Alternative to the 12v 45ah battery?

Discussion in 'Gen 4 Prius Care, Maintenance and Troubleshooting' started by mark27lim, Jun 25, 2018.

  1. mark27lim

    mark27lim Active Member

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    so..my 2yo toyota(yuasa oem) 12v 45ah battery has worn out. it can’t hold a charge more than 10.5v even though i have tried topping up distilled water and epsom salts and trickle charging it for 2 days. i suspect one of the six cells is shorted.

    In the interim i’ve jury rigged a $20 7.5ah vlra for the past few days and it seems to be working fine (see photo). biggest issue is securing the loose cables now that the full size battery structure is not there to support them (using green comscord).

    I’m also using like 18awg for the connecting wires which seem puny compared to the 200+ amp rated heavy gauge cables. But i suspect they will suffice as long as the hv battery system doesn’t fail in such a way that the 12v is ever needed to crank start the ice? ...and i remember to turn on headlights only when hv system is engaged.

    If things are still okay after a month i may consider keeping it for longer term. The prius replacement battery is really expensive >$200. Otherwise perhaps the smallest capacity automotive lead acid that can fit.
     
  2. William Redoubt

    William Redoubt Senior Member

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    Today's cars measure everything. Putting in the wrong battery may subject you to other failures or fault codes. I'd just pay the $$. BTW, the original battery is guaranteed for 84 months, so you should be able to get a prorated deal.
     
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  3. alanclarkeau

    alanclarkeau Senior Member

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    I would be surprised if that arrangement lasted very long - a battery has to be firmly clamped down, as if it's allowed to rattle could damage the battery.

    It will never have to crank the ICE - there isn't a 12v starter motor. But I'm not sure what the total load would be - lights, computers, wipers, fans, demisters (incl mirror), window winders (particularly using global open/close) - but I suspect could easily exceed the "new" cables.

    The last thing you want it a wet night with lights, wipers and demister on - turn your indicators to go round a corner and not have enough juice to keep your computers running - and it stop mid-corner.

    I'd go get a new battery.
     
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  4. Jarkko

    Jarkko Junior Member

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    Gel battery won't last very long. The car will be charging it with a higher currents than the battery could absorb.

    Lights alone should be doable for the battery. If you end up using other high current accessories without car fully on (turn on without break pedal), the wires and connectors could start heating or melting. I am not sure what loads are on 12V (AC and power steering would be the worst ones if they are on 12V).

    Another risk with tiny battery and thin cables is short circuit. The fuse in Prius is 200A. I think your setup is not able to generate such a current, so short circuit would remain present until something else melts, burns, or (in the very best case) just battery fails.

    My wote also for a bigger battery in the long run :)
     
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  5. jerrymildred

    jerrymildred Senior Member

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    Sorry if this sounds harsh, but you're making some dangerous mistakes and I don't want your situation to get even worse.

    If the battery wasn't fatally damaged before, it is now. Probably no chance for a prorated deal on a warranty replacement after you disregarded the warnings, opened it up and added water. (And epsom salts!!??) But give it a try.

    And with those wires in your picture, I see a fire in your future. Put in the right battery before you have some REALLY expensive repairs.
     
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  6. TMR-JWAP

    TMR-JWAP Senior Member

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    All I can say is wow......
    and...Jerry beat me to it.

    A 2016 with a jerry rigged 12v. (n) Is this even a serious post or is Mark27 screwing with us?

    +1 for innovation I suppose. Sometimes you gotta do what you gotta do, but...

    "If things are still ok after a month I may consider keeping it for longer term........"

    That's like a -5 million.o_O
     
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  7. Lucifer

    Lucifer Senior Member

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    Make the thread into a poll, 100% of responders will agree, get that battery out and put either a yellow top or an oem battery in, saving 200$ will cost thousands.
     
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  8. sam spade 2

    sam spade 2 Senior Member

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    12 V is 12 V. Doesn't matter where it comes from.....in general.

    Maybe he doesn't have the same warranty provisions where he lives.
     
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  9. padroo

    padroo Senior Member

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    How many miles do you have on your Prius?

    This is not an AGM battery in a 2016.
     
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  10. bisco

    bisco cookie crumbler

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    there are no drop in alternatives currently, and u.s. quotes run upwards of $500. not sure about singapore.

    strangely, this new gen 4 12v seems as bad or worse than the past generations, other than it is no longer in the cabin.
     
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  11. sam spade 2

    sam spade 2 Senior Member

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    Really ?? But the replacement CAN be, and probably should be.
    They are superior in every way.
     
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  12. Mendel Leisk

    Mendel Leisk Senior Member

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    Most of the cars I'm involved with have a conventional flooded acid battery in the engine bay, and no problems with them: good lifespan, hold charge, prices around $135 typically. What's not to like?
     
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  13. jerrymildred

    jerrymildred Senior Member

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    I didn't think about the Gen 4 not needing AGM. But what are the epsom salts for?
     
  14. mark27lim

    mark27lim Active Member

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    thanks everyone who posted their advice, concerns, warnings etc. i am grateful for this community of support and also steering us away from the cliff edge (!)

    Shall aim to replace the rig with a proper battery. i was rereading the previous thread on “12v group size” and found out that the stock battery is made by furukawa batt co and is a refillable wet cell (not yuasa as previously mistaken). The listed dimension of 190x170x207 edit:175mm not 170

    http://www.furukawadenchi.co.jp/research/tech/pdf/fbtn72/fbtn72_09.pdf

    finds a few matching compatible models at least on the bosch catalog that also has the correct +/- terminal orientation and BHD (base hold down) configuration:

    https://az.bosch-automotive.com/documents/1763888/1782870/Bosch_Battery_Holistic_Brochure_2016_17_AP_69436.pdf/622ff1fc-67a3-6abd-a505-c90003997a9a

    will update again if i can get a quotation on a fitment compatible bosch vs the stock.
     
    #14 mark27lim, Jun 25, 2018
    Last edited: Jun 25, 2018
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  15. mark27lim

    mark27lim Active Member

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    unfortunately my prius was bought with a 3rd party 3year 100k km warranty and although i’m only at 2year50k km, the fine print does say the aux battery is excluded :( tks for those who suggested though.

    still, 2 years in our climate
    is pretty normal for all our automotive batteries. i was kind of hoping with the prius not cranking at all that this time things could be different. maybe a year or two more than everybody else. but no dice. it’s our 365days of summer heat that’s to blame i bet. but yeah i guess i can’t complain mine already lasted 2 years, fair time for a new one.
     
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  16. mark27lim

    mark27lim Active Member

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    some you tubers say that if distilled water alone didn’t revive the batt, adding epaom salt solution will help desulfate the plates. .. i know i know fake news rite? lol
     
  17. Mendel Leisk

    Mendel Leisk Senior Member

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    Some smart chargers have a "desulphate" cycle as part of their charging regimen. My CTEK Multi US 4.3 for example. I think I've got that name right. Close enough.
     
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  18. sam spade 2

    sam spade 2 Senior Member

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    Well I guess it's all a matter of perspective......and definition.
    Conventional batteries need the electrolyte level checked every few months or so.
    They usually have a life span of maybe 4 years.
    AGMs are sealed and have a typical life span more like 7 years.
    They are a bit more expensive but less hassle and longer life.
     
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  19. jerrymildred

    jerrymildred Senior Member

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    I hadn't heard of that before. Since you had no warranty on your battery anyway, it was worth a shot. ;)

    @Mendel Leisk mentioned smart chargers with a desulfate setting. I've only tried it once and it didn't help. It had been deep discharged and I think it was just too far gone. But I would definitely try it again in the same situation.
     
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  20. padroo

    padroo Senior Member

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    I looked around a while ago an it looks like the AGM battery for a Chevy Spark would fit the Gen 4 Prius.
     
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