External Power to Heltec ESP32

I have a few Heltec ESP32’s (V2) which are running Meshtastic 1.2.45. These Heltec ESP32’s are getting power from external battery packs (ANKER brand). After about 10 minutes the ESP32 MCU looses power from the EBP or the EBP stops providing power to the ESP32 MCU.

Could this problem could be ameliorated if the ESP32 MCU had an attached battery? Any suggestions would be appreciated. Thanks.

Most powerbanks are designed to charge phones and will turn itself off when the phone is using zero or little power. Our boards are probably below this limit.
Do you have the same problem if wou connec the Heltec to a usb wallplug (like the one you use to charge your phone)?