Gen 2 2004 Prius 200k miles. Bad battery cells. How hard is module replacement?

Discussion in 'Gen 2 Prius Care, Maintenance and Troubleshooting' started by DCGen2Prius, Jul 20, 2020.

  1. DCGen2Prius

    DCGen2Prius New Member

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    2004 Prius owner - it's been a very reliable 16 years.

    I began having weird battery charge/discharge monitor behavior after it was not driven for weeks at a time beginning with the covid shutdown.

    downloaded the dr. prius app and in looking at the battery it looks like 2 modules have bad behavior - showing a higher voltage when charging and lower voltage when discharging than all the other 'blocks'. 14 blocks? modules? 2 cells each block/module? do i have this correct? fools prius into quickly showing fully charged then fully discharged much too fast -and when problem was initially discovered after car sat too much during lockdown - battery wouldn't charge when engine on in park even for a long time.

    when i first discovered the weird behavior - and got vsc/and red triangle - i read codes and did some daily driving to try and 'revive' the battery thinking it was bad that it just sat for weeks

    . then discovered the dr. prius app that would show the voltages and performance of the 14 battery modules. (see attached screen shots).

    also battery fan has been coming on I hear the intake next to rear passenger side seat - and in a recent drive the battery temperatures showed over 120 degrees F!

    Ok - so - I am an engineer and pretty good at DIY stuff- appliance fixing, conventional car repair, computer building/upgrading, etc. I also am comfortable with household electric, etc., directed install of solar panels on my house, so I can carefully take this battery out and replace the bad modules/cells if it's not too bad/hassle.

    I've also found 2 "refurbished" hybrid battery places in the DC area on CL - one maryland, one fredericksburg that will put in a 'refurbished' battery for around $500. that seems pretty good - with maybe a 6 months or 1 year warranty. Hard to know where their modules are from - how balanced/healthy they are.

    However this battery has given no issues for 16 years of gentle prius driving - and I feel like I'd rather replace the offending modules - if it's not too terrible a job - since i 'know where the rest of my battery came from". Or are my good cells just ready to fail now that 2 have gone?

    Will I need a Prolong Harness? A hobby Battery cell charger/recharger? Have found the Dolj and dydx posts/guides - and some youtube videos. I know this is asked/posted alot - what are the best most comprehensive posts I need to start with. What do I need to buy? Where to get good reliable replacement modules? Are my good modules - likely good for a long time once I replace the two 'bad' modules? Or will this be whack a mole.

    This car has been handed down in our family and is a secondary car and will mostly be the teenager's local car to high school (when that exists again) - and sometimes commuting car. we've bought a newer prius with the collision avoidance/radar cruise control for road trips, etc. It's possible we'd sell it within a year or two and it would be nice to have it performing well with good battery for that.

    Have looked at the new battery products - I guess I'd like to try and fix this for $100-200 and my time - but if it's too excruciating - $1500 seems attractive. Was thinking $500 was good for a 'refurbished' battery - but is that really just a used battery of unknown cells/matching and I'll be back here again soon?

    Sorry to ramble - I am busy but have a little time to try and replace bad cells.
    What do I need minimum to do cell testing/matching/balancing.
    Where should I buy my replacements - what's best way to help ensure non-replaced cells are affected the least and not stressed by the replacements.
    And absolute safety warnings - disconnecting of all the cells from being in series seems important. There's another harness/switch that needs to be disconnected with great care?

    Having trouble posting dr. prius screen shots - will try in subsequent post.

    i'll try a couple links to dr prius screen shots- cells go red when on sustained nearby downhill as battery seems to reach fully charged mode - but it's just the 2 modules causing this? screen shots of error codes and recent 'charging' and 'discharging' screen shots during driving. Codes are HV Battery ECU error, P3000, and P0A80.

    thanks for any advice for my gen 2 battery 2 failing modules delimna. sorry so rambling.

    found these posts helpful-
    Gen II Prius Individual Battery Module Replacement | Page 121 | PriusChat
    Gen II Prius Individual Battery Module Replacement | Page 121 | PriusChat


    Screenshot_20200604-154653.png Screenshot_20200621-125715.png Screenshot_20200621-200300_resized.png Screenshot_20200621-200541.png
     
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  2. PriusCamper

    PriusCamper Senior Member

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    I have to head out, but I'll reply in detail soon... In the meantime, clear the error codes and force charge the pack (aka: car in drive w/foot on brake, emergency brake on just in case and accelerator pedal floored) And then see how long car goes with regular driving before warning lights come back on and post more screenshots.
     
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  3. broski

    broski Junior Member

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    If you are somewhat mechanical, can write numbers down and operate a stopwatch, you can replace battery modules.

    To me it looks like you'll need at least four modules (2 per block). The lazy, but effective way to do this, assuming the rest of your pack is relatively evenly balanced, is to discharge two of them, to get a decent average of how much charge remains. Then discharge and recharge the replacement cells, to the same stage of charge as the average of the two you discharged (this SHOULD be close in voltage, but do NOT use voltage, either under load or at idle to match). You can do this with a hobby charger that costs $50, it may just take a while to do so. Discharging the replacement cells you get can easily be done with a light bulb to speed things along, but don't let them get too low -- let the charger discharge them the rest of the way.

    That's the short of it. If you want to be thorough, you do this, but with the entire pack. I'm lazy and this has worked for two cars so far, so I'm going to keep doing it :v

    There's a ton of threads you can read for the rest of the info, go search.

    The only other thing I'll say is, if you plan to keep the car for 5 years, go buy a full set of new cells from the vendor on here. That's well worth not having to touch the thing again.
     
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  4. ericbecky

    ericbecky Hybrid Battery Hero

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    Great advice from folks so far.

    If you have some basic tools and patience you can replace modules. Sockets, screwdriver, trim removal tool , inch-pound torque wrench.

    You posted some good questions and thoughts in your "ramblings". I'd be happy to chat on the phone about the ideas you've laid out so far. Call me at 608-729-4082

    The real.quesrion is how far down the rabbit hole you want to go.

    Sometimes doing an "okay" job is good enough. There's a good chance you can swap the bad modules, closely match voltage using equipment you have around the house, and just keep on truckin'. No need to do do fancy rebalancing of all the modules, quantifying capacity, etc

    If you want to go full bore and buy a bunch of equipment, and other goodies, that's fine too. I'd be happy to discuss any of it.

    I sell modules to folks on this forum and as part of the sale I offer support along the way. Even if you don't buy them from me O still would be happy to talk.

    There are basic videos out there about removing the pack.

    Once out it's not much more to open the pack. Go slow. Don't have pets or small kids around. Leave yourself lots of time. Ask lots of questions.
     
  5. Prodigyplace

    Prodigyplace Senior Member

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    Normally I would agree but they are backordered 5 months.

    I would recommend buying theProlong reconditioning system and a couple of modules from Hybrid Automotive. They try to match the mileage of your existing pack.
     
  6. ericbecky

    ericbecky Hybrid Battery Hero

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    Due to Covid, Hybrid Automotive has had some delays. Not too bad. A couple of weeks? But it's an ever-changing situation. Check the web site for latest details.
     
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  7. DCGen2Prius

    DCGen2Prius New Member

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    Thanks so much to each of you for your advice and kind help and advisement to be careful. I will follow up with more detailed questions/response to your questions/suggestions. Thank you! Empowering to get friendly encouragement and advice.
     
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  8. DCGen2Prius

    DCGen2Prius New Member

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    PriusCamper - thanks. Have done some version of this over the past several months once I discovered battery anomalies - and found my way to Dr. Prius. I have cleared codes a couple times - notice the fan immediately stops it's constant running when I did this. However on recent shots (and now it's really hot outside) I noticed battery temps in the 120's - is that high/bad/damaging? Have never had pets in the car - but it is 16 years old including raising 2 kids along the way so could be some vent/intake crud i guess.

    Can I do damage to good cells operating it/trying to force it to charge with the two bad modues in there?
    when you say force charge, in drive, foot on brake - how long do i try this for? (seconds?minutes?)
    And you say "see how long the car goes with regular driving before warning lights come back" - you mean after the flooring while stopped to force charge - i.e. how long to try the force charge before driving it around?
    I had always thought it charged in Park - and you can rev it in Park - but you're saying in Drive. Thanks- just to be clear how long I should try this force charge mode - and exactly what you meant for me to do after.
    And should I worry about battery temps/fan running/etc.

    Thanks!

    EricBecky where do you sell modules/cells - what is best way to get cells that will match and behave well with my remaining good cells - giving me the best chance and this lasting for a few years at least.

    Broski - thanks for those thoughts - that is the way I think i'd lean on doing this. What is the worst that can happen if I don't try and match/rebalance all the cells - and only replace/match/balance the offending cells? That there are other weak cells undiscovered and I oculd find them now? Or is it that the replacements will 'attack' the good remaining cells - hastening their demise. i.e. is doing it somewhat 'quick and dirty' - cause another failure - or just that while the battery is out I can use full balancing/testing to root out other cells that are ready to go but haven't reared their heads yet. - Thanks all!
     
    #8 DCGen2Prius, Jul 21, 2020
    Last edited by a moderator: Jul 21, 2020
  9. mlsimmons

    mlsimmons Junior Member

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    I have recently gone through a similar situation on a 2005 Prius with 220K miles- I knew the battery was somewhat marginal since it did do the up and down charging symptoms when driving it regularly so I ordered a NewPrius Battery - however after it sat for over a week in mid March I got the red triangle regularly repeating and Dr. Prius and Torque apps indicated a bad block 9. unfortunately due to CV19 the new battery was backordered too long for me to wait, as I needed a drive-able car. I found a fairly local (50 miles away) supplier of reconditioned cells for $15 each and picked up 4 of them. I took the battery apart over a weekend, measured the voltages and found one of the cells in block 9 failed with only 6 volts compared to all the rest above 7. I put two of the replacement cells with the highest as received voltages in block 9 and moved the remaining block 9 cell to replace the lowest voltage cell in the other blocks (I think it was one of the block 14 cells). I then hooked up all the negatives and all the positives to balance all the voltages and put it all back together. Initially it seemed to work fine but after a few days the two new cells in block 9 were enough better than the rest so that block voltage approached the delta V amount that came close to tripping the red triangle. It was good enough to drive and the more frequently I drove it got a bit better. But still the NPB backorder was still well out there. I then found a local auto recycler that was selling a complete battery assembly for $200 (given the CV19 they had too many on hand and were discounting them to reduce their stock). I intended to use it as a unit to take my time on to convert to the NPB while still having a car to drive. When I got home and checked it, all the cells looked pretty good so I purchased two Imax B6Ac hobby chargers and went through the discharge/recharge process like the Russian guy on Youtube shows how- it took a while but all of the cells now exceed 6000MA when discharged down to 6.3 volts. So I think I now have a pretty good used battery - and of course just in time for the NPB to be delivered a couple of weeks ago. In any event the quick fix that I did with the two replacement cells is still working even with the reduced driving due to work from home and CV19 limitations. It still does the discharge/ recharge thing but is way more stable than when I first purchased the vehicle in December of last year. I have found working on the batteries to be really easy and a couple of Youtube videos and tidbits on how to set up the chargers from this list to be extremely helpful (including dealing with the buss bar corrosion cleaning) In retrospect given what I need the car for,I probably could have gotten away with using all four reconditioned cells and doing the hobby charger thing on the original battery (with maybe a bit of wack-a-mole down the road as one or more of the old cells went the way of the first one that went bad). I will probably still install the NPB since I already paid for them, to see if my mileage will improve- although I am curious how this reconditioned $200 battery will perform as well. I might just install it and use my original battery to convert to the NPB before reinstalling it - or maybe find a dead battery Prius locally and get some of my money back as I suspect not using the $200 battery will hasten it's demise
     
  10. PriusCamper

    PriusCamper Senior Member

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    Nice to hear from you again... You might get more replies if you add some paragraph spacing in above block of text... It was a battle to read through it all without getting lost amid the words. Anyways, sound like you're well learned on all the details of the best way to work on packs. Have you done much deep cycling / reconditioning of other packs yet?
     
  11. mlsimmons

    mlsimmons Junior Member

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    I set the hobby chargers for each cell at 7000ma for max charge and charged at 3 amps, discharged to 6.3V at 2 amps repeatedly - one of the chargers was a SKYRC brand, the other was a generic brand - the SkyRC had a "re-peak 2 times menu item that the generic one didn't ( although I don't really know what that did differently). After doing this I would only recommend the SKYRC unit and not try to save a few bucks as it seemed to give more consistent results. Some of the cells only took a couple of charge/discharge cycles to get above the 6000ma discharge rate - one almost made it to 6500 - the better ones were on the outside of the pack as expected - blocks 8,9 and 10 took more, one of those took about 8 cycles to get over 6000

    When you ask about deep cycling/recycling, how does that differ from the process that I used? Is that the Prolong charger type of charging?
     
  12. PriusCamper

    PriusCamper Senior Member

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    Well... Measuring amount of energy making its way into the battery requires very expensive lab grade electronic gear. The SkyRC chargers are only measuring how much electricity is being sent, not how much is being received... Some of the electricity dissipates as heat and NiMH don't last long if they get too hot! Also the prolong charger is designed to send an oscillating pulse, which is the most efficient way to clear up the poorly conducting crystallization. The NiMH algorithm in SKYRC chargers does this a little bit, but not as well as Prolong device. As for discharging, at first, I too was apprehensive about going much lower than 6v and if you had $30K in gear like my buddy Joe has, there would be no reason to discharge lower than that. But in my experience discharging down to 1volt with light bulbs yields better results if you're using inexpensive DIY gear. Also I charge up from that low voltage in stages with lots of fans blowing to keep the heat away. I also use a thermal camera to search for cells that are running too hot so I know they need to be replaced before they fail.
     
  13. eelfner

    eelfner Curious Dude

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    I went through this with my son's 2005 Prius. Fun project to find and replace the bad cells. Easily doable with standard tools. Low risk of shock. A bit tedious as I recall, because the cells are linearly installed (think donuts on a rod), and you might have to take a bunch apart.

    He had bought the car used. Seems some cells had already been replaced. After we replaced 2 and reassembled. No reconditioning. The car ran for 3 months before another failure. This time he bought a used battery from a low mileage wrecked 2009 Prius for $300. Been going strong for almost 2 years.

    I have 2 other Prius's, 2009 and 2007. If either was worth keeping and I had the battery fail, I'd look out Green Bean Battery | Reconditioned Hybrid Battery Company. $1500 for the lifetime of the car (and is transferable), East Coast of US only! I have no experience or relation to them. Just something I can across while trying to help my son.

    Good luck
     
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  14. mlsimmons

    mlsimmons Junior Member

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    Thanks for the information on how you do it- Sounds like you remove the battery cover when you are using your Prolong charger to measure the charging temps real time. I assume that you have done numerous rebuild/refirbs. How long does it usually take using the light bulb discharge method for each cell to get down to 1 volt or do you do it in blocks (2 cells at a time)? Once down to one volt what would be the best recharge amps setting to recharge at so as to not damage the battery and what stages/steps do you use to bring them back to full volts? in a typical used battery in Gen 2 and 3 cars, what is the amount of cells that get replaced for running too hot?
    I originally bought this car to simply use as a temporary driver while I fixed the head gasket on my normal driver. But, being an engineer, the technology in these cars have been fun to research and learn how it all fits together
     
  15. PriusCamper

    PriusCamper Senior Member

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    --Prolong Charger is so you don't have to take the battery out of the car and don't have to take the main cover off... The first two rounds of reconditioning can be done this way as long as you don't have any bad modules. The the third round too... But I prefer to build load test and self-discharge test data on a spread sheet and eliminating corrosion so pulling the pack is needed for that

    --Light bulb discharge of a module (6 cells) down to 1 volt takes somewhere around 45 mins, sometimes faster, sometimes slower depending on overall health. I sues a 12v 50w and a 12v 20w halogen bulbs on a module and switch to just one bulb when voltage gets low.

    --Recharge amps I decided on were based on the 120amp fuse divided by 28 modules or ~4.3amps recharge, though sometimes I push it to 4.4amps. However, these sells because they're lined up in series can handle a hundred amps, so maybe my logic isn't as clear as it need to be. But in all honesty it's probably my impatience making this determination. Lots of cooling fans and not charging up from 1volt all at once was a lesson I had to learn the hard way when water balloons over module vent partially inflated.

    --Yes, if you have an engineering backround a Prius will keep your mind way more entertained and engaged in learning way longer than a standard fossil fool vehicle.
     
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  16. Prodigyplace

    Prodigyplace Senior Member

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    You said yourself replacing cells only worked for 3 months. That is basically what Green Bean does. Having them replace the pack every few months gets tiring. If they were not backordered you could get a kit of new cells for $1600 basically giving you a new battery. The only recommended cheaper alternative is to get a pack from a low mileage junk Prius.
     
  17. PriusCamper

    PriusCamper Senior Member

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    Yes, but GreenBean does way more testing and analysis than DIY builders can do and somtimes their rebuilds last a few years, not just a few months. If I had one of their packs I'd definitely make use of their lifetime warranty for as long as the company survives, which likely won't be much longer...
     
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  18. ericbecky

    ericbecky Hybrid Battery Hero

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    I have a full set of Best hybrid battery cells in stock and ready to ship.
    Contact me directly if you are interested in purchasing it. 608-729-4082
     
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  19. Prodigyplace

    Prodigyplace Senior Member

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    If this a competitor to newpriusbatteries? I have not heard of them before.
     
  20. ericbecky

    ericbecky Hybrid Battery Hero

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    LOL. Not a competitor. More like a customer of his.

    I work on hybrids for a living.
    Been working on hybrids for over 15 years.

    I happen to have a set of his here. Among all kinds of other hybrids batteries I install.
     
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