Geez, thanks guys!
OK, went to one of the two batteries in the Chev 3500 - these are about two months old - it read 13.6 volts.
Went back to trailer batteries. Did each one individually and both read 6.8 volts....exact same; which seems strange to me to be the same.
There are 3 sets of black and white wires going out of the compartment and three with blue connectors going to the little trip switch in the battery compartment.
Need to get the batteries checked I know. It would not surprise me they are shot - it is just the identical that gets me wondering.
Thanks.