It's best to have 2 batteries, one for use and one for the charger. This way one is ready to go whenever your devise battery has run out of power. Only problem with this idea is the cost is almost the same as a complete drill kit that includes 2 batteries. Makes you think about the price of batteries. I see many kits for $ and the replacement batteries for them run $ each. They must be giving away the drill and rechargers knowing the battery sales will make up. Happy drilling.