HV Battery Cell Replaced, Now What?

Discussion in 'Gen 2 Prius Care, Maintenance and Troubleshooting' started by KyeLee Stephenson, Jul 11, 2016.

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  1. KyeLee Stephenson

    KyeLee Stephenson New Member

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    Hi all, last week I got a whole array of warning lights, including the triangle of death. Took it in to my local mechanic who diagnosed it and told me it was the HV Battery, and total cost would be around $3500 to replace it. So, as a temporary fix until I can come up with that kind of cash, we did some DIY and just replaced the bad cell. Everything went well, just some minor troubles toward the end with the engine not turning on, which we fixed by switching the orange switch on the battery and disconnecting and then reconnecting the 12V battery. It was driving great, until u got to work this morning and all the lights came on again. What am I missing? Any advice would be welcome, thanks in advance. :)
     
    #1 KyeLee Stephenson, Jul 11, 2016
  2. JC91006

    JC91006 Senior Member

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    You have to determine if the replacement module you put in is actually a good module. Then you have to make sure it's capacity is a good match to the rest of your pack.

    What you are doing is a very unreliable repair. There's a lot more to repairing a battery module than just swapping out a module.

    If I had to guess, it would be you have more than 1 failed module.......and/or the module you put in is not a good match to the rest of your pack. It also can be the module you put in is also a failing module.
     
    #2 JC91006, Jul 11, 2016
  3. KyeLee Stephenson

    KyeLee Stephenson New Member

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    thanks for your quick reply. We tested each module before putting in the new one, all were 8V. We tested them again after installing the new one and they all ready 8V again, so we were feeling pretty confident about putting it back in. I did read somewhere though that you are supposed to charge the battery as a whole after doing so, which we did not do. Not sure how accurate that statement is, though.
     
    #3 KyeLee Stephenson, Jul 11, 2016
  4. JC91006

    JC91006 Senior Member

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    8 volts doesn't really mean anything as most modules fail when they start dropping in voltage. you have to read the codes in the car to determine which block has failed and look at those modules
     
    #4 JC91006, Jul 11, 2016
  5. KyeLee Stephenson

    KyeLee Stephenson New Member

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    Right. We did some research, between 7.5 and 8 is about where each cell should be. It said cell #4 when we diagnosed it. We tested all of them to be sure, but it was #4. All of them tested at 8V except that one, which tested at 6V. We tested the replacement cell beforehand, as it was refurbished, it read 8V. I am confident in the replacement we did, and the replacement cell has a 6 month unlimitrd miles warranty, it is meant to be temporary. Could there be something we missed while placing it back into the car? Maybe the fan or vent?
     
    #5 KyeLee Stephenson, Jul 11, 2016
  6. JC91006

    JC91006 Senior Member

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    You need to read the codes on the car. I'm pretty sure it's the new module that you put in that's not compatible or is a failing module.

    I'm not really sure how you can buy a refurbished module that cannot be refurbished
     
    #6 JC91006, Jul 11, 2016
  7. bisco

    bisco cookie crumbler

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    welcome! the reason you're saving up the $3500. is because replacing one cell is hit or miss. some get lucky, and think they've beat the system, and some don't.
    if you can do all that yourself, why not look around for a new battery closer to $2,000.?
     
    #7 bisco, Jul 11, 2016
  8. KyeLee Stephenson

    KyeLee Stephenson New Member

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    Unfortunately I had to get the prius as a last minute replacement for my other vehicle that died on me, and as a 20-something year old gal who's still trying to go to school, I don't have much of anything saved up at the moment. Especially not anywhere close to $1000, nonetheless $2000 or $3500. :( just need the car to last me another year while I try and save pennies! The dealer had said the battery was replaced already when I bought it, but on top of this I had to have the combination meter replaced as well a month after buying it. No warranty on the damned thing either.
     
    #8 KyeLee Stephenson, Jul 11, 2016
  9. fotomoto

    fotomoto Senior Member

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    Read this entire FAQ (it's very short): Texas Prius Battery Replacement

    An autoparts store can read some (but not all) of the codes for free.
     
    #9 fotomoto, Jul 11, 2016
  10. JC91006

    JC91006 Senior Member

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    Get the codes read and it'll save you a lot of time and headache in guesswork
     
    #10 JC91006, Jul 11, 2016
  11. bisco

    bisco cookie crumbler

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    understood. not many warranties cover 10 year old products. sorry for your troubles, i wish you all the best!(y)
     
    #11 bisco, Jul 11, 2016
  12. jadziasman

    jadziasman Prius owner emeritus

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    The open circuit voltage (OCV) of a module isn't all that helpful in determining the state of health of an HV battery. Practically useless in fact. It's unfortunate that novices like the OP don't read up on what they should be doing before attempting a repair. Without adequate preparation, a second repair soon after the first is practically inevitable.

    Most modules are very close in OCV but act quite differently when a load is applied. Only by testing all 28 modules for voltage drop
    over time is it possible to weed out the weak modules and have reasonable success in getting an HV battery to last six months
    or more. Balancing the modules is also important since an out of balance battery throws DTCs.
     
    #12 jadziasman, Jul 11, 2016
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  13. jeff652

    jeff652 Senior Member

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    Try load testing each module to see which one(s) are causing the issue. A voltage test without load is not a reliable indicator of cell/module health. We make a simple inexpensive load tester, or you can build one for yourself:
    Prolong™ Battery Module Load Tester - Hybrid Automotive
     
    #13 jeff652, Jul 13, 2016
  14. stockdaddy

    stockdaddy Member

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    You need to drive the car around and get live data on each of the battery modules. If you have an android phone then a bluetooth code reader is an easy option to keep a code reader in your car at all times.
     
    #14 stockdaddy, Jul 15, 2016
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