu)充(chong)(chong)(chong)電(dian)(dian)(dian)(dian)(dian)壓后(hou)，不(bu)是(shi)(shi)停止充(chong)(chong)(chong)電(dian)(dian)(dian)(dian)(dian)了，還(huan)會繼續對(dui)電(dian)(dian)(dian)(dian)(dian)池(chi)充(chong)(chong)(chong)電(dian)(dian)(dian)(dian)(dian)的(de)(de)，轉(zhuan)換(huan)(huan)電(dian)(dian)(dian)(dian)(dian)流(liu)適當高一(yi)(yi)點有利于(yu)避免過分失水和熱失控。
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(dian)電(dian)流在(zai)2A左右，遠離極限充(chong)電(dian)電(dian)流。