Back in the day, when cell phones first came out, the batteries didn’t last very long, so I got into the habit of charging my phone each night before I went to bed and that guaranteed I always had a full charged phone. 
Over time I noticed that the amount of talk time would start to go down, presumably because I was “overcharging” my battery and causing “memory” to decrease the capacity of my cell phone battery. At least that’s what I was told. :rolleyes:
Fast forward to now, and my new Apple iPhone 4S. I bought a bedside charger for it and once again have been charging it almost every night, whether it needs to be charged or not. Am I damaging the battery by charging it even though it isn’t fully depleted, or are batteries “smarter” now and I really don’t have to worry about how often I charge it?
I would like to think that cell phone engineers have somehow accounted for someone like me.
No, you aren’t damaging it at all by frequently charging. In fact, it is *better *to charge it frequently, even if it’s not low.
So I literally run it once a month until it is completely dead? I would think that wouldn’t be good for the iPhone, but what do I know. :smack:
The quirky problems of batteries are largely solved by today’s technology, and they left behind a residue of myths and superstitions. Do what you need to do, or what you like to do with your battery so that you get the best usage out of it.
The phone AND the battery each have their own protective circuit that will not allow the battery to be completely drained. The phone’s circuit should kick in first and safely shut itself down before the battery’s own circuit kicks in.
Lithium batteries have a rather narrow optimum voltage range, and they prefer to usually be somewhere in the middle of it. That’s why, once a battery is fully charged, it’s better to stop charging it and start using it. The longer the battery stays at either extreme of its range - high or low - the less life expectancy it will have.
As for Apple’s recommendation to deplete the battery once a month, I’m fairly certain that will not actually help the battery. I’m pretty sure that is only in order to calibrate the way the phone measures the battery meter so that it can give you an accurate percentage of the battery’s remaining charge.
Li-ion batteries actually like some of what was considered abuse of the older batteries. The longest life will be about 40% charged and will go down as you approach 100% as well as 0%.
So ideally you want to keep your phone in the mid range to maximize life. Depending on your situation you may want to charge it every other day instead if you have enough power to do this. You may also not want to fully charge the battery to 100%, and yes leaving it fully charged is a bit harmful for the battery - though not in the overcharging sense, but just because it’s at 100%.
Now for the electronics that monitor the battery, they need to be calibrated. This is done with a full or almost full charge/discharge cycle and helps the electronics get the best use of the battery, so there is a recommendation to do some full cycle every so often such as monthly. When you do this I would recommend recharging as soon as practical when the phone reaches the auto shutdown point at 0%, you don’t want to leave your phone long in this range as it is damaging to it.
I have a car radio that has a iPhone dock and usually use that to recharge it while playing music through it, only occasionally recharge it via the standard method. This will sometimes not bring it to 100%, depending on where I’m going, but it is actually better for the battery.
Finally, the iPhone4 and 4s is actually easy to replace the battery and the batteries are pretty cheap, online I have seen them for under $5 and ‘kits’ that include the tools to replace them and the battery packaged together (really just a special screwdriver) for under $8 - the only thing that may be difficult is you will be working with 3-4 small screws. With it that cheap and easy to replace, you need to ask yourself is it worth the effort, or should you just use it in a way that is easy for you and just be ready to spend an extra $8 down the road and after the Apple warrantee is up.