2008 prius 12v dies if i sit in car without starting it.

welcome to priuschat! it is odd, but you should probably replace the 12 volt. at the very least, test it. if it's draining just because the sks is running, it's probably borderline.

 

If it's the original 12v from 2008 then it needs replacing. Obviously check it yourself but the fact it needed jump starting and failed a couple days later sounds like a knackered 12v to me.

They're not that expensive to replace, though are quite rare for non original.

 

1) never not be in ready, if you are using electricity.

2) the Toyota battery at the dealer has a 84 month warranty. Optima, Excide, O'Reilly. NAPA and others sell the specific Prius battery you need, externally vented, AGM battery with JIS posts. Group S46B24R

 

+1
And be sure your new battery is fully charged and have the charging voltage tested.
If you make a lot of short trips and/or leave the car sit for days and days with no use, consider getting a battery tender.

The 12V battery in most all hybrids is small and prone to premature death in many circumstances.

 

Do you use AA batteries? have a bunch in a drawer, not sure if they're dead or good? Right there: a digital multi-meter would be good investment for you, allow you to sort out which are duds. Then with your car's 12 volt, hook it up, find out for yourself: 12.5~12.6 volts? Pretty good shape. 12.3~12.4 volts? Not so good. Lower? Time for replacement, or try a charger session. The latter's another good investment.

For your specific situation, it could be sitting in the car with your fob is imposing a slight drain, tipping the situation, like you're thinking. Still, if the battery's the original, it's overdue for a change.

 

do it in the morning before starting the car.

 

And not when the car is switched on and charging.

Ideally leave it a couple days and test it first thing.

 

agreed, i think it's the battery.

 

we'll be waiting!

 

I had premature dealth of my 12V battery twice in my gen III prius. The first one toyota replaced for free. The second time, I went after market. It just is too much of a PITA to do at the dealer again. So far so good on this one. My car just turned 5 years old.

I think at 6 years old your battery is just ready to go, its not premature. Get it tested for free at one of the shops. I tested mine at pep boys because they had a battery sale when it had to be jumped. Lots of places will test it for you.

 

your borderline, which is probably why you're having intermittent problems.

 

oh, right. i was gonna say that but thought, no way...

 

There may be a way to change that behavior.

 

Do you run your lights constantly, depending on the car to shut them off when you stop? If this is your practice, you may not be aware that your lights are staying on after you shut down the engine, but not until you open the driver's door. Your lights may have been burning that whole time.
phil via Nokia