Similar to the Additionally model, the Battery Tender Junior is a completely automatic battery charger using a "float" feature which allows for it to get left hooked up on the battery terminals, charging as it depletes and only as required. It's suggested that you choose to demand these batteries each https://hukums.com/products/xtra-power-100-mm-1000-watt-angle-grinder-with-accessories-11800-rpm-xpt-402