Can you leave rechargeable batteries on charger 24/7 or is it bad to batteries or does the charger automatically quit charging the battery when it is fully charged?
modern chargers drop down to trickle charge after the set charging period, either by the timer or the sensing of internal resistance or capacitance, it is far better to flatten a battery right out and then recharge it rather than keep trickle charging it when it is partially charged, this is particular noticeable with cordless phones and similar items, ni cads develop memory effects due to this, which is a cause of their demise.
IT IS NOT OK TO LEAVE A BATTERY ON THE CHARGER 24/7 UNLESS.the charger is a SMART charger. That means it has a microprocessor inside the charger to cut back the charge rate as the battery reaches maximum charge. IT IS NOT A FUNCTION OF THE BATTERY, it is a function of the charger. If the charger is not a smart charger, the charger will attempt to keep charging. This will eventually dry out the electrolyte inside the cell. If you dry out the battery, it will not hold a charge, and will need to be replaced.
It is perfectly okay to leave it 24/7. Battery technology has improved over the years (Although it is real slow as compared to other electronics). There are certain batteries with chips inside and know when to stop. Examples like laptops batteries or cellphone batteries, they are charged, recharged or left charging forever and you don't see any significantly damage done to them. Obviously, you can expect certain wear and tear as electrons move around the batteries when they are left on charger, but it is just so insignificant to be even bothered with. Charge all you want and you will do just fine.
Most chargers *should* automatically quit charging when the battery is full, although some cheaper ones don't (most really old ones don't either). If you don't know, don't assume, and simply unplug it or your batteries might cook/leak/explode. Ni-Cd and Ni-MH batteries will both heat up when they're nearing full charge (and when overcharging). If your battery is a Li-Ion, the charger almost certainly stops charging automatically when it's full, because Li-Ion batteries tend to catch fire and/or explode if they overcharge, although the batteries themselves are supposed to have safety mechanisms built in to keep this from happening (although depending on the mechanism it might permanently shut down the battery). In any case, just about every charger for a Li-Ion battery will automatically stop charging when it's full, and they can usually be left plugged in.
