There are 2 types of USB chargers, neither are standard. If I try to use my satnav USB charger on my BB, it will only charge for a brief period, maybe 2 seconds, and then stop charging. If I use my BB charger on my satnav, I can't use it because it thinks it's plugged into a computer. I'm not exactly sure how the chargers differ, maybe it's as simple as a resistor across the data pins, but the BB just needs to think it's connected to a computer to charge, there doesn't need to be any software involved.