|Batteries are best if allowed to run down most of the time before charging (especially if NiCad type). Use it without charging until it goes down to 20% or less (once in a while, run down until the low battery warning) and see if it charges up. If it does, there is no worry unless battery life is short. If it does not charge, I would suspect the charger/cord set first (see if someone has the same brand/similar model charger you can borrow to see if it helps). When you really need to make sure that you have a full battery for the next day, by all means charge it regardless of its charge state, but normally, resist the urge to 'just top it off'.|
You have to be a little bit crazy to keep you from going insane.
If all else fails, read instructions.