Prius won't start

go to your trunk take out the black plastic that's covering up your spare tire once you've done that your battery is on the right side sounds like you need to jump your battery so do that one time either with another car or with a battery charger and you should be fine after that

 

I wouldn't recommend a jump start unless absolutely necessary. Prius electronics are sensitive. But since you're back there, carefully remove the battery and take it to your auto parts store of choice and have them run a diagnostic. Then purchase a suitable replacement after they tell you it's toast.

 

Yes, you need an auxiliary (12v) battery replacement. This battery is commonly neglected, and it doesn't give the typical signs of needing replacement as in conventional cars (slow cranking).

 

I wouldn't recommend pulling the battery out taking it to your nearest auto parts and replacing a perfectly good battery just because it failed on you once does not mean the battery is deficient

 

Well, if it's the original, it's time. Be prepared to be shocked at the price.
The battery may be persuaded to last the rest of this year, but it sounds like it's just about history.
The cold and leaving it for 3-5 days is what caused it to show you it needs replacement.
If you can afford one now, I'd replace it. Peace of mind knowing it won't die on you again soon.

You can boost it using another battery from the fuse box under the hood. There's a red "flip over" plastic device covering the boost point. Be -very- careful to get the polarity correct. The positive goes to the boost point, the negative to the chassis under the hood.
If you use another vehicle, they don't have to have the engine running. The Prius draws very little current as the 12V does not crank the engine, it just powers up the computer systems. You can even boost the Prius with a gel cell "alarm battery".

 

It's very easy to measure voltage on aux +12v, check it idle and with load.

 

The car is 6yrs old with 85k on the clock. One morning it wouldn't start. To me, this is good indicator that it would probably be a good idea to replace the battery. If you have a light bulb in your house that burns out, do you walk around in the dark? No...you replace it ! The battery and the light bulb have an expected life cycle. Your battery is at the end of the bathtub curve for reliability.

 

For a peace in mind why not to check if it is really the battery?

 

^^^ I agree ! A simple way to do that is to use a multimeter. A 12v battery will maintain at least 12.2 volts even in a low state of charge. One way is to put a load on the battery ( turn on headlights ) for about 5 minutes. Turn off the headlights and after about 10 minutes check the voltage across the terminals. If the voltage is below 12v ( let's say, around 11.5 v) the battery is most likely expired.

 

Yes, agree.

 

2010 model. October 2018. Similar problem, first drove to my destination,parked but would not turn off completely, dashboard lit up, flashed etc. dashboard lights died but a whining noise continued for hours plus a strong smell of sulfur. Had to use the metal key to lock and unlock the doors but not the hatchback door. Have to go from inside take everything off the trunk (quite easy) and opened the back via the small latch that you have to pull (wasn't easy to locate). Jump started and drove home to re-charge the 12v battery which was dead so drove to AutoZone and replaced the original battery (2010) (~$200 3yr warranty), everything runs just fine and no more smell or whining noise as well.

 

congrats and welcome!