此類充電器構造簡單：一般由電源變壓器和四個二極管構成的橋式整流電路組成。充電的整個過程電壓保持不變，當電池的內阻隨著充電過程越來越小，因此充電電流也越來越大，產生的熱量也越來越多。電池快充飽時發熱量最大。加速電解質的分解，從而縮短了電池的壽命。早期的廠家生產的充電器采取(qu)“小心駛得萬年船”的策(ce)略，用(yong)小電(dian)流充(chong)(chong)(chong)電(dian)，一般(ban)不超過100mA ，這樣電(dian)池(chi)充(chong)(chong)(chong)到最(zui)后，發熱不至于太大，從而(er)延長電(dian)池(chi)壽命。缺點是(shi)充(chong)(chong)(chong)電(dian)時(shi)間(jian)長。現在(zai)生產這類的廠家，采用(yong)中電(dian)流充(chong)(chong)(chong)電(dian)，100～200mA 充(chong)(chong)(chong)電(dian)時(shi)間(jian)大大縮(suo)短，但是(shi)以(yi)犧牲電(dian)池(chi)壽命為代價。傻瓜型充(chong)(chong)(chong)電(dian)器只(zhi)能用(yong)時(shi)間(jian)來控制充(chong)(chong)(chong)電(dian)，它(ta)只(zhi)適合于深充(chong)(chong)(chong)深放的五號、七(qi)號鎳鎘、鎳氫電(dian)池(chi)。

    充(chong)(chong)(chong)電(dian)(dian)時間：T = 1.5C/I（ C是(shi)(shi)電(dian)(dian)池容量(liang)，I是(shi)(shi)充(chong)(chong)(chong)電(dian)(dian)電(dian)(dian)流）例：如果有個1000mAh 的(de)(de)電(dian)(dian)池放在(zai)充(chong)(chong)(chong)電(dian)(dian)電(dian)(dian)流是(shi)(shi)50mA的(de)(de)充(chong)(chong)(chong)電(dian)(dian)器(qi)上充(chong)(chong)(chong)電(dian)(dian)，充(chong)(chong)(chong)電(dian)(dian)時間就(jiu)是(shi)(shi)30小時。辨(bian)認(ren)這(zhe)類充(chong)(chong)(chong)電(dian)(dian)器(qi)的(de)(de)方法(fa)：當插(cha)上電(dian)(dian)源插(cha)頭(tou)后，充(chong)(chong)(chong)電(dian)(dian)指示燈一直亮(liang)著。街上賣的(de)(de)10～40元以內的(de)(de)均是(shi)(shi)這(zhe)種(zhong)充(chong)(chong)(chong)電(dian)(dian)器(qi)。