Hi, I have a old battery recharger (20+ years) that still works. It can recharge 4 AA sized batteries. I was wondering if I can use this charger to recharge 2100mAh rechargeable batteries. Obviously these didn't exist when this charger was manufactured. I was wondering if I need to buy new charger for it (as far as I know there is no reason why I can't use the old charger but want to check here first since incorrect use of batteries can cause messy explsion ). Thanks.