I've unplugged my shore power and will let the coach sit for 12 hours. What should the battery voltage be after this time frame with a couple lights on with healthy batteries and a full charge
Thanks
You cannot use the vague draw of a couple of lights and get a good answer. You would need an expensive tester. If you completely charge the batteries and unhook them for over 3 days the voltage will tell you somewhat how good they are. My good ones will be 12.8 after sitting 4 days.
Mine are usually between 12.80-12.60 after sitting with no load. But to check them you will need to unhook the ground cable so on draw.
Ok. I'll remember that. Thanks
Regarding the above information you have provided, with "a couple lights on", no starting voltage at rest, etc., their is no right answer. I thought you had a Victron BMV-712 or similar device, that would moniter your batteries, to give you your state of charge, amps in or out and ah used, voltage at rest, etc.? If not, you will need one to establish your own normal, or what your "what should the voltage be".
https://youtu.be/tV055vmZgvY
I bought 3 of these to test three batteries at the same time. Two would match your setup.
250W DC 12V Discharge Battery Capacity Tester Module With DC Electronic Load... (https://www.ebay.com/itm/250W-DC-12V-Discharge-Battery-Capacity-Tester-Module-With-DC-Electronic-Load-Dig-/264524294316)
You will need 12 volt power supplies that put out 12 volt exactly
Plus cabling.
Real lab grade testing equipment.