I had an interesting conversation with a customer this morning and the customers scenario went like this: A customer with a 4G iPod states that his iPod overheats and his battery is completely drained when attached to his computer's USBs port. In addition his backlight does not work unless connected to AC power.

We discussed software settings: iPod has backlighting, so you can see the display in low light. This will help save your battery power so your battery will last longer. You can configure the iPod so the backlight turns on for a set amount of time when you press a button or move the scroll wheel. See your manual for specific instructions, but in short you can have backlight always on or have it off after a period of time between 2 and 20 seconds.

There is also a condition with iPods called the Black Screen of Death (iPod users have named this condition not I) where an iPod's screen gets dark after a few minutes of operation and the back of the iPod gets hot hot. It is a condition where the iPod itself is defective.

But what to me is interesting is that the iPod was only getting hot when connected to a USB port. It reminds of the worst possible condition of lithium ion or lithium polymer.

The worst condition is keeping a fully charged battery at elevated temperatures, which is the case when running a battery powered device on AC power for extended periods of time. If used on main power, the battery inside a device will only last for 12-18 months. Also the battery will not all of sudden stop working but over time gradually lose the capacity to power your device little by little.

This raises the question then; should a battery pack be removed when the device is running on main AC power? Considering the fact that a fully charged battery operates at an internal temperature of 113F and then keeping a battery in the device and keeping it fully charged will create a constant state of elevated internal temperature and ultimately cause a decline in battery capacity over time.

Removing the battery in a device then will protect the internal circuitry from maintaining a high internal temperature. It is interesting how Apple warns against the iPod battery from being operated at high temperatures over 95F. It seems then that a prolonged USB connection to an iPod will indeed cause a battery to decline gradually since the battery can be charged via a USB connection. Obviously the longer the prolonged connection then the faster the battery capacity decline!

But since removing an iPod battery is not the easiest thing to do use the USB connection in temporary states and you will avoid most overheating issues with your iPod battery and help prolong its life.