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Fitting mobility 12volt AGM battery.

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

  1. magnumrtawd

    magnumrtawd Member

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    Why did you change the mount? I thought the dimensions were the same.
     
  2. Britprius

    Britprius Senior Member

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    Some vehicles in the US are fitted with a smaller battery "usually non SKS models" and consequently a smaller battery tray. Fitting any of the alternative batteries including Optima, Exide, or even the larger Prius OEM battery requires the larger tray, or the old tray cutting to take the longer battery.

    John (Britprius)
     
  3. R-P

    R-P Active Member

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    Any pics of this? I don't remember having a tray.

    I've made a list of batteries that might fit, based on your battery-maximum size numbers. I am still contemplating calling the dealer if they will let me at it with several of their batteris to testfit.
    According to the numbers, I might even know of a 90Ah battery that fits...:ROFLMAO:

    [​IMG]

    Explanation: all measurements in mm and red values mean they are too large. The upper table is inchvalues I got from Britprius converted to cm and mm.
    B means Width, D means Depth, H means Height.

    I DID NOT LOOK AT THE TERMINALS, so this 90Ah battery has screwposts and many may be the wrong way round.
    Prices were written down quite some time ago, so probably not accurate anymore.
     
  4. magnumrtawd

    magnumrtawd Member

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    Is a Toyota batt less, desirable just because of price?
    I can purchase in my area
    the toyota batt. for 170us.
    2 direct replacements from aftermarket parts for 168 & 175 $
    or a Ub 12550 12v 55ah with out a vent for 127$

    Which is a better Battery? The price is not that important.

    I probably will trade this car in the next year. It has 93-K but in great shape. Just would like the the gen 3 upgrades.
     
  5. Patrick Wong

    Patrick Wong DIY Enthusiast

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    I would buy that, then.
     
  6. magnumrtawd

    magnumrtawd Member

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    Is there a date code on the factory battery?
     
  7. Patrick Wong

    Patrick Wong DIY Enthusiast

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    Yes, you need to remove the battery bracket, then you can see the date code in DDMMYY format.
     
  8. 2007blueprius

    2007blueprius Member

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    I brought this up before but left it alone afterwards as my battery was still holding up, we recently parked the car for a while and it's dead, so back on task, the mobility was my first choice last I looked into this, but I do have a handfull of lithiums on my hands, and I am no stranger to tinkering with them, question is, what do we know on the stock charging system, lead acid batteries are rated at 12v but we all know they get charged a bit higher, I have 3.2v lifepo's, 3.6v and 3.7v lipo (laptop 18650's), I'd like to try and make one, question is how would I go about it, a 3.7v lipo gets charged to 4.2v, 3 of those is 12.6v fully charged, 11.1v discharged, is that close to factory lead acid specs? the 3.6s get charged to 4.1v, and the lifepo 3.2 to 3.6, four of those empty vould be 12.8v, full 14.4v, so who knows anything about the prius charging the oem battery and which of those would work better, I'd be curious to give it a go
     
  9. Patrick Wong

    Patrick Wong DIY Enthusiast

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    The Prius DC/DC converter maintains 12V bus voltage at around 13.8V when the car is READY. You'll have to figure out what battery configuration will work best with that charging voltage.

    Further, your new battery should be able to produce approximately 40Ah to be consistent with the original equipment battery specs.
     
  10. Britprius

    Britprius Senior Member

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    I agree with Patrick The Prius does maintain a charged lead acid battery at around 13.8 volts, but a discharged battery can be charged at a voltage as high as 14.6 volts, and may be even higher.

    John (Britprius)
     
  11. 2007blueprius

    2007blueprius Member

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    ok so a lifepo is empty at 3.2 full at 3.6 that gives me for a 4s pack 12.8 empty, 14.4 full, they can withstand charging voltages up to 3.8v 15.2 max if need be, I have some 20 ah pouches from a plug in kit, they are a bit damaged from abuse, no good for traction but as a float I recon they may do for a while, worth a shot since it apears I need a battery, 4s2p that would give me a 13.8v (3.45v/cell) 40 ah, well whatever is left of them, I actually have 8cells that are pretty bad for ev use, I've tinkered with them quite a bit and they all act very similar to another, granted those need some sort of bms, thou there's not much left to destroy, came across these http://www.hobbyking.com/hobbyking/store/__10328__hobby_king_battery_medic_system_6s.html a while back, they are just balancers, they try and keep the cells even, I think they will do for an experiment
    I have 8 more cells half of the way and another 3kwh which are actually pretty decent, I think it is worth a shot, what do you all recon? I am asking because some of you tinkered with this quite a bit and took several measurements, do you think such a setup at least in theory might do? I'll be the guinea pig and give it a go, I need a battery anyhow, I have most of this stuff laying arround, 40AH sounds like a lot, in reality not sure all is needed but with all the systems like steering heat fans pumps, not sure if they are all 12v, maybe that is why the prius uses a deep cycle type it really does not need much to power up, and even than, the 12v feeds off the traction pack right? I have had a weak battery for at least 6 months now since I first had to jump it and it did fine till we parked it for a couple weeks,
    any thoughts or concerns much apreciated, ask twice and maybe you woint blow up, that should be my new motto
     
  12. Britprius

    Britprius Senior Member

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    Once the Pius is made ready all the systems run from the DC to DC converter not the 12 volt battery. It can actually be removed.
    The reason for the 40 AH is the continuous discharge of the Prius entry and alarm systems. These can take there toll on the battery if the car is left standing for a few weeks.
    Remember a deep discharge on a lead acid battery is only to 50% of it's capacity. Even 25 Mah works out at 16.8 AH over 4 weeks.
    John (Britprius)
     
  13. 2007blueprius

    2007blueprius Member

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    got it that explains why my car is dead, I pareked it for the winter, it's been a couple weeks I think my battery fiest acted up last year when I first came across this thread, so in theory if used regularily even a 10 ah would do fine, parking for a while is the issue, as for lithium versus lead acid, 80% of 40ah is about the same as 50% off 55ah I believe that was the stock, I have the ses key thingy, granted those cells I plan on tinkering with are funky, I have some good ones that I can use later, figured I'll try those since I have no other use for them otherwise.
    that beeing said, one of those battery tenders thingy would not be a bad ideea if you are going to park the prius, or even a quick disconect/ messes up the settings but oh well.
    now I believe those 20 ah pouches run about $40 each, 8 of them is $320, with some other materials and that balancer, something like this would run $400, not so cost effective, but I got the cells allready, funky and used I just dont have to spend the$, on the other hand if this works and they were built out of say brand new A123 ( I believe those are the better ones) one would never need a battery ever again, if it Iddles for the most part cycles are unlimited, few deep discharges here and there, further more with those lithiums, a decent bms would cut the discharge below a certain threshold, you loose your radio settings but don't need a battery.
    so that beeing said, looks like the voltages/specs match, I should build one for the sake of it see how it goes, do I have your go ahead? granted there's no guarantees but if you believe it should work given the tinkering you done so far that is good enough for me.
     
  14. Britprius

    Britprius Senior Member

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    You would need to monitor charge current and voltage for a while to make sure you are not overcharging the cells. There are Lithium batteries on the market to replace those in vehicles, but they are very expensive, and I do not know what systems if any they have built in for charge regulation. Also beware of the obvious dangers of reverse polarity, and all that comes with it connecting to the Prius.

    John (Britprius)
     
  15. 2007blueprius

    2007blueprius Member

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    I have a pretty good ideea of what to do, with lithium you need over(dis)chargeprotection, 13.8v, works to be about 3.45v/lifepo cell it's perfectdead smack in the middle usually the resting voltageafter a full charge, by the sounds of it it will operate verry simmilarily to the traction battrery between 40% and 80% and it does not have a bms, the problem will rise when parked for a significant time, just like the oem (which does not have any protection) it will clifdive
    there are ways to go about it but I recon maybe instead I should look for one of those cheap solar pannels to trickle charge it, that would not be a bad ideea regardless, I believe some of the ne models have it as an option, the balancers I mentioned are just to keep all individual 4 blocks at the same voltage, they will overcharge together (unlikely they should be ok to 3.8/ 15.2v total the prius wont push that, discharge, maybe if parked, they will go low and implode just like the stock one but that is no different, nor anybody bothered to protect the lead acid one, with a relay and voltage sensing it can be done and disconected before that threshold, but it may not be such a bad ideea to spend the effort toward a small sollar trickle charger, bit of unchrted teritory there.
    so I just pulled the oem out, I believe I have the tall one, forgot how to go about it, no AH on the label s46b24r, what is thet 46 AH? I remember the small one was 35AH large one I thought it was more, about to mess with it can you tell me more about what I have here?
     
  16. 2007blueprius

    2007blueprius Member

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    I read through some other threads, what is all this about 100amps, that is a concern, these cells of mine are good for 1/2 c continuous, that is 20 amps, short bursts of 1c, maybe 2 c, that would be 80a, but what in the heck for? ohms law still aplies, if the voltage difference between the battery and converter is say 1/2 v no way either will push 100 amps, any truth to that?
     
  17. Britprius

    Britprius Senior Member

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    I believe that is the larger battery rated at "and there seems to be conflicting evidence here" either 40 or 45 AH. Both the smaller (35 AH) and larger batteries are the same height. The smaller capacity battery is shorter in length and uses a smaller battery tray. S46B24R is the battery type designation, and the numbers/letters are a code not relating directly to the battery capacity.
    Added to the discharge of the Prius systems you must also add the self discharge of the battery it's self, and although not large "typically around 3% per month for an AGM battery" it is significant.

    John (Britprius)
     
  18. 2007blueprius

    2007blueprius Member

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    so realisticaly the stock is safely good for 20 some AH safely, those 20 ah lithium are good for 20 ah safely, a 40 ah pack would be plenty ( if they were in good condition ) what about those large amp #'s I read about, sounds like bogus to me
     
  19. Britprius

    Britprius Senior Member

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    The internal resistance of the battery comes into play here. The voltage difference between the battery and the charger goes directly across this resistance. In the case of the Prius HV battery this is typically 0.024 ohms for a module pair "12 cells in series" or 0.002 ohms per cell. Ohms law gives the current at 0.5 volt:- .5 divided by .002 = 250 amps.

    John (Britprius)
     
  20. 2007blueprius

    2007blueprius Member

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    ok so what does that have to do with the 12v battery, it's not like it will ever see 100-150 amp loads or charge currents, the stock would not hold up to that either