Using the Makita BL1840BSC2 starter pack is easy. First, charge the 18V LXT Lithium-Ion 4.0Ah batteries using the included charger. It takes about 90 minutes for a full charge. You can check the battery charge level with the integrated L.E.D. indicator. Once the batteries are charged, insert them into your Makita 18V bare tools or the included sander. When using the tools, remember that the Star Protection Computer Controls™ are working to protect the tool and battery from overloading, over-discharging, and overheating. For maintenance, keep the batteries in a cool, dry place. Avoid dropping or exposing them to extreme temperatures. The charger has a built-in fan to cool the battery during charging, which helps optimize battery life. Also, make sure to use the batteries only with Star Protection tools marked with the Star Symbol™ or a Yellow Battery Receiver. This starter pack comes with a 3-year limited warranty, so if you have any issues, you can contact Makita for support.