I can't help with the Li voltage level, but the "Open Ground" fault with a Honda (or any portable) generator is an known phenomenon. The surge protector expects a normal shore power supply which has a grounded plus leg. Portable gennies don't have this. You need to buy or build a "bonded neutral" plug to make the surge protector happy.
Here are a few previous discussions on this topic:
https://www.montanaowners.com/forums...ad.php?t=36921
https://www.montanaowners.com/forums...ad.php?t=84078
https://www.montanaowners.com/forums...ad.php?t=56406