Exalt Lipo Warmer Sleeve is perfect for that.This is meant to be used in a lipo bag, and is not completely flame retardant on its own. It is made out of flame retardant material. It features a super flexible wire, blacked out heating elements, and is more reliable. This does have 4 heating elements one on each side, this ensures equal and controlled heat distribution.Heating your Lipo Battery before charging has Pros and Cons We feel Consumers need to be aware of:

    Pros

• Heating a battery before you charge it, allows for a flatter discharge curve less fade while you run.
• It also decreases the Internal resistance of a battery, increasing punch.
• Allows same results lowering IR with out effecting Battery Life Span.

    Cons

• Increase Chances to harm the battery if you overheat the battery. (Caution Keep under 120 F)

This updated design features a button that is securely sewn in place, yielding a more polished appearance while enhancing the product's overall longevity. Also, the female USB-C connector allows for seamless integration with various cable types, providing compatibility with an array of USB and USB-C charging options on various chargers.