ORIGINAL: bruce88123
If you are trying to say that you can use the orig wall-wart charger with a 6 volt pack - WRONG! It will never fully charge. Oh, maybe in a couple of months but doubtful.
No...
Your assuming that the charge voltage & current MUST match the battery voltage exactly, which is not the case.
In fact in many chargers like my Accucycle, the voltage is stepped DOWN as is the amperage output as the battery nears a full charge.
I've taken 3000mAh 6V packs and changed them for a few days on a 4.8v 100mA charger. When I subsequently discharged them to test capacity I found it little different than what my computer controlled chargers will do when set to "full" ( 100% ) charges.