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Can the Traction Battery Health be Estimated ?

Discussion in 'Gen II Prius Main Forum' started by SageBrush, May 1, 2012.

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  1. SageBrush

    SageBrush Senior Member

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    Our G2 Prius has about 150k miles on the odometer and continues to be rock solid. However, since it is used in an environment that is likely more stressful than average, and my away-from-home daughter may adopt the car sometime in the near future, I am wondering if I can gauge battery health and perhaps take action to avoid a precipitous email in the future.

    My first thought is to use a reader to meter the voltages of each module pair when the battery SOC has been drained to low to identify weak modules. This is just a WAG, and I am hoping our collective wisdom and battery experts can help come up with a decent test.

    Decent would mean:
    Battery stays in-situ for the test;
    Metering equipment costs < $100;
    Both single module and diffuse wear patterns can be identified;
    Test able to identify with > 90% accuracy, battery that will likely fail within six months.

    Thanks all!
  2. jdcollins5

    jdcollins5 Senior Member

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    With the SGII rev 4.05+ we have been able to begin reading the battery module voltages, resistances, plus overall battery temps and battery fan air temps in the Gen III. I do not know that anyone has been able to figure out how to do this on Gen II.

    According to the Gen III Repair Manual, the Battery ECU does a pretty good job of monitoring these battery parameters and reporting any discrpencies. I would think that the Gen II had similar diagnostic monitoring and reporting.
  3. DaveinOlyWA

    DaveinOlyWA 3rd Time was Solariffic!!

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    Sure it can, but might be difficult since its never fully charged or discharged. On the Leaf; the rumor is that it must be discharged to under 20% SOC to determine an accurate level. what many Leafers have done is installed an aftermarket SOC meter that measures "GIDs" a which is a unit equal to 80 Wh. a "fully" charged Leaf is 281 GIDs (in this reference, full charge is actually what is "seeable" by us. this works out to be 22,480 Wh out of a possible 24,000 Wh or 24 Kwh battery pack. the Contactors drop out at 4 GID which means that we have about 277 GID or 22 Kwh to use. Turtle mode happens around 21½ Kwh)

    now the theory behind the meter is its ability to measure the stored charge which should allow one to measure the degradation as it happens which means that a battery that only gets to say 253 GID will have lost 10% of its range.

    to date; there is one Leafer who has experienced a loss of range and its highly likely it came from dealer that way. it was a demo and some theorize that the Dealership kept it at full charge for extended periods of time which is not recommended in order to have Leaf ready for any test drives.

    we have a Leafer in WA who have exceeded 36,000 Miles in 11 months (probably near 40,000 by now) and has no degradation showing so far and he drives right to his range limit TWICE a day

    Happy May All!!
    Prelim Stats for April; Prius went 1386 miles at a cost of $121.76 and averaged 47.8 MPG. Leaf drove 1347 Miles at cost of $33.12 and averaged infinite MPGs!
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  4. David Beale

    David Beale Senior Member

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    You can take the car to a dealer and have them read out and print for you the battery module conditions. It can give you a good idea whether one or more modules is "drifting" with respect to the others. This drifting would be the start of the road to failure.

    Should cost less than $150.
  5. HaroldW

    HaroldW Active Member

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    Sounds like a Leaf may be the way to go for commuters, Dave? H
  6. SageBrush

    SageBrush Senior Member

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    Thanks, David.

    What information is provided on each module ?
    Can I read the same info with a scangauge or the "torque" app ?

    Perhaps I should run this test during a drive up and down a hill ?
  7. ccdisce

    ccdisce Active Member

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    I do not mean to change the direction of this thread.

    The Priidash 'shareware' does some battery monitoring so you may want to check into the PC postings and the Forum that has been set up by 2009prius. He made a posting a few months back on interpreting the results.
    You will need to get Cygwin-X running on a Laptop in addition to high speed OBD2 scanner.
  8. usbseawolf2000

    usbseawolf2000 HSD PhD

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    With Torque app, you can view the voltages of all 14 battery blocks (a pair of modules).

    There is Delta V that shows the difference in voltage between Min and Max block voltage. The best thing about Torque app is, you can view the data in realtime graph.

    On my 06 with ~160k miles, I usually see 0.1V to 0.3V difference. I believe the threshold to trigger CEL is 1.2V. If one of your module is weak, the voltage delta will be high.
  9. seilerts

    seilerts Battery Curmudgeon

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    Cheapest method is Priidash + road test. Try to count Coulombs during a continuous discharge. Open circuit voltage is completely uninformative unless the battery has sat for a few weeks.

    A more thorough test would be to put the entire assembly on an HV charger. Charge the battery until the first modules begin to heat up. Discontinue charging, and let sit for 30 minutes. Then, discharge through a current meter at 6.5 +/- amps until the lowest module hits 6.0V. If you record more than 4 amp-hours, the battery should last for 6 months, barring a random failure of 1 cell in 1 module.
  10. SageBrush

    SageBrush Senior Member

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    Thanks!

    I wish I was not such a dope about electricity. Does a low block voltage identify a weak module ?
  11. SageBrush

    SageBrush Senior Member

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    Is this still true if the monitoring is during a road test that fills and depletes the battery to green and purple (bars) SOC ?
  12. usbseawolf2000

    usbseawolf2000 HSD PhD

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    A block = 2 Modules = 12 Cells.

    If you know a block with weaker voltage, it could be one or both of the module. At least you'll know which of the two modules to look at.

    Monitoring in everyday driving in realtime may not be as accurate but I think I should be able to tell if a module start to get weaker.

    Since your daughter is driving the car daily, perhaps you'll need to do an extreme road test in EV mode.
  13. uart

    uart Senior Member

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    I've got a question about Pridash if anyone could please give me a quick answer. Currently I don't have a scangauge or OBD scanner of any type.

    Question: If I get a generic OBD2 scanner then can I use Pridash with any old laptop running Linux or Windows XP + cgiwin?

    Presently I've got nothing and I was thinking about soon getting a "scangauge 2". Would I be better off to get a generic OBD2 scanner and a run Pridash?

    Thanks. :)
  14. usbseawolf2000

    usbseawolf2000 HSD PhD

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    Not sure about generic one but OBDLink SX works with PriDash. It plugs into computer with a USB cable. It is about $50.
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  15. Britprius

    Britprius Senior Member

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    Uart I run Priidash with a cheap elm327 rip off (£9 UK Ebay) unit and a 14year old IBM thinkpad running windows XP. There is a windows version of Priidash so no need for cgiwin but you do need service pack2 or higher. My device will only run up to 500k baud but a device that will run at 2g would be better. I am really impressed with both the dashboard and the logging facility.
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  16. uart

    uart Senior Member

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    Ok thanks, that sounds good. I'll check the price and availability of that one and the one usbseawolf mentioned and go from there. I've got a couple of old laptops I could use (around the P3 1GHz or early P4M 1.5 GHz vintage I think). Is USB2 a must? I think the P4M one has USB2 but the other's got the older slow USB.

    I don't have any objections to loading one up with linux, but if it can run on XP-sp2 then that's all the easier for me, because that's what they'll currently be running. :D
  17. Britprius

    Britprius Senior Member

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    USB is really a must have but mine is the early standard, so either will be fine and as I said before cygwin is not required if you use the windows version of Priidash.

    My old laptop is PentiumII 363MHZ and run Priidash fine.
  18. The Electric Me

    The Electric Me Go Speed Go!

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    I can understand the desire to pre-emptively want to head off battery failure. Especially if handing the vehicle off to a son or daughter.

    But given all the parameters involved in obtaining the "estimate" and then the options even if an estimate is obtained?

    Seems to me the best approach is the old "If it aint broke, don't fix it" approach.

    As potentially troubling as it might be to get an E-Mail from a daughter suddenly stranded by a failed traction battery, and as daunting as immediately having to deal with that reality might become?

    That "type" of risk happening exists with any and all vehicles that approaching that age and mileage.

    Transmissions can fail, starters...engines...

    I guess my vote, is hand the vehicle off to the daughter, with the understanding that you are handing her a Prius with higher miles, and battery failure risk attached.

    In general it seems there are some warnings when failure becomes imminent, so I don't define it as a safety risk.

    In the meantime, trying to head off battery failure before it happens? Doesn't seem worth the effort.

    Once a battery has aged....it simply becomes at risk for failure. You could replace modules...but that's no guarantee other modules wouldn't start to fail.

    I kind of think...you simply ride the horse...as long as you can ride the horse. Then make a decision when the reality manifests.
  19. usbseawolf2000

    usbseawolf2000 HSD PhD

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    True. Trying to figure out the health of the battery may cause some damage. That's why I prefer to monitor it in my normal driving.
  20. jdcollins5

    jdcollins5 Senior Member

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    Agree. I have monitored mine mainly just to get an idea of what is "normal" so that if I do have any battery issues in the future I know how to recognize what is not normal.
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