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)定電(dian)壓(ya)高(gao)0.1V，電(dian)池(chi)因此(ci)熱失控而充(chong)(chong)脹(zhang)了；也接(jie)到通知說：電(dian)壓(ya)比(bi)規(gui)定定低(di)0.1V，電(dian)池(chi)欠(qian)充(chong)(chong)，提前(qian)報廢。一(yi)個千(qian)分之幾的誤差造成如此(ci)嚴重后果，真是失之毫厘(li)，謬(miu)之千(qian)里之外，鉛酸蓄(xu)電(dian)池(chi)果真有這么神秘嗎？為了解開(kai)困(kun)擾電(dian)動車充(chong)(chong)電(dian)中的這個謎團，做如下實驗。
用(yong)一個(ge)水槽盛滿水，電(dian)(dian)(dian)池(chi)放在(zai)水中，在(zai)電(dian)(dian)(dian)池(chi)上方有(you)一個(ge)收集氣體用(yong)的(de)倒扣的(de)漏斗，漏斗頂端裝(zhuang)有(you)可以計量(liang)(liang)氣體容量(liang)(liang)的(de)注(zhu)射(she)針筒。充(chong)電(dian)(dian)(dian)用(yong)可調穩壓(ya)電(dian)(dian)(dian)源，用(yong)兩(liang)只四位半數字萬用(yong)表測(ce)量(liang)(liang)充(chong)電(dian)(dian)(dian)電(dian)(dian)(dian)流和充(chong)電(dian)(dian)(dian)電(dian)(dian)(dian)壓(ya)。
試驗時(shi)(shi)間(jian)(jian)(jian)是在冬季(ji)，水溫5℃。實(shi)驗條件是統一(yi)用2A電(dian)(dian)(dian)流(liu)充(chong)(chong)(chong)電(dian)(dian)(dian)，最充(chong)(chong)(chong)電(dian)(dian)(dian)電(dian)(dian)(dian)壓分(fen)(fen)別(bie)用43V、44V、45V輪循環依(yi)次進行，浮充(chong)(chong)(chong)轉換電(dian)(dian)(dian)流(liu)一(yi)律400mA，記(ji)(ji)錄下每次的(de)充(chong)(chong)(chong)電(dian)(dian)(dian)時(shi)(shi)間(jian)(jian)(jian)，包括充(chong)(chong)(chong)電(dian)(dian)(dian)末期(qi)隨時(shi)(shi)間(jian)(jian)(jian)電(dian)(dian)(dian)流(liu)下降各點數據、開(kai)始析氣電(dian)(dian)(dian)壓，按時(shi)(shi)間(jian)(jian)(jian)記(ji)(ji)錄析氣量(liang)。電(dian)(dian)(dian)池充(chong)(chong)(chong)完后(hou)，用萬(wan)分(fen)(fen)之幾精度的(de)電(dian)(dian)(dian)量(liang)臺記(ji)(ji)錄放電(dian)(dian)(dian)容量(liang)。充(chong)(chong)(chong)入電(dian)(dian)(dian)量(liang)是在計算(suan)紙上讀出時(shi)(shi)間(jian)(jian)(jian)電(dian)(dian)(dian)流(liu)曲線與坐(zuo)標(biao)之間(jian)(jian)(jian)的(de)面積（電(dian)(dian)(dian)容量(liang)就是充(chong)(chong)(chong)電(dian)(dian)(dian)電(dian)(dian)(dian)流(liu)對時(shi)(shi)間(jian)(jian)(jian)的(de)定積分(fen)(fen)）。數據見(jian)下表：
充號
最高(gao)電壓
V
充電電流(liu)
A
浮充電壓V
切換電流A
充入電量Ah
放出電(dian)量
Ah
析氣(qi)電壓
V
析氣量
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(shi)，放電(dian)容量為10Ah。
得到試(shi)驗(yan)數(shu)據后，最(zui)感(gan)到驚異的(de)(de)是(shi)：充(chong)(chong)(chong)(chong)(chong)入電(dian)(dian)(dian)(dian)(dian)(dian)(dian)量(liang)的(de)(de)多(duo)(duo)少(shao)幾乎與(yu)充(chong)(chong)(chong)(chong)(chong)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)壓(ya)無(wu)關。很(hen)多(duo)(duo)人認為充(chong)(chong)(chong)(chong)(chong)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)壓(ya)低電(dian)(dian)(dian)(dian)(dian)(dian)(dian)池(chi)(chi)(chi)會(hui)充(chong)(chong)(chong)(chong)(chong)不滿，電(dian)(dian)(dian)(dian)(dian)(dian)(dian)池(chi)(chi)(chi)會(hui)提前鹽(yan)化(hua)報(bao)廢(fei)，特(te)別是(shi)在(zai)冬季氣(qi)溫(wen)較低的(de)(de)時候(hou)。而這次試(shi)驗(yan)正好是(shi)在(zai)冬季，水(shui)溫(wen)只(zhi)有5℃，試(shi)驗(yan)的(de)(de)中(zhong)心電(dian)(dian)(dian)(dian)(dian)(dian)(dian)壓(ya)值(zhi)是(shi)44V，上下偏差(cha)1V，相對誤(wu)差(cha)是(shi)2.3%。在(zai)用43V和45V充(chong)(chong)(chong)(chong)(chong)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)的(de)(de)情(qing)況下，充(chong)(chong)(chong)(chong)(chong)入電(dian)(dian)(dian)(dian)(dian)(dian)(dian)量(liang)和放(fang)出(chu)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)量(liang)相差(cha)無(wu)幾，與(yu)大(da)(da)家公認的(de)(de)看(kan)法大(da)(da)相徑庭(ting)，試(shi)驗(yan)是(shi)用的(de)(de)同(tong)一(yi)組電(dian)(dian)(dian)(dian)(dian)(dian)(dian)池(chi)(chi)(chi)，同(tong)樣的(de)(de)充(chong)(chong)(chong)(chong)(chong)、放(fang)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)條件，輪番做同(tong)樣的(de)(de)測試(shi)，實驗(yan)數(shu)據重復同(tong)樣的(de)(de)規(gui)律，可(ke)排(pai)除偶然因素(su)干擾，試(shi)驗(yan)數(shu)據是(shi)準確可(ke)信(xin)的(de)(de)。從(cong)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)池(chi)(chi)(chi)充(chong)(chong)(chong)(chong)(chong)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)原理上看(kan)，只(zhi)要(yao)充(chong)(chong)(chong)(chong)(chong)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)源電(dian)(dian)(dian)(dian)(dian)(dian)(dian)壓(ya)高(gao)于(yu)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)池(chi)(chi)(chi)端電(dian)(dian)(dian)(dian)(dian)(dian)(dian)壓(ya)，都會(hui)給電(dian)(dian)(dian)(dian)(dian)(dian)(dian)池(chi)(chi)(chi)充(chong)(chong)(chong)(chong)(chong)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)，一(yi)直(zhi)到電(dian)(dian)(dian)(dian)(dian)(dian)(dian)池(chi)(chi)(chi)中(zhong)的(de)(de)活(huo)性(xing)(xing)物(wu)(wu)(wu)質(zhi)轉換完成。充(chong)(chong)(chong)(chong)(chong)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)最(zui)高(gao)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)壓(ya)，也就是(shi)充(chong)(chong)(chong)(chong)(chong)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)源開始由恒流(liu)區轉變到恒壓(ya)區，這種轉變是(shi)由電(dian)(dian)(dian)(dian)(dian)(dian)(dian)池(chi)(chi)(chi)自(zi)身充(chong)(chong)(chong)(chong)(chong)入電(dian)(dian)(dian)(dian)(dian)(dian)(dian)量(liang)多(duo)(duo)少(shao)、活(huo)性(xing)(xing)物(wu)(wu)(wu)質(zhi)反應(ying)(ying)了多(duo)(duo)少(shao)決(jue)(jue)定的(de)(de)，充(chong)(chong)(chong)(chong)(chong)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)壓(ya)的(de)(de)高(gao)低，僅是(shi)能進行電(dian)(dian)(dian)(dian)(dian)(dian)(dian)化(hua)學(xue)反應(ying)(ying)的(de)(de)條件，只(zhi)要(yao)高(gao)于(yu)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)池(chi)(chi)(chi)開路(lu)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)壓(ya)就會(hui)給電(dian)(dian)(dian)(dian)(dian)(dian)(dian)池(chi)(chi)(chi)充(chong)(chong)(chong)(chong)(chong)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)，多(duo)(duo)少(shao)物(wu)(wu)(wu)質(zhi)能參與(yu)反應(ying)(ying)由電(dian)(dian)(dian)(dian)(dian)(dian)(dian)池(chi)(chi)(chi)自(zi)身決(jue)(jue)定。從(cong)這個思路(lu)理解，就不難得出(chu)，充(chong)(chong)(chong)(chong)(chong)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)壓(ya)高(gao)低對電(dian)(dian)(dian)(dian)(dian)(dian)(dian)池(chi)(chi)(chi)容(rong)量(liang)沒有多(duo)(duo)大(da)(da)影響。
電(dian)(dian)池在42.5V～43.5V時(shi)開始析(xi)(xi)氣,而析(xi)(xi)氣的速度與(yu)(yu)充電(dian)(dian)電(dian)(dian)壓(ya)有關(guan)。到充電(dian)(dian)結束時(shi)，總析(xi)(xi)氣量與(yu)(yu)充電(dian)(dian)最高(gao)電(dian)(dian)壓(ya)有關(guan)，43V與(yu)(yu)45V總析(xi)(xi)氣量相差10位(wei)（注：以單格(ge)允(yun)許(xu)極限失(shi)水10克，18格(ge)相當240公升氣體，該電(dian)(dian)池45V時(shi)失(shi)水并不大）。 在充電(dian)(dian)末(mo)期電(dian)(dian)流下(xia)降(jiang)區時(shi)，只(zhi)要降(jiang)低電(dian)(dian)壓(ya)到42.5V時(shi)，析(xi)(xi)氣立即停止(zhi)，這時(shi)充電(dian)(dian)電(dian)(dian)流稍小一點，還會依著原來的規律下(xia)降(jiang)。
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(chong)(chong)(chong)的(de)(de)目的(de)(de)僅是(shi)免(mian)于(yu)充(chong)(chong)(chong)電(dian)(dian)末期(qi)大量析氣失水，只要把(ba)電(dian)(dian)壓(ya)降到析氣點(dian)電(dian)(dian)壓(ya)以(yi)下，但也不能低(di)于(yu)電(dian)(dian)池(chi)端電(dian)(dian)壓(ya)而停止向電(dian)(dian)池(chi)充(chong)(chong)(chong)電(dian)(dian)。前面說過，在浮(fu)充(chong)(chong)(chong)電(dian)(dian)壓(ya)下，充(chong)(chong)(chong)電(dian)(dian)電(dian)(dian)流的(de)(de)走勢基本(ben)還(huan)是(shi)依著原曲線(xian)下降，一般還(huan)補足5%的(de)(de)容量。所(suo)以(yi)浮(fu)充(chong)(chong)(chong)電(dian)(dian)壓(ya)應在的(de)(de)范圍是(shi)低(di)于(yu)析氣電(dian)(dian)壓(ya)（42.5V），高于(yu)電(dian)(dian)池(chi)充(chong)(chong)(chong)足電(dian)(dian)以(yi)后的(de)(de)開路端電(dian)(dian)壓(ya)（約40V）。
浮(fu)充(chong)(chong)(chong)轉(zhuan)(zhuan)(zhuan)換(huan)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)流，只不(bu)(bu)過(guo)(guo)(guo)是(shi)選(xuan)擇在(zai)充(chong)(chong)(chong)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)末(mo)期(qi)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)池(chi)(chi)活性物(wu)質(zhi)反應接近尾聲，充(chong)(chong)(chong)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)流自動下(xia)降(jiang)到某一點時(shi)(shi)，切換(huan)浮(fu)充(chong)(chong)(chong)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)壓(ya)的(de)記(ji)號(hao)，不(bu)(bu)少(shao)(shao)人以(yi)(yi)為浮(fu)充(chong)(chong)(chong)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)流高(gao)(gao)(gao)了電(dian)(dian)(dian)(dian)(dian)(dian)(dian)池(chi)(chi)會充(chong)(chong)(chong)不(bu)(bu)滿是(shi)概念不(bu)(bu)清(qing)，充(chong)(chong)(chong)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)壓(ya)只要(yao)高(gao)(gao)(gao)于電(dian)(dian)(dian)(dian)(dian)(dian)(dian)池(chi)(chi)端電(dian)(dian)(dian)(dian)(dian)(dian)(dian)壓(ya)，都會對電(dian)(dian)(dian)(dian)(dian)(dian)(dian)池(chi)(chi)充(chong)(chong)(chong)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)，只不(bu)(bu)過(guo)(guo)(guo)有(you)(you)用(yong)戶看(kan)到指示(shi)燈紅轉(zhuan)(zhuan)(zhuan)綠后提前去用(yong)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)池(chi)(chi)，這種情況是(shi)不(bu)(bu)多(duo)(duo)的(de)，一般都是(shi)夜間充(chong)(chong)(chong)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)，到早晨綠燈已(yi)亮(liang)了多(duo)(duo)時(shi)(shi)。有(you)(you)的(de)廠家(jia)使用(yong)說明書(shu)上(shang)提醒用(yong)戶，在(zai)轉(zhuan)(zhuan)(zhuan)綠燈后繼續(xu)充(chong)(chong)(chong)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)2小(xiao)時(shi)(shi)，是(shi)很(hen)好(hao)很(hen)正確的(de)。所以(yi)(yi)沒(mei)有(you)(you)必要(yao)刻意去追求浮(fu)充(chong)(chong)(chong)轉(zhuan)(zhuan)(zhuan)換(huan)點的(de)高(gao)(gao)(gao)低，一般新電(dian)(dian)(dian)(dian)(dian)(dian)(dian)池(chi)(chi)末(mo)期(qi)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)流約為50mA，失(shi)(shi)水(shui)以(yi)(yi)后，酸比增高(gao)(gao)(gao)，那時(shi)(shi)可(ke)達500 mA以(yi)(yi)上(shang)。從(cong)析(xi)氣速率與電(dian)(dian)(dian)(dian)(dian)(dian)(dian)壓(ya)的(de)關系(xi)上(shang)來看(kan)（上(shang)圖），早點脫離析(xi)氣區(qu)為好(hao)，一方(fang)(fang)面(mian)(mian)，一方(fang)(fang)面(mian)(mian)可(ke)以(yi)(yi)減少(shao)(shao)析(xi)氣量(liang)，另一方(fang)(fang)面(mian)(mian)，電(dian)(dian)(dian)(dian)(dian)(dian)(dian)池(chi)(chi)用(yong)了一段時(shi)(shi)間，末(mo)期(qi)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)流增高(gao)(gao)(gao)，但還能低于我(wo)們設定的(de)轉(zhuan)(zhuan)(zhuan)換(huan)點電(dian)(dian)(dian)(dian)(dian)(dian)(dian)流，否則電(dian)(dian)(dian)(dian)(dian)(dian)(dian)池(chi)(chi)一直在(zai)最高(gao)(gao)(gao)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)壓(ya)充(chong)(chong)(chong)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)下(xia)，大量(liang)失(shi)(shi)水(shui)，引發熱控，充(chong)(chong)(chong)脹(zhang)充(chong)(chong)(chong)壞電(dian)(dian)(dian)(dian)(dian)(dian)(dian)池(chi)(chi)。有(you)(you)人固執(zhi)地(di)強調(diao)，浮(fu)充(chong)(chong)(chong)轉(zhuan)(zhuan)(zhuan)換(huan)點高(gao)(gao)(gao)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)池(chi)(chi)會欠充(chong)(chong)(chong)，前面(mian)(mian)已(yi)討論過(guo)(guo)(guo)，切換(huan)到浮(fu)充(chong)(chong)(chong)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)壓(ya)后，不(bu)(bu)是(shi)停止(zhi)充(chong)(chong)(chong)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)了，還會繼續(xu)對電(dian)(dian)(dian)(dian)(dian)(dian)(dian)池(chi)(chi)充(chong)(chong)(chong)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)的(de)，轉(zhuan)(zhuan)(zhuan)換(huan)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)流適當高(gao)(gao)(gao)一點有(you)(you)利于避免過(guo)(guo)(guo)分失(shi)(shi)水(shui)和(he)熱失(shi)(shi)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)電電流(liu)在2A左右，遠離極(ji)限充(chong)電電流(liu)。