12 vt battery - is the dealer right??!!

i agree with the dealer. if it ain't barroque, don't fix it! my daughters 04 is still on the original battree.

 

Use the car diagnostic mode to test.

 

No, I do not agree.

First of all, when you are doing your battery voltage measurements, you should do this after the car has rested overnight. This will dissipate the surface charge that exists after the battery has been charged while the car has been READY.

A fully-charged AGM battery in new condition will measure 12.9V when the car is IG-OFF. If you measure 12.2V or lower then I would replace it.

11.5V under IG-ON condition is the lowest that I would accept. If the voltage was 9.5V when the car is IG-ON, then it is quite likely that the car either would not start or else would exhibit glitchy behavior, of which we have seen numerous posts.

I would prefer to err on the side of replacing the battery in advance of a failure. Other owners prefer to wait for the battery to fail before taking action. If you enjoy that sort of drama (and don't object to the increased cost of performing repair under emergency conditions), then peace.

 

In addition to Patrick's excellent post, I would mention that when you do decide to replace the battery, one good choice is elearnaid.com's Optima Yellow Top Kit. It is a better battery that fits, they provide the hardware to make it work.

12 Volt (12v) Toyota Prius Auxilary Battery for 2004, 2005, 2006, 2007, 2008, 2009 and 2010 with installation kit

 

Hi Bernie. Whether or not the 11.5 volt reading indicates a problem depends a lot on how long that reading lasted. The 12V battery must supply a brief surge of current when the car is first started, so if this 11.5 volt reading was just for one second or so then I wouldn't worry about it.

Try taking the following three measurements (preferably at least several hours after driving the car).

1.Voltage when car is fully off (this is the open circuit voltage).

2. Voltage when placed in accessory mode (hit power on without foot on brake).

3. Voltage in accessory mode with headlights on (just normal low beam). This one will probably drift downward a little bit while you're watching it, take a reading after about 10 to 20 seconds.

 

Frankly, I surprised that your dealer said that everything would be fine
down to 9.5V.

That's a far cry from what the majority of bad battery stories posted
here report. 10.5V is the lowest reported reading I've seen where
the car operated, but erratically at that. Typical low battery problems
include: the car won't start, the car won't turn off, significantly reduced
MPG's, and a very dramatic display of warning lights on the dash.

What with colder temps coming on, the battery readings after an
overnight cold-soak -- that's when they should be taken -- will be even
lower.

It seems like now is the time to get that new battery.

Hmm... maybe your dealer runs a towing service as well.
If it comes to this, tell him to send his flat bed truck.

 

Your daughter's battery is living on borrowed time. She should replace it.

 

I replaced the 12V battery on my '06 at ~98K miles with the elearn aid deal. The original battery (Denso) was reading 11.9V at rest. I didn't want to risk having to jump start the car which I've read has inadvertently damaged the inverters of some posters.

 

Good post. This is the first car where i will be replacing the 12v sonner rather than later. Because of the many reasons i have read in posts, such as giving false error/ lower mpg ect.

 

I look at that 12 Volt Battery like any other preventative maintenance item. If it dies unexpectedly you will loose a day or more getting it fixed when you need your car for something important. Let alone the cost or damage done to it getting towed to the shop and paying whatever they say just to get it back.

Shop around now or DIY on your own planned schedule.

Bob

 

So true.

A work associate also owns a 2G. He is a competent DIYer and certainly could replace the 12V battery himself.

A few months ago, he told me he spent $400 last winter to replace the 12V battery. I replied, how could you possibly spend so much?

The good news was that he owns four cars so he has plenty of alternate transportation. The bad news was that his Prius, the daily driver, was parked in such a way so that he could not get any of the other cars out of the garage. Since this was a work day, he was in a rush, so he paid for a tow truck ($100) to tow the Prius to the dealer.

Then the dealer tech diagnosed ($100) that the problem was the 12V battery. The dealer then charged $200 for the battery and installation.

If he had planned the 12V battery change in advance he might have paid $139 MSRP for the replacement battery and enjoyed a 30 minute project. But no. Instead he paid $400 for unneeded drama.

Each winter, I've noticed a few forum stories that have followed a similar story line.

 

i wonder how long a battery can last?

 

Wow what a story! Was the 12V battery so dead that it couldn't even be jumped? Stories like this would be a good motivation for the Prius owners to at least check the battery voltage frequently even if they want to maximize the battery service time thus opt not to change it on a fixed schedule.

 

...and that built-in battery diagnostic procedure is given here:
http://priuschat.com/forums/newbie-forum/73400-weird-stuff-happening-mpgs-dropping-test-battery.html

 

At the time this happened, it was not clear to my work associate that the 12V battery was the problem, given the stress inherent in the situation where the car was not behaving as expected.

Of course, should this happen to any of us and we didn't have a digital multimeter available, we would think about looking at the interior cabin lights to assess their brightness which provides a clue to the 12V battery voltage level. We also would probably turn on the headlights (briefly) to see how bright they are, thus testing the battery's ability to provide power under a moderate load.

I'm sure that there are some Classic owners who still have the original equipment 12V battery installed. However, the capacity of said battery will be quite low and in the event of an emergency it is doubtful that battery will have much reserve to draw upon. Also, if the owner doesn't pay attention to clues manifested by cabin light brightness etc., then one day that owner will be stuck in a parking lot when the car won't start on a cold winter night.

 

The dealers a goof ball and doesn't know the first thing about batteries. For total peace of mind, heed Pat's advice.

 

Depends on who you talk to, the car, the type of battery, the climate.

I had a 1987 Nissan Sentra (bare bones model - but got up to 40 mpg on the highway!) that started acting flaky in 1994 or '95. Occasionally it wouldn't start but I would wiggle the battery connections a little and then it'd be okay. But one time this happened when I was on a ferry crossing the Potomac, and they were getting the farm tractor out to pull me off the ferry before I got it started (the other cars were waiting for the return trip, and I was the only car still on the ferry). That's when I decided to replace the battery, which was probably about 8 years old by that point.

My current battery is 3.5 years old, maybe I should check it before winter. Usually they last 5 - 6 years in my experience though. The Prius has a little different 12V battery than most.

 

How long can a battery last? A very long time. I usually let my household's nonhybrids go to near failure. One went 9 years, typical is about 7.

How long will a battery last? Far less for average drivers, most of whom live with battery-damaging hotter summers, colder winters, or both. Drivers who must have a specific car running on any specific day, and cannot simply hop into a spare vehicle until they have time to replace their own battery, will usually find that this sort of brinksmanship will cost more money than it saves.

 

I note elsewhere that when Patrick replaces the 12v battery he uses the OEM battery and not the Optima. I keep wondering why.