Hidden discreetly in an easily accessible pocket is the small battery that operates the heat at the touch of a button. It’s a compact, rechargeable lithium ion battery and weighs about 100 grams.

The battery has three heat settings so you can control the heat. On the lowest setting, the battery can heat the coat for around five hours; on the highest heat setting it lasts around three hours. The exact time is determined by the outside temperature.