You'll be fine. What kind of charger do you have? If it's a wall-wart charger, do your grandson a favor, and get a REAL charger so he doesn't have to wait two or three hours for the pack to charge up. (Actually, NiMhs prefer to be left in a CHARGED state, unlike LiPo) A good charger that can charge both NiMhs and Lipos can be had for $50, and will charge a depleted pack in under an hour. You buying from a local hobby shop, or online?