I have a 2010 Volvo S80. It seems like half of the vehicle works and always has a battery problem. After two brand new alternators and 6 new batteries from Walmart I figured it was the wiring. But after speaking with someone who owns the same year, make I'm told it's the aftermarket battery.

Google suggested H6 battery from Walmart but looking at it now I've noticed that it doesn't even fit in the tray (too small). Does anyone else have any experience in this department with this vehicle?

Would like to just get the correct battery if that is the issue.