1. What is the optimum 12 volt aux battery voltage range 2. Why does 12 volt battery voltage effect MPG
A new battery should read around 12.8V with no load, and should stay above 12V under accessory load. An old battery will take energy (in the Prius' case from the inverter) to try to maintain voltage, energy that normally moves the car.
Thanks for the quick reply. I recently replaced the aux battery with a Optima Yellow Top....MPG was 51.2 after about a 100 miles or so , on hilly terrain and battery voltage after sitting over night was 12.86 Previous MPG was 47-49 on basically the same roads Thanks again......from Arkansas
In a HEV design, all energy comes from gasoline. The 12v is charged by the ICE spinning the generator. If the battery is weak, then more and more gas is needed to try and keep it topped off. Kinda' like leaving your a/c on all the time; an unnecessary drain. The same process holds true for the main HV battery. If it's weak, your mileage will go down.
That sounds good. My Optima, installed last September, seems to hang out around 12.6~12.7. The car is not driven daily, maybe every second day on average.
