As always it is very important to practice the highest level of battery safety when using mods and kits that require external batteries. It is absolutely crucial that when you purchase new batteries that you also purchase a smart charger and that you always carry your batteries in a case. If the wrap on your battery starts to display signs of wear, make sure you get them rewrapped or replace them as soon as possible. If your mod requires the use of two batteries always use the same married pair of batteries. NEVER MIX AND MATCH! If you have any questions about your batteries or battery safety do not hesitate to reach out to customer service for help!