Hi, I am brand new to this forum but an old EE. I finally decided to order one of these testers. I would like to use a rechargeable battery instead of the 9V one. I am planing on using an 18650 Li-Ion with one of these cheap USB PowerBank (<$1 on eBay and I have plenty of these batteries). These PowerBanks have a small charger for the Li-Ion and a step-up PWM for the 5V output. My idea is to use the circuit to charge the battery and to replace the linear 5V regulator on the tester. A fully charged battery will probably last me over a year if it wouldn't self discharge before that.
My question is, the tester monitors the battery voltage on PC5, does it do anything with that information, like shutting down everything if it thinks that the battery voltage is low (Li-Ion is ~3.7V)? Would I need to reprogram the AVR, or the battery voltage monitoring is just for the user information.