dovepa via EV wrote:
Isn't that what a trickle charger does? I know lots of people who leave them on all the time.
People mix up "float" and "trickle" chargers all the time. But they are quite different devices.
A "trickle" charger delivers a more-or-less constant CURRENT, regardless of the battery's voltage. This is the correct type for nicads and nickel-iron cells that can stand a continuous charging current.
Trickle chargers are very simple, and dirt cheap -- often nothing but a transformer and rectifier. So this what most consumer charger are.
If you use a trickle charger on a lead-acid or lithium pack, you are likely to overcharge it and slowly destroy it.
A "float" charger delivers a more-or-less constant VOLTAGE, regardless of the battery's state of charge. This is the correct type for lead-acid, lithium, and other types that cannot stand continuous charging.
Float chargers require some kind of voltage regulation. This adds a little cost; but modern electronics are so cheap that it's not much more.
If you use a float charger on nicads or nickel-irons, the battery will never reach full. Or if the battery is hot so its voltage is less than the fixed float voltage, then it overcharges and murders the battery from overheating.
You'll notice I left out nimh (nickel metal hydride). They are kind of an odd duck. *Neither* float nor trickle charging are appropriate for them -- both can destroy them from overcharging. You need to use a charger that is smart enough to charge them fully, and THEN SHUT OFF. Don't try to keep the charger on forever.
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