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Uneven battery use

Discussion in 'Prime Fuel Economy & EV Range' started by Kedavis, Oct 12, 2019.

  1. Kedavis

    Kedavis Member

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    I got a 2019 Prime Advanced a few months ago. I never let the EV battery go dead. I use EV Auto for highway driving and EV for city driving. My gas tank is at 3/4 (or it could be 7/8) after 600 miles. I’ve never filled the tank.
    Tonight I went to a concert a few miles away. It was mostly highway driving. The temperature when I left (after not having driven for a day) was in the 70s. When I got to my destination, the EV battery said 92% (I had charged it fully the day before).
    I came home after a few hours and the temperature was in the 60s. I took the same route on mostly level ground. When I got home the EV battery said 63%.
    How does the same route at roughly the same temperature take 8% one way and 29% the other way? Traffic was pretty much the same each way, although it might have been a bit lighter on my return trip.
     
  2. dubit

    dubit Senior Member

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    To be honest, I'd say what you experienced is not all that uncommon. The same thing happens in a vehicle with a gas engine as well. Even in my own Prius C I see the same thing two or 3 times a week. Multiple factors are involved. Wind direction, heat on or off, the ability to maintain a constant speed vs getting on or off the throttle. Even the smoothness of the pavement. (we have many here that are rock/chip seal) These rock chip roads give me worse mileage than a regular paved road.

    Maybe some Prime drivers can pop in and give you a heads up if they are experiencing this as well. :)
     
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  3. Raytheeagle

    Raytheeagle Senior Member

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    Any elevation changes one way versus another?

    We’re you waiting awhile to get out of the concert?

    I wouldn’t be worried about this as you’ll just charge your Prime back up and you’ll never know what happened;).

    When I do short trips around town, I notice a slight difference in battery charge percentage due to many factors, but I just plug it in when I’m home and then the charge resets:).

    I just drive it(y).
     
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  4. Salamander_King

    Salamander_King Senior Member

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    The same route but on the to and back from usually have quite different driving conditions unless you live totally flat land with no wind. As @Raytheeagle pointed elevation difference is a big factor. Wind direction is another. The temperature difference between the 70s and the 60s is also a factor. Especially for short distance round trips, those variations effect can be some times very big.

    For my routine commute of 18 miles oneway, my morning commute always takes more EV. When I do all 100% EV, it is 60% in, 40% back is usual.
     
    #4 Salamander_King, Oct 12, 2019
    Last edited: Oct 12, 2019
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  5. fotomoto

    fotomoto Senior Member

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    The don't call them "guess o' meters" for nothing.
     
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  6. sam spade 2

    sam spade 2 Senior Member

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    What he said.
    You are putting too much faith in what the "meters" are telling you.
    If you look hard enough you will find other "discrepancies" too.

    Did you get this car to worry about.......or to have reliable economical transportation ?
     
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  7. bisco

    bisco cookie crumbler

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    is the gauge linear?
     
  8. Salamander_King

    Salamander_King Senior Member

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    Comparing SOC % displayed on MID to the real SOC % read by Hybrid Assistance App, it is linear.

    Screenshot 2019-10-12 at 5.10.36 PM.png
     
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  9. bisco

    bisco cookie crumbler

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    why don't you let your battery go dead?
     
  10. NSXT

    NSXT Active Member

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    My situation when I go to work I don't use much EV as I get a lot of downhill and regen quite good. On my way home EV drains fast; ie: uphill.
     
  11. Blue-Adept

    Blue-Adept Active Member

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    Don't worry. So many factors to calculate. Dropping my daughter at school 6 miles away. All downhill. Only use between 5% and 10% of the battery. On the way back up the hills 10% to 18% used uphill for those 6 miles back. Winter. 12 miles will use over 50% of the battery.

    The GOM meter is not linear.
     
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  12. Kedavis

    Kedavis Member

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    So I can use EV driving all the time.
    Looking back at yesterday's trip, I had the A/C, heat, & fan off both ways. It may have been more uphill going home. I spent 3 hours at the concert but when I originally left home the car had been idle for over 24 hours.
    Also, as I mentioned, there was less traffic on the way home so I may have been going faster.
    I am not worried about the difference, only curious.
     
  13. mr88cet

    mr88cet Senior Member

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    He said it was mostly flat ground. I interpreted that to mean no high elevation hanged, but perhaps just few hills?
     
  14. bisco

    bisco cookie crumbler

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    i think you can google the elevations
     
  15. mr88cet

    mr88cet Senior Member

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    Well, he quoted percent numbers, by which I presume he means that he has the MID display showing actual battery percent charge level, in which case it’s not GoM-accuracy question, let alone a “guess” of any sort.
     
    #15 mr88cet, Oct 13, 2019
    Last edited: Oct 13, 2019
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  16. mr88cet

    mr88cet Senior Member

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    Gag! Writing on the fly... Try that again...

    He said it was mostly flat ground. I interpreted that to mean no big elevation change, but perhaps just meant “not hilly”?
     
  17. Salamander_King

    Salamander_King Senior Member

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    I can't find anywhere in OP's comment mentioning road being "flat". Did I miss that comment before he edited, maybe?
     
  18. Kedavis

    Kedavis Member

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    According to Google Maps, the distance was 3.6 miles. The elevation at my home is 112 meters. The concert hall is at 26 meters, meaning I had to go up 86 meters or 282 feet from the concert hall to home. I already mentioned that the temperature was about 75 one way and 65 returning, and the traffic was a bit lighter on the way home. My speed on the highway was 70 mph and on city streets 25 mph (probably 2.6 miles highway and 1 mile city, maybe slightly more). I don't know the wind speed or road composition, but I didn't notice a breeze and I would guess mostly asphalt.
     
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  19. Salamander_King

    Salamander_King Senior Member

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    That elevation difference would result in large difference in EV efficiency. I am not surprised to see almost four times more battery power to come home uphill. BTW, the elevation difference between start and finish can be near zero, but if you have hills in between you can have difference in EV efficiency. Low grade uphill is better on EV, if you have steeper uphill on one way, you will be penalized more.
     
    #19 Salamander_King, Oct 13, 2019
    Last edited: Oct 13, 2019
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  20. fuzzy1

    fuzzy1 Senior Member

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    All Prii are very sensitive to the elevation difference between start and finish.

    I have an empirical rule of thumb that for my Gen3, 10,000 feet of elevation gain (+/- about 15%, depending on load) is equivalent to a gallon of gasoline. I.e. that much climb costs an extra gallon of fuel compared to the same distance on the flats, while that much descent can save a gallon of fuel if it is shallow enough to avoid braking losses.

    With this rule applied to a Gen3, a 0.1% grade will cause about a 5% MPG difference between ascent and descent, at common highway speed. The Gen4 is somewhat more efficient, which causes the underlying math to produce a somewhat wider spread percent. Electric battery use should show a similar difference.

    282 feet in 3.6 miles is a 1.5% grade. This is huge when figuring Prius MPG.
     
    #20 fuzzy1, Oct 13, 2019
    Last edited: Oct 13, 2019
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