My battery is fully charged, but it can't power the heated vest/jacket.

First, please check if your battery is 7.4V 7500mAh (2024 version and before). 

If yes, you can follow these steps to get the heated apparel work. 
(The 7500mah battery has dual output, 5V and 7.4V. The vest/jacket can only be powered by 7.4V output. If you choose 5V, the vest/jacket will not heat up.)

To choose 7.4V output, here are the correct steps. 
1) Unplug(if you already plug the battery into the vest/jacket) and re-plug the battery into the heated vest/jacket. 
2) Long press the battery button to turn on the battery. 
3) Short click the battery button to choose the output. 
4) Long press the light buttons on the chest to turn on the vest/jacket. You can choose which parts and the heating levels you want. 

You can also watch this operation video. 

If this doesn't help, please emailservice@arrislife.com to get more specific help.