Testing Prius V I've noticed that the 12V battery is very small. Though, there is a bit more room in the trunk where the battery is. I was thinking of replacing this battery with Optima Yellow Top (I have a spare one). My other Optima Yellow Top battery is 13-years old and still in use. I hope the dealer will not void the warranty because of 12V battery swap :-/ 2.) Is anybody using Ultra-Gauge with their Prius?