[nelly48237]

actually, both of you are right. batteries have cells in them, and when a battery completely drains, the cells can get damaged... and when cells get damaged, they can no longer hold a charge. as time passes, more cells gets damaged and the battery life runs out faster. so mswlogo, you are partially right. as for completely draining a battery to make it work longer, this too works... when done correctly. sometimes a damage cell can correct itself when all of the power is drained out of the battery and its recharged. it's something like resetting a phone to correct a problem or turning your computer off and re-starting it. so EtherealRemnant, you are partially correct too. when it's not okay to drain a battery completely is while using it and it dying while using it or using it when it has very little power because it creates a high current draw and this is what can damage some of the cells. as for leaving it charging all day. it is good to keep it charging when not using it. however, when the phone says the battery is fully charge, you should take it off the charger because over charging a battery can also damage some of the cells. it like when you give a guy a boost with jumper cables to jump start his car. when his car starts, you need to take off the cables as soon as possible so the it is not receiving an overcharge from getting charge from two different sources; the car alternator and the car giving it a jump. i am a license electrician, thats how i know about this