I am building an asset tracking device based on an old Android smartphone and a power bank (i.e. a battery bank with a USB port). I want the phone to last for a week or two, sending GPS coordinates over mobile network. I want to leave the phone permanently plugged into the external power bank, hoping that the power bank would power the phone as long as it has charge, then the phone should revert to using its internal battery and last another two-three days.
I got a 20,000Mah power bank, but it has a feature that detects that the phone stops charging (i.e. stops drawing current from the bank and goes into trickle charge mode) and the power bank powers itself down. So, in effect, I am only getting one charge out of the power bank. To make it charge the phone again I would have to hit the power button on the power bank, but I can't do this since I want to leave the phone unattended.
Does anyone know whether all power banks have this "charge complete" detection electronics? Any ideas how I can do what I want to do?