Replacement of 12 volt auxiliary battery

[dzitlow]

Where can one obtain a replacement for the 12 volt auxiliary battery in the Prius? What are the specifications (e.g., product name, capacities, etc) and prices of the replacement 12 volt auxiliary battery?

[DanMan32]

Toyota dealer mostly. There have been some that made retrofits of other types.

1. Needs to be sealed. There should be no way to spill any elecrolyte.

2. Needs to be vented if there are chances of dangerous gasses that will, or can be released.

3. Needs to be 12V. 13.8V to be exact. The DC-DC converter determines if it goes into charge mode (14V) based on sense voltage.

4. Needs to have 28AH capacity. Can be greater if space allows.

5. Needs to be able to tolerate large charge currents, at least for a short term. The OEM battery is said to take a 3A charge current, though it baffles me that the DC-DC converter outputs 80-100A with no current regulation to the OEM battery, other than the fuseable links' inherent resistances.

6. Needs to be able to provide 100-150A. Granted, it won't provide this for long with a 28AH battery.

6. Needs to fit or be retrofitted to the provided storage space in the underhatch.

7. Needs to have the right posts, or the wires altered to accomodate the new posts.

[dzitlow]

Found what appears to be replacement for Prius 12 volt auxiliary battery. Check out at www.westcobattery.com/_page.php?bid=20&vid=-1. Does this battery and its characteristics make it suitable as replacement for the Prius 12 volt auxiliary battery?

[dzitlow]

Westco Battery 12v13m Sealed AGM Battery. CCA 475 Length 7.5" Height 7.25" Width 5"
Weight 25 lbs. MSRP 89.95 includes shipping

[DanMan32]

You mean 12V31M, http://www.westcobattery.com/miata.html ?
I believe someone did a writeup on retrofitting such a battery. Post terminal clamps had to be replaced.

CCA not relevant here, you can't draw more than 150A without blowing the fuseable link, and you aren't cranking anything with the aux battery.

[jtrosario]

I've had to replace my Classic Prius 12V battery and now my 2004 Prius 12V battery, here's some ideas:

For the classic, model year 2001-2003, try this solution:
http://www.elearnaid.com/12vobaforpr2.html
This is a 12V31M Westco Sealed battery for US$108.95, you'll also need a kit which includes parts needed to adapt to standard terminal size here:
http://www.elearnaid.com/pakitforup12.html for US$25.00

I had purchased the 12V31M Westco elsewhere and went to a few auto stores getting post adapters, a new negative cable, vent tubing, and fashioning wood blocks for making the hold down work, and would have rather have had a kit like the above had I known about it.

For the 2004-2008(so far) Prius, try this:
http://www.elearnaid.com/12vo1topraub.html
D51-YT Optima Yellow Top Sale price: US$140.00, you'll also need a kit which includes parts needed to adapt the standard terminal size here:
http://www.elearnaid.com/pakitforinop.html for US$10.00

I went with a replacement at my local Toyota dealer(today) that they had in stock and replaced the existing battery myself after 4 winters on my 2004 model with Smart Key and Navigtion(purchased 12/1/03):

Toyota part number: 28800-21170 (also marked S46B24R on the battery itself and on the outside of the box Toyota sells you the battery in), I paid $138.70(apparently list price), better price here:
http://www.toyotapartscheap.com/
just search by factory part number 2880021170 to find it for US$110.96
No kit needed, it's an exact match to the battery being removed.

An amount of effort was needed to unscrew the 9 bolts & screws(using 10mm and 12mm socket wrenches) to move the large plastic vent out of the way, move the brake assist out of the way, remove the battery bracket, detach the vent tube, and move the positive and negative cables out of the way to remove the old battery. When placing back in, I would recommend this order:
1. Install new battery with battery bracket(1 bolt, 1 screw)
2. Re-install large plastic vent(1 bolt, 1 bolt/screw) Take care not to lose that bolt/screw and really reach for it.
3. Re-attach the vent tube.
4. Re-install the brake assist unit(2 bolts to floor, 1 on top of assist unit)
5. Re-attach positive post.
6. Re-attach negative post(Please leave this for last, because, as you'll see, there is only one way to tighten with the 10mm socket wrench. Gently turn the negative connector so that the socket wrench can be placed back in, and so that others can get to it later on. This will also allow you to remove the negative connector in the future without taking the rest of this jumble apart)

And although I left all my positive connections connected to each other before and after removing the connector from the postive terminal, I would still highly recommend this great description with pictures for taking the above listed items apart(for either/any battery replacement 2004 or above):
http://www.techno-fandom.org/~hobbit/cars/prius-12V/

Good luck and have fun!!

-John T

P.S. I had tried the Sears route, but the technician took one look at the vent tube and said he could not install their recommended battery for the Prius because it would vent into the passenger compartment. He also said he would get the entry removed from the Sears database for Prius for safety reasons. My opinion is to stick with these(or other batteries) that can be vented via a tube outside as in the original design of both the Classic and current Prius.

[Doc Willie]

Anybody know enough about battery technology to say whether the one from eLearnAid above is actually a better battery, and worth it ?

[jtrosario]

Hope there wasn't any confusion in my previous post, eLearnAid doesn't make batteries, but is only a reseller.

The 3 batteries mentioned are:

Westco 12V31M (for 2001-2003 Prius if post connectors are adapted to standard size)
Optima Yellow Top D51-YT (for 2004+ Prius if post connetors are adapted to standard size)
Toyota 28800-21170 (S46B24R - matches original on 2004+ Prius with smart Key and Navigation, does not need to be adapted)

For me, my goal was to get a replacement battey that would be as good or better than Toyota's AND would be properly vented to the outside. I found WestCo's from other forums and previous posts here and have been very satisfied with 3 years of use(on my 2002), so far. I am also satisfied with the original battery from Toyota(on my 2004) and replaced it with the same, but with price quotes from $110 -$199 battery only and $175-$300 installed, I was looking for "other" solutions to consider.

IF I were to adapt the connectors to fit a standard post battery like WestCo's again(or the Optima I was considering), I would purchase the $10-$25 kit from eLearnAid, instead of finding and/or making the parts myself, simply from a time savings perspective. (However, I am using their quick disconnect switch on my 2002 for multi-day cold weather parking, nothing too special, was just tired of jump starting in the cold when parking at the airport for a week)

Since, I did not find a replacement battery solution like this for my 2004 elsewhere on this forum, I thought I would post my findings for anyone else interested in adapting 3rd party batteries more easily, or simply some links, and some info to help replace their existing 12V on their own. (Special thanks to Techno-Fandom's "hobbit" for their post which encouraged me to take apart the "jumble" in my 2004 and replace my own 12V battery)

Making a more standard, and yes, much less expensive battery fit and work for starting, but have the potential to gas into the passenger compartment was not satisfactory to me or my family.

[satwood]

Can you describe for me the symptoms that lead you to conclude you needed a new battery in your 2204 Prius? I'd just like to have that reference point when my 2007 needs one someday.

Thanks

[rigormortis]

please see my post in the technical forum

http://priuschat.com/forums/showpost...6&postcount=17