Mountain Driving Net Gain On Battery Charge

Discussion in 'Clarity' started by K8QM, Sep 10, 2018.

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  1. K8QM

    K8QM Active Member

    The following is totally unscientific and (as always) YMMV.

    We just returned from a trip to the mountains and while there I noticed an interesting phenomena. We arrived at Roan Mountain State park in Tennessee with just over 50% charge. Since there were no charging facilities available we did all our driving in HV. When we left the park two days later our charge was just under 100%.

    We had two drives to Johnson City, TN which were each about 30 miles that did not seem to have any appreciable in charge however what did make a difference were our three trips to Carvers Gap.

    The trip from the State Park to Carvers Gap is roughly 8 miles with about a 2,500 foot elevation change. The speed is 40 but the nature of the road means much of it is driven below that speed. On the way up the mode was constantly switching from using battery assist to ICE only and the bees were present (I did shoot a video of that). On the trip down we basically used the regen paddles to control our speed in all but the sharpest curve. It was clear to see on the battery display the increase from each trip.

    So, at least on this particular road less battery assist is used getting up the hill than regen is available coming down. Although not surprising that there would be a net gain I was surprised that 24 miles over two days was enough to see a difference.

    Now time to prep for Florence which is making a beeline for Raleigh. Good luck and safe travels for anyone else who has to deal with this one.


    BTW I knew I could charge in Boone, NC so I made good use of my gravity powered battery!
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  3. weave

    weave Active Member

    So you were in HV mode the entire time? We've pretty much figured that when in HV mode it tries to maintain the current battery charge, like if it drops below a bit it will charge a bit from the engine. Probably when doing mountain driving it messes up its normal assumptions and with a lot of regenerative braking it slowly builds the battery up. What's surprising is it doesn't switch to EV mode for a greater portion of time to let it settle back to its baseline.
  4. K8QM

    K8QM Active Member

    Yes on the HV and agreed about the maintaining charge. On the two longer trips during the weekend (30+ miles) we had no net change in battery charge level as is typical and the car cycled through different modes as we drove. My two guesses about why the car never went EV only on the three trips up the mountain are that the grade started within a mile of starting the trip so the battery was almost immediately being drained to assist the climb and/or with the grade being 6% (or greater) the algorithm considered the power demand too great to switch to EV only.

  5. Viking79

    Viking79 Well-Known Member

    Lifting a mass of 4500 lbs 2500 feet is a potential energy of about 15,242,608 J, or 4.23 kWh. The car can't regen all of that, but can get up to maybe 60% depending on speeds and such.
    Last edited: Sep 11, 2018
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  6. PHEV Newbie

    PHEV Newbie Well-Known Member

    Your experience confirms my experience on a mountain grade near my home. I've mentioned the experience on another thread but I'll repeat it here with your experience as context. In HV, when I have ample battery charge (I had said greater than 50-60% but maybe that should be >60%), the car combines ICE and battery to power me up that grade with ample power and no "angry bees". I can easily keep pace with the speediest vehicles in the left lane here. With a lower battery charge (I had said <40% but perhaps that should be <55%), I find the car relying entirely on the ICE to generate electricity while maintaining the charge in the battery. That is very unpleasant with very high revving and the little engine just can't provide enough electricity on its own to provide much speed. I ended up behind the semi-trucks in the right lane going a snail's pace when this happened (left lane cars going 60 mph up the hill, which would be no problem in the first scenario). Lesson is, if you're on a road trip, keep your battery topped up in case of major uphill climbs. Do not ever let your battery get depleted unless you know you're going to stay on the flats.
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  8. K8QM

    K8QM Active Member

    We've had a lot of trips to West Virginia and Virginia and I always leave 50% battery for the mountains which has always been enough except for one visit to Shenandoah National Park when I got the angriest bees I've ever had!

  9. K8QM

    K8QM Active Member

    Thanks for adding the math! (3x4,23) x.6 =7.614kW over the 3 trips which is about half a charge.

  10. weave

    weave Active Member

    I live near Skyline Drive. Are you aware they have some electric charging stations along the road? Like at Skyline and I believe Big Meadows.
  11. K8QM

    K8QM Active Member

    Absolutely! We stayed at SNP two weekends this Summer and took advantage of both charging stations! I was shocked that we only had to wait our turn one of the four times we charged.

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