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(cai)取“小心駛(shi)得(de)萬年船”的策略，用(yong)小電(dian)(dian)(dian)(dian)流充(chong)電(dian)(dian)(dian)(dian)，一般不超過100mA ，這(zhe)樣電(dian)(dian)(dian)(dian)池(chi)充(chong)到最(zui)后，發(fa)熱不至(zhi)于太大(da)，從而延長電(dian)(dian)(dian)(dian)池(chi)壽(shou)命。缺點是(shi)充(chong)電(dian)(dian)(dian)(dian)時間長。現在生產這(zhe)類的廠家，采(cai)用(yong)中電(dian)(dian)(dian)(dian)流充(chong)電(dian)(dian)(dian)(dian)，100～200mA 充(chong)電(dian)(dian)(dian)(dian)時間大(da)大(da)縮短，但是(shi)以犧牲電(dian)(dian)(dian)(dian)池(chi)壽(shou)命為代價。傻瓜型充(chong)電(dian)(dian)(dian)(dian)器只(zhi)能用(yong)時間來(lai)控制(zhi)充(chong)電(dian)(dian)(dian)(dian)，它(ta)只(zhi)適合于深(shen)充(chong)深(shen)放的五號、七(qi)號鎳(nie)鎘(ge)、鎳(nie)氫(qing)電(dian)(dian)(dian)(dian)池(chi)。

    充(chong)(chong)(chong)(chong)電(dian)(dian)(dian)(dian)時(shi)間(jian)：T = 1.5C/I（ C是(shi)(shi)電(dian)(dian)(dian)(dian)池容量，I是(shi)(shi)充(chong)(chong)(chong)(chong)電(dian)(dian)(dian)(dian)電(dian)(dian)(dian)(dian)流）例：如果有個1000mAh 的電(dian)(dian)(dian)(dian)池放在(zai)充(chong)(chong)(chong)(chong)電(dian)(dian)(dian)(dian)電(dian)(dian)(dian)(dian)流是(shi)(shi)50mA的充(chong)(chong)(chong)(chong)電(dian)(dian)(dian)(dian)器上充(chong)(chong)(chong)(chong)電(dian)(dian)(dian)(dian)，充(chong)(chong)(chong)(chong)電(dian)(dian)(dian)(dian)時(shi)間(jian)就是(shi)(shi)30小時(shi)。辨認這(zhe)類充(chong)(chong)(chong)(chong)電(dian)(dian)(dian)(dian)器的方法：當插上電(dian)(dian)(dian)(dian)源插頭后，充(chong)(chong)(chong)(chong)電(dian)(dian)(dian)(dian)指示燈一直(zhi)亮著。街上賣的10～40元以內的均是(shi)(shi)這(zhe)種充(chong)(chong)(chong)(chong)電(dian)(dian)(dian)(dian)器。