Our original intent was to power the light using any standard USB power bank. However, upon testing various power banks on the market, we discovered they are designed to charge devices rather than power lights. Most have a power management scheme wherein they shut down when not needed for charging. That is, when they detect a current draw below a prescribed level, the typical power bank thinks the device is fully charged and it's okay to shut down. That doesn't work for running our light at lower brightness settings or on flash mode.
So we designed our BatPaks to stay ON as long as the light is ON... until they exhaust their energy supply. And we use a 4 hour timer where the BatPak stays ON regardless of the current draw. The benefit of that is you can turn ON the BatPak and stow it in your pocket, pouch or pack. Then when you need the light you simply hit the power button on Ra.
The BatPak2 and BatPak3 have three USB ports. The end port (furthest from the charge port) is recommended for charging phones and other devices as the 4 hour timer will shut off the light here. If that happens you simply turn on the BatPak to resume using the light. Better yet, use the other two ports for your lights.
In summary, your power bank should work fine at higher brightness levels. But to benefit from all the functionality of the Ra light, you'll need the Kogalla BatPak.