Replacing the 12V Auxillary Battery

There be no electrical difference. Prius 'issue' is a vent tube to expel rare, unwanted gases from the common area, inhabited by you as well as the thing.

Your $138 price from Toyota is lower than I have heard before. The standard suggestions have been elearnaid's battery and terminal kit (google it), or the same battery from MK with you making the terminals compatible.

If you choose to believe that venting is not a critical requirement, a world of non-vented, about-30-amp-hour, 12 volt batteries opens up to you. Those could cost as little as $30.

Fair warning, the issue of needing venting remains somewhat contentious! As I have said so much already, expect to hear some strong opinions on the subject.

Back to basics, if you use a battery much smaller than 30 Ah, it will not manage the key-off parasitic load for very long. If OTOH you choose one larger, it will certainly weigh more and your task is that it should fit in the space available.

Please never use any lead-acid battery in Prius without securing it well in place. Make its terminals free of corrosion, and keep them that way. That's about it.

 

tochatihu, isn't the 2002 Prius the sedan? If so, the battery vent is on the side of the car.

 

I replaced the stock Toyota battery with a Honda Civic battery- you need to order the version with the correct terminal orientation, but it's similar enough in size that you require minimal modifications to the bottom tray (it's got slightly greater width and about the same depth), and you have to fiddle a bit to get the top securing strap down (it's a tiny bit taller).. Then the battery terminals on the vehicle have to be replaced with North American sized parts.. The ground terminal is easy, just buy a pre-wired terminal and replace the OEM version; this is is IMO better than just replacing the terminal because the OEM ground wire is somewhat thin, and the replacements are typically much heavier gauge.. For the positive terminal, I got a "marine" terminal with the wingnut fastener on top- replace the wingnut and bolt with the original nut and bolt from the OEM positive terminal, and the new terminal basically bolts in place on the end of the original positive wire without any need to drill or hacksaw bits and pieces off..

Best thing is that the new battery is a true AGM battery with no free electrolyte (all in the mats) vs the OEM battery which the Toyota literature claims is AGM, but in reality is a regular wet cell with sloshing electrolyte inside..

I did *NOT* put any kind of vent tube in my car (a Classic Prius) because the new battery is AGM and has far lower gas emissions than the original liquid filled version and additionally, the hybrid battery cooling/vent system also happens to have a duct ending in the 12V battery well and this big duct by itself is much more effective in dissipating any hydrogen emissions than the tiny rubber hose which was probalby put on as a "just in case" measure..

 

<div class='quotetop'>QUOTE(efusco @ May 13 2007, 10:21 PM) [snapback]441376[/snapback]</div>

Actually, the fact that he's looking for a replacement means that the OEM battery has *NOT* lasted the life of the car.. 5 years is pretty average for the life of a lead-acid car battery.. I don't know about you, but I fully expect my Prius to last a lot longer than that..

I decided to go with a larger standard battery because #1, it's got a much higher capacity than the OEM and if I park it outside in an airport park-and-fly lot for 2 weeks in a Canadian winter, I'm absolutely *not* worried that I might come home to a dead car.. The fact that the battery was half the cost, even with the new terminals, and easily available from any auto-parts store was also a big plus.. Lastly, I've long beein of the opinion that the 12V charging regimen used by the Prius is suboptimal and results in the battery being only partially-charged much of the time, which leads to sulfation damage and premature battery death, and the AGM alternative battery is much more resistant to this than the old flooded plate style construction of the OEM battery..

 

There is no direct drop-in replacement. Anything other than an OEM battery will need new cables to fit the posts. The Optima Yellowtop as sold by eLearnaid (Google it) comes with an adapter kit, detailed instructions, and fully charged.

But what you really need is a new dealer. A dealer installed battery should cost in the neighborhood of $200, not $400. You are in luck in that you live within driving distance of Luscious Garage, hands-down the best Prius repair shop on Earth. Look 'em up.

 

I installed the Optima YellowTop from Elearnaid about two months ago on my '06 w/99K miles and it is still working well. The connector conversion kit wasn't too difficult to install and I saved the original cable in case I want to switch back to OEM for some reason in the future. I would recommend it.

 

I suggest that you call around to the various dealers in your area, as MSRP of the 12V auxiliary battery is $139.

If you should find that you cannot purchase the correct battery at a reasonable price then you might consider this alternative but you will have to replace the battery terminal connectors:
12 Volt (12v) Toyota Prius Auxilary Battery for 2004, 2005, 2006, 2007, 2008, 2009 and 2010 with installation kit

 

what dealer was it?

 

See my previous post:
http://priuschat.com/forums/gen-ii-...66601-battery-replacement-economy-method.html

 

Never go to a stealer for your auxiliary battery. I replaced mine with a nice yellow top Optima batt from Advance Auto. AA may not have them in stock, but they can order the batt for you. It was a perfect fit with exhaust connectors and all.

 

I found the Optima battery that is a direct replacement without needing the kit for $150.82 with free shipping. There is currently $10 off until 7/25 with coupon code W301013.

Optima Part No. 8171-767 - YellowTop Deep Cycle Batteries