Good idea about using the daily driver battery. but my daily driver battery has said terminals only. At one point I disconnected the battery terminals just to insure they were clean. I clean them regularly so it was a shot in the dark. I noted the voltage before disconnect was 11 something, close to 12 volts. While the battery was disconnected I put the meter on it and could see the voltage drop. When I reconnected it was down to 11 volts.
If the voltage was dropping while disconnected it must be the battery not being able to hold a charge and not the generator/voltage regulator or a bad ground.
