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“小(xiao)心駛得萬年(nian)船”的策略，用(yong)(yong)小(xiao)電(dian)(dian)(dian)(dian)(dian)流(liu)充(chong)(chong)電(dian)(dian)(dian)(dian)(dian)，一般不(bu)超(chao)過100mA ，這樣電(dian)(dian)(dian)(dian)(dian)池充(chong)(chong)到最(zui)后，發熱(re)不(bu)至于太(tai)大(da)，從而延長電(dian)(dian)(dian)(dian)(dian)池壽命(ming)。缺(que)點是充(chong)(chong)電(dian)(dian)(dian)(dian)(dian)時(shi)間長。現在生(sheng)產這類(lei)的廠家，采用(yong)(yong)中電(dian)(dian)(dian)(dian)(dian)流(liu)充(chong)(chong)電(dian)(dian)(dian)(dian)(dian)，100～200mA 充(chong)(chong)電(dian)(dian)(dian)(dian)(dian)時(shi)間大(da)大(da)縮短，但(dan)是以犧牲電(dian)(dian)(dian)(dian)(dian)池壽命(ming)為代(dai)價(jia)。傻瓜型充(chong)(chong)電(dian)(dian)(dian)(dian)(dian)器(qi)只能用(yong)(yong)時(shi)間來控制充(chong)(chong)電(dian)(dian)(dian)(dian)(dian)，它只適(shi)合于深(shen)(shen)充(chong)(chong)深(shen)(shen)放的五號、七號鎳(nie)鎘、鎳(nie)氫電(dian)(dian)(dian)(dian)(dian)池。

    充電(dian)(dian)(dian)時(shi)間：T = 1.5C/I（ C是電(dian)(dian)(dian)池容量，I是充電(dian)(dian)(dian)電(dian)(dian)(dian)流）例(li)：如果有個1000mAh 的(de)電(dian)(dian)(dian)池放在充電(dian)(dian)(dian)電(dian)(dian)(dian)流是50mA的(de)充電(dian)(dian)(dian)器(qi)上(shang)充電(dian)(dian)(dian)，充電(dian)(dian)(dian)時(shi)間就是30小時(shi)。辨認這類(lei)充電(dian)(dian)(dian)器(qi)的(de)方法：當插上(shang)電(dian)(dian)(dian)源插頭后，充電(dian)(dian)(dian)指示燈(deng)一直(zhi)亮著。街上(shang)賣的(de)10～40元(yuan)以內的(de)均是這種充電(dian)(dian)(dian)器(qi)。