12V Battery's Life Expectancy

At least for the Gen II, typical 12V battery service life is ~4 years.
Lengthy service in extremely hot or cold climates results in some
unquantifiable reduction.

That said, a few owners have reported the battery lasting up to 6 years.

Leaving a door or the rear hatch ajar, or the interior lights on overnight
will usually result in the 12V battery being run down and the car will not
start. The 12V battery is needed to boot-up the various computers and
ECUs, and to bring the HV battery on line.

Having to jump start a Prius is a potentially costly event.
If the cables/polarity of the jumpstart battery are reversed, even for
just a moment, there is a strong possibility that you can damage one
of the computers, at some $2K replacement cost.

Be very careful, and don't allow anyone else to jump start your car.
As a safeguard, you can buy jumper cables that have built-in circuitry
to prevent reverse polarity.

 

My personal preference is to replace it after 4 years, regardless of condition. As times goes by it becomes increasingly likely that it will fail, even if you've never had a mishap such as leaving lights on. Four years just seems a good balance between risk and expense, for me.

Our usuage is regular. On the other hand, people with emergency vehicles, ambulance police, etc., will replace batteries bi-yearly, or even yearly.

 

My magic number is normally 5 years, I recently forgot and ran 5 years 2 months on my other car and the battery died. I may only do 4 on the Prius because of the battery problems people have been having.

 

The advice above will help keep you out of trouble but I would recommend checking the voltage at the battery with a volt meter twice or more a year. This will help you keep tracks of your battery condition.

 

Still on the original 12V for my 2006. We don't drive much, so ours sits for days and weeks at a time. Our climate is pretty easy on batteries. Likewise this one has only suffered one "lights left on" episode, so it hasn't been abused.

Given its age, I keep a jump box in the back, but have only used it the one time my wife left the map light on.

Tom

 

My 2007 Touring 12v battery lasted 4.5 years, died while I was shopping for our new 2012 IV. I had left the '07 running while looking at a '12 after removing a CD to test the player on the '12. I expect our new 2012 IV 12v battery to last a minimum of 3 to 4 years.

 

In addition to the previous comments, a number of people have reported that gas mileage drops precipititously when the 12v battery begins to fail, even when not noticeable by performance. My 2010 with 53,000 miles has suddenly gone from low 50 mpg to low 40 mpg. Has anyone heard of a 12v battery failing this early?

 

MY Prius was built in January of 2005...I replaced my 12v battery November 2011 ...That's 6 years and 11 months......never had a problem with battery. I checked voltage last November and voltage was 9.95vdc. I decided it was time. I replaced it with an Optima battery. I figure I'm good for 7-10 years now. :cheer2::rockon::cheer2:

 

Because of work load and weather, I have not driven my 2010 Prius for nearly 3 weeks,
I was in the garage a few days ago and thought I should charge the 12V battery. I opened the under hood fuse box and hooked my BatteryMINDer trickle charger/ maintainer/ desulfator to the jump start terminal and let it do it,s thing.

I was not too happy to see that at the 1.3 amp charge rate, it took 18 hours for the charger to switch from charge to desulfate / maintain mode, so I suspect the 12V battery was atleast 50% discharged.
The BatteryMINDer charger/ maintainer/ desulfator units are one of the best avalible, one of the few maintainers that are rated for use on a sealed AGM battery like what is used in the Prius.

The little BatteryMINDer units come with two plug in 12V wiring harness, one with ring terminals for permenent installation on the battery posts, the other with battery clips.
It's a bit clumsy to open the fuse box and connect at the jump start terminal, so I will install the permanent harness on the battery , with the plug and batteryMINDer in the below floor storage tub, where it is easy to acess to plug in for those times when the Prius sets too long.

If not allowed to do much deep cycling,I suspect the original battery should last 10 years.


EDIT: I just finished installing the BatteryMINDer permanent wiring harness in the battery compartment and storage tub. took all of 10 minutes, Why did I not do this 3 years ago when the car and 12V battery were new. :-(

Here is a link to the BatteryMINDer charger / maintainer./ desulfator.
http://www.northerntool.com/shop/tools/product_200332201_200332201

 

I have 56,000 miles on my 2010, still getting lo to mid 50's on the mpgs.

 

The battery in my 2005 lasted 7 years and 65000 miles. Fortunately it died in my driveway.

I did notice that my mileage wasn't as good for the last year or so. I averaged around 47 - 48 rather than the 52 -53 that I had been getting.

I think I'll replace the one in my 2012 at around 5 years or so.

 

My 2010 was built in August 2009. I have just replaced the battery but I stupidly allowed it to go completely flat a couple of times.

 

Is the 12v battery life based on time, mileage or both? I have 56,000 miles on my 2010 (purchased in Oct. 2009).

 

Temps play a part in it too.

 

Just replaced my 12 volt battery on my 2005 Prius with 136k miles. I guess 8 years is not bad.

 

Mine lasted over 7 years in a NYC Yellow Taxi. 160000 miles. Incredible. 2005 prius

 

Check the fluid level in your battery 2 times a year. If you need to add denatured water, ok and This will extend the life of the battery

 

Zander

you can not add the water to Toyota 12v battery.