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Does cool weather effect HV-batt capacity much?

Discussion in 'Gen 2 Prius Technical Discussion' started by uart, May 22, 2012.

  1. uart

    uart Senior Member

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    I posted recently about how my traction battery seems to be showing some signs of weakness by filling to 8 green bars mach more rapidly than it used to do. See: http://priuschat.com/forums/gen-ii-...ndications-hv-battery-weakness-91k-miles.html

    Since we're now approaching winter here in the southern hemisphere, I'm just wondering how much the cooler temperatures might be influencing this?

    Not that it's exactly cold btw, I'm really only talking temperatures around 50F to 55F here.
     
    #1 uart, May 22, 2012
  2. qbee42

    qbee42 My other car is a boat

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    I see that with my 2006 Gen II. With cold weather, the main culprit is increased operation of the ICE to make heat. When the ICE is running, it generally produces some charge, so the battery SOC gets on the high side.

    I see it more than I did initially, which I attribute to some reduction in battery capacity. I wouldn't worry about it unless the SOC begins to swing quickly from one extreme to another.

    Tom
     
    #2 qbee42, May 22, 2012
  3. uart

    uart Senior Member

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    Sorry Tom I should have pointed out that I'm not even using any heat yet. Like I said it's only 50F to 55F, so nowhere near freezing.

    This is strictly a regeneration issue, as in when I regenerate down a hill it fills much quicker than it used to. I'm pretty sure my battery has lost some capacity, but just clutching a straws really to wonder if the slightly cooler temperatures are maybe just a part of the issue.
     
    #3 uart, May 22, 2012
  4. tdelker

    tdelker Junior Member

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    I have had my 2004 for a little under 4 months here in Colorado. I never saw green bars until just very recently when the temperature is warmer, so it actually seems to be that warmer temps decrease the capacity, or warmer temps allow for more recharging? Just my observation...

    Tom
     
    #4 tdelker, May 22, 2012
  5. jdenenberg

    jdenenberg EE Professor

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    The HV battery warms up quickly in use (power dissipated in the effective series resistance) so I doubt that the cold(er) weather is an issue. It's time to attach a good tool to the OBD2 connector and read out the module pair voltages and resistances to see if your battery balance is deteriorating.

    JeffD
     
    #5 jdenenberg, May 22, 2012
  6. bisco

    bisco cookie crumbler

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    50-60 degree weather is perfect for me. no heat and the car seems to love it. of course, 70's may be better for engine warm up time. anything higher and i've got the a/c on.
     
    #6 bisco, May 22, 2012
  7. uart

    uart Senior Member

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    Yeah good idea Jeff. I don't have one at the moment but it's something I've been thinking about getting. Looks like I'll have to get one soon.
     
    #7 uart, May 22, 2012
  8. qbee42

    qbee42 My other car is a boat

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    You don't have to use cabin heat; the ICE runs to heat itself and the catalytic converter.

    However, if you are just seeing it during regeneration, it is probably diminished capacity in the battery. The temperatures you describe should improve battery capacity, not hurt it.

    Tom
     
    #8 qbee42, May 22, 2012
  9. uart

    uart Senior Member

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    Yeah that's true. I haven't noticed this problem in previous winters, so it has to be the battery capacity.

    Actually the car is still running great and getting very good MPG. If I didn't live in a hilly location I guess you'd hardly even notice it. It more or less feels like the first six bars are behaving as normal, but the seventh bar is very much reduced and the eight bar virtually non-existent (in terms of the energy it takes to fill them).

    Today for example I was driving down a long hill that's not very steep, no braking but just a bit of simulated engine braking at about 45 MPH. I drive this regularly and normally this hill wont even get it to 7 bars (starting from 6), but today it took it to 8. And the funny thing is that I was watching the SOC closely to see if it would hit 7 bars, and nearly at the bottom it was still on six. Then I had to stop at a red light at the bottom, only from 40 MPH, and just that last bit of regeneration took it to 8 bars (from 6). Heck, I didn't even see the 7th bar come up. I'd already decided it wasn't going to get past 6 bars and took my eye off it for 20 seconds as I slowed down. After I stopped at the lights I looked and to my amazement it had risen to 8 bars (from 6) on what I'm estimating cant have been more than about 70 W-hrs of energy. Something is definitely wrong with that.
     
    #9 uart, May 22, 2012
  10. bisco

    bisco cookie crumbler

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    you probably would benefit from a scangauge, but wouldn't a weak battery affect mpg's? we just sold our 04 with 94K and i don't know about the battery, but it was still getting the same mpg's as new.
     
    #10 bisco, May 22, 2012
  11. uart

    uart Senior Member

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    No, it doesn't necessarily affect MPG that much. Everything works exactly as normal except the 7th and 8th bars don't seem to store as much energy as they used to. It does mean that decending large hills you might lose a bit of energy that could otherwise have been stored, but this alone doesn't seem to have much impact on overall the MPG.
     
    #11 uart, May 22, 2012
  12. seilerts

    seilerts Battery Curmudgeon

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    It is quite likely that you can nurse another year or two out of your battery, maybe more. When you find a regular oscillation between 1 bar and 8, combined with lower MPG, you'll know that failure is right around the corner. I think a quick jump to 8 bars is a sign of SOC error, where the computer sets the level by current@voltage@temperature lookup table, rather than Coulomb counting.
     
    #12 seilerts, May 22, 2012
  13. wjtracy

    wjtracy Senior Member

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    I recently made a similar post: seeing the GREEN much more now at 100K miles. One possible "cause" in my mind was installation of Optima battery. The other possible cause was running the ICE for heat in the winter. Not seeing GREEN anymore now that air cond is on more often in the warmer weather. So A/C really is a major factor. If A/C off all the time then GREEN is SEEN.
     
    #13 wjtracy, May 23, 2012
  14. finman

    finman Senior Member

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    our 2004 and 2005 (both 110,000 miles) are showing no such issues. must be the nice runs to the coast and back (53 MPG average for these trips)...130 miles roundtrip with a start of 200 feet all the way up to 770 feet, then back down to sea level. repeat for the return trip. 60s and 70sF temps, 2 passengers, no real cargo. Some green bars but mostly blues in the middle. gotta love it! it's those pesky short 4 mile trips that seem to hurt MPG. and the rain. about 46-48 MPG then. It's all good though.
     
    #14 finman, May 23, 2012
  15. qbee42

    qbee42 My other car is a boat

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    Argon Labs did serious testing on the Prius and found little reduction in mileage with half battery capacity. Toyota planned for degradation.

    Tom
     
    #15 qbee42, May 23, 2012
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