The best way to keep your rechargable batteries is to keep them partially charged or better to keep them fully charged if you can. There is battery memory where if a battery is left at a low level for a long period of time it my not charge up to maximum levels later. ( google it ) For the average guy, just try to charge it up when in storage. For the person that uses it every day for work, charge it up at the end of the day. These days it seems just cheaper to get a new drill/charger/battery when you old one wears out.