12 volt battery dead

I have the same year Prius and my car's 12v battery died primarily due to neglect. I had the car in storage and my friend was supposed to drive it every few weeks but there were times he wasn't able. Long story short, the battery finally died and would NOT take a trickle charge. My friend did the installation and it is a little tricky if you're not that handy (I'm not). The battery is in the rear hatch passenger side. If you feel uncomfortable doing it, just bring it to a reputable mechanic. He'll probably have it done in 1/2 hour.

What did Toyota charge you for the battery? I bought mine online from a dealership in the midwest and with shipping it was less than $120.

 

Hi Bob,

$130 is a good price at the dealer.

You are in the vicinity of the 12V battery. Can you see the red plastic cover over the positive terminal of the battery?

To get into the hatch, you have to unlock the driver's door with the mechanical key hidden in the fob. Then crawl into the hatch. Remove the folding hatch panel and the black plastic tray on top of the spare tire. Find the little lever that will unlock the hatch lock on the hatch floor. Then you can raise up the hatch.

There is no way to unlock the parking pawl in the transaxle, without first restoring 12V power to the car.

You'll need a set of metric sockets (10, 12 mm sizes) and a ratchet wrench. You'll also need a box wrench to remove the battery terminal connectors (9mm or maybe 10 mm, I forget which).

You will have to remove the traction battery ventilation duct that runs over the 12V battery, and also remove the brake power supply that is next to the 12V battery, in order to gain access. No need to remove the wiring harness connector that attaches to the power supply.

Once you get to the 12V battery, you'll have to remove the battery cable negative terminal where it attaches to the body of the car (easier than trying to remove the cable at the negative terminal) and then lift up the red plastic cover while removing the positive terminal connector. Then remove the 12V battery bracket. The positive terminal connector and fuse block are attached to the bracket with a plastic pin, you can remove both parts as one assembly.

Work carefully and pay attention to what hardware is coming from what location so that you can replace everything. Note how much force you are using to remove the hardware and try to exert similar force when tightening. Good luck.

BTW, to reduce the incidence of emergencies such as the one you've faced, I suggest owners should replace their 12V battery based upon time in service rather than wait for a failure.

 

If you don't want to climb into the back area, you can also jump start the car from the jump point under the hood. Once the car is started, you can open the hatch as normal.

 

My 2005's 12 volt battery got a dead short after about a year. Toyota replaced it under waranty.

 

Thanks for this detailed description. What is the suggested "time in service"? Our original 2004 12v battery was dead this morning. No lights were left on. Of course I didn't notice whether the driver's door was possibly ajar. I did the battery check and it came up a few tenths short on all three test modes, so I'm not sure if that is serious or not.

PA P

 

I replaced the 12v battery after 3 1/4--3 1/2 years when it wouldn't start as a preventative measure so I wouldn't get stranded in NY. The replacement lasted ~6 weeks before failing at the office. I recommend checking the voltage regularly.

 

It's been posed time & time again ... the OEM aux battery is NOT designed with cranking amps in mind. If you get 3 or more years out of it ... consider yourself very lucky & replace it NOW. Replace it with the optima ... which has also been re-posted on PC, ad nausium. With the yellow-top installed, you'll never look back.



.

 

Since you live on the East Coast with frigid winters, I'd say that four years would be a good service life. You did quite well to eke out six years.

I assume that you drive the car enough to keep the battery charged up - my guess is that the car is driven almost daily, and has logged >=10K miles per year?

 

I just stopped by to see what the expected life of the 12v battery would be, as I think mine's starting to get a bit twitchy in this weeks bitter cold. It's now four years old (exactly, to the day) - and my 2006 had problems starting yesterday. One system startup just seemed somewhat unsmooth, as if it couldn't make up it's mind. It christmas-tree-of-doomed for a second, then started up on it's own. Then later that day it refused to start up on the first attempt at all.

I killed it once while it was young while tinting the windows, and the symptoms seem identical. Flashing transmission indicator, fuel gauge alternating between full, and flashing one pip, all lights lit up - doesn't want to power off, but doesn't want to power up either.. seems to be a dead ringer for insufficient 12v current...

But I couldn't for the life of me remember if 4 years of life was longer than expected, or shorter than expected. But it sounds like I did well, and it will get replaced tomorrow....

(Turned off SKS in the meantime)

-Ken

 

Unless $200 is nothing to you, you should test the battery first. It might save some expense or trouble.

 

I had all kind of gremlins until i replaced mine at 5.5 years

 

I would say that a battery "test" is reliable to the extent that if you determine the battery is bad, it probably is.

However, if you rely on a voltage test or a load test to determine the battery is good, your test might be lying to you.

The best "test" is to fully charge the battery, then put it back into service. If you continue to have problems, then replace the battery and be done with it.

 

I didn't stumble upon the thread with test instructions on it until later this evening - had no idea that function was in the maintenance menu. (Haven't given that menu a second glance in over 3 years). Neat!

Unless I did something completely wrong - 10.2 volts cold. 14.4 volts running. And it started indecisively again this evening. I draw the conclusion that it's not holding a charge well, may have been borderline for some time, and this weeks bitter cold was the last straw.

-Ken

 

Hi Ken,

A reasonable conclusion, as long as you've been driving the car enough so that the battery has had plenty of opportunity to be charged.

 

Ken,

A reading of 14.4v running is too high! Check it again and if it is really that high get the charging system checked out a dealer. A high charging voltage can cook our little 12v batteries.

JeffD

 

I hate to say it, but when it's 15 degrees and the only set of jumper cables available have clamps that are too big for the horribly undersized (+) terminal it makes it a real pain to get that thing hooked up. On top of that, in the dark it's difficult to find a good (-) point to hook up the negative terminal.

 

Regarding the + terminal, maybe if you connect a paper clip or alligator clip to the dedicated jump start terminal, then you can clamp the jumper cable to the clip.

Regarding the - side, use one of the nuts that secure the top of the driver's side suspension strut.