My 2008 Prius won't start, it is about 35F outside, the interior lights are dimmed from inside the car... The power lock wont work, I have to manually lock the doors. This previously happened about a couple days ago, and I left it alone for a couple hours and it worked, and on my screen it gave me a weird error message about transmission error due to not being parked on even surface.. It seems like my battery is dead, I have about 65000 miles on it, and I take really good care of it, I recently had it's 600000 mile checkup, and I have a full tank of gas in it, and I have just had my oil changed. Please help
Those are all prime indicators of low 12V battery voltage. You should put a charger on it and top it off, but replacement is the wise choice. It is about 5 years old and that is where the statistics start become increasingly common. If it is weak, trying to limp along for a while can leave you stranded. And if a jump start becomes necessary at some point, be very careful to observe correct polarity.
OP may want to test it first before shotgunning it. Method is here, this is most meaningful when done after being turned off overnight, before going 'Ready' in the morning: Weird stuff happening? MPGs dropping? Test The Battery
As others have already said this is almost certainly the 12 volt battery after five years of service. A good replacement battery available in your area is the Exide Edge FP-AGM51 JIS. Many on this forum recommend the Optima battery, but the Exide has more capacity than the Optima and the OEM battery it also has a four year full replacement guaranty. Price around $160 money off coupons are available.
I just changed my battery today, got the OEM for 177 due to a nice parts guy that gave me a discount from 197. Labor would have cost another 100 plus tax, so I put it in myself. If it wasn't buried under so much stuff and tucked into the back corner with a exceptionally long telescoping ratchet attachment needed, it could have been a 10 minute deal. Instead I had to go to the store to get the long ratchet arm, etc. Overall though, even with hassle of reaching up under the carpet to remove then replace that screw for the air duct it took about two hours, an hour of which was running to the store. Ran the test after and I am good to go! Do they make it hard to get to in order to discourage owners from replacing? With the right tools I can replace that thing in 10 minutes now (known because I dropped a screw behind the thing when closing it all up and had to completely remove then reinstall again - oops). Save the 100 to 150 and do it yourself if you can! What I replaced was the original battery so it lasted about four years and 120,000 miles.
It is installed in a hard to get at place for sure But we have to live with it. I have never heard of anyone moving the 12V to-date. Good project for someone! H
