mahjongg wrote: ↑
Fri Sep 21, 2018 4:26 pm
Try it, if you get undervoltage warning, then your powerbank is not suitable to power what you are doing with the PI.
how much current is needed depends on what you are doing, for example adding power hungry USB devices, or running GPU intensive software will draw more current.
Also of possibility could be a bad USB cable or connections.
From my experience, this is the more pressing concern. The Pi will run quite happily off even 0.5A (just the Pi), but the USB connections add large impedance causing a voltage drop.
There is also the possibility of fake or misleading specs. I have seen some USB power supplies claim 2.1A, yet after inspection, the chip inside is only rated for 0.7A, so I do not know where the 2.1A comes from.