Mroutlaw, forgive my for being blunt, but your post is wrong and could be very dangerous with lithium ion
batteries and charging.
Mr Anderson, don't use a 6v source, will likely damage the charger and possibly the battery. You
can use a computer USB port. USB 2.0 (used since 2000) can sustain a 500mA current without a problem. New USB 3.0 ports can sustain 750mA.
Without knowing the exact input voltage specs for the charger I don't think the risk is worth the reward when there are 5v USB sources in such an abundance these days. Even most new cars have a 5v USB port now.