Update:
Their truck has an IBS battery management system and the batteries are Die Hard Platinum 205RC 31M5013-1(-5 pssgr side) 1150 CCA but we can't see the date of mfr.
They want to stress test the batteries at the local auto parts store (as well as check the terminal connections). Can this be done with both batteries hooked up still in the truck? Or do we need to remove them and stress test them individually? I will post results when I have them to share our findings.
Thank you for the input so far gentlemen.
J
Ah! IBS introduces some other possible causes... I have the same setup.
First, press the power check button on the IBS unit.
If it shows low power on the main but power on the 2nd battery... Press the LINK button.
This will allow the 2nd battery to power the vehicle, and usually means either your main totally died, or--more likely--has a terminal that is a little loose.
So if you have power on battery 2... when both batteries are connected, press the link button and see if it starts up.
If you can start after pressing link...again, check that your main battery terminals are super tight (as in, you can't grab and turn them AT ALL, as this would typically indicate that the main battery terminals were loose.
If you have good voltage on both batteries and it still won't start...or you have NO lights on the IBS control unit...disconnect both batteries for several minutes, then reconnect them.
This may reset your IBS battery controller. Now reconnect batteries TIGHTLY and try again.