On board charger will regulate no matter how many Amps you put in it. It is better or the sake of charger if it's stronger. If you would hook up that
dna into some 500mA power unit, it would just keep that unit in constant maximum load because the on board charger would initially try to pull 1A or 2A, or what ever he is set to. On the other hand if you would hook up 2A power unit to charge via 1A on board charger, you wouldn't overload power unit, and on board charger would work within his specified parameters... So yes, it's ok.