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post #1 of 4 (permalink) Old 03-01-2010, 08:03 AM Thread Starter
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Default 12V Battery change

I think my '05 12V battery should be replaced since it's going on 5 years now. Anyone changed out one on your own? Do you have some limited time to swap one without losing all the computer settings? Thanks.

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post #2 of 4 (permalink) Old 03-01-2010, 02:27 PM
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Default Re: 12V Battery change

I would wait until the battery actually dies, unless money is no object. It is really obvious when it starts to go bad, the vehicle starts to throw codes; and our classic Prius displays the triangle of death. This usually occurs several times, intermittently; however, our 2002 has remained drivable. This usually gives you a few days to get the 12-volt battery changed, before it actually fails and the car won't run.

You will lose the radio station settings, etc., but most of the important things will still be there after the battery is changed.

Changing the battery is easy for most people that have done this on a regular vehicle (it's pretty much the same). The difficulty is in finding a replacement someplace other than the dealer. We got ours here:


I do not work for this company, but have purchase two batteries from them (both the "Miata" battery for the classic Prius). They also sell an Optima battery that should provide good service for the newer Prius's.
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post #3 of 4 (permalink) Old 03-01-2010, 06:55 PM
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Default Re: 12V Battery change

If your 05 still has its original battery replace it now. If you wait for it to die, you can be in trouble. Keep in mind that you cannot shift the Prius out of Park without the 12v system in operation. When I replaced mine on my 04, I used the Toyota battery.
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post #4 of 4 (permalink) Old 03-02-2010, 01:31 PM
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Default Re: 12V Battery change

I changed my 12V battery at about the 5-year mark. Although it showed no sign of trouble, my "reasoning" was this:

1: My climate conditions are more or less normal. Hot summers, cold winters but nothing extreme like AZ or MN.
2: "Normal" life for a lead-acid battery is 4-6 years, and I had good reason to expect "normal."
3: I plan to keep the car until I can get a plug-in Prius, i.e., at least two years and maybe more.
4: Therefore, the battery would most likely need replacement before I sell the car.
5: Therefore some more, why wait 'til it fails? If I have to replace it later, it may be after a failure, and will probably be somewhat more expensive.

The only reason to try to eke out more battery life, it seems to me, is if you are planning to sell the car soon and hope you don't have to replace it at all, or if you are going to keep it more than 10 years, in which case, try to get as much as you can from each one. I suspect most of us are in
the five to ten year range.

Incidentally, I tested the old battery after replacing it, and found that it retained about 2/3 of its original capacity.

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