The number of times you can reuse a disposable alkaline cell will depend both on how old the battery is and what kind of charger you have. Some chargers claim to be able to recharge these batteries up to 15 times while others can only manage 5. This is assuming it is a brand new battery that has only just run dry. Older cells that have remained dormant for a long time may be less able to take a charge. Charging alkaline batteries reduces their capacity, meaning you will get less run time from them after every charge. Over time, your batteries will become permanently flat, but you will have gotten considerably more use out of them than if you had only used them once.