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121R oversized battery replacement for Prius Prime 140R battery

Discussion in 'Prime Care, Maintenance and Troubleshooting' started by Gokhan, Mar 25, 2022.

  1. Gokhan

    Gokhan Senior Member

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    One of the ailments of Prius Prime is that the 12-V battery (so-called auxiliary battery) has a small reserve capacity and it tends to drain because the owner keeps the traction-battery charger plugged, only does short trips, etc.

    This the OEM battery:

    BCI: 140R
    DIN: H4
    EN: LN1
    CCA: 445 A
    reserve capacity: 76 minutes

    L x W x H:

    8.125'' x 6.9375'' x 7.5''
    207 mm x 175 mm x 190 mm
    positive post on the right

    https://www.oreillyauto.com/detail/c/super-start/super-start-premium-battery-group-size-140r-h4-/ssb140rprm/ssbi/140rprm

    This is the oversized replacement battery:

    BCI: 121R
    DIN: N/A
    EN: N/A
    CCA: 600 A
    reserve capacity: 100 minutes

    L x W x H:

    8.25'' x 7'' x 8.5''
    208 mm x 177 mm x 215 mm
    positive post on the right

    https://www.oreillyauto.com/detail/c/super-start/super-start-premium-battery-group-size-121r-/ssb121rprmj/ssbo/121rprmj

    So, the oversized battery has the same length and width but it's an-inch-taller. It has 32% higher reserve capacity and 35% higher CCA. The question is, does the hood have enough vertical clearance too accommodate its an-inch-taller height?

    Moreover, the Australian Super Start batteries are top-rated on Consumer Reports.

    Battery reference:

    Battery group sizes and cross reference chart with pictures | BCI, EN, DIN codes

    BCI Group 140R battery dimensions, equivalents, compatible alternatives
     
    #1 Gokhan, Mar 25, 2022
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  2. Salamander_King

    Salamander_King Senior Member

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    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.
     
    #2 Salamander_King, Mar 25, 2022
    Last edited: Mar 25, 2022
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  3. Salamander_King

    Salamander_King Senior Member

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    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.
     
    #3 Salamander_King, Mar 25, 2022
    Last edited: Mar 25, 2022
  4. Salamander_King

    Salamander_King Senior Member

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

    upload_2022-3-25_20-31-36.png

    And here is the battery of PP (2020 PP LE)
    upload_2022-3-25_20-33-43.png

    Oh, I see, the photo is taken from the side of the car... I see, they are the same.
     
    #4 Salamander_King, Mar 25, 2022
    Last edited: Mar 25, 2022
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  5. jerrymildred

    jerrymildred Senior Member

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    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.
     
    #5 jerrymildred, Mar 25, 2022
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  6. Gokhan

    Gokhan Senior Member

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    So, is there an extra-inch vertical clearance for the 121R battery?

    By the way, the minimum C/20 (2-hour) capacity required by Toyota is 45 Ah, which seems to correspond to an 81-minute reserve capacity according to the ACDelco data. Therefore, aftermarket 140R batteries, which have about a 76-minute reserve capacity, are falling short of the Toyota minimum spec. LN1 batteries, albeit being identical in size to 140R batteries, have a higher C/20 Ah rating and reserve capacity—50 Ah and 90 minutes.

    https://www.dstgateway.com/ACDelcoDocuments/BatterySpecifications.pdf
     
    #6 Gokhan, Mar 26, 2022
    Last edited: Mar 26, 2022
  7. Salamander_King

    Salamander_King Senior Member

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    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?
     
    #7 Salamander_King, Mar 30, 2022
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  8. Gokhan

    Gokhan Senior Member

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    Reserve capacity in hours @ a 25-A discharge current is proportional to the 20-hr (C/20 discharge) Ah capacity rating, the latter of which is for a much slower discharge, typically by more than a factor of ten or so slower. A 20-hr 45 Ah battery should have a reserve capacity @ 25 A of 81 minutes (45 × 1.8). It is 90 minutes @ 25 A for a 50-Ah-@-20-hr capacity rating (50 × 1.8), albeit the proportionality factor of 1.8 is not set in stone, as the capacity not only depends on the discharge rate (a higher discharge rate results in a smaller capacity) but also on the quality, construction, and type of the battery.

    A 295-A CCA is pretty small—I'm not sure if it might be because it is measured at a lower temperature or using a different procedure.

    By the way, 140R is not really the OEM battery. OEM battery is LN1, which has a higher reserve capacity/Ah rating.

    https://www.dstgateway.com/ACDelcoDocuments/BatterySpecifications.pdf
     
    #8 Gokhan, Mar 30, 2022
    Last edited: Mar 30, 2022
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  9. ducatiduke

    ducatiduke Junior Member

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    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?
     
    #9 ducatiduke, Dec 21, 2022
  10. Salamander_King

    Salamander_King Senior Member

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    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.
     
    #10 Salamander_King, Dec 21, 2022
    Last edited: Dec 21, 2022
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  11. Elektroingenieur

    Elektroingenieur Senior Member

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    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.
     
    #11 Elektroingenieur, Dec 21, 2022
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  12. BiomedO1

    BiomedO1 Senior Member

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    @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...
     
    #12 BiomedO1, Dec 23, 2022
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  13. Gokhan

    Gokhan Senior Member

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    It is probably not a good idea try to mess with oversized batteries.

    There shouldn't be much physical difference between BCI 140R, DIN H4, and EN LN1.

    However, note that Toyota also specs reserve capacity and CCA in addition to size; so, get one with the minimum specs. However, reserve capacity is stated in two different ways and the CCA is stated in two or three different ways, complicating things.

    Toyota TrueStart battery, unlike the OEM is battery, is H4.

    I don't have a good answer on flooded vs. AGM, but the quality of both seem to greatly vary and overlap.

    I have never had any issue with the Prius Prime battery. I left it undriven for more than a month at times. The people who have issues are doing something wrong.
     
    #13 Gokhan, Dec 23, 2022
  14. ducatiduke

    ducatiduke Junior Member

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    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.
     
    #14 ducatiduke, Dec 23, 2022
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  15. ducatiduke

    ducatiduke Junior Member

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    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.
     
    #15 ducatiduke, Dec 28, 2022
  16. Salamander_King

    Salamander_King Senior Member

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    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.
     
    #16 Salamander_King, Dec 28, 2022
  17. ducatiduke

    ducatiduke Junior Member

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    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%?
     
    #17 ducatiduke, Dec 28, 2022
  18. Salamander_King

    Salamander_King Senior Member

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    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.
    upload_2022-12-28_11-37-55.png

    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
     
    #18 Salamander_King, Dec 28, 2022
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  19. jerrymildred

    jerrymildred Senior Member

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    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.
     
    #19 jerrymildred, Dec 29, 2022
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