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2002 Prius battery refurbishment underway; how many modules should I replace?

Discussion in 'Generation 1 Prius Discussion' started by Barrett Weislow, Mar 26, 2023.

  1. Barrett Weislow

    Barrett Weislow New Member

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    Hello all,

    I'm Barrett, and I'm new to Priuschat. I'm hoping that one of you with experience in battery refurbishment could take a look at where I am at and offer any guidance on how many modules you think I should replace, and give me any other tips or feedback, if you have it.

    The car is a 2002 Prius with only 65k on it and in good shape. It threw a P3006 code so I brought it in to a hybrid shop where they performed a load test (results attached). Block 5 was off at 14.62V. A full replacement through Toyota was all they offered, just under $3k.

    So, I do my research on DIY refurbishing, find this forum, watch Igor Kadulenkov's YouTube video and decide to go for it. I bought a couple 4-channel hobby balance/chargers and using the spreadsheet provided by Igor, have been tabulating the mAh while cycling each module with the following parameters:

    Charge rate: 3.0A / Discharge rate: 1.0A / Discharge cutoff: 6.0V / Overcharge cutoff: 7500mAh

    A Discharge of 5000mAh or greater was considered good, below 4000mAh considered poor, with a new module rated at 7500mAh.

    After many weeks cycling the modules, with some receiving nearly 75 charges and discharges, here's where I stand:

    At the start of refurbishing, almost all of them were in poor condition, but now only 4 discharge below 5000mAh; 1 that was completely dead and which failed the load test, another that after reaching 5000mAh at one point, reversed the gains it had made in capacity and started falling back below 5000mAH. Then, there are 2 more that plateau around 4750mAh and don't seem to want to improve.

    My question then is, can I consider all of the modules that discharge above 5000 good, or does the number of cycles it took to get there factor in? If so, what is a reasonable cutoff point? Igor doesn't go more than 10 cycles before determining it needs replacing but that could just be due to the fact that it is unpractical for most people to do this at all, let alone spend months on the refurbishing process.

    Additionally, should I rearrange the modules, transpose their position in the bank, or group them according to their final mAh? If so, how?

    I'm attaching my results, which can be found on the "My Capacity Test Sheet" of the attached spreadsheet. Please note that "n/a" was due to one of the balance chargers only saving the data for the last cycle recorded.

    Thanks in advance to anyone who took the time to answer!
     

    Attached Files:

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  2. Bruce Berquist

    Bruce Berquist Junior Member

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    Thank you for giving some good details. You definitely have a Battery assembly that does not need to be replaced and refurbishing it is the most reasonable action to take. You are doing great so far.

    What I see in what you have shown is that you have 4 modules that I recommend you replace.
    #3 is undoubtedly bad
    #9 is also bad by looking at its performance in charging and discharging voltages.
    #5 appears to be good everywhere accept for in the load test. it might be on its way to failing.
    #16 is a good module but some discrepancy in the figures, that come close to creating an out of balance SOC (state of charge), could mean that it might begin failing in the future.

    When I refurbished the Battery Assemble on my 2003 Gen1 (240k miles on the original battery assembly), it was very similar to your situation. I replaced 5 modules, 3 of which were bad, and 2 had discrepancies that made them questionable for future reliability.
    The Battery assembly and charging system perform perfectly now, and after well over 2 years of operation since the refurbishment, the estimated lifetime reading still sets at 92%.

    In regard to module placement in the assembly, it is easier for me to describe the modules as "cells" since the assembly is made up of 38 cells, 19 modules of 2 cells which are divided into blocks. I put similar and matching cells together in the same modules. I put the modules of best readings and condition in the middle and the others to the outside. I did this mostly in consideration of heat and cooling.

    I hope this helps you out.
     
  3. Tombukt2

    Tombukt2 Senior Member

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    As long as you're looking at your time is about free then by all means you have free labor and plenty of it and the space to work on and do your thing I shouldn't be any problem how did the bus bars and the nuts look those seem to be very important on these assemblies usually your bus bars are turning black by now and the nuts holding the bus bars to the plates and all of that are frosted and look like general h e l l. Sometimes rectifying that can make amazing things happen all of a sudden but then again that's a lot of nuts a lot of bus bars etc but if you have the time and your labor is not worth that much to you than by all means I mean to me at the time I spent $1,300 at the dealer so 1486 whatever it was that seemed to be like a smoking deal be done in 5 minutes drop it in the car and drive 13 more years so that's what we did I didn't have the time as you.
     
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  4. sam spade 2

    sam spade 2 Senior Member

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    In answer to the question posed in the title of this thread.............
    ALL of them. Seriously.

    And rather than rehash a discussion that has already been beat to death on here many times.............
    You could have done a search and some reading ahead of time.
    Really.
     
  5. ammdb

    ammdb Active Member

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    If this includes labor, a $3k new Toyota pack replacement isn't bad for a car with only 65k miles on it. If replace by Toyota I recall that includes a two year warranty on a battery pack that should last another ten plus years.
     
    #5 ammdb, Mar 26, 2023
    Last edited: Mar 26, 2023
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  6. Tombukt2

    Tombukt2 Senior Member

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    Yes I paid 1460 ish . And did the 50 minute install myself I realize I don't get the two-year warranty but I don't think I'm going to need it and if I really pushed at my local Toyota dealer where I bought the batter they would probably warranty it for me if it was a clear fail so I'm not too worried about that they know me pretty well over there and don't give me too much grief and there's a big paper trail I mean in reality at the end of the day it doesn't matter who dropped the battery in and connected to relays and put the plug back in right No because if you mess that up initially you would never get the car out of the stall or create a fire or whatever happened so there would be no two years to make
     
  7. ammdb

    ammdb Active Member

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    I paid about the same and did the DYI install, but last time I checked price has gone up over $2k for the part. The Toyota parts departments I used is currently listing it as "This Product Is Not Currently Available".

    upload_2023-3-26_19-11-41.png
     
    #7 ammdb, Mar 26, 2023
    Last edited: Mar 26, 2023
  8. Tombukt2

    Tombukt2 Senior Member

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    Yeah I've heard that lately that's the deal out of stock classified as new old stock if you can find it all that business I did find a Panasonic cells new I cannot remember what the deal is on them per piece but still I guess if I have to do that and buy a set of bus bars and nuts we could do that but right now I don't have to do anything everything's done so we're waiting on another one to fail I guess I've got a G3 with the cord stored for the battery issue and it doesn't like to go into EV mode until it's been running a few minutes to charge up and it's a junkyard battery that I got two three years ago and just dropped it in this 2010 and it's been driving Uber and all that nonsense through the pandemic cars hardly ever at home or stopped I guess that's why it's not blown up and keeps running It seems as soon as you stop one of these things for a few minutes all the problems start so if you're running one of these a taxi or a delivery vehicle might go to 666 and just croak or a little less if it's sitting at home going to work and coming back I guess all this can come on a lot quicker It just seemingly seems that way.
     
  9. Tombukt2

    Tombukt2 Senior Member

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    Last I checked the Panasonic cells in the correct amount we're about $1,300
     
  10. Barrett Weislow

    Barrett Weislow New Member

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    Hey everyone, thanks for you input and apologies for not replying sooner, I had a family emergency and dropped many balls. I just wanted to provide an update on my project in case anyone was interested.

    I spent several more months refurbishing the modules, bought 15 replacements on eBay for under $15 each, and in the end I was able to restore all but a few to above 6000 mAh. I cleaned the bus bars, bought some new nuts, soldered a few of the broken terminals that read the block voltages, and applied Oxguard to all of the contacts.

    l then put all the modules in parallel and used copper wire to string them together, charged them up, and then let them sit for about 18 hours to balance the voltages. I put the strongest modules in the middle where the heat builds up and the weaker ones on the ends. I reinstalled the traction battery, gave the car a tune up and Voila! No triangle of death, no engine codes, and I'm getting over 42 mpg on average after driving the car for over 300 miles this last week.

    Obviously, this ended up being a much longer and more involved DIY project than I anticipated and I can't recommend that others try it. Or at least if you do, set a much stricter threshold for replacing the modules and don't run 100-200 cycles like I did. (For example, Igor in his YouTube video decides which modules need replacing after only 5 cycles.)

    However, it was a fun and educational experience and I learned a new skill. I've already found other uses for my hobby chargers and have refurbished some lead-acid motorcycle batteries and a lithium ion battery as well. I'll provide another update when the battery fails again, which will hopefully be some years out!
     
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