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Cruise Control vs 'Power Control'

Discussion in 'Model S: Battery & Charging' started by randvegeta, Jan 25, 2017.

  1. randvegeta

    randvegeta Member

    Dec 24, 2016
    I wanted to share my experience with 'long distance' driving and saving energy.

    My office is around 100km away from where I live and I visit that office around 2-3 times per week. My 2014 S 60 has around 250km of rated range at 90% (it's Winter and well below freezing!) so I have enough range for a return trip.

    Lithuania is mostly flat, but there are some low gradient slopes that affects power consumption greatly when Cruise Control is on.

    Baring in mind there is often rain, ice and snow on the road these days, in order for me to make the round trip, I need to limit my speed to around 90-100km/h.

    Before, when I got on the highway, I would just set the speed and let the car maintain the speed, and I noticed that my power consumption would typically sit at around 20kw. When hitting a slight downhill section of the road, the car would regen a little (but only marginally) and when hitting the uphill section moments later, the power would shoot up to 30-60kw!

    Even though the gradients are fairly modest, it seems to make a difference. It seems such a waste to actually apply the brakes on the downhill, which produces only a marginal amount of power, only to then waste it all (and more) on the uphill just moments later. It would make much more sense to actually allow the car to increase speed, and use the momentum to help the car on the uphills.


    Last week I started driving without cruise control and manually control the power output myself. I get on the highway, and stick to 15kw output power (you need a steady foot). My average speed was around 90km/h at 15kw.

    I found that on the downhill sections, I was able to pickup a good deal of speed (over 110km/h). Uphill, of course I slowed down, but actually the decrease in speed was very slow and gradual. I would normally be able to reach the apex of the hill before dropping below 85km/h. It felt like around 2 - 3 second per km/h of lost speed. Certainly it seemed to pick up much faster on the downhill sections.

    Overall travel time (average speed) was very similar but power consumption was noticeably when controliiing the power, rather than the speed. If memory serves me correctly, I was able to achieve around 170wh/km controlling the power, whereas I would get around 195wh/km using cruise control. So this is around a 12% reduction in power for the same distance at pretty much the same average speed.

    Perhaps Tesla should implement a 'power control' feature as this may be very helpful to improve range.

    Anyone else notice this?
    • Like x 3
    • Informative x 2
  2. widodh

    widodh Model S 85 and 100D

    Jan 23, 2011
    Middelburg / Venlo, NL
    Yes, very much! For true hypermiling you should not use CC and look forward. Driving through hills you can indeed speed up by keeping the power meter around 0kW and have the car pick up some speed.

    Uphill you do exactly as you describe. That way I've been able to get to very low values as well on mu S85 and got over 400km out of a single charge during summer days that way.
    • Informative x 1
  3. mattmass

    mattmass Member

    Sep 1, 2014
    I think a power control could be really interesting! I've often found TACC to accelerate too hard at times.

    I'd also like a low-medium-high option for how aggressively the CC tries to maintain speed. Could be a great tradeoff for reducing power. Double-points if the car took into account the presence of a car behind you, to not annoy people following too much.
  4. ItsNotAboutTheMoney

    ItsNotAboutTheMoney Well-Known Member

    Jul 12, 2012
    That is what hypermilers call Driving With Load (DWL). It's an efficient way of driving. It's not absolutely _the_ most efficient way of driving, but it's easy to do and you can have opportunities to do it as long as you don't always have someone behind you.
  5. GSP

    GSP Member

    Dec 28, 2007

    @jerry33 has consistently lowered his engery consumption by not using cruise control with his Model S, and his Prius before that.

    So others have also noticed this result.


    PS. Welcome to the hypermiling club. :)
  6. gavine

    gavine Petrol Head turned EV Enthusiast

    Apr 1, 2014
    Southern New Jersey
    I wanted this in my wife's Buick Enclave. That thing would downshift 2 gears on slight grades just to maintain speed when I would have been perfectly happy to lose 2-3 MPH and stay in 6th gear. Basically, the thing panicked as soon as the speed dropped a little and would practically floor it to would awaken sleeping passengers! I would have to manually drop the CC speed on hills to avoid this downshift. So nice not having to deal with this anymore (Model X).

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