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Mountain Driving Trip Report 66.8 mpg

Discussion in 'Prime Fuel Economy & EV Range' started by Mark McIntyre, Jul 10, 2017.

  1. Mark McIntyre

    Mark McIntyre Member

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    We just took our PP on a multi-day, multi-pass, mountain road trip from Boulder to Crested Butte. We began with a full charge on the traction battery (TB) on the first day and I experimented with driving in HV mode while still having the battery fully charged and switching from HV to EV on climbs and descents.

    With little TB charge left I filled up and drove several hundred more miles without plugging in at all. For me, the strategy that seemed to work best was to drive in HV mode as a default. Before reaching a long climb I would put it into forced charge mode to fill the TB to it's capacity (which seems to be 25.2 miles of range when charging via the ICE). Once on the climb I could see that the car was using both the ICE and the TB. Nearing the top of a pass I would kick it in to EV mode. The TB would be mostly depleted at the top and then it would recharge on the descent.

    I had plenty of power for the climbs and the car performed great overall. As I returned back to town I decided to fill it again since it would be a rare opportunity to check mileage having no plug in charge on that tank. That's where I arrived at the 66.8 MPG. This is using Fuelly. The trip odometer was stating 66.9 - amazingly close to the actual. I think this is phenomenal. Love this car.
     
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  2. xvs

    xvs Member

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    Thanks for the posting Mark. When on long downhill sections I thought I noticed that my battery does not charge above the non-EV line on the charge indicator. How do you get it to charge into EV mode using regenerative braking (if you can)?
     
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  3. bisco

    bisco cookie crumbler

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    great trip and write up. talk about putting prime through its paces, congrats!(y)
     
  4. NJ-PrimeAdvanced

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    A couple of quick questions based on this driving report above, so that I can learn:
    1) when downhill driving, do you recharge battery quicker when you switch to EV mode? but wouldn't having HV mode and ICE running recharge even more as the power from ICE would not be needed for propelling the car forward and thus it would be used to charge battery mode?

    2) does having B mode on when driving downhill help in recharging the battery quicker /or/ is it that its only advantage is that it saves your braking pads by using engine braking power and makes downhill driving easier (as in a non-hybrid car)?

    3) when going uphill, of course use HV mode to have more power (ICE+Electric Engine), but do you get any additional advantage of having some of your 25-mile EV range still remaining in that more battery power can be used to assist in hill-climbing or will the HV mode manage well-enough on its own (ie: when 25-mile range is fully used up)? I guess my question is when I know that I will be going uphill, should I make sure that I still have a few miles left in my EV range? (this is what the OP was aiming for when using the CHG mode for 20+ miles prior to the hill?)

    4) I get that HV is usually recommended during highway driving and EV during city (or slow-moving traffic) driving... however: it looks like most people when they have a full charge, will use up the full 25 mile EV range first by driving exclusively in EV mode and then automatically go into HV mode, and then not being able to back into EV until a recharge.. but it sounds like a better strategy is to switch manually to HV as soon as you're on a highway (>60mph) even when still fully charged, to be able to save the 25-mile range battery for when entering a city later on? (of course if you're only doing city driving, then stick with EV all the way, but if your commute is a mixture of city and highway and is more than 25 miles, then why deplete your EV range completely by doing EV exclusively until it runs out?)

    5) does using the CHG mode a lot cause any damage to either the battery or the engine? should you use it sparingly or no real issues using it a lot (eg when you don't have access to a charger at home or work and want to use EV a lot in city driving).

    Thank you kindly for any answers so that I can learn. I realise it's a lot of questions, but I'm new to this :)
     
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  5. heiwa

    heiwa Active Member

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    It is an amazing car! I just drove about 280 miles with one charge, part of which included some up and down hills on CA Hwy 20 from Williams to Fort Bragg. Average of the day was 73.3 MPG on the display. I had 7 miles of EV range left when we arrived at the destination because of regen despite my efforts to use it up.

    Posted via the PriusChat mobile app.
     
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  6. Mark McIntyre

    Mark McIntyre Member

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    Good questions. Will try to reply but don't have all the answers.
    1. I think that the recharge rate is the same on descent in HV or EV mode. The ICE was not kicking in while descending, even if I was trying to do a forced recharge. The TB can only handle so much as a recharge rate. I would switch back and forth between D + braking and B without braking depending upon the grade.
    2. I think the answer is yes - to both. B saves brake pads and does, slightly, accelerate recharging. If I began to slow to a pace that traffic behind me was catching me I would switch back to D.
    3.My experience is that there is a distinct drop off in power when the TB is depleted (to the 20% level) vs. having some EV range present plus the ICE kicking in on a climb. If I want to climb quickly (and I do, I always have my car in Power mode) then having some EV range showing while in HV mode is very advantageous.
    4. I think the strategy you have outlined is best. If I know I am going to exhaust my EV range on any given day on a trip, then I would begin in HV mode and use the TB as reserve for driving in a town that I am passing through or for a climb that I know I am going to make. I find the performance hit to be... disappointingly large if I have no TB left beyond the 20% reserve.
    5. I don't know but I would suspect that the Toyota engineers would not allow a mode that would infact damage the TB. But I will say that the TB charges at an amazingly fast rate in either Forced Charge Mode or descending compared to just plugging it in.
     
  7. heiwa

    heiwa Active Member

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    I am no expert, but many on PC have mentioned on similar thread that B on HV mode is less efficient because it uses engine break to slow the vehicle. I would use HV mode while ascending, and EV mode while descending. DRCC worked just like people have reported while descending and required no B mode to controle speed on the road ways that had wide sweeping turns. However, as soon as the turns became tighter, I had to switch off DRCC and GO manual. The rate of charging while descending felt much more effective compared to PIP.

    Posted via the PriusChat mobile app.
     
  8. NJ-PrimeAdvanced

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    So reading the thread, it looks like putting the car into EV mode when going down a long hill is the current consensus as it maximises recharging the battery, but I found this in another thread, which actually recommends EV Auto instead of EV:

    "Once again it is the little things that make a big difference. Like when I discovered that EV Auto going down a mountain would bring the ICE on during the short uphill stretches, but my EV range went crazy(85 miles of travel used 24 miles of EV range). 7000 feet of elevation drop can be turned into quite a bit of EV range by this car when use the right modes."

    Sounds like "EV Auto" gives you the best of both worlds in that it prioritizes EV, but switches on the ICE when it can be advantageous?
     
  9. Lee Jay

    Lee Jay Senior Member

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    Power mode doesn't give you any more maximum power, just a touchier throttle pedal.
     
  10. heiwa

    heiwa Active Member

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    I have driven the same path from Williams to Fort Bragg on CA Hwy 20 with both 2014 PIP and Prius Prime 3 years apart. The available power on Prime is noticeably more than PIP's. As my son described PIP as a fat old lady that cannot (no disrespect to "fat" and/or "old lady"). I had no problem maintaining and gaining speed ascending HV ECO mode. Per the energy indicator, the car was using both ICE and EV during ascent. As someone said elsewhere, "Just drive" appears to be sufficient to gain an amazing efficiency. I'm impressed!

    Posted via the PriusChat mobile app.
     
  11. Mark McIntyre

    Mark McIntyre Member

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    Understood. I do drive in power mode almost all the time. I would rather be light in my foot than have the car make me be a pedal masher.
     
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  12. Oniki

    Oniki Active Member

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    I'm skeptical about the regen argument but depending on the decline slope EV can be advantageous for low kW driving where the drivetrain is extremely efficient.
     
  13. stevepea

    stevepea Senior Member

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    Having never used the Charge mode (normal SoCal driving doesn't require it), I was curious about what you wrote there.
    (1) How long would you say it took to charge the TB from depleted to full? (while driving, I'll assume)
    (2) You mentioned 25.2 is the capacity when using the charging mode. Do you remember, did you happen to look at the battery icon and see that it was full? Because as we all know, the EV "Range" number can vary from 20ish to 40ish. I guess I'm just asking if the charging "stopped" because it hit the number "25" (which it figures is full enough) or because the TB capacity was actually full, and at your current driving, "Full" just turned out to be "25.2"?
    (3) How much power does it take away while charging? Is it about the same feel as when the car tries to re-charge the battery every once in a while, while driving in regular HV mode? Or does it really pull a lot of power away?
     
  14. priuscatprimeguy

    priuscatprimeguy Senior Member

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    CHG mode only charges the battery to 80% of actual EV range. In about 30 minutes