121R oversized battery replacement for Prius Prime 140R battery

I've read in the Gen4 thread that someone used a 26R size group battery successfully as a replacement. AFAIK, the engine compartment layout of Gen4 is the same as PP, so it should also work in a PP.

It has (L x W x H) 8 3/16 x 6 13/17 x 7 3/4 inches (8.1875 x 6.8125 x 7.75 inches, 208 x 173 x 197 mm). which is closer to the OEM LN1/H4/140R size.

 

Here is the link to a comment on using 26R on Gen4 unmodified.
12V battery group size | Page 8 | PriusChat

EDIT: After looking at the photo on the Gen4 with this 26R battery... I have a feeling it looks different layout than the PP engine compartment? Can someone confirm if the Gen4 engine compartment, especially the location of the 12v battery is different from that of PP?

EDIT2: I think they are the same layout. The pics below are taken from the left side for Gen4 and at an angle from the left front corner for PP.

 

This is the photo from the link above by @Mike Mc. He says it is the 2016 Gen4 Prius fitted with a 26R battery.



And here is the battery of PP (2020 PP LE)


Oh, I see, the photo is taken from the side of the car... I see, they are the same.

 

Yes, they are the same. We have a 2017 Prius and a 2017 Prime. I've measured voltages on the Prime many times and have replaced the 12V on the Prius. Same everything. Takes about 10 minutes to replace, BTW, even after cleaning the sand out of the battery tray.

 

Just test is by placing something about an inch high on top of the battery and see if the hood closes.

I don't know how the Ah, Reserve capacity and CCA are related, but the OEM GSYUASA 12v battery that came with my PP says 20HR, 45Ah, CCA: 295 A. It has a much smaller number for CCA than most aftermarket batteries of the same size. It does not have a reserve capacity number on the battery, but if it is proportional to CCA (which may not be), then it may be smaller than the 76 min you stated?

 

Is it me or do they not make an AGM battery for a 2017 Prius Prime? I can't find one for either the 121R or the 140R... Anyone figure this out?

 

The OEM battery that came with PP is not AGM. It is located under the hood not in the cabin space. Toyota used a regular flooded lead-acid battery. There is an AC Delco AGM battery that comes in a LN1 size group, but I have not read anyone actually replacing the OEM battery with it.

 

See my previous posting.

No, both designations refer to the 207 × 175 × 190 mm case size and arrangement only. 140R is a BCI Group Size, and LN 1 is defined in the EN 50342-2 standard; neither designation implies anything about capacity. Anyway, if the original battery follows any standard other than Toyota’s own specifications, it would be SBA S 0102, published in Japan.

 

@Gokhan; stop by dollartree and pick-up some Playdough. roll it out to 2-inch height and place it on the highest point of the battery/mounting post. Slam the hood and measure the crush depth - now you have your answer..

Please post results...

 

I hear you... I just hate dealing with batteries and AGM batteries for me have lasted a long time. The last one I replaced lasted over 11 years.

 

One thing that I have been trying to figure out is when the 12 V accessory battery is charged. I will assume it does when the ICE kicks on with the alternator, but for 90%+ of the time for me, I only use traction battery. Does it get charged (a little) while driving in EV mode? Lastly, for the life of me, I do not understand why during the traction battery charging does the 12 V accessory battery not get low level charge if it is needed? With all of the technology that is has, I think they missed the boat on this one.

 

If you are driving PRIUS either PP or a regular Prius, then there is no alternator in your car. The 12v battery gets charged when the car is in READY state and from the traction battery. No need for the engine to be on. But for a regular Prius, it is likely the engine will start fairly frequently. For PP, the 12v battery does get charged while the traction battery is being charged. It is just not charged fully.

 

Ok... I am driving it on a regular basis and it is a 2017 PP. When and what is the READY state? Also, when you state "not charged fully", does it stop charging at say 70%?

 

Press the brake and push the START button. If you can drive the car, then the car is in the READY state. Meaning the hybrid system is functioning normally. You do not have to have the engine on.


Read my opening comment on this thread, you get an idea of what happens while the traction battery is being charged. How far the 12v battery gets charged while plugged in will depends on how deeply the 12v battery was discharged before plugging in and how long the traction battery was charged and other unknown issues, such as how cold/hot, what other components of the car needed to operate, etc.

Hopefully, ultimate 12v battery charging system discussion on PP

 

Don't overthink it @ducatiduke. If you are driving the car, or if it's ready to drive (READY mode), it's maintaining the 12V battery just like any other car. Otherwise, Prime owners would have dead 12V batteries all the time. Some of these guys go for weeks or months without the ICE turning on.

 

I replaced mine with an AC Delco AGM Group 47.
Group 47 is longer than stock: 246mm vs 207mm
but is identical to stock in the other 2 directions,
and has the correct terminal type/size/location.

I cut the front and rear of the plastic tray off, and I also cut the (unused) mounting flanges off the battery on those ends.
Obviously, be very careful when cutting the tray, due to wiring underneath it.
Obviously be very careful cutting the battery flanges off flush, because destroying a new battery would make it a bad day.

It goes in fine, with the right rear corner (viewed from in front of the car) butting up to the curved sheet metal of the wheel well.
The front of the battery comes very close (maybe 3mm) to a sheet metal assembly in front of the battery.
I was tempted to slot and bend that to give a little extra room, or at least have the battery near a flat sheet metal surface rather than the bare edge of sheet metal. But I didn't.
I was also tempted to dimple the wheel well to move the back corner rearward to leave more room in front, but I didn't.
I am considering placing a smalll place of steel plate between the battery and the edge-on sheet metal, but have not yet done so.

Basically, it fits, it is held very firmly in place, and if you're in a frontal crash, your battery is not coming out of it in one piece,whether the clearance in front of it is 4mm or 50mm. Having an AGM is already a safety improvement for that reason, to not be spraying loose liquid battery acid under the hood and out the front of the car.

The battery I got used to be called ACDelco AGM 47PG (Professional Gold)
Then it changed to being ACDelco AGM 47G115
(the 115 being its 115 minute reserve capacity, compared to 90min for my OEM Toyota/Yuasa)

I bought it from Summitt Racing online for I think $153 delivered.
No core charge, you get the battery for that price, no need to return a battery.
Go ahead and sell the battery for scrap, or turn it in to O'Reillys for store credit, whatever.
There are two versions of it. One is usually in stock at Summitt, one is special order.
Very slightly different spec, I forget the difference.

Is it worth the hassle of doing Group 47AGM, versus just any 140R?
Probably not, for most people.
But for me, yes.
I was willing to play brain surgeon for 5 minutes with a cordless oscillating tool to have more reserve capacity.
Note that I do car camping for a month at a time, and then carry a LiFePO4 battery and a power station also,
so I am not dipping into the car battery as a house battery, but the extra reserve capacity helps if I have a door/hatch open with the car off, etc. I do also carry multiple ways of charging batteries or jumping the car.