My Raspberry Pi 3B+ is running Kali Linux on the official 7" display. I am using an Anker power bank that says: "5V=6A (3A max per port)" in the description. When using the Pi, it constantly shows the Low Power lightning bolt symbol. I plugged a USB Safety Tester between the battery and the Pi and it displays that the Pi is pulling about 1A when it shows the lightning bolt. Why is this happening?
The "Low Power lightning bolt" reports low Voltage - nothing to do with current.
Either your power supply is inadequate or your cables are too thin.