2008 Prius 3 month old 12 volt battery, no check engine light no codes did the battery check on the information display red 11.9 . when driving up Hills HV drains super fast and start to lose power while driving through the Rocky Mountains from Las Vegas to Denver. Engine revs up higher but does not seem to be charging HV battery. Battery will charge going downhill but as soon as you start going uphill battery drains. City Driving drives fine. I've also replace spark plugs and cleaned mass air flow sensor. Not sure what to do or what it could be. And will it be okay to drive back to Las Vegas. Any help would be appreciated.
You're just getting symptoms of a weak battery. You'll be ok driving still but planning on reconditioning or replacing that hv battery soon You should check you oil level make sure there's enough oil
Like JC91006 says...you will be ok to drive back to Vegas...I had an 04 do the same thing as it gets older...Just make sure your oil level is on the dot on the dip stick when forcing the engine in the mountains...The battery in the back ultimately will have to be rebalanced or a few cells replaced...sounds like the voltages in the cells are reduced, hence the up and down charges that are aggravated by mountain driving...City driving doesn't tax the battery as hard, this is why it seems fine in the city...
