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Bad Traction Battery Module(s)

Discussion in 'Gen 2 Prius Technical Discussion' started by Terry Tampa Bay, Oct 14, 2015.

  1. Terry Tampa Bay

    Terry Tampa Bay New Member

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    Vehicle:
    2006 Prius
    Model:
    Two
    2006 Prius with 125,000 miles. Last summer I got the red triangle of death and ended up replacing one of the battery modules because it was much lower voltage than the others (6.6V as compared to all the others that were 7.7V or so). Worked great for better than a year. About two months ago the red triangle of death re-appeared - I suppose I shouldn't have, but I drove the car almost daily with the red triangle since then. About 10 days ago I drove the car and noticed that the charge state was way down at the lowest purple charge state (fully discharged) - and that was after driving many miles at a steady 45 mph - the charge state would normally be near fully charged. I drove it back home and the charge never went up - engine running constantly. Clearly something was foobared.

    Today, after leaving the car sit for the past ten days, I yanked the traction battery and checked the voltages of all the modules. Most are between 7.53V and 7.57V. The few other outliers are 7.50V, 7.40V and 6.34V. Clearly, the bad module that has triggered the red triangle of death is the 6.34V module. I have a spare (bought as a good used module one year ago) module that is currently at 7.47V (it has been a bit more than a year since it was last charged). I should think it would be a fine thing to replace the 6.34V bad module with my spare. Correct?

    Is the module with the 7.40V a concern - is 7.50V a concern? As long as I have the darn thing out, should I replace it?

    I did have one high voltage module at 7.62v, but that was the replacement module I installed last summer. Can I correctly presume that is not a concern?

    I do have a Hybrid Automotive grid charger (for balancing the Prius traction battery) and their setup for discharging/cycling the traction battery (with light bulbs, etc.).

    Input? Thanks!!!

    Terry in Tampa Bay, Florida
     
    #1 Terry Tampa Bay, Oct 14, 2015
  2. greasemonkey007

    greasemonkey007 Active Member

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    You need to load test all of them, IMHO. Check the voltage, hook up a load (like a headlight) and after a minute or so check the voltage again to see where it fell to. Try to keep the time under the load the same on all of them. That will tell how they will hold up. All the voltage drops should be really close to the same. If one drops considerably more than the others, pitch it. Then by all means do the balance on the pack. I would probably do a discharge and re-balance as well. I still haven't played with my light bulb discharger yet. But I've got a pack in mind for it when I can get time to do it.
     
    #2 greasemonkey007, Oct 14, 2015
  3. Terry Tampa Bay

    Terry Tampa Bay New Member

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    Two
    Greasemonkey007 wrote: "You need to load test all of them, IMHO. Check the voltage, hook up a load (like a headlight) and after a minute or so check the voltage again to see where it fell to. Try to keep the time under the load the same on all of them. That will tell how they will hold up. All the voltage drops should be really close to the same. If one drops considerably more than the others, pitch it. Then by all means do the balance on the pack. I would probably do a discharge and re-balance as well. I still haven't played with my light bulb discharger yet."

    Yes, I've heard of load testing but didn't know exactly what to do. What you state makes sense. So I take an automotive 12V incandescent headlight and let each module power it for one minute - correct?

    Last year when I replaced one module, afterwards I did the full discharge and rebalance cycle. But I never did it again. The guy I bought the equipment from recommended that I do it regularly (at least the balance part) and some interval - I don't remember how often. Any idea how often it should be done? I seem to recall that he suggested that after I got my battery back together last year that I do the discharge/rebalance several times - but I only did it the one time. Any idea what should indicate to me that I should ever do the full discharge/rebalance cycle?

    Oh and, do you have any idea whether the module with the 7.40V a concern - is 7.50V a concern? As long as I have the darn thing out, should I replace it? Or perhaps let the load test tell me how they are doing?

    Thanks for responding.
     
    #3 Terry Tampa Bay, Oct 15, 2015
  4. greasemonkey007

    greasemonkey007 Active Member

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    1.) Yes, that is what I do. I number all the modules starting from the ecu end. Then I record all the voltages on a sheet of paper, then write down the voltage under a load as well as the voltage drop.
    2.) The frequency of the rebalance is up to you and the health of the battery. I would say every 3 to 6 months for a healthy battery, more often if your battery graph goes up and down really quickly and gas mileage decreases noticeably. If that's the case you may want to do a discharge.
    3.) I would discharge it to 1V/cell or 6V/module, then recharge it. Let it set for a while to let the voltage come back down to normal (7.8 to 7.9 or so). Then I would load test it. You may have to do more than one cycle to get the battery pack where it needs to be. Like I said, I haven't used my discharger yet. On the 1st discharge I would only take it down to 1V/cell or 6V/module. I've went as low as 3V/module with my RC chargers. You can step it down in increments, say 6V/module then rebalance. Then 4.5V/mod and rebalance. Then 3V per module and rebalance. Once you get the pack like you want it, let it set for a while for the voltage to come back down to normal before starting the car.

    Hope this helps.
     
    #4 greasemonkey007, Oct 15, 2015
  5. jeff652

    jeff652 Senior Member

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    I would recommend cycling the pack 3 times with our charger & discharger, then load test each module. You can load test using the incandescent automobile headlight bulb as already mentioned. Wire the headlight bulb in series so that both the low and high beam are creating load. Record the voltage just before the test and and the end (after one or two minutes). Be sure to use the same amount of time for all load testing of all modules.

    All modules that have a larger voltage drop than the rest of the pack should be replaced. This will not be hard to spot after the test is done and data is compared.

    After replacing the bad modules, you need to again cycle the pack using your Hybrid Automotive Prolong Battery reconditioning system two or three times to help the new and existing modules equalize with each other and have the highest possible capacity.

    After this is done and you are back on the road, you need to charge & balance the pack once every 6-8 weeks for 24 hours. Do a full reconditioning (charge->discharge->charge) 2-3 times per year or more as needed. Anything less than this will not deliver the best results from your Hybrid Automotive Prolong Battery reconditioning system.

    :)
    Jeff
     
    #5 jeff652, Oct 16, 2015
    Frank1234 and usnavystgc like this.
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