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Quantitative Results of Grid Charge/Discharge

Discussion in 'Gen 2 Prius Technical Discussion' started by S Keith, Dec 6, 2015.

  1. dolj

    dolj Senior Member

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    The reason for the three stage charge/discharge regime is to lower the risk of damaging any one particular module. Apart from that gem, I will have to let the experts Steve/Brad/Jeff speak as to what you should do going forward.

    I presume, as you have said you are at 188 V, you are on the second discharge cycle after fully charging from 17 V. If you don't hear from anyone else to the contrary, if it were me, I'd pick up at the second discharge to 84 V. BTW, at 188 V, you should be using the 2x 75 W bulbs already (should have changed at 196 V).

    I hope some others will chip in.
     
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  2. MtBiker

    MtBiker Junior Member

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    I updated my post before I saw your last reply and indicated I did change to the 2x75W load at 182V. I was planning to go to 134V like the first discharge cycle but then changed to the second discharge cycle now that I understand the charts.

    Update: I switched to the 2x25W load at 140V and will let it go down to 84V before fully charging it again. I'm then going to configure my Prius just to the point that it can be driven and hope to be able to drive it to work on Tuesday. I have a Traction Battery Health Monitor and will post the data and graphs (d&g) I get after I drive it to and from work. I have d&g from just before it failed so it should make for an interesting comparison.
     
    #142 MtBiker, May 22, 2016
    Last edited: May 23, 2016
  3. MtBiker

    MtBiker Junior Member

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    Well, the charge/discharge cycles I performed did not fix the problem, for a very good reason. Although I messed up the first up/down cycle, I completed the second up/down per the HA charts, drove it for about a half mile and the Triangle of Death returned with the P0A80 (Replace Hybrid/EV Battery Pack) code. So, I measured each of the module voltages at no-load and then again after 2 minutes under load with a Prius headlamp. The following is my data and plots. It's interesting how the modules tend to get worse the more middle-of-the-pack they are. Heat is the enemy, for sure. Module 15 is obviously bad. I'll try replacing it and go through the up/down cycles again, correctly this time, but I'm not sure if 8, 12, 14, 17, 18, 19 & 20 should be considered on the way out as well. Any opinions?

    Module Voltages on 5-24-16.JPG
     
    #143 MtBiker, May 25, 2016
    Last edited: May 25, 2016
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  4. jeff652

    jeff652 Senior Member

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    I agree #13 needs to be replaced. If you have the time, cycle the pack a few more times (3-4 more times) and retest to evaluate the other marginal ones. Often a few more cycles alone is enough to bring them back. If you'd rather not invest that much time and have the budget for it, replacing them as a preventive measure might not be a bad idea. We can refer you to a couple reputable module suppliers if you would like :)
     
  5. jeff652

    jeff652 Senior Member

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    Thanks, this is correct. It's ideal to step the load down as you get into the deep discharge levels, but we do have customers who miss the change point, and all of them have been fine. When this happens, either switch to the lower wattage bulbs if still discharging or begin charging if done. Continue with the rest of the process as recommended and you should be fine :)
     
  6. Bobakanoosh

    Bobakanoosh Junior Member

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    Alright so I ran into what I think could be a big problem. I got off work and set up to discharge with 2X 200W bulbs (first discharge cycle). I had an emergency and had to leave, and forgot to drop the bulbs to 25w before I left. When I got back the pack was at 15V. I immediately unplugged the bulbs and plugged in the charger. What are the chances that I caused some serious damage to my pack?
     
  7. jeff652

    jeff652 Senior Member

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    very low. We have had several customers accidentally do this. We accidentally did it ourselves a couple times. In all cases, after charging and balancing the pack, they recovered fine and showed no ill effects. If you continue with the three cycle reconditioning as recommended, you should be fine as well. :)
     
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  8. Bobakanoosh

    Bobakanoosh Junior Member

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    Well that makes me feel better! Thank you! I'm charging it back up right now and hopefully by the time I get off work today it's ready for a discharge. Should be back on the road Monday!
     
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  9. MtBiker

    MtBiker Junior Member

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    Thanks for the reply, Jeff. I assume you meant #15 needs to be replaced instead of #13.

    I didn't have time for additional testing so I ordered a used module from a supplier recommended by the HA representative I spoke with on the phone when I called about the replacement multi-meter for my Simple Discharger. I've already received the meter and the module is scheduled to arrive today. I'm going to disassemble all the modules and reassemble them according to their load deltas, with the highest deltas toward the outside of the pack (best thermal transfer) and the lowest deltas will be in the middle (worst thermal transfer) with all others assembled accordingly based on their delta.

    My thought is, based on my chart above, the modules get, and stay, hotter longer the farther inside the pack they are located. Hence, this may be why #15 went tango-uniform first and why the other middle modules, for the most part, have higher load drop deltas. I'll take the modules that have been subjected to the most heat over their life and move them out toward the ends of the pack, in the order of their deltas, with the hope they will now stay cooler and, thus, help extend their remaining life.

    I'll perform the same load test on the module that arrives today and assemble it in the pack based on it's results. I will, of course, ensure the correct polarity for each of the new module positions matches the original polarity and the sense wires on the bottom are replaced in the original positions. I'll then run a complete 3-cycle reconditioning, re-run the load test on all the modules and, if all looks good, put things back together to the point I can perform a road test.

    What a way to spend a Memorial weekend!
     
    #149 MtBiker, May 27, 2016
    Last edited: May 27, 2016
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  10. SFO

    SFO Senior Member

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    First let me say how glad I am that Steve left this thread up for the rest of the PC community- needless to say he is missed by many of the regulars here :( .

    Does anyone have additional grid charger/discharger updates, quantitative of otherwise that they would be willing to share?
     
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  11. WilDavis

    WilDavis Senior Member

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    I posted the results of my use of the Prolong equipment over the past two years (2 full 3 phase cycles and 3 and 4 quickies) (see threads passim) and I'm planning to do another full recondition at the end of June. At the moment, the overall fuel consumption is in the mid-40s, the best ever is 59, and the SoC spends most of it time in the high-60s (best I've seen is 81%) since I started using the Prolong Grid Charging stuff. - hope this helps - Wil :)
     
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  12. tvpierce

    tvpierce Senior Member

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    What was your overall fuel consumption before using the Prolong charger?
     
  13. Brad wije

    Brad wije New Member

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    Why cant we do the full discharge by cutting the power to the engine and pressing the ON button until with full AC the battery shows last line discharged? .
     
  14. srellim234

    srellim234 Senior Member

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    If the cells are imbalanced to any extent, discharging any of them too low can reverse polarity in an individual cell that isn't quite up to par. It helps to be able to read actual and accurate numbers telling you where your discharge is really at. Waiting for the bars to disappear is kind of like reacting to the idiot lights on the dash to come on. When the oil light comes on or the engine too hot light comes on damage has already been done to the engine, often times major damage.

    I would think that the method you ask about runs a high risk of actually killing your battery.
     
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  15. jerrymildred

    jerrymildred Senior Member

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    On top of what @srellim234 pointed out, you would discharge the HV battery way too fast with that much load. As the voltage drops, it's essential to lower the current. You'll notice, using the light bulb discharger that as you approach the bulb changing voltage, the voltage starts to drop more quickly. If you don't change them, it will plummet and you'll reverse a cell before you know it.
     
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  16. jdenenberg

    jdenenberg EE Professor

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    Just in case the above two warnings are not enough, reversing a cell destroys it (it becomes a short circuit) and you will have a permanently failed module that reads 1.2 volts lower than the other modules.

    JeffD
     
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  17. dolj

    dolj Senior Member

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    If it worked we would do that rather than invest $700 in a charge/discharge system.

    Simply, it does not do anything useful and will not work. End of story.
     
  18. Prodigyplace

    Prodigyplace Senior Member

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    The ECUs will only discharge the pack to 20%, IIRC.
    The reconditioning process carefully discharges lower that the Prius allows and charges above the 80% level the Prius allows. that extended careful charge & discharge is basically the "secres sauce" of the Prolong reconditioning system.
     
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  19. jerrymildred

    jerrymildred Senior Member

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    Lately, we've seen a few people pretty seriously drain their HV batteries by continually trying to start an engine that won't start. I suspect that one could pretty thoroughly destroy the battery that way. I'm just as open to correction as to confirmation if I'm wrong about that.
     
  20. dolj

    dolj Senior Member

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    Fairly sure you're correct. Read of more than a few accounts where a reasonably new (5 yo maybe?) battery was destroyed by the driver running it down driving it to the next gas station in an out of gas situation. The Gen 2 will run it flat in an out of gas event.

    Read of a few too that got away with it.
     
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