Wow! let's see if I can understand this:
Originally Posted by CHUCK52
2018 Thor Hurricane 29M
Boon docking, had battery power. - So everything worked normally?
ran generator to charge batteries. use store on. - So batteries got low; so you ran the generator to charge the batteries - pretty standard stuff, obviously the generator started and ran.
Batteries charged if at all. - Gotta help me out here; what are your trying to say?
ran for hours. - Ran the generator for hours? Batteries did NOT charge?
Ran RV, batteries charge up fine using RV alternator. - So the house batteries charge as expected from the RV engine and alternator.
Got home and next day, no battery power at all. use store on. Battery tests to 12.7 V. - Without being plugged into SP you have no DC power in the RV and you believe the USE/STORE latching relay is in the USE position.
Plug into shore power, all works. - With SP the Converter is now supplying power to the DC buss.
Test at 100 amp breaker, no reading. - Tested voltage? Neitherr side read 12 VDC to ground or you tested from one side of the breaker to the other? What exactly did you test?
You think you're confused?
The 100 Amp DC breaker connectes the house batteries to the hydraulic pump and generator starting circuit. You obviously have not problem there as your generator starts.
There is a 50 Amp DC breaker that connects the house batteries to the USE/STORE latching relay and DC buss. Locate it, check it., reset it, then place your USE/STORE switch in USE.