I actually meet a problem to power any devices with a powerbank USB battery.
It is fully charged and I tried to power a simple LED with resistor (I've tried to get into VSS of a L293D before) through a micro-usb connector on the test circuit side.
When I connect the powerbank, the LED shines for about 30s, and then it stops suddenly, the voltage drops to 0V.
It seems to be a sort of electronic protection, or a lack of information from the device, back to the powerbank.
I've tried to short pinout DATA- and DATA+, put a 220ohm resistor between D-, D+, shorted D- and D+ to ground, but none of these "solutions" worked.
Is there anyone who know what is going on ?
Note : If I plug a "standard" device like a RPI, an electronic cigarette or a smartphone, it works without stopping the charge process after 30s...