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Green Battery on MFD

Discussion in 'Gen 2 Prius Technical Discussion' started by CrazyLee, Nov 23, 2014.

  1. CrazyLee

    CrazyLee Member

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    II
    Lately I have been getting 7 bars and all green. It has become easier to achieve this condition. A few times I have gotten 8 green bars.


    If I start out with 6 blue bars on the battery it would quickly turn green. By hypermileing and long slow stops seems to make it happen. This is usually happens when I'm in town and driving 30 to 50 mph.


    I used my Mini VCI to monitor the battery as shown below. I had green bars when I drove into my driveway. I turned off the engine (IG-off) to keep the green bars and hooked up the Mini VCI.


    I had to charge up the battery by holding the brake on and flooring the throttle because it dropped out of the green condition. I decided to see if I could get 8 green bars and I achieved that too.


    The voltage shown is slightly low from the highest voltage because I didn't save it as quickly as I should have. It was over 17 volts for each battery block. What I have shown is sufficient to see the battery condition. The next time I run the Mini VCI I'll do a quick save.


    My Prius is a 2004 base car with 149,900 miles on it (almost half way to the dooms day 299,999). I bought it this summer with over 143,000miles on it.


    I was amazed to see that the battery condition was so good especially since it is going on 11 years of age.


    Last month I drove from my home in Muskegon, MI USA to Lansing MI for slightly more than 100 miles with a green 7 bar battery. It didn't matter if I had the cruise on or not. I didn't see 8 bars on that tip. When I got off the expressway it lost the green and went to blue and 6 bars. On the trip back, I got a green 7 bar battery for a while, but it dropped back to blue for the rest of the trip.



    The Battery controller seems to like green bars, except when I just achieve them. It will go towards exhausting the battery to drive the car. You would expect that. What I found out is if you tease the charging with the throttle you can pump much more energy into the battery. It is tricky at first as the exhaust mode is dominant at first. (The hardest part is watching the traffic on the road, since I found myself gawking at the MFD constantly!) I found by quickly accelerating and the releasing the throttle you can get the flow arrow to turn from orange to green. Then by holding the throttle you can keep the green there. Actually there is two modes for this, You will see if you accelerate with a green battery charging and hold that acceleration rate it will stay green too. My mileage is only 33 mpg though. I did see 8 green bars at least twice while doing this. But it didn't last long since the Battery controller dumps the voltage to drive the car.

    About everything I have read is don't keep the green bars, burn them off.


    I don't think that is true. We know that the Battery controller can't charge any more than 80% charge. So there isn't any danger of overcharging the battery. What I see is the battery is getting a better balance. I'll use the highest voltage of 16.91V as a max, and multiply by 14 that gives me the total voltage = 236.74 volts. This isn't an average, just a measure of the voltage to easily see what the battery is getting I'm too lazy to mess with an average since this is just reference.


    As 207 volts is what I have read about in battery voltage as normal, then 236.74 is close to the high voltage. The added voltage trickles down to the weakest cell and builds it up.


    There are 168 cells in the battery pack and the extra 30 volts or so, has to go somewhere.


    What I think is happening is that it brings up all the lower voltage cells to their peak 80% amount. This results in a natural balancing of the cells.


    I think that is true since I usually get a green 7 bar battery often, even as many as three per day, just driving around town on errands. I have observed that is happening more often as well. I think this means that the battery is improving.


    Maybe there is a better explanation.


    I'm not an electronics engineer trained in battery science either.

    I did work in the electronics business repairing TV's for over 35 years.


    Battery Voltages and Internal Resistance


    Battery Block Vol -V01 16.85 V
    Battery Block Vol -V02 16.90 V
    Battery Block Vol -V03 16.85 V
    Battery Block Vol -V04 16.86 V
    Battery Block Vol -V05 16.81 V
    Battery Block Vol -V06 16.90 V
    Battery Block Vol -V07 16.83 V
    Battery Block Vol -V08 16.89 V
    Battery Block Vol -V09 16.86 V
    Battery Block Vol -V10 16.88 V
    Battery Block Vol -V11 16.85 V
    Battery Block Vol -V12 16.88 V
    Battery Block Vol -V13 16.85 V
    Battery Block Vol -V14 16.91 V
    Internal Resistance R01 0.024 ohm
    Internal Resistance R02 0.024 ohm
    Internal Resistance R03 0.024 ohm
    Internal Resistance R04 0.024 ohm
    Internal Resistance R05 0.023 ohm
    Internal Resistance R06 0.023 ohm
    Internal Resistance R07 0.024 ohm
    Internal Resistance R08 0.024 ohm
    Internal Resistance R09 0.024 ohm
    Internal Resistance R10 0.024 ohm
    Internal Resistance R11 0.024 ohm
    Internal Resistance R12 0.024 ohm
    Internal Resistance R13 0.023 ohm
    Internal Resistance R14 0.024 ohm


    Happy Hypermileing
     
  2. wjtracy

    wjtracy Senior Member

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    Yes we are in the green all the time in cold weather the heat makes the enigne run and you get more green days. In the summer the A/C takes you down a notch
     
  3. Aaron Vitolins

    Aaron Vitolins Senior Member

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    Quick question, once my car reaches 8 green bars, it stays there for a little bit then it seems to just dump the battery till about 5 blue bars. Does yours do the same? I know it trys to burn off that extra bar quickly, but it seems to always do to much. It never does that if it's only at 7 bars, it stays at 7 awhile until it slowly goes back to 6 bars. Thanks!
     
  4. Tony D

    Tony D Active Member

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    Mine does the same, especially in Winter when the ICE is running more. I see green bars every morning on the way to work, none on the way home due to incline all the way home
     
  5. bisco

    bisco cookie crumbler

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    sounds like your hybrid battery is on the way out.
     
  6. Aaron Vitolins

    Aaron Vitolins Senior Member

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    Words of encouragement from Bisco... Lol!
     
  7. bisco

    bisco cookie crumbler

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    i call 'em like i see 'em.:cool:
     
    Aaron Vitolins likes this.
  8. Tony D

    Tony D Active Member

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    No beating around bush there alright Bisco!
     
  9. uart

    uart Senior Member

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    Hi Aaron. Myself and several other members have this same issue, I have written several posts on exactly this topic. Anyway, the quick explanation is that your battery has lost some capacity and its coulomb counting is a bit out of whack.

    The more detailed explanation is that when it reaches near full state of charge, the battery controller detects this and sets the coulomb count to reflect this state. (BTW, Coulombs are just the unit that charge is technically measured in.) So then as you use this charge the coulomb count reduces steadily, and the SOC slowly reduces accordingly.

    If however your battery has reduced capacity then it reaches a low state of charge sooner than the coulomb counting predicts, and when the battery controller detects this then the coulomb count effectively has to be recalibrated. In other words, the battery controller eventually recognises that the SOC is lower than expected and starts adjusting its value accordingly. This is where you may see one or more bars of SOC get wiped out unexpectedly quickly. Some of us with this issue see the SOC (bars) continue to fall even while the engine is running and the energy monitor display is showing green arrow into the battery.

    I don't think this means that your battery is necessarily just about to die or anything. Mine has been like this for about 3 years and over 90,000 km, but is still hanging in there. It might be a plan to try and minimise the number of occasions that you get these full 8 green bars though. I find that using "B" mode on moderate descents can help.

    TBH I think a lot more people with somewhat aging Priuses probably have this issue than what is reported. Most people just don't look at what's going on with the SOC closely enough to notice something subtle like this.
     
    #9 uart, Nov 24, 2014
    Last edited: Nov 24, 2014
  10. Britprius

    Britprius Senior Member

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    Your battery health is fine. All green bars is more common in the winter for reasons already stated. In cold weather there is no advantage in burning off this energy as your wasting fuel. The extra 30 volts you are seeing is distributed between the 168 cells, and as such represents 0.17 volts per cell at a charge level of about 80%. Perfectly normal as are your module internal resistances,and for a reference level my readout is below.
    My battery is often at all green bars summer and winter. This is possibly because of the terrain or my driving style, but it is no different from when the car was new "2008" and now has 110,000 miles. Look at the post below and you will see that at 8 green bars on the display the voltage will be at around 17.1 volts for a module pair representing 81% charge at 1.425 volts per cell. At 100% charge "something the Prius does not do" the voltage per cell will be at 1.49/1.5 volts.
    Also below is a screen shot of my battery readout at 55% state of charge.
    Screenshot from TechStream - HV battery aficionados rejoice

    nb.JPG

    John (Britprius)
     
  11. Aaron Vitolins

    Aaron Vitolins Senior Member

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    Thanks guys! Good information, I do have a grid charger and used it a few months ago. Don't have a discharger though. I wish I did, because my battery performance is very good but it has low capacity
     
  12. uart

    uart Senior Member

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    Yeah, but it's nearly 10 years old and yours only sounds slightly reduced. There is such a thing as normal wear and tear, or normal aging. Some of us see the SOC drop rapidly to a lot lower than 5 bars when it's coming down from the full 8 bar SOC, mine sometimes drops to 2. Honestly your issue sounds like it's relatively mild, I wouldn't stress over it too much.
     
  13. Aaron Vitolins

    Aaron Vitolins Senior Member

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    Thanks! Good to know. Probably next year when I have a better paying job I might look in to buying a pack out of a newer prius and installing it. By that time I'll hopefully be at 250k miles
     
  14. Britprius

    Britprius Senior Member

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    If you intend going that route I would advise you to get a battery from a late gen3 and swap the modules. (same size) The gen3 modules have a lower internal resistance and a higher maximum current handling. This means in the gen2 they will be less stressed, and should give an even longer life than the gen2 modules.

    John (Britprius)
     
  15. bisco

    bisco cookie crumbler

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    well, we're all on the way out, in a manner of speaking, aren't we?
     
  16. Aaron Vitolins

    Aaron Vitolins Senior Member

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    That makes sense, do they have more capacity than the g2?
     
  17. Britprius

    Britprius Senior Member

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    No they are same capacity. Adding extra capacity is not as easy as you may think with the Prius. If we could it would be much easier to turn it into an EV just by adding extra batteries.

    John (Britprius)