Should I Replace My 6-Year Old 12V Battery?

Yes replace it asap. Only because unlike any other car out there on a Prius its somewhat dangerous to expose the car to a jumpstart.

So you want to avoid that possiblity at all costs.

Many many posts of major electrical damage using a jumpstart. Most likely by people inadvertently reversing the polarity of the jump leads which for some unknown reason happens alot to a Prius.

Here's the standard very simple & easy boot battery test to convince yourself:

http://priuschat.com/forums/newbie-forum/73400-weird-stuff-happening-mpgs-dropping-test-battery.html

 

I agree with Ed, not just because of the consequences of reverse-polarity jumping (and the age of your battery), but also because of the sudden, peculiar, and potentially serious symptoms of a dying Prius 12V battery. (Do a good search here if you need more.) I replaced mine as a preventive maintenance measure after 4 years.

 

Also make sure the replacement battery is fully and properly charged BEFORE you install it. The way the Prius handles 12 v battery charging, if you install a "new" battery only partially charged, you will have a chronically undercharged battery and shorter battery life

With my former 2004 Prius, and now my '07 FJ, I leave the battery plugged into a VDC Electronics Battery Minder whenever I'm not driving the vehicle

With my FJ, I was somewhat surprised after going over all the maintenance records, how much I drove it the past year: 6,458 km over 12 months

Due to business travel, the FJ can sit in my attached garage for upwards of 2 weeks at a time. The Battery Minder keeps the battery at the proper charge, and desulphates the battery too

 

Agreed, replace it. At the very least, when it fails, it'll be a hassle (and of course Murphy's Law indicates that it will happen in the rain, at 2:00 in the morning, in a questionable neighborhood, with your teenage daughter driving the car).

 

Hi berryman. Do the test as I outlined in the following thread and post your results here.

See : http://priuschat.com/forums/gen-ii-...conditioning-12v-aux-battery.html#post1188923