12V Battery

The Prius 12v battery has becoming a hot topic. Early Gen 3's 12v battery is coming to its end of useful life so a lot of owners are scrambling to replace their batteries. Talking about which battery fits in a Prius vs which battery is designed for the Prius is pretty useless. If a particular battery is the only one available to you in your area then you have no choice but to buy it. Now, there's always option 2, buy a battery that's not made to fit the Prius but designed for the Prius application (deep cycle AGM.) There's already a thread about fitting wheelchair battery in the Prius. I've also provided detail instructions on how to replace the Prius's S46B24R with a much larger group 25 battery.
If you want to stick with OEM replacement batteries, you can read my thread about the Prius battery and what's available. It has alot of information about the OEM battery and aftermarket OEM fit batteries available in the US.
You can read britprius's wheelchair battery here
If you want to install the biggest battery you can fit in the Gen 3 Prius check out this thread.

 

To which I can add that a "wheelchair battery," or "mobility battery" as Britprius called them, is not really as specialized as those terms imply. They're typically identical to same-size general-purpose or "universal" AGM batteries sold for many different purposes (including not only wheel chairs, but also APS systems, power gates, solar power systems, emergency exit lighting, etc.).

I adapted a common size 35AH "universal" AGM battery for use in my Prius, and it's behaving well, so far.

 

I am sure someone will flame me for this, but I have always thought this when it came to alternative batteries rather than sticking with the OEM or something that is at least "plug and play" (no mod's needed). What is the next owner going to go through when he or she finds out that the owner before has modified his or her car? And to make matter's worse, what if that poor soul is stuck with having to deal with a dealer.

I could only begin to imagine what a dealer would charge to install a OEM battery after someone else had modded the Prius to fit a battery such as described above. I am aware of BritPrius's post's concerning the wheelchair battery, plus the yellow tops, the D51's and all the rest of the post's concerning the 12 volt. Prius Chat has TON's of them. I do realize that it would be stupid to convert back to OEM after a aftermarket mod has been done, but surely some poor damsel in distress somewhere will do this at some point in time. I am now donning my asbestos underwear

One additional point for clarification. I am referring to the fact that not all alternative 12 volt batteries will come with the JIS post's. Once the Prius has been modded for anything other than the JIS posts, the above applies. If the next battery is still JIS and fit's the battery tray, then the above information does not apply. Remember I said " Plug and Play"...

 

There are only 2 connections to the battery posts, what's so hard?

 

Besides the battery posts, there are 2 other things to consider. 1, non spillable battery. Because the battery is inside the cabin and near the rear bumper, any rear end accident may puncture the battery, If you use regular battery, the acid could splash allover the interior and possibly to your person. 2, Venting. Because the battery in mounted inside the cabin, there's a possibility that hydrogen could build up inside the cab if not properly vented. These issues must be addressed first before installing any battery in the Prius. Sure there are tons of batteries out there. I've spent a few weeks searching which battery will work and which won't. I've contacted several battery companies. In the end majority of the batteries out there got eliminated. Exide AGM and its rebrands were one of the few that would work in a Prius that met all 3 criteria.

 

I haven't seen anyone advocating use of a "spillable" battery. All AGMs are "non-spillable," so your #1 is not a relevant objection. My battery is fully vented through the original vent plumbing, to address the very remote hypothetical possibility of becoming a mini-Hindenburg.

Dorunron, no modifications to the car are needed, not even easily reversible ones. For some other sizes that have been suggested, they would be.

 

Hmmm. IIRC, the Gen II section of Prius Chat has post's where mod's were done and non AGM batteries were being used. Even BritPrius's post about the mobility battery used a battery that had threaded holes, rather than JIS post's. He modded the way the cables were hooked up. See post #9 here for all the details. Fitting mobility 12volt AGM battery. | PriusChat

And if you dig even more you find this guy in post #9 telling folks how he went to WalMart and bought a traditional flooded battery and put it in his Prius. 12 volt battery replacement info | PriusChat

Before Yellow Top came out with the latest one that has the JIS posts, folks were ordering the D51 Toyota Prius 12 Volt Auxiliary Battery with install kit for 2004 + including Plug in and using a kit Installation Kit for Optima battery in Prius from Elernaid to make it work. The kit contained cables that would fit the SAE posts that came on the D51 battery. That is great to make the battery work, but from then on you are forced to use that D51. And who is to say that the D51 with those SAE posts is even available today? But the modded Prius is still out there... Elernaid still has it's website up, but I wonder if they still have these batteries, and if they don't what's the guy or gal supposed to do when he or she is down on the side of the road or 500 miles from home? Call AAA? Not everyone can afford that? Where is this info found? Prius Chat of course in the Gen II Section Post #6 Replacement of 12 volt auxiliary battery | PriusChat

Even if all you do is simply change the cables to SAE instead of JIS, you are modding the car. And that is where the problem lies. How is the next owner going to react when they are out in the middle of no where and have to work with rigging done by someone who was simply trying to save a buck.

I do agree that "today" the mod's are no longer necessary. But that is and was not the case a few years back. And the info is still out there that folks are reading today and to make matters worse all those Pri that were modded in the past are still out there too unless they are in the scrap yard which I seriously doubt. Just because you are driving a Gen III does not mean that everyone is. The Gen II's and even Gen I are still out there.

Look at it like this. How would you feel if you bought wheels for a certain size that is supposed to be on your car (OEM) and then found out afterwards someone had modded your car and changed the bolt pattern? Yes, I know that is a extreme example but it drives home my point.

 

That's kinda like using a "high mileage" oil. I'd heard the term, finally read up on it: it works, at least in part, by swelling rubber seals around valve stems, helping them reseal. Only problem, once you've done this, if you subsequently switch back to to regular oil, the seals can contract to even looser than before.

 

Yeah, but aren't you cutting off the OEM clamps, crimping on regular ones? How many times can that be done, is there enough length?

 

No you don't. The terminals are all bolt on. The ground cable is replaced. Everything is bolt on and can be returned to OEM. You just need to keep all the OEM parts. If you bothered to read on how it's done, you would know. Don't just assume once it's modded it's set in stone.

 

Before this goes any further, I am going to say this. How do we know that the Pri that have been modded the individual saved the parts as written above. Furthermore, is the soul who gets stuck with this rigging going to understand what it will take to get back on the road. Not everyone out there reads Prius Chat AND not everyone out there is a DIY person.

Those of us here are blessed by the knowledge that is shared throughout the community. But I have no doubt that there are many Prius drivers out there that don't read Prius Chat and have no clue about what I have been talking about. "Imagined Dilemna"? Hardly, the links I posted shows that there is no imagination involved, just facts.

 

$15?

90982-05060 90982-05060 / POSITIVE TERM
12 VOLT

$20.99

82123-47020 82123-47020 / NEGATIVE CABLE
12 VOLT

$22.63

Link: BATTERY for 2009 Toyota Prius

 

You don't have to get it from the dealer. I got mine from eBay. Besides, Just keep the original parts and leave it by the battery.

 

A cheap flooded lawnmower battery like that would get you home in an emergency, but might not be a great idea long-term. Besides the potential for acid splashing in a crash, and hydrogen generation, I'd worry about the build-up of acidic gunk that some flooded batteries accumulate.

For whatever it's worth, my battery is the same physical size as those flooded lawnmower batteries, but is AGM. It required no cable-cutting or other modification of the car. I did add spacers to secure it, and a small piece of tubing to connect to the OE vent hose. It cost about a third the price of rip-off Prius batteries. How long it will last remains to be seen.

 

My winter mileage is much better this year since I added the bigger group 25 - 12v battery.
Most years I would always be at 47mpg (scan gauge II). This winter I see 50mpg since the change.
My summer is 52 to 53mpg.

Even coming off the highway on the off ramp, coasting down the ICE shuts off.

Can't wait to see if my summer mileage improves.

I say change the Gen 3 12v now at the sign of the first electrical alarm indicator on the dash board.
That got rid of my strange traction control light for no apparent reason and yellow triangle at a different time.

my2cents.