Prius 12V Starter Battery

[dhoward]

In browsing this forum I notice that it does not take to much to discharge the small 12V starter battery. What is the life expectancy of this battery? In my experience in a non-hybrid vehicle the battery should last 3-5 years. Granted, the Prius 12V battery is only used to get the electronics on and enable the main battery to activate the engine so its load is small and short duration but how long before this battery should be changed out. I live in New England and I would not want to be caught in a cold snap and the battery dies. Testing them does not always tell you the truth and a real cold night could sap it.

[tochatihu]

(dopelganger deleted)

[tochatihu]

I would say the life is quite variable, but your 3-5 years is not a bad estimate. For example my 2001 needed a new one after 4 years.

All that can go out the window if the battery is ever completely discharged (by a light left on for example). In a discharged state the battery can suffer greatly, especially in winter. A new car on the dealer's lot can have its battery damaged before the buyer ever sees it. We think that this has happened.

If you are handy with a digital voltmeter, you can measure yours at the underhood-charging points when its off. You could get similar info w/o a meter, with the car off, from the 'hidden diagnostic screen'. Not sure I know how to access that in the 2007 though. Yours is in good shape if it says 12.2 or above or thereabouts.

Replacement batteries are a bit of an issue because Toyota sells theirs for an awful lot. There are other vented batteries available. Use of an unvented battery in Prius remains somewhat controversial.

When this battery is 'on its own', the brake fluid pump can briefly ask for about 30 amps. This is the worst they ever see, unless you add certain accesories

[jamarimutt]

After 3 years and 62,000 miles the 12v battery is still going strong.

[dmckinstry]

<div class='quotetop'>QUOTE(jamarimutt @ Jun 3 2007, 05:07 PM) [snapback]454635[/snapback]</div>

After 3 years and 62,000 miles the 12v battery is still going strong.
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I suspect that as with me, your car is driven nearly every day. And of course, nothing left on over night. I've only got a little over 49,000 miles on mine, but don't doubt that it should last another year or more.

Dave M.

[jayman]

I began to have trouble with my 12 vdc battery less than a year after purchasing the car. I attribute most of the trouble to commutting at -40, with the electric defrost on all the time. I finally put in a VDC Electronics Battery Minder and it works well at keeping the small battery properly charged and conditioned.

http://priuschat.com/index.php?showtopic=27552

Now that I'm frequently away on business, using my Battery Minder is even more important. Over the past two weeks I was away on business, then at my hobby farm on vacation. Tomorrow I'll take the Prius for a quick spin to do errands, and probably won't have to worry about the battery.

I also use battery tenders on my new FJ Cruiser, the tractor at my hobby farm, and the old Ford pickup at the hobby farm.

[dhoward]

Thank you all for your responses. It seems that the 12V battery is somewhat of a weak sister compared to a "normal" car's 12V battery. I have left a dome light accidentally on, in a non-hybrid vehicle, and had no problems starting it the next day. It seems that the Prius battery is very easy to accidentally discharge and its life expectancy after that is severely reduced. What is the availability of this battery when it has to be replace? Is it only carried by Toyota or do any other retailers, who sell batteries, stock them?

I have had the car for 2 months and love it. My primary concern is because of the technology I am locked into the dealer for service. All my other cars have always been serviced by a local mechanic who I trust. When I have had a problem they are 5 minutes away and I can just take the car over to them to look at. Going to the dealer is a little more complex and unfortunately more costly.

[David Beale]

Well, the anti-Prius (2001 Pathfinder) battery was still going strong after 7 years of use when I traded it in! And that's in "real winter" country, like jaymans. I'm hoping my Prius battery will last as long (fingers crossed). I -was- very careful to keep it full of fluid, adding distilled water at least once a year. Can't do that with the Prius battery. With the Prius, keeping it fully charged is the only thing we can do to maximize battery life. A "battery tender" is not a bad idea.

So far, nobody has found an exact replacement anywhere but from the dealer. It's rather expensive from there as well - in the $250 range. Larger dealers should have one in stock, or available from the Toyota Parts warehouse in a few days. Smaller dealers not so much.

One -could- replace it with something like an Optima #51 yellow top. But that would take some work.