[super__dan]

Gents, I think this is a fairly budget charger with an inbuilent power supply that can only do 3A max if running straight off the mains.

Chris, you should ideally charge at between 5 - 6A everytime, and not alter it (much). I would suggest 3A is too low and may effect punch, it will also take bloody ages.

If my assumption is correct on the charger, you should aim to always use a 12V battery or 12V power supply to charge from.

Dan