Fitting mobility 12volt AGM battery.

Discussion in 'Gen 2 Prius Care, Maintenance and Troubleshooting' started by Britprius, Mar 3, 2013.

  1. R-P

    R-P Active Member

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    Yes, it was aimed at you ;).
    If the battery is NOT empty, the charge current won't be that much and it should work just fine: the 100A that the DC-DC inverter can supply is only used when the battery demands it. Even a 1.2Ah battery will be able to supply the 20A needed for starting the car and the chargingcurrent will drop to probably a few hundred milliamps within half a minute. Problem is that you cannot be sure of that.

    Obviously the constant draw will empty any battery in time, but if you were to run the car every day, the 7Ah would imho work just fine. As long as you don't run your lights or your radio while not in ready mode...

    Assuming 20A and a 2V drop, you might get away with a 0.1 ohm resistor. I considered advising a few diodes, one pointing toward the battery and one away from it, so the voltage at the battery will always be 0.6V lower than the charging voltage (but the voltage coming from the battery during booting up the computers would also loose 0.6V or so). But I think the Prius has a sensingwire that measures AT the battery terminal and adjusts the DC-DC converter output, so that will only work if the sensewire is before the diode into the battery.


    BTW, I haven't touched on GEL vs AGM vs normal lead-acids vs other obscure types.
    Most (older) cars will pretty much put out a constant maximum voltage. As long as your battery is spec'd to withstand that chargingvoltage AND it is far from empty, I don't see much issue in running just about any size battery that is big enough to supply the startingcurrent.
    Just to be clear: I WON'T actually do this nor am I responsible for anyone trying nor am I advocating it, but imho, it would work just fine.
     
    #421 R-P, Jun 26, 2019
    Last edited: Jun 26, 2019
  2. sugar land dave

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    Thanks for the thread Britprius! The info helped me select and install a Duracell DURDC12-55P deep cycle battery today. At slightly over 42 pounds, it is the biggest battery that I could fit while still keeping the tray and hold down bracket.

    I will try to add pictures later, but I did want to say that the previous battery was an optima yellow top 36ah which was throwing random errors up until the day it died. The new battery fixed all that, firmed up the brakes and seems to help with brighter lights. I will try to post pictures when I have some more time.

    Thanks again, John!
     
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  3. sugar land dave

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  4. sugar land dave

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    IMG_20190907_180713.jpg
    Remove 3 bracket bolts to move black diode box out of the way. Note battery hold down bracket is using the longer bolt (supplied with the battery) to replace the short OEM bolt.
     

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    #424 sugar land dave, Sep 7, 2019
    Last edited: Sep 8, 2019
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  5. sugar land dave

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    M6 by 40mm bolt with nut to attach positive. About $1.50 at hardware store.
     
    #425 sugar land dave, Sep 7, 2019
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  6. sugar land dave

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    M6 nut and bolt supplied with battery to attach ground clamp.
     
    #426 sugar land dave, Sep 7, 2019
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  7. sugar land dave

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    IMG_20190907_180727.jpg Location of the 12 volt auxiliary battery. Avoid the silver shield of the traction battery seen in the left of the picture.
     
    #427 sugar land dave, Sep 7, 2019
    Last edited: Sep 8, 2019
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  8. tvpierce

    tvpierce Senior Member

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    Thanks for the info.

    Did the ground clamp not fit the negative post on the battery?
     
  9. sugar land dave

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    No, the posts on this battery are much bigger than the posts on an OEM or Optima battery.

    This is a deep cycle battery for electric wheelchairs, alarm systems, commercial battery backup devices, and other things which can not afford a failure. The manufacturer claims this battery can be 100 percent discharged 150 or more times without failure. It is a 55ah battery which replaced the 36ah Optima battery which was probably too small for my sks Prius.

    It did fix a lot of little glitches my car had developed and now the lights are brighter and the car seems to run better. $175 well spent in my personal opinion.
     
  10. PriusCamper

    PriusCamper Senior Member

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    Once you get the terminal post challenge resolved with the right hardware you'll be very please. You made a wise decision to buy this one instead of the overpriced junk they recommend for Prius at auto parts stores.
     
  11. sugar land dave

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    I used the M6 bolts which came with the battery. The posts have horizontal holes through them. Only had to buy one long 40 mm M6 bolt for the positive connection. Closed up and back in service. Wish I had this battery sooner!
     
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  12. Dxta

    Dxta Senior Member

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    I'm just wondering. Can this sort o battery be used on regular cars too?
     
  13. PriusCamper

    PriusCamper Senior Member

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    Regular car batteries are designed for maximum power / cranking amps to the starter motor... Mobility/computer batteries that are ideal for Prius are not designed for that and would NOT last long in a regular car.
     
  14. R-P

    R-P Active Member

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    I think it is something along the lines of:
    - starterbattery has thin plates that have lots of surface area, hence a lot of chemical reactions can take place simultaneously. This means a lot of electrons can be available all at once (electrons = current)
    -deep-cycle has thicker plates, less prone to warping if discharged to the same level as a starter battery, but less surface area, hence less capable of providing huge startercurrents.

    I would venture to say that for the same formfactor, deepcycles will be heavier and more expensive, purely from a material(cost) point of view.

    Guestimate: electric wheelchair is 10-30 amperes continuous use, startercurrent is hundreds of amperes during starting.
     
  15. anon_prius

    anon_prius New Member

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    Gen 3 owner here. I am planning to go with this solution, look good?

    Mighty Max UB12550 12V 55Ah:
    Mighty Max UB12550 12V 55Ah 21ST CENTURY SCOOTER PLUS SCOOTER WIDE SLA AGM Batte 785123662488 | eBay

    QuickCable SAE to JIS:
    QuickCable SAE to JIS Pencil Post Automotive Battery Terminal Conversion PAIR! | eBay

    I figure that I can just bolt the SAE portion of the adapter through the terminals on the scooter battery and then use the stock JIS terminal clamps onto the JIS portion.

    Does this seem like a good plan?
     
  16. R-P

    R-P Active Member

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    Sounds good. But I am not sure the bolt will tighten enough to clamp the batterypost from both sides with the conversion-posts. I think it will be fine, but make sure: you want as much contact area (and cross-section area) between the battery posts and the cable that is eventually hooked up to it. Even if we are not starting a car with it...

    And obviously, if the conversion-posts somehow cannot clamp it properly from both sides and crack/break while mounting them, just use only the bolt ;)

    Personally I did not use a conversion kit and I have screw-in terminals, Even then, the battery is actually too high to properly fit (just 2 millimeters, no big deal, beware I am Gen2 owner). But your battery-tabs might be protruding even further, so decide in the car what is the best mounting-option.
    I could cut away some plastic, to make thebattery and cover sit flush, but couldn't be bothered.

    My battery:
    [​IMG]
     
    #436 R-P, Sep 12, 2019
    Last edited: Sep 12, 2019
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  17. anon_prius

    anon_prius New Member

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    That's a good point. Maybe I'll buy some washers to go over the bolt and fill the gap between the clamp so I don't need to tighten it down as much. Any idea what size those clamp down bolts typically are?
     
  18. R-P

    R-P Active Member

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    Just measured an old batterypost, of which the bolt is unfortunately fused to the nut by rust, so I could not tighten it...

    I would have suspected it to be M6 (6mm diameter bolt), but it appears to be 5mm (tape measure, didn't have my caliper at hand). The gap that the bolt should tighten is also 5mm and it doesn't appear to be that tightened down. So if the tab is also 4-5mm I think it will work fine.

    You will probably point both terminals toward eachother, so obviously also make sure you are in no danger of any of the potst hitting either the batterybay (= metal) or more likely, the battery-hold-down-clamp (in Gen2 also metal).

    (Actually, only the PLUS battery post is important, but it is good practise to have neither make direct contact. During a holiday, the Hertz rentalcar that I had that didn't have the battery tightened down, so it was jumping around in the engine-bay. And when I demanded they fasten it because a short of the PLUS-terminal to the hood (2cm without it jumoing around) might have fatal consequences, they just looked at me as if they had just smoked a bong... But eventually they did bolt it down... That was the same Hertz that said my car had been rented out (plane had an hour delay) so I could choose between a smaller model (with the battery jumping around) or one without rear seatbelts (I was standing at the counter with wife and three kids). There were so many other things wrong with that holiday that I didn't even get round to asking Hertz' main office to give their view on the above... I assume that in the US, with their claim culture, something like that would have been fixed before I could say 'consumer rights')
     
    #438 R-P, Sep 12, 2019
    Last edited: Sep 12, 2019
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  19. TMR-JWAP

    TMR-JWAP Senior Member

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    It looks like the black plastic tray and the tray cover should still fit normally. Does the battery cover plate still fit normally or is it raised up?

    I'm a bit curious about options. My 12v (stock Toyota SKS battery) was manufactured in 2011. I was messing around a month or so ago and did a "reconditioning" cycle overnight using a regular charger and was concerned I may have damaged it. After I realized my mistake, I tested the battery and it tested at 325 cca, which was lower than it had ever tested.

    I acquired another Gen 2 Tuesday night (more on that later) and decided to test the battery. It had been sitting for a few weeks and showed 12.05 volts and 125 cca. Tester showed it needed to be charged. No joke... This was a day after I drove it about 20 miles to get it home. I decided to test my 2007 battery again and it's testing at 425 cca again. Apparently I didn't damage it. If the battery in the newly acquired 2005 doesn't take a charge, then I'll probably buy a new one for my car and move mine to the new 2005. Looking at options for a new battery, but want my trunk panels to still fit normally.
     
  20. Anti

    Anti New Member

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    I'm looking at putting in a Costco battery that is 500CCA and also is a 51R 850251 If I can hook up the terminals. Is there something that I am missing and why I shouldn't do this?
     
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