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(dian)(dian)壓(ya)(ya)高0.1V，電(dian)(dian)池因此熱(re)失(shi)控而充(chong)脹(zhang)了；也接到通知說：電(dian)(dian)壓(ya)(ya)比(bi)規定定低0.1V，電(dian)(dian)池欠(qian)充(chong)，提前報廢。一個千(qian)分之(zhi)(zhi)幾(ji)的誤差造成如(ru)此嚴重后果，真是(shi)失(shi)之(zhi)(zhi)毫厘，謬之(zhi)(zhi)千(qian)里(li)之(zhi)(zhi)外，鉛酸蓄電(dian)(dian)池果真有這(zhe)么神秘嗎？為了解開(kai)困擾電(dian)(dian)動車(che)充(chong)電(dian)(dian)中的這(zhe)個謎團，做如(ru)下實驗。
用(yong)一個(ge)水(shui)槽(cao)盛滿水(shui)，電(dian)(dian)池(chi)放在(zai)水(shui)中，在(zai)電(dian)(dian)池(chi)上方有(you)一個(ge)收集氣(qi)(qi)體用(yong)的倒扣的漏斗(dou)，漏斗(dou)頂端裝(zhuang)有(you)可(ke)以計量氣(qi)(qi)體容量的注射針筒。充(chong)電(dian)(dian)用(yong)可(ke)調穩壓電(dian)(dian)源(yuan)，用(yong)兩只四位(wei)半(ban)數字萬用(yong)表測量充(chong)電(dian)(dian)電(dian)(dian)流和充(chong)電(dian)(dian)電(dian)(dian)壓。
試驗時間(jian)是在冬季，水溫5℃。實驗條件是統一用(yong)2A電(dian)(dian)(dian)流充(chong)電(dian)(dian)(dian)，最充(chong)電(dian)(dian)(dian)電(dian)(dian)(dian)壓(ya)(ya)分別(bie)用(yong)43V、44V、45V輪循環依次進行，浮充(chong)轉換電(dian)(dian)(dian)流一律400mA，記(ji)錄(lu)下(xia)每次的充(chong)電(dian)(dian)(dian)時間(jian)，包括充(chong)電(dian)(dian)(dian)末期隨時間(jian)電(dian)(dian)(dian)流下(xia)降各點數據、開始(shi)析氣電(dian)(dian)(dian)壓(ya)(ya)，按(an)時間(jian)記(ji)錄(lu)析氣量(liang)。電(dian)(dian)(dian)池充(chong)完后，用(yong)萬(wan)分之(zhi)(zhi)幾精(jing)度(du)的電(dian)(dian)(dian)量(liang)臺記(ji)錄(lu)放電(dian)(dian)(dian)容量(liang)。充(chong)入(ru)電(dian)(dian)(dian)量(liang)是在計(ji)算紙上讀出(chu)時間(jian)電(dian)(dian)(dian)流曲線與坐標(biao)之(zhi)(zhi)間(jian)的面積(ji)（電(dian)(dian)(dian)容量(liang)就是充(chong)電(dian)(dian)(dian)電(dian)(dian)(dian)流對(dui)時間(jian)的定積(ji)分）。數據見下(xia)表：
充號
最高電壓
V
充電(dian)電(dian)流(liu)
A
浮充電壓V
切換電流A
充入電量Ah
放出電量
Ah
析氣電壓
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)，放電容量(liang)為10Ah。
得(de)到試(shi)(shi)驗(yan)數據(ju)后，最(zui)(zui)感到驚(jing)異的(de)(de)(de)(de)是(shi)(shi)：充(chong)(chong)入(ru)電(dian)(dian)量的(de)(de)(de)(de)多(duo)(duo)少(shao)(shao)幾乎與(yu)充(chong)(chong)電(dian)(dian)電(dian)(dian)壓(ya)(ya)(ya)無關。很多(duo)(duo)人認為充(chong)(chong)電(dian)(dian)電(dian)(dian)壓(ya)(ya)(ya)低電(dian)(dian)池(chi)(chi)(chi)(chi)(chi)會(hui)(hui)充(chong)(chong)不滿，電(dian)(dian)池(chi)(chi)(chi)(chi)(chi)會(hui)(hui)提前鹽(yan)化報廢，特別(bie)是(shi)(shi)在冬季氣(qi)溫較低的(de)(de)(de)(de)時候(hou)。而(er)這(zhe)次試(shi)(shi)驗(yan)正好是(shi)(shi)在冬季，水溫只(zhi)(zhi)有5℃，試(shi)(shi)驗(yan)的(de)(de)(de)(de)中心電(dian)(dian)壓(ya)(ya)(ya)值是(shi)(shi)44V，上下偏差1V，相(xiang)對誤差是(shi)(shi)2.3%。在用(yong)43V和45V充(chong)(chong)電(dian)(dian)的(de)(de)(de)(de)情況(kuang)下，充(chong)(chong)入(ru)電(dian)(dian)量和放出電(dian)(dian)量相(xiang)差無幾，與(yu)大家(jia)公認的(de)(de)(de)(de)看法大相(xiang)徑庭(ting)，試(shi)(shi)驗(yan)是(shi)(shi)用(yong)的(de)(de)(de)(de)同(tong)一(yi)組電(dian)(dian)池(chi)(chi)(chi)(chi)(chi)，同(tong)樣(yang)的(de)(de)(de)(de)充(chong)(chong)、放電(dian)(dian)條件，輪番做同(tong)樣(yang)的(de)(de)(de)(de)測(ce)試(shi)(shi)，實驗(yan)數據(ju)重復同(tong)樣(yang)的(de)(de)(de)(de)規(gui)律，可排除(chu)偶然因素干擾(rao)，試(shi)(shi)驗(yan)數據(ju)是(shi)(shi)準確(que)可信的(de)(de)(de)(de)。從(cong)電(dian)(dian)池(chi)(chi)(chi)(chi)(chi)充(chong)(chong)電(dian)(dian)原(yuan)理上看，只(zhi)(zhi)要充(chong)(chong)電(dian)(dian)源電(dian)(dian)壓(ya)(ya)(ya)高于(yu)電(dian)(dian)池(chi)(chi)(chi)(chi)(chi)端電(dian)(dian)壓(ya)(ya)(ya)，都(dou)會(hui)(hui)給電(dian)(dian)池(chi)(chi)(chi)(chi)(chi)充(chong)(chong)電(dian)(dian)，一(yi)直(zhi)到電(dian)(dian)池(chi)(chi)(chi)(chi)(chi)中的(de)(de)(de)(de)活(huo)性物(wu)(wu)質(zhi)(zhi)轉換完成。充(chong)(chong)電(dian)(dian)最(zui)(zui)高電(dian)(dian)壓(ya)(ya)(ya)，也就是(shi)(shi)充(chong)(chong)電(dian)(dian)電(dian)(dian)源開始由(you)恒(heng)流區轉變到恒(heng)壓(ya)(ya)(ya)區，這(zhe)種轉變是(shi)(shi)由(you)電(dian)(dian)池(chi)(chi)(chi)(chi)(chi)自身充(chong)(chong)入(ru)電(dian)(dian)量多(duo)(duo)少(shao)(shao)、活(huo)性物(wu)(wu)質(zhi)(zhi)反(fan)應了多(duo)(duo)少(shao)(shao)決定的(de)(de)(de)(de)，充(chong)(chong)電(dian)(dian)電(dian)(dian)壓(ya)(ya)(ya)的(de)(de)(de)(de)高低，僅是(shi)(shi)能(neng)進(jin)行電(dian)(dian)化學反(fan)應的(de)(de)(de)(de)條件，只(zhi)(zhi)要高于(yu)電(dian)(dian)池(chi)(chi)(chi)(chi)(chi)開路電(dian)(dian)壓(ya)(ya)(ya)就會(hui)(hui)給電(dian)(dian)池(chi)(chi)(chi)(chi)(chi)充(chong)(chong)電(dian)(dian)，多(duo)(duo)少(shao)(shao)物(wu)(wu)質(zhi)(zhi)能(neng)參與(yu)反(fan)應由(you)電(dian)(dian)池(chi)(chi)(chi)(chi)(chi)自身決定。從(cong)這(zhe)個思路理解(jie)，就不難得(de)出，充(chong)(chong)電(dian)(dian)電(dian)(dian)壓(ya)(ya)(ya)高低對電(dian)(dian)池(chi)(chi)(chi)(chi)(chi)容量沒有多(duo)(duo)大影(ying)響(xiang)。
電(dian)(dian)(dian)(dian)池(chi)在42.5V～43.5V時(shi)開始析(xi)氣(qi)(qi),而(er)析(xi)氣(qi)(qi)的速度與(yu)充電(dian)(dian)(dian)(dian)電(dian)(dian)(dian)(dian)壓有關(guan)(guan)。到(dao)充電(dian)(dian)(dian)(dian)結(jie)束時(shi)，總析(xi)氣(qi)(qi)量與(yu)充電(dian)(dian)(dian)(dian)最高電(dian)(dian)(dian)(dian)壓有關(guan)(guan)，43V與(yu)45V總析(xi)氣(qi)(qi)量相差10位（注：以單格允(yun)許極限失水10克，18格相當240公升(sheng)氣(qi)(qi)體，該電(dian)(dian)(dian)(dian)池(chi)45V時(shi)失水并不大(da)）。 在充電(dian)(dian)(dian)(dian)末期電(dian)(dian)(dian)(dian)流下(xia)降區時(shi)，只要降低電(dian)(dian)(dian)(dian)壓到(dao)42.5V時(shi)，析(xi)氣(qi)(qi)立即停止，這(zhe)時(shi)充電(dian)(dian)(dian)(dian)電(dian)(dian)(dian)(dian)流稍(shao)小一點(dian)，還會(hui)依著(zhu)原(yuan)來的規(gui)律下(xia)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(mian)于充電(dian)(dian)(dian)(dian)末(mo)期大量析(xi)(xi)氣失水(shui)，只要把電(dian)(dian)(dian)(dian)壓(ya)降到析(xi)(xi)氣點電(dian)(dian)(dian)(dian)壓(ya)以(yi)下(xia)，但也不能低于電(dian)(dian)(dian)(dian)池端電(dian)(dian)(dian)(dian)壓(ya)而停止向(xiang)電(dian)(dian)(dian)(dian)池充電(dian)(dian)(dian)(dian)。前面說過(guo)，在(zai)浮充電(dian)(dian)(dian)(dian)壓(ya)下(xia)，充電(dian)(dian)(dian)(dian)電(dian)(dian)(dian)(dian)流(liu)的(de)走(zou)勢基本(ben)還(huan)(huan)是依(yi)著(zhu)原曲線下(xia)降，一(yi)般還(huan)(huan)補足(zu)(zu)5%的(de)容(rong)量。所以(yi)浮充電(dian)(dian)(dian)(dian)壓(ya)應在(zai)的(de)范圍(wei)是低于析(xi)(xi)氣電(dian)(dian)(dian)(dian)壓(ya)（42.5V），高(gao)于電(dian)(dian)(dian)(dian)池充足(zu)(zu)電(dian)(dian)(dian)(dian)以(yi)后的(de)開路端電(dian)(dian)(dian)(dian)壓(ya)（約40V）。
浮(fu)充(chong)(chong)(chong)(chong)轉(zhuan)(zhuan)換(huan)電(dian)(dian)(dian)(dian)(dian)流(liu)，只不過(guo)是(shi)(shi)選擇在充(chong)(chong)(chong)(chong)電(dian)(dian)(dian)(dian)(dian)末期(qi)(qi)電(dian)(dian)(dian)(dian)(dian)池(chi)(chi)活性(xing)物質反(fan)應接近尾聲(sheng)，充(chong)(chong)(chong)(chong)電(dian)(dian)(dian)(dian)(dian)電(dian)(dian)(dian)(dian)(dian)流(liu)自動下(xia)降到某一(yi)(yi)(yi)(yi)點(dian)(dian)時，切(qie)換(huan)浮(fu)充(chong)(chong)(chong)(chong)電(dian)(dian)(dian)(dian)(dian)壓的(de)記號，不少人以為浮(fu)充(chong)(chong)(chong)(chong)電(dian)(dian)(dian)(dian)(dian)流(liu)高(gao)(gao)了(le)(le)電(dian)(dian)(dian)(dian)(dian)池(chi)(chi)會(hui)充(chong)(chong)(chong)(chong)不滿是(shi)(shi)概念不清，充(chong)(chong)(chong)(chong)電(dian)(dian)(dian)(dian)(dian)電(dian)(dian)(dian)(dian)(dian)壓只要(yao)高(gao)(gao)于電(dian)(dian)(dian)(dian)(dian)池(chi)(chi)端電(dian)(dian)(dian)(dian)(dian)壓，都(dou)會(hui)對電(dian)(dian)(dian)(dian)(dian)池(chi)(chi)充(chong)(chong)(chong)(chong)電(dian)(dian)(dian)(dian)(dian)，只不過(guo)有(you)用戶(hu)看到指示燈(deng)紅轉(zhuan)(zhuan)綠后(hou)提前(qian)去(qu)用電(dian)(dian)(dian)(dian)(dian)池(chi)(chi)，這種情(qing)況(kuang)是(shi)(shi)不多的(de)，一(yi)(yi)(yi)(yi)般都(dou)是(shi)(shi)夜間充(chong)(chong)(chong)(chong)電(dian)(dian)(dian)(dian)(dian)，到早(zao)晨綠燈(deng)已亮了(le)(le)多時。有(you)的(de)廠家(jia)使用說明書上(shang)提醒用戶(hu)，在轉(zhuan)(zhuan)綠燈(deng)后(hou)繼續充(chong)(chong)(chong)(chong)電(dian)(dian)(dian)(dian)(dian)2小(xiao)時，是(shi)(shi)很好(hao)很正確的(de)。所以沒有(you)必要(yao)刻(ke)意去(qu)追求(qiu)浮(fu)充(chong)(chong)(chong)(chong)轉(zhuan)(zhuan)換(huan)點(dian)(dian)的(de)高(gao)(gao)低(di)，一(yi)(yi)(yi)(yi)般新電(dian)(dian)(dian)(dian)(dian)池(chi)(chi)末期(qi)(qi)電(dian)(dian)(dian)(dian)(dian)流(liu)約為50mA，失(shi)水(shui)以后(hou)，酸比(bi)增(zeng)高(gao)(gao)，那時可達500 mA以上(shang)。從析(xi)氣(qi)速率與電(dian)(dian)(dian)(dian)(dian)壓的(de)關系上(shang)來看（上(shang)圖(tu)），早(zao)點(dian)(dian)脫離析(xi)氣(qi)區(qu)為好(hao)，一(yi)(yi)(yi)(yi)方(fang)面(mian)(mian)，一(yi)(yi)(yi)(yi)方(fang)面(mian)(mian)可以減(jian)少析(xi)氣(qi)量，另一(yi)(yi)(yi)(yi)方(fang)面(mian)(mian)，電(dian)(dian)(dian)(dian)(dian)池(chi)(chi)用了(le)(le)一(yi)(yi)(yi)(yi)段時間，末期(qi)(qi)電(dian)(dian)(dian)(dian)(dian)流(liu)增(zeng)高(gao)(gao)，但還(huan)能低(di)于我們設定的(de)轉(zhuan)(zhuan)換(huan)點(dian)(dian)電(dian)(dian)(dian)(dian)(dian)流(liu)，否則(ze)電(dian)(dian)(dian)(dian)(dian)池(chi)(chi)一(yi)(yi)(yi)(yi)直(zhi)在最高(gao)(gao)電(dian)(dian)(dian)(dian)(dian)壓充(chong)(chong)(chong)(chong)電(dian)(dian)(dian)(dian)(dian)下(xia)，大量失(shi)水(shui)，引發熱(re)控，充(chong)(chong)(chong)(chong)脹充(chong)(chong)(chong)(chong)壞(huai)電(dian)(dian)(dian)(dian)(dian)池(chi)(chi)。有(you)人固(gu)執地強調，浮(fu)充(chong)(chong)(chong)(chong)轉(zhuan)(zhuan)換(huan)點(dian)(dian)高(gao)(gao)電(dian)(dian)(dian)(dian)(dian)池(chi)(chi)會(hui)欠充(chong)(chong)(chong)(chong)，前(qian)面(mian)(mian)已討論過(guo)，切(qie)換(huan)到浮(fu)充(chong)(chong)(chong)(chong)電(dian)(dian)(dian)(dian)(dian)壓后(hou)，不是(shi)(shi)停止充(chong)(chong)(chong)(chong)電(dian)(dian)(dian)(dian)(dian)了(le)(le)，還(huan)會(hui)繼續對電(dian)(dian)(dian)(dian)(dian)池(chi)(chi)充(chong)(chong)(chong)(chong)電(dian)(dian)(dian)(dian)(dian)的(de)，轉(zhuan)(zhuan)換(huan)電(dian)(dian)(dian)(dian)(dian)流(liu)適當高(gao)(gao)一(yi)(yi)(yi)(yi)點(dian)(dian)有(you)利(li)于避免過(guo)分失(shi)水(shui)和熱(re)失(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(dian)電(dian)流(liu)在2A左右，遠離極限充(chong)電(dian)電(dian)流(liu)。