12 volt battery

Absolutely it's the right thing to do. If the 12v battery dies on you, you're stuck. You can start the car, you can't shift into neutral, and if you try a jump start and accidently reverse the polarity, you're going to spend some big bucks. The small 12v battery has a typical life span of 4-5 years

 

Mine had a bad cell at 5.5 years all king of strange stuff starts to happen mine was shutting down the car, mine cost 138.00 at a dealer the minute it was in the gremlins stopped.
DO IT Now!

 

That amount is reasonable for dealer replacement. But you can check the battery yourself before spending the money.

If you have a voltmeter, measure the "12V" battery voltage at the jump point under the hood with the car off. 12.6V is normal; if it's less than 12.0V, it's dying.

Otherwise use the built-in self test procedure given here:
http://priuschat.com/forums/gen-ii-...has-cold-weather-done-my-beautiful-prius.html

 

Also consider the elearnaid Optima option if you don't mind a little DIY. $159 12 Volt (12v) Toyota Prius Aux Battery

- D

 

I agree with Mr. Schumacher; don't buy a new battery just because it's 5yrs old. In some parts of the country (like San Diego, where I live) batteries may last 8-10yrs. Test it periodically, and replace it when voltage drops below 12V.

 

I have a voltmeter but where do I check the voltage, at the battery terminals or somewhere under the front hood.

 

The accurate place to check would be at the battery terminals.

Alternatively, you can measure at the dedicated jump start terminal located under the red plastic cover within the main relay/fuse box near the inverter. However the voltage might be slightly lower there due to resistance in the battery cabling.

When you measure battery voltage, you first need to wait several hours after the car has been IG-OFF so that surface charge will dissipate. If the battery reads only 12V, it is very close to dead at that point and you have been running a risk of no-start for some time.

If you would be unduly inconvenienced by failure of your car to start, you might choose to replace the battery sooner, rather than waiting for the battery voltage to decline to 12V.

 

If you are north of the Mason/Dixon line, I would consider five years a reasonable life expectancy for the 12 volt battery. If you are some lucky Son-Of-A-Gun who lives in SoCal, then perhaps more.

 

If you chose to replace the 12 vdc battery, ensure you fully charge it with a good automatic battery charger, before installation

 

As Patrick wrote, leave the car off for several hours before measuring. Measuring at the jump point under the red cap under the hood is convenient and, with the car off, it will be sufficiently accurate (with the car off the current and therefore the voltage drop are small). If you have a dealer install a new one, the dealer is *supposed* to charge it fully immediately before installing it. If you buy the eLearnaid Optima battery they will charge it immediately before shipping it to you.

 

I recently bought the correct 12V battery for my 2004 from my local Toyota dealer and the battery measured 12.9V out of the box. I was pleasantly surprised to find that.

I also bought a 12V battery for my HiHy from the dealer, and that one measured 12.6V (which is supposed to indicate 75% charge) so I charged it up before putting it into service.

 

I had to replace the 12v battery in my 2005 Prius today because the car displayed the CEL and suddenly felt like it had no power while driving on the freeway, along with the engine shuttering severely like it was trying to turn off at every stop. The battery monitor went from 5 blue bars to 2 purple bars, then back to green. I made it home, replaced the battery, and problem solved! I am at 146k miles.

 

Our 12 volt battery died over night. We have 35,000 miles on a 2007. AAA doesn't seem to carry the battery. It's 4th of July weekend and our mechanic called Toyota and they told him it would take a day - which means next Tuesday the 5th.

I'm wondering why AAA doesn't carry that battery.

 

You could have tried charging the battery.