Range question

Aptera Community Aptera Discussions Range question

Aptera Community Aptera Discussions Range question

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  • Range question

     Joshua Rosen updated 1 month, 1 week ago 8 Members · 15 Posts
  • Bojan Majdandzic

    Member
    August 16, 2021 at 11:29 am

    I wonder if the mentioned ranges for the battery packs is a theoretical range with battery charge of 100% to 0% or the practical 80% to 20%.

  • Joshua Rosen

    Member
    August 16, 2021 at 11:40 am

    It’s 0-100, EPA numbers are always 0-100. Real world range should always start with 80% of the EPA number to leave room at the top to protect the battery and at the bottom to give you some margin for getting to your destination. You should then derate that number for speed and temperature. They haven’t said if they will have a heat pump so I’d assume that they won’t which means that in winter the range will drop by as much as 40% if you have the heat on. Speed also matters, the range at 75 will be less than the EPA number, if you are on a back road on a perfect day you can beat the EPA number. For example yesterday I did a 100 mile round trip to Jaffery NH in my Model 3, I averaged 199Wh/mile, the EPA number for the 2019 AWD Model 3 is 234. The temperature was 75 so no effort was needed by the AC and I was entirely on back roads which meant that my speeds were between 30 and 45 MPH.

    • John Malcom

      Member
      August 16, 2021 at 1:04 pm

      Good post! All who are configuring their Aptera should take this information into account when picking range, especially where some of these limiting conditions exist for a significant amout of time in a year

    • Bojan Majdandzic

      Member
      August 17, 2021 at 11:24 am

      Thanks!

    • Harry Parker

      Moderator
      August 18, 2021 at 11:27 am

      Good replies here so far.

      The only thing I wanted to add is that charging to 100% won’t significantly harm the battery if it doesn’t sit at that charge level for long. Tesla and others suggest charging to 100% only for long trips where you need the maximum range on that trip and then timing the charge to reach 100% only minutes before you are ready to use the battery. And I’ve heard that there is nothing wrong with running thee battery down to 5% or less IF there is a charger at the destination.

      So getting 90 to 95% of the estimated range is OK for the Aptera’s battery, if done right, and perfectly normal.

      As I live on top of an 800 foot hill, I’d leave some room at the top of the charge so that regenerative braking would top off the battery on the way down for long trips.

      As others have mentioned, driving speed, weather conditions and elevation changes all impact the range. If Aptera’s trip software is as smart as some, it will offer suggestions as to where to recharge and for how long along the way, taking into account all those factors to give an accurate battery usage estimates for particular destinations.

  • Paul Evans

    Member
    August 16, 2021 at 1:04 pm

    I manage to find the question & answer spreadsheet and looked up “heat pump”.

    The answer on line 74 was “yes”.

    • Joshua Rosen

      Member
      August 17, 2021 at 9:39 am

      They hope to have a heat pump, until the production car is announced it’s best to assume that they won’t have one, at least not at first. They are based in San Diego, people who live in San Diego are unlikely to understand how important heat pumps are. Tesla didn’t start putting heat pumps into their cars until last year, my Model 3 doesn’t even have a heated steering wheel. The largest market for EVs is California so they will be able get away without a heatpump for a while.

    • George Hughes

      Member
      August 17, 2021 at 12:35 pm

      Remember Sandy Monro is instrumental in getting the Aptera set for production and if you know anything about it, you know he likes to combine functions. The moving of heat, either away from or toward people and the battery is a critical element in all EVs. The point is it is a central part that determines other parts, all of which are in the process of being specified.

      These folks are now entering production hell as they seek to define the most efficient way to source, manufacture and ultimately assemble this ground-breaking vehicle.

      That the substitution of resistive heat vs. a valve and modifications of the AC compressor would probably have a weight penalty as well, not to mention the re-engineering of other affected parts means the heat pump is almost certain to stay.

  • Fanfare 100

    Member
    August 16, 2021 at 6:45 pm

    I believe those to likely be conservative ballpark numbers. Because it’s always best to under-promise. Bare in mind that there will be other variables which will impact range. An all-wheel drive version will consume more electricity than a 2-wheel-drive one. So, a 2-wheel-drive one will likely rive a further distance than what is advertised to allow for the all-wheel one to achieve the stated objective. Also, if you are using an off-road package it will lower your range. Given the already light weight of the car, if the car is driven by a petite person and their purse it will have a longer range than if driven by a sumo wrestler and their giant duffel bag. Temperatures that are too hot or too cols will also lower range. And, as I saw a certain person on this forum inquiring on whether or not one can drive with the camper package on … well, I would expect that to severely dampen the range. lol

  • Joshua Rosen

    Member
    August 19, 2021 at 11:11 am

    Aptera has to buy their parts from suppliers so they won’t be able to do the type of integration that Tesla does. Sandy Munro kvells when he looks at a Tesla because they integrate every system, he beams over things like the octovalve like he was the mother of a new born baby. When he takes apart other cars he sees a mass of wires and hoses because those cars are pieced together from a basket of parts bought from outside suppliers. The degree that this effects cars built this way is pretty amazing. He just took apart the MachE, the rear drive unit was a nasty kludge but he thought the front drive unit was better than Tesla’s, same car, two different motor suppliers. Aptera should do better than that because it’s a small team designing the car, it sounds the Ford’s front end people have never met their rear end people. However Aptera will be limited by what they can buy, they also have a very small engineering team so they will have to prioritize what they do first.

    BTW on a side note. I’ve been working for or consulting to start ups for 40 years. It is far far better for a company to have too little money than too much. When you have limited resources you have to make hard decisions quickly and you are forced to simplify your system, at the end of the day you get something out the door on time and it’s clean and elegant. If you are swimming in money you delay decisions and you try to throw everything including the kitchen sink into the system, that’s a recipe for disaster. Aptera is in the limited resource boat, if they have to delay adding features to get the first version of the car out the door then that’s what they should do. Ship something that’s good enough now and steadily improve it later.

    • Andrew Ball

      Member
      August 19, 2021 at 3:34 pm

      Absolutely!!! To the last part of your statement! Make a model and proudly claim it is a bata for public trial make it available to purchase with free updates, patches, and fixes available. How many of us would be excited to be part of the bug fixes and real world testing? Sign me up! The world needs to see this on the road!

  • Fanfare 100

    Member
    August 19, 2021 at 12:33 pm

    Does anybody happen to know what the best speed is for the best range, regardless of what this speed may be and what kind of range could be expected?

    • Joshua Rosen

      Member
      August 19, 2021 at 2:39 pm

      Slower the better, The kinetic energy equation is K = 1/2MV^2 where M is the mass and V it the velocity. The drag equation is related, it’s D = (Cd * r * V^2 * A)/2, where Cd is the coefficient of drag, r is the density of air and A is the area. As you can see from both equations they are a function of the square of the velocity. ICEVs mask this because they are so horrendously inefficient in city traffic, they either keep running when they are stopped or all of the components have to be accelerated back to a working speed when the resume running. ICEs also have very narrow power bands which they mask with multispeed transmissions, this exacerbates their inefficiency at low speeds. Electric motors don’t work that way, they don’t consume any power when they are stopped and they are very efficient at all practical speeds. The other advantage that EVs have is that they can recover a lot of energy when they decelerate via regen braking. Accelerating an object is converting potential energy into kinetic energy. Decelerating is the reverse process, with regen braking you are converting the kinetic energy of the moving car back into potential energy that’s stored in the battery. With friction brakes all of that rolling energy in the car has to be converted into heat which is then lost to you forever. The bottom line is that because EVs have many fewer parasitic losses the basic energy equation dominates so the effects of speed are much more pronounced.

      • Harry Parker

        Moderator
        August 19, 2021 at 7:11 pm

        Yes, the general rule is slower the better for all the reasons you mentioned.

        Of course, there is a lower limit. 0 mph uses infinite KWH per mile. The car uses a certain number of watts just sitting there, keeping the computers going, the lights on, and the air at a nice temperature.

        Until we know what the standby current of a powered on Aptera is, we can’t determine its best hypermiling speed.

      • Joshua Rosen

        Member
        August 20, 2021 at 7:07 am

        One more thing to add, weather. Not just temperature which causes parasitic losses from the heater but also rain. If you look at the drag equation, the r term is the density of air. Water has a lot more resistance than air, you’ll see significant increases in energy usage when it’s raining.

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