A rechargeable 7.4V lithium-ion battery to power your 7V gear - 3500 mAh of power makes it one of the most powerful heated clothing batteries around. Four power settings allows you the temperature control for your comfort levels 25% = 105° F 50% = 115° F 75% = 125° F 100% = 135° F Will work with many other brands of heated clothing (push button temp control items excluded) Lasts 3-10 hours on one charge (depending on the clothing item & temperature setting) 3500 mAh of power lasts longer and heats up faster than most 7V heated clothing batteries Life of the battery is about 500 charges Note: Extreme cold and extended periods of time without use can affect battery life. Charge periodically to at least 25% to extend battery life. Warning: Do not leave battery powered gear turned on while unattended. Battery should not be submerged in water.