Salvage Traction Battery

Discussion in 'Gen 2 Prius Technical Discussion' started by seilerts, Jan 20, 2011.

  1. seilerts

    seilerts Battery Curmudgeon

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    Recently, a thread on transaxle replacement was inadvertently hijacked with a discussion about salvage parts, particularly traction (high voltage) batteries. Patrick Wong and jk450 still have some questions, so I decided to start a new thread.

    Around Christmas, I took delivery of a couple of batteries. All that I want are the cells, which are being re-purposed. The two batteries came from the same yard.

    The average junkyard is, shall we say, less than conscientious about the details. The batteries had the terminal/relay cover (Toyota calls this battery carrier panel No. 6) floating loose. Once removed from the car, there is no way to attach this panel other than nuts+bolts or zip ties. One had the orange service plug floating loose as well.

    The other battery had the orange service plug installed.

    [​IMG]

    The service plug completes the circuit in the 28 module battery string via a fuse, 120 amp if I remember correctly. If the service plug is installed, then the battery side terminals of the system main relays are at the full potential of the battery. Normally, white plastic caps cover the terminals for added protection, but these are miscellaneous bits not likely to be included by the junkyard.

    [​IMG]

    To Patrick, the frame wire side terminals of SMR2 and SMR3 can only be energized when the car is in Ready. But the battery side terminals of SMR2 and SMR3 are always hot.

    [​IMG]

    To jk450, since the battery side terminals of SMR2 and SMR3 are hot, a good reference for the hazard level would be the two hot legs of a 220V circuit. But in this case, the only human protection is a 120A fuse, which is really no protection at all! For lack of the #6 panel and the terminal caps, it is quite possible for someone to brush a hand up against those terminals during handling and receive a fatal shock.

    To everyone, please do be careful around traction batteries! The orange plug should ALWAYS be removed as soon as possible during any service involving the high voltage system, and should NEVER be installed unless the battery is bolted down inside the car with all connections and safety covers in place. The pictures in this post are to illustrate the potential risk, and even using Cat III gloves and multimeter it still made me nervous. Toyota goes a step further safety-wise in recommending that the socket for the service plug be taped over with electrical tape whenever the plug is removed.
     
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  2. Patrick Wong

    Patrick Wong DIY Enthusiast

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    Thanks for the post and photos. I can understand that if the cover is missing or loose, then a substantial shock hazard exists.

    I'm wondering what the battery modules looked like when you removed the top cover of the battery case? Any leaking electrolyte or corroded hardware, for example?

    Also, what was your price for those batteries, and the model year/odometer reading of the vehicles that the batteries came from? Thanks.
     
  3. David Beale

    David Beale Senior Member

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    A further warning. While the voltage is similar to a 230 VAC circuit (the 230 VAC circuit actually has a higher peak voltage and will also leak current due to capacitive coupling), the hazard with DC is MUCH greater. You can let go of a 230 VAC circuit -before- it fatally burns you (if you are lucky), but you CAN NOT let go of a DC circuit. It causes your muscles to cramp and hold the device you inadvertently grabbed! I have some experience in this area. I won't be doing that again (not a Prius battery, -only- a 90V DC supply). You will get VERY wary of DC high voltage once you are bitten, IF you survive. Please ensure you don't test this assumption.

    I believe it is commandment #8 of the "Ten Commandments of Electronics" that says:
    "Verily, verily I say unto thee, never service high voltage equipment alone, for electric cooking is a slothful process and thy might sizzle in thine own fat for hours on end before thy Maker sees fit to end thy misery and drag thee into His fold."

    The installed battery has a ground fault protection device to keep you "safe", but once you are messing with the raw battery, all bets are off! BE SAFE!
     
  4. jk450

    jk450 New Member

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    I didn't state anything that even remotely resembled that. Why would you say that I did?

    Why were you nervous, if you were using appropriate safety equipment?

    Remove the service plug and measure the voltage across the two service plug socket terminals.

    What is the voltage reading, and why?
     
  5. jk450

    jk450 New Member

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    Read up on "let-go" current. If you can't find your own sources, start here:

    http://www.clintoninstrument.com/download/effects of frequncy on let-go currents.PDF

    AC or DC

    Electrical Injuries: eMedicine Emergency Medicine

    AC and DC Electric Shock Effects Compared

    Now review your previous statement, above. Do you still think it is accurate?
     
  6. Flying White Dutchman

    Flying White Dutchman Senior Member

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    yes! pics if the cels inside would be nice
    and what year maybe miles would be great to

    and are you planning on doing a cap. test
     
  7. seilerts

    seilerts Battery Curmudgeon

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    This one came out of an '04 with 95,000 miles. The physical appearance is pristine: no electrolyte leakage, swelling, etc. I love the pack assembly -- it is a home run compared to an IMA battery. I'll run some capacity tests eventually.

    The two exposed terminals are where the leads for the service plug connect.

    [​IMG]

    The bottom side of the battery. The wires are thermistor leads.

    [​IMG]
     
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  8. Patrick Wong

    Patrick Wong DIY Enthusiast

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    I've heard that Honda traction battery life is not what it should be. If true, I'd be interested in knowing the reasons for that.

    Would it be reasonable to repurpose salvage Toyota battery modules for use in Honda vehicles?
     
  9. seilerts

    seilerts Battery Curmudgeon

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    Honda has two problems: inferior module construction, and poor battery management. Honda uses D cell NiMH batteries that are spot welded into "sticks" in groups of 6, which are then arranged in a 3 x 7 grid inside the battery case (with one empty slot), and there is a large muffin fan which draws cabin air across the modules to cool them. As a result, the heat dissipation is uneven.

    Battery management is poor for two reasons. There is no provision for rebalancing modules, other than "recalibration". If one module runs lower than the rest, i.e. hits near-zero SoC, that triggers a negative recal, where IMA takes engine power to recharge the entire pack, not just the affected modules. Over time, the imbalance divergence grows, and the stress on modules at the extremes increases, ultimately resulting in a failed module and the IMA light coming on. Whereas, the Prius can rebalance modules in the background, and failures are much, much less frequent. I wonder if Toyota has or licensed a patent somewhere on balancing. On the thermal side, the fan goes into high gear at a higher temperature than on the Prius, and only has 4 states: off, low, medium, and high. High kicks on at 53C. When NREL published testing results on an Insight in 2001, they were concerned about the thermal effects on long term reliability, and it is possible that real world results are even worse than they thought at the time.

    Few of the early Honda hybrids made it past 150,000 miles on the original battery pack. I purchased my Insight with 159,000 miles on the clock and having a bad pack, and it was already a pack that had been replaced at least once. I think it is very rare for at the early Honda hybrids to go more than 150,000 miles on the original pack.

    So, yes, I am planning to put 20 Prius cells into my Insight. It sure beats giving Honda $2600 for a new pack, or trying to refurbish the old one along the lines of hybrid-battery-repair.com. But there are challenges, such as getting them to fit in the existing form factor, and making sure that they are adequately cooled. It's a long term project.
     
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  10. Patrick Wong

    Patrick Wong DIY Enthusiast

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    Hmm, this sounds similar to the NHW10 Prius that was one step up (at best) from a science experiment and was only sold in Japan.

    What is the physical configuration of the current model Honda traction batteries? I hope they have evolved beyond D-cells?
     
  11. seilerts

    seilerts Battery Curmudgeon

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    As far as I know, they still use cylindrical NiMH modules, but fewer of them in the newer cars. I thought I read somewhere that Toyota has an exclusive agreement with Panasonic for prismatic modules, but I can't find the reference now.
     
  12. statultra

    statultra uber-Senior Member

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    My Accord Hybrid has D cell Ni-Mh batteries arranged in a similar fashion to the Prius battery with block voltages of roughly 15 volts, 120 cells at 1.2 volts per cell.
     
  13. seilerts

    seilerts Battery Curmudgeon

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    Right, the Accord has the same rough config as the Insight and HCH, but a different module construction. It was the 2010 Insight that seems to have dropped down to 84 cells.

    Have you had any problems with your Accord traction battery yet?
     
  14. statultra

    statultra uber-Senior Member

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    Nope no problems so far, the IMA system seems to let the battery go down much more than the HSD system, if I was to floor the gas pedal for a long period of time I would eventually run out of assist and the battery would show no bars. When I first fixed this car, I didnt hook up a ground cable by accident and ended up starting the car like a ordinary vehicle ( using the starter ). I guess the advantage to the IMA is that if the battery does go bad at least the car is driveable.
     
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