GEM battery schematic

Hello, I’ve inherited a 2000 E825 72 volt GEM. My goofball ex brother in law put in new batteries. Of which, 4 of the 6 are new and the other two are good. However I suspect the front two batteries may have been installed improperly. The system blinks green/yellow and a warning buzzer is intermitent. The online manual surprisingly does not have a schematic. Can any offer advise with this. Thanks S