檢測普通鋅錳干電池的電量是否充足，通常有兩種方法。第一種方法是通過測量電池瞬時短路電流來估算電池的內阻，進而判斷電池電(dian)量(liang)是否充足；第二種方法是用電(dian)流(liu)表串聯一只阻值適當的(de)電(dian)阻，通過測(ce)量(liang)電(dian)池的(de)放(fang)電(dian)電(dian)流(liu)計算出(chu)電(dian)池內阻，從而判斷電(dian)池電(dian)量(liang)是否充足。

    第一種方法(fa)的(de)最大(da)優(you)(you)點(dian)是(shi)簡便，用(yong)萬用(yong)表的(de)大(da)電(dian)(dian)(dian)(dian)流檔就(jiu)可(ke)直(zhi)接判斷出干(gan)電(dian)(dian)(dian)(dian)池(chi)(chi)的(de)電(dian)(dian)(dian)(dian)量，缺點(dian)是(shi)測試電(dian)(dian)(dian)(dian)流很(hen)大(da)，遠(yuan)遠(yuan)超過干(gan)電(dian)(dian)(dian)(dian)池(chi)(chi)允許放電(dian)(dian)(dian)(dian)電(dian)(dian)(dian)(dian)流的(de)極限(xian)值，在一定程度(du)上影響干(gan)電(dian)(dian)(dian)(dian)池(chi)(chi)使用(yong)壽命。第二種方法(fa)的(de)優(you)(you)點(dian)是(shi)測試電(dian)(dian)(dian)(dian)流小，安全(quan)性(xing)好，一般不會對干(gan)電(dian)(dian)(dian)(dian)池(chi)(chi)的(de)使用(yong)壽命產(chan)生不良影響，缺點(dian)是(shi)較為麻(ma)煩(fan)。

    筆者用MF47型萬用表對(dui)(dui)一節(jie)新2號干(gan)電(dian)(dian)池和一節(jie)舊(jiu)2號干(gan)電(dian)(dian)池分別用上述兩(liang)種(zhong)方法(fa)進行測試對(dui)(dui)比(bi)。假(jia)設ro是(shi)干(gan)電(dian)(dian)池內阻(zu)(zu)，RO是(shi)電(dian)(dian)流表內阻(zu)(zu)，用第二種(zhong)測試方法(fa)時，RF是(shi)附(fu)加的(de)串聯電(dian)(dian)阻(zu)(zu)，阻(zu)(zu)值3Ω，功率2W。

    實測(ce)結果如下。新2號電(dian)(dian)(dian)池(chi)E=1.58V（用(yong)(yong)2.5V直流(liu)(liu)電(dian)(dian)(dian)壓(ya)檔(dang)測(ce)量），電(dian)(dian)(dian)壓(ya)表(biao)(biao)內阻(zu)為(wei)50kΩ，遠大于ro，故可近似認為(wei)1.58V是電(dian)(dian)(dian)池(chi)的(de)電(dian)(dian)(dian)動勢，或稱開路電(dian)(dian)(dian)壓(ya)。用(yong)(yong)第一種(zhong)方(fang)法時(shi)，萬用(yong)(yong)表(biao)(biao)置(zhi)5A直流(liu)(liu)電(dian)(dian)(dian)流(liu)(liu)檔(dang)，電(dian)(dian)(dian)表(biao)(biao)內阻(zu)RO=0.06Ω，測(ce)得(de)電(dian)(dian)(dian)流(liu)(liu)為(wei)3.3A。所(suo)以ro+RO=1.58V÷3.3A≈0.48Ω，ro=0.48-0.06=0.42Ω。用(yong)(yong)第二種(zhong)方(fang)法時(shi)，測(ce)得(de)電(dian)(dian)(dian)流(liu)(liu)為(wei)0.395A，RF+ro+RO=1.58V÷0.395A=4Ω，電(dian)(dian)(dian)流(liu)(liu)500mA檔(dang)內阻(zu)為(wei)0.6Ω，所(suo)以ro=4-3-0.6=0.4Ω。

    舊2號(hao)電(dian)池用(yong)第一種(zhong)方(fang)法測量(liang)時，先測得開路電(dian)壓E=1.2V，電(dian)表內阻(zu)RO=6Ω，讀數(shu)為(wei)6.5mA，萬用(yong)表置(zhi)50mA直流(liu)(liu)電(dian)流(liu)(liu)檔，ro+RO=1.2V÷0.0065A≈184.6Ω，ro=184.6-6=178.6Ω。用(yong)第二種(zhong)方(fang)法，測得電(dian)流(liu)(liu)為(wei)6.3mA，ro+RO+RF=1.2V÷0.0063A=190.5Ω，ro=190.5-6-3=181.5Ω。

    顯然兩種測試方法的結果基本一致。最終計算結果的微小差別是由于讀數誤差、電阻RF的誤差以及接觸電阻等多方面因素造成的，這種微小誤差不致影響對電池電量的判斷。如果被測電池的容量(liang)小、電壓高（例(li)如15V、9V疊層電池），則應將RF的阻值(zhi)適(shi)應增大。