Rechargeable batteries are generally used for power tools to make them more portable and not require an electrical outlet during use. A charger is used to keep the rechargeable battery charged when it runs out of power. The chargers can either plug into an outlet or they have portable power cells that can charge for up to one hour. Our selection includes rechargeable batteries from brands such as: DeWalt Milwaukee Makita and more It is recommended that you charge at least two batteries before you start a big project so that you want have to wait for one battery to recharge and pause in the middle of your project.