Thanks, FoxKat. I've read - and learned from - some of those posts but will go to read the others. One question - I am of the impression that it does not hurt my phone to leave it on a charger even if it's charged. I have it plugged into AC via a USB where I sit sometimes even though it's already charged. Am I correct in my impression that there is circuitry within it to prevent damage from overcharging? Thanks.
SallyC, again you are spot on. The circuitry knows the capacity of the battery and the highest safe voltage the battery can be pushed to. At normal charging rate when the battery begins nearing a full charge (indicated by the voltage and also the rate of ascent), the charging circuitry will switch from a normal charging rate, and instead go into a very slow trickle charge to top off the battery gently. Once the battery is completely charged, the circuitry will stop the charging altogether. If left on the charger, it will also monitor the battery voltages and, just as all batteries lose charge slowly, it will detect when the voltage dips slightly and will intermittently supplement the charge with a slow trickle charge when needed to bring it back to a full charge state and keep the battery topped off.
To address your concernt, it used to be taboo to keep a device on the charger if it had Nickel Cadmium (NiCad) rechargeable batteries, and to a much lesser extent Nickel Metal Hydride (NiMH) batteries. NiCad batteries are known to suffer from a problem known as the "memory" effect where they begin to perform at the capacity they are typically used to and recharged from. So if you charge them fully, then use perhaps 50% of its designed capacity, then charge again and use 50%, after many cycles of that type, they will eventually be unable to hold more than the 50% capacity they are always asked to supply.
Furthermore, if they are either charged too long (left on charge as your concern was), not charged fully before being drained or not drained fully, the memory effect can begin to take hold and reduce capacity. This is most frequently experienced by people with portable home phones which often are placed back into their docks after every short phonecall and sit there essentially 24/7. They start to run down quicker and quicker each time they're used until eventually they won't hold a charge at all - then it's time to replace the batteries. Lastly, if NiCad batteries are left completely drained without recharging for extended periods of time, they will eventually cease to be able to take a charge at all, rendering them completely useless and virtually irreparable under most consumer applications.
Lithium Ion (Li) and Lithium Ion Polymer (LiP) batteries are a far more evolved animal than the ones mentioned above. They can supply greater voltages, greater amperages, do so in faster timeframes for high current drain, can be charged quicker, stored with a charge that will last longer, and are significantly smaller and lighter. The advantages do come with some added risks such as overheating, and in some very rare and extreme cases, even explosion and fire. This is why it is ALWAYS recommended to use ONLY the APPROVED chargers ESPECIALLY when charging Li batteries.
In short, there is almost nothing you can do when using your smart phone under normal circumstances that will damage the battery, as long as you use the "APPROVED CHARGERS". All bets are off if you use a charger that is not designed for your particular phone since the charger is designed with your phone's specific battery in mind. Minimum voltage before damage, maximum charge rate before risk of overheating, maximum voltage before risk of fire, etc., are all engineered into the charger and charging circuitry with the particular battery's specifications in mind. Use the wrong charger and you may either damage or circumvent those protective circuitries, potentially risking a catastrophic failure.
