My prius C has a 6 year old Toyota True Connect battery. The car sat for a few days and I needed to put some air in the tires. I connected my OBD to the Dr. Prius app and turned the key just enough to turn on the accessary electronics without turning on the engine. I wanted to see if I could run the air compressor from the 12V plug without turning on the engine. Well, the Dr prius app said the 12V battery was at 11.87V, so I turned on the engine. In a couple of seconds I looked down at the app and it was now at about 14.2V. Did the engine really fully charge the 12V that fast? I thought it takes at least 30 minutes of ready mode or driving to charge a 12V battery.
The only way to test the battery voltage is at rest, after any surface charge has worn off. Best to get a free load test at most auto parts stores
You can't trust your lying eyes and don't seem to understand what the DC-DC inverter is suppose to be doing. Turn your car off and check your 12V in 30 minutes to see where your actually at.
The 14.2 volt reading shows the 12 volt charging inverter has ramped up the voltage to pump electrons into the 12 volt battery. You can't get a true reading of the 12 volt battery's state of charge while the inverter is running.
