2012 Prius deader than a doorknob in the garage. Can't even get the trunk open.

Note that this is the 12V battery, not the big expensive hybrid battery.

You should be able to open the hatch from the inside, crawling back and pulling up the floor mat to find the inside mechanical release. Then you could remove the 12V battery and charge it on a bench. Or just replace it.

The under-hood points ought to work, if the battery isn't too dead to charge. But keep the charging current under 4 amps.

 

Should charge the auxiliary battery, give you power to open the back up to get to that auxiliary battery.

Posted via the PriusChat mobile app.

 

did you leave a light on?

 

That is why I changed the interior lights at risk to being left on, to LEDs. Doesn't cure the problem, but gives vastly more time to discover and fix it before the battery dies. With a respectable choice, overnight mistakes won't drain the battery.

 

mine is 5 years old. still close to new, but i have never run it down. if it won't start in the morning, crawl in back, open the hatch and replace it.

 

I've got 7.5 years on our 12 volt and still kickin. Just completed a charge cycle on it this weekend to desulfate it. Do that every other month on our 2010 Prius and the wife's 98 4Runner. Got over 6 years on that battery as well.

Something must have been left on or there was a parasitic draw of some kind.

But only the OP knows that answer.

 

Not necessarily. Depending on use and abuse and climate and random luck of the short straw, batteries seem to start giving up the ghost around three years. By six years, most of those remaining are living on borrowed time, and by 8 or 9 years, nearly all have returned to the lead recycling smelter.

My household, in a relatively mild climate compared to the OP, and going all the way to failed or difficult starts, normally gets 7 to 9 years on non-hybrid automotive batteries. Some folks prefer to avoid stranding risks by preemptively changing batteries before that stage.

After being parked unattended for a month, my Prius displayed clear signs of battery weakness last week. Age 4.8 years. That prompted me to top if off with an overnight charge, and move the portable jump pack from another rig to this one. Whether or not I replace it this winter remains under consideration.

 

Definitely a better option. I changed my running lights to led as well. Cheap and why not draw less current on the main system.

Posted via the PriusChat mobile app.

 

Which charger do you use for desulfination?

 

It's called BatteryMINDer 1510. Available on Amazon for like $50.

Good little setup I learned about on here from reading a post by @jdenenberg .

I figured if it was good for a EE prof, it would work for me.

 

Dang it. I just dropped $60 for a 5 amp charger, but it doesn't do desulfination.

Well...Northern Tools, BatteryMinder Model #12177 (1.35 AMPS) on sale for $24!

 

I'm partial to CTEK, currently using a 4.3 mostly, have the 3300 also. With us the car tends to sit idle 2~3 days at a time, and then sometimes it's just a short run for groceries. I've taken to just leaving the charger on pretty much all the time; installed the quick connect to expedite this. Once it's gone through a complete cycle it subsides to a "float" mode, just occasionally giving a little boost of electrons.

The thing is, all the time the battery's installed, there is a low level parasitic draw. If your car's getting a steady weekday commute of 20~30 miles the parasitic draw is not a factor, I think. But lots of idle time like ours, yeah.

 

Once you get a little charge into the battery the car should go into "ready" for you. Once in "ready" the car is safe to drive, though it's possible if you shut it off without the charger connected it could go dead again. Anyway, then you can decide which battery you're going to replace it with (it's time). You can use the stock one from the Toyota dealer, an Exide AGM one from a parts place, or even an Optima yellow top. If you're not comfortable changing it yourself let the dealer do it if you have a half decent one.
It's not unusual for the 12V battery to die at 4-6 years.
Do keep in mind the Prius has a noticeable "parasitic drain", and once the 12V battery gets over 4 years old it may loose enough capacity that the parasitic drain will kill it overnight. Some last longer, some even less. Leaving lights on will make it happen sooner.