Replace OEM 12V battery with Group 25 AGM

Discussion in 'Gen 3 Prius Accessories and Modifications' started by cproaudio, Jul 9, 2015.

  1. sam spade 2

    sam spade 2 Senior Member

    Joined:
    Mar 31, 2018
    5,936
    2,357
    0
    Location:
    USA
    Vehicle:
    2017 Prius c
    Model:
    Four
    That's because it is actually SEALED up to some preset "pop off" pressure which should never be reached in normal use.
    The vent tube is overkill.

    THEN.....the electronics that Harbor Freight sells is cheap Chinese JUNK.
    I would never buy any of it, except for the little red multi-meter for $7 that seems to work quite good.
    That includes batteries.
    Especially one of lower capacity than the original.

    Overall a VERY bad plan, in my opinion.
     
    C Wagner likes this.
  2. C Wagner

    C Wagner Member

    Joined:
    Dec 19, 2020
    154
    41
    0
    Location:
    Boston
    Vehicle:
    2004 Prius
    Model:
    N/A
    Actually, the little red HF multimeter isn't that good - I only found this out when doing the hybrid HV battery rebuild and balance. It's off vs a couple of more expensive meters I checked it with by xx tenths of a volt. It didn't matter once I knew that, but it was important to know for the max discharge and charge voltage points. As it happened the module charger itself was off too!
     
  3. sam spade 2

    sam spade 2 Senior Member

    Joined:
    Mar 31, 2018
    5,936
    2,357
    0
    Location:
    USA
    Vehicle:
    2017 Prius c
    Model:
    Four
    I'm sure that their "quality control" isn't that good overall but...........
    I'm on about my tenth one now and haven't found that problem with any of them.
    I presently have: one at home. One in each car. One in my Spyder. One in my fishing cabin and one on the boat.
    But I seldom use it for anything except checking the "automotive" batteries and flashlight cells.

    At $7 each, the 6 I presently have cost me about $42. Less than one "good" meter.......and I don't have the problem of needing a meter at one place and having it BE at another.
     
    C Wagner likes this.
  4. C Wagner

    C Wagner Member

    Joined:
    Dec 19, 2020
    154
    41
    0
    Location:
    Boston
    Vehicle:
    2004 Prius
    Model:
    N/A
    I think all of those HF meters were free when I got them, with coupon. Alas, now they are charging for them...
     
  5. Grit

    Grit Senior Member

    Joined:
    Aug 22, 2017
    5,302
    3,740
    1
    Location:
    Wilkes Land
    Vehicle:
    2012 Prius
    Model:
    Four
    id love to see that under many cycles with engine always off does to the life span of the 12v bat.
     
    C Wagner likes this.
  6. black_jmyntrn

    black_jmyntrn Member

    Joined:
    Oct 23, 2020
    217
    94
    1
    Location:
    Los Angeles, CA
    Vehicle:
    2013 Prius Plug-in
    Model:
    Plug-in Advanced
    C Wagner likes this.
  7. C Wagner

    C Wagner Member

    Joined:
    Dec 19, 2020
    154
    41
    0
    Location:
    Boston
    Vehicle:
    2004 Prius
    Model:
    N/A
    Yes, it will be interesting to see. I note that the OEM battery for non-SKS is 35AH also, so this kludge is not so much an under powered kludge as a size/post one. I ordered U1-SAE adapters from ebay and a special JIS to SAE adapter for the car-side connector (why did Toyota use JIS on US priuses and SAE on Japanese priuses, as I've been told???) The major impediment to my new battery from Harbor Freight is that they are holding back the 20% coupons these days, it's cold outside in Boston and the old OEM 2012 battery is holding at about 11.8 in these March temps!
     
  8. Joele3

    Joele3 Active Member

    Joined:
    Jan 1, 2010
    108
    181
    0
    Location:
    Bay Area
    Vehicle:
    2010 Prius
    Model:
    III
    Fits like a glove. Going on 7 years on OEM battery. I'm running two amplifiers, wanted to throw in a larger battery. Thanks for the info on this thread. I ordered the adapters on ebay. I noticed sometimes my car wouldn't shut off. ICE would always stay idling until I would turn off the car. I read on another thread replacing the battery fixed it. So far I haven't noticed it doing the same thing. Up next is new struts or coils. So hard to find parts in stock for the V.
     

    Attached Files:

    C Wagner likes this.
  9. black_jmyntrn

    black_jmyntrn Member

    Joined:
    Oct 23, 2020
    217
    94
    1
    Location:
    Los Angeles, CA
    Vehicle:
    2013 Prius Plug-in
    Model:
    Plug-in Advanced
    I'm working with a few vendors, they have springs for the V, not lowering but heavy duty ones that can provide lift if you want.
     
  10. C Wagner

    C Wagner Member

    Joined:
    Dec 19, 2020
    154
    41
    0
    Location:
    Boston
    Vehicle:
    2004 Prius
    Model:
    N/A
    I wanted to update those lurking and the future thread readers, that I did go buy a 35AH AGM battery and have installed it - and after a couple of days and some cornering, it's still great.

    I'd read here that a 35AH AGM SLA (unvented though) would be fine. I noted that the non-SKS cars used a battery of about the same size. I resolved to turn off SKS if I go away on long vacations. I also noted that some have said the official 45AH OEM battery costs about $250 (you install) at my dealer and the 35AH battery was sometimes available at about 1/4 that price, so even if the battery lasted not so long, due to SKS drain it a few too many times, it would probably be worth trying.

    I waited desperately for a Harbor Freight coupon and planned to buy a battery that used to be a better price but is now $75. No 20% - after waiting a long time, ... I bought a Mighty Max from Ebay for about $60 delivered. It seems good.

    A conversion was needed. I had to seek out a priuschat aficionado who sold me a small part that changes the car's terminal clamps from JIS to SAE (US standard). $20 I also needed tab to post adapters. Those were $10 on Ebay for U1 to SAE. Don't overtighten, or your tabs will rotate! Anyway, after those modifications, the new little battery went in to the place where the big battery was before. It was shimmed so it doesn't slosh around and will stay clamped down.

    The immediate thing I noticed, vs an 8 year old OEM battery that couldn't really hold a charge, is that it seemed MPG is 2-3 higher. My test wasn't scientific, but might be even better as I had been driving mostly without A/C or heat and without headlights during day. On the day I drove the car 200 miles, mostly highway, on a stretch I'd driven a few weeks ago with the old battery, I used the A/C, heat and headlights most of the time -- and got the 2-3 mpg higher.

    I may work on figuring out where to drill a hole in the Mighty Max battery to attach the car's vent pipe, but I'll probably do this after the MM battery warranty is over...
     
    tangerino likes this.
  11. bzbee

    bzbee Junior Member

    Joined:
    Apr 30, 2016
    25
    10
    0
    Location:
    Texas
    Vehicle:
    2011 Prius
    Model:
    Two
    Bought a 2011 Prius a couple of weeks back. Battery was showing 12.4V resting voltage at the charge points under the hood. So decided to pull out the battery and see how old it is.

    The battery is branded "Precision Parts" - seems to be store brand of AutoNation, https://www.autonation.com/promos/batteries
    It is a Group 51 lead acid (wet) battery with the SAE battery posts filed/chopped all around to make it fit the smaller JIS connectors on the Prius (wish I took some pics before I put it back in). The stamp on the battery is 9EJ231323, the '9E' I think means 2019-May as the manufacture date. With overnight charging with a trickle charger (like Battery Tender), it came to 13.2V so I think it is decent shape, but I am uncomfortable with how it is installed.

    I've am considering upgrading to a Group 25 AGM battery for the additional capacity, but there seems to be only one option available to me locally: the Champion AGM battery (Part # 25-550CHAGM) for $187 + taxes at Pepboys.

    Everyone seems to be carrying only the flooded lead acid batteries or the Optima AGM which I don't want. Unfortunately no Rural King here in Texas. So, are there any online options for purchasing a Group 25 AGM battery at a decent price, the ones I found on Amazon or all over $200.

    Or maybe I should consider one of those Deep Cycle AGM batteries for mobility scooters. Saw a forum thread on that too.
     
  12. NewHybridOwner

    NewHybridOwner Active Member

    Joined:
    Nov 21, 2018
    531
    245
    0
    Location:
    W. Michigan
    Vehicle:
    2015 Prius
    Model:
    Four
    My battery chargers all have separate settings for Deep Cycle batteries: different charge requirements.
     
  13. Markee

    Markee Member

    Joined:
    Apr 6, 2014
    295
    37
    12
    Location:
    South Florida Broward County
    Vehicle:
    2013 Prius
    Model:
    Four
    I just replaced mine I used a Genuine Toyota TrueStart replacement battery Part number 0054421171325
    You can find them online for around $200
     
Loading...