涓流就是以低速率且恒定方式对电池提供很小的充电电流。

大部份充电池充满后，由于自放电现象（Self-discharge）会不停流失电量。若继续以相同于自放电率之小电流充电，可维持电量。大部份充电池特别是镍镉电池及镍氢电池都有自放电现象；若要电池随时可用，要以提供涓流之充电器长期接驳。新发明之低自放电镍氢电池（Low self-discharge NiMH battery）可部份解决此问题。对锂离子电池不建议采用此种充电方法。

Trickle charging means charging a fully charged battery under no-load at a rate equal to its self-discharge rate, thus enabling the battery to remain at its fully charged level. A battery under continuous float voltage charging is said to be under float-charging.