What's the cheapest way to replace/rebuild my hybrid battery?

Discussion in 'Gen 2 Prius Main Forum' started by Prius92, Jul 6, 2022.

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  1. Prius92

    Prius92 Active Member

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    So I'm pretty sure my HV battery is on it's last leg..here is some events that have been occurring.

    1. I rarely get a "green battery" anymore.

    2. It takes almost 15 seconds to go from 0-60.

    3. Sometimes when I floor it to pass someone around 60mph..the engine revs like it should, but I barely gain any speed, yes this is on flat ground..it's almost like I'm flooring it in neutral.

    4. Sometimes the battery indicator goes into the purple on the highway. The A/C is on, but I've never seen it go into purple on the highway before.

    5. Dr. Prius shows the HV battery going down to 185v when I give it gas at 55.

    6. Flooring it from a dead stop after making the battery green (holding it in drive)...it doesn't seem to accelerate as quickly anymore.

    With that said..what's the most inexpensive way to rebuild or fix it? I've spotted some 09's with less than 80k at $800 for the hybrid battery, or is age more against me than just miles?

    I'm very handy and have all kinds of multi meters..can one swap a few cells out, or does normally the entire back need to get replaced?

    Thanks
     
    #1 Prius92, Jul 6, 2022
  2. Prius92

    Prius92 Active Member

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    So online it's saying Gen 3 battery cells are interchangeable with Gen 2 (just the cells, not the entire pack).

    I found a wrecked 2014 with 80k...hybrid battery is only $500. Would I be better off swapping the cells out of it?
     
    #2 Prius92, Jul 6, 2022
  3. alftoy

    alftoy Senior Member

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    Yes, nice score for $500
     
    #3 alftoy, Jul 6, 2022
  4. TMR-JWAP

    TMR-JWAP Senior Member

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    If your battery is not coding out, you could very easily have a problem somewhere else. Maybe something going on with the engine not making enough power...
     
    #4 TMR-JWAP, Jul 7, 2022
  5. Prius92

    Prius92 Active Member

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    Engine is making plenty of power. If I remember correctly, the engine isn't really "connected" to the drivetrain, but the HV battery makes the drivetrain go, so if it's weakened, I'd imagine it would be like any low battery and not help the gas engine move as quickly.

    I also tested it with the Dr Prius App and it said the capacity/lifetime was "at replacement levels".

    I got it out tonight in 30 minutes, working on getting the bus bars off and checking the cell voltages.
     
    #5 Prius92, Jul 7, 2022
  6. prius16

    prius16 Active Member

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    Fwiw,

    Code:
    https://www.youtube.com/watch?v=ZmHpSyTsfm0

2004 - 2009 Prius P112 Hybrid Transaxle (eCVT) Operation
Oct 30, 2010 Weber State University (WSU) - Automotive Technology Department - Transmission Lab. Toyota Prius Electronic Continuously Variable Transaxle (eCVT) model P112.
WeberAuto
Approx 15mins.
     
    #6 prius16, Jul 7, 2022
    Last edited: Jul 7, 2022
  7. Prius92

    Prius92 Active Member

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    All cells measured between 7.70-7.75 volts, not a single cell was off.
    The bus bars are pretty dirty, as seen here:


    What else could cause the HV battery to discharge so quickly on the highway, could the AC compressor be at fault?

    Should I do a load and capacitance test of the cells, while they are out?

    Could the dirty bus bars be at fault?

    It's obvious someone has worked on the battery before I got the car at 120k back in 2019, there are random sharpie marks on the cells, and the bolts holding the cells in from the bottom..half were missing.
     
    #7 Prius92, Jul 7, 2022
  8. ammdb

    ammdb Active Member

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    Gen2 modules only have one screw per module on the bottom.

    Since all the modules have close to the same voltage and you're not getting any battery related engine codes, to get performance back look into reconditioning your pack.

    Prolong Value Reconditioning Package - Hybrid Automotive

    Also check the battery cooling fan to make sure it's clean and running.
     
    #8 ammdb, Jul 7, 2022
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  9. TMR-JWAP

    TMR-JWAP Senior Member

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    What else could cause the HV battery to discharge so quickly on the highway?
    Pretty much only 2 things...insufficient engine power or something is causing serious drag which is making all engine power go toward trying to maintain speed. The battery is draining itself trying to provide electrical assist.
    But I've been known to be wrong, every now and then...

    If 'random sharpie marks' are the red marks on the sides, that's 100% oem.

    Look at the serial number on the top of each module. The first 4 are the date code,
    #1 and #2= day of the month
    #3 =month (1-9, x, y, z for Jan-Dec)
    #4 = year (G=2005, H = 2006, I=2007, J=2008, K=2009, L=2010

    IDK if Dr P app provides it, but you could easily look at charge limit and discharge limit the car is placing on the HV battery. It's usually something like 25kw and 21kw or something similar. Hybrid Assistant app displays it. Techstream displays it also. That limit will be adjusted by the ECU as needed to protect the battery. Avery cold morning or very hot day may see the limits dropped to 12kw until it gets to a better temp. A bad module may drop it to 5kw. But module issues would code. Maybe your car thinks its 5 or 150 degrees outside and has reduced the battery limits?

    The car is pretty smart. If it wasn't throwing a battery code, the car doesn't think anything is wrong with the battery. I wish you luck and hope you get it resolved. Keep us updated.
     
    #9 TMR-JWAP, Jul 7, 2022
    Last edited: Jul 7, 2022
  10. bisco

    bisco cookie crumbler

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    what is doc prius giving you for life expectancy?
     
    #10 bisco, Jul 7, 2022
  11. PriusCamper

    PriusCamper Senior Member

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    Not sure why no one has mentioned it but there's nothing wrong with your battery pack other than a lack of maintenance (deep cycling/reconditioning) to break up the poorly conducting crystallization that occurs in all Nickel-Based batteries as they age: batteryuniversity.com/article/bu-807-how-to-restore-nickel-based-batteries

    The thieves who run Toyota decided they'd rather not inform their customers about the fact nickel based batteries require periodic reconditioning to restore capacity and instead sell you a brand new pack after you go past the setting that won't throw error codes even down to 50% capacity, which sounds like where you're at.

    The good news is for a $100 you can build your own system to deep cycle your battery pack 3 times to restore it back to 96% capacity and this will last 18 months before needing it again. The instruction manuals at hybridautomotive.com are useful for this, but their product pricing is not so if you want to save $600 you can build your own: Build Hybrid Battery Maintenance Gear For Under $100 | PriusChat
     
    #11 PriusCamper, Jul 7, 2022
    Last edited: Jul 7, 2022
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  12. Prius92

    Prius92 Active Member

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    Well right now I'm doing a discharge test using a 55w fog light bulb, I've been running a timer 2 minutes and recording the before and after voltages.
    I've done 10 cells, and as of right now the voltage is going from 7.69 to 7.39 on each cell, which is good.
    As far as reconditioning goes..it is my understanding you discharge and recharge the cells 3-5 times, right?
    What is the voltage to discharge them completely down to? My charger can charge/discharge but I'm not sure what the voltage cutoff is for reconditioning.

    It's also astonishing at how well these batteries are made. 14 years (cells are original 2008), 188,000 miles and so far all still work well.
     
    #12 Prius92, Jul 7, 2022
    Last edited: Jul 7, 2022
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  13. Prius92

    Prius92 Active Member

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    Here is the results:
    Cells before discharging
    Lowest: 7.66v
    Highest: 7.69v

    Discharger: H11 Foglight bulb, 55w.

    Cells after 120s connected to discharger:

    Lowest: 7.35v
    Highest:7.39v
    I'd say that's rather good, eh?
     
    #13 Prius92, Jul 7, 2022
  14. TMR-JWAP

    TMR-JWAP Senior Member

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    If that statement is true, it leaves just one question.....where is your problem?
     
    #14 TMR-JWAP, Jul 7, 2022
  15. Prius92

    Prius92 Active Member

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    It has to be either in the dirty bus bars which increase resistance..or something else. My battery was going purple on the highway, and for the past few weeks I've rarely got a full set of "green" segment bars on the display.

    Coupled with the fact 0-60 is bogged down a good 3-4 seconds than normal, sometimes not having much power to pass (despite engine revving)...I'm hoping it's just these bus bars and not one of the motors (MG1,MG2) or something else causing it to act weird despite no codes.

    I've cleaned and repaired the engine to pretty much brand new (despite obvious internal wear an ICE would have at 188k), new plugs...two new injectors, cleaned the throttle body, MAF, replaced PCV and air filter, checked the throttle position sensor, etc.Even hooked it up to my car scanner and checked all the values of things like the O2 sensors, fuel trims, etc. All within normal.

    Engine runs like a sewing machine and purs like a kitten on WOT, so the performance issue has to be in the hybrid system.
     
    #15 Prius92, Jul 7, 2022
  16. TMR-JWAP

    TMR-JWAP Senior Member

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    My battery was going purple on the highway,

    Isn't that odd. At steady highway speeds, the engine should be providing all the power and the battery should essentially be on a float charge (just an amp or two or three), maintaining somewhere around 50-60% SOC. About 5 blue bars. There should really be no drain on the battery.
     
    #16 TMR-JWAP, Jul 7, 2022
  17. Prius92

    Prius92 Active Member

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    Well the A/C drains it quite a bit. In fact if I'm at a light for longer than 5 minutes on a warm day, it sometimes goes all the way to empty.

    But I did try everything out with the A/C completely off, no change.

    If redoing the cells don't fix it..I'm not sure how hard it is to find a parasitic load on a hybrid system.
     
    #17 Prius92, Jul 7, 2022
  18. bisco

    bisco cookie crumbler

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    never heard of one
     
    #18 bisco, Jul 7, 2022
  19. PriusCamper

    PriusCamper Senior Member

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    A parasitic drain on the hybrid system has specific error codes to let you know... And even though the resting voltages of your modules are good, the next test is a load test, which means hooking up a standard headlight bulb, or anything that's about 12v / 50w up to each of the 28 modules for two minutes to record voltage loss. A functional module will only lose 0.2v to 0.4v at the 2 minute mark.

    If there's a way we can see what your battery data looks like while driving via Hybrid assistant & Hybrid Reporter app, or via Dr. Prius app we could help you get a better sense of the problem.
     
    #19 PriusCamper, Jul 7, 2022
  20. Prius92

    Prius92 Active Member

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    I'd like to recondition them while out, but this is the part that is confusing.
    The prolong site mentions discharging the 1st time around to 0.8v per cell, or 4.8 volts per module.

    Thing is, I can leave a bulb on it to get down to 4.8...but when I disconnect it, the voltage leaps up to 5.8-6.2

    So do you discharge it to 4.8 with a bulb and then disconnect it and not worry about what the voltage is after the load is removed?
     
    #20 Prius92, Jul 7, 2022
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