Have you had problems charging your Apple Watch with a power bank?
If it seems to only charge for a few minutes and the power block goes to sleep after the watch face has, try turning off nightstand mode. As shown above, head to Settings – General – Nightstand Mode and toggle it off. My watch would stop charging about every 15% until nightstand mode was turned off. After that step, it charged to full capacity without a problem.
Nightstand Mode On Your iPhone
To toggle nightstand mode using your iPhone, go to My Watch, General, and toggle Nightstand Mode on or off. Either of these steps should result in your Apple Watch getting a full capacity charge using an Apple-compatible power bank.