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    Heat is the Enemy

    post your recommendations of how we should prevent heat.

    #2
    I do this by limiting the current on my 72V system. I have the max current set to 30A. On a very hot day (e.g. 100 degrees F), my 325 pound (bike + cargo + rider) rig finishes the 5.6 mile commute at a whopping 95 degrees C, this with a 50H motor (50mm magnet height) and extremely heavy wheels. I always recommend that people use the largest motor in order to prevent motor heat.

    Also, I lay off the regenerative braking if the motor temp is getting high. The regen sure seems to heat up the motor. Normally, I use the regen as my primary braking system because changing the brake pads is expensive.

    I use a 24 FET controller (on a passive heat sink) when an 18 FET would do. The 24 FET controller stays pretty cool. I highly recommend people to use a 24 FET controller in order to prevent controller heat.

    In the future, I might put in some ferrofluid when I have the motor side covers off. Maybe I won't wait and I will remove the side covers just to add ferrofluid!

    I am not sure it is the best idea to have the controller right next to the motor, as on a BBSXX. If I were on that engineering team, I would have vehemently argued against this. For this reason, I would choose the Cyclone if I were to use a mid drive.

    I also try to keep my total weight to a minimum (body fat, bike weight, cargo weight and even battery weight). I never take food or drinks to work; I buy them once I am there. I also use the bathroom before I ride. Why haul more than is needed? It adds to heat.

    I have a motor temp sensor, and I keep an eye on it. If I see anything over 99 degrees C, I stop riding and let the motor cool.

    Are we concerned about battery heat here? One could use a higher capacity battery than is needed in order to keep battery temps down.
    Last edited by commuter ebikes; 10-08-2017, 08:38 PM.

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      #3
      Most people know that the increase in heat is proportional to the square of the increase in current [P=(i^2)R], but many people do not know that [P=(v^2)R] which tells us that the increase in heat is proportional to the square of the voltage.

      I deal with these equations by using the minimum current and voltage that I need, together with the largest motor available and a controller with extra MOSFETs.

      Comment


        #4
        I don't own a hub motor...yet but you have ferrofluid(https://lunacycle.com/luna-ferroflui...-coolant-10ml/), drilling holes, high end has water cooling, I dunno maybe ride in the winter.

        Comment


        • commuter ebikes
          commuter ebikes commented
          Editing a comment
          This product link says heat "causes damage to the coils, hall sensors or phase wires". I would add to this "damage to the magnets at temperatures above 130 degrees C" (for those who would continue to ride at motor temps above 130 degrees C). At 150 degrees C, you have hosed your motor. A CA V3 shuts off at 150 degrees C. Edward Lyen told me to stop riding at 90 degrees C. I have ridden a Crystalyte 4060 around at 127 degrees C, and it was undamaged. What do you guys think should be the cutoff (the point at which you stop riding and let the motor cool)? 90? 100?
          Last edited by commuter ebikes; 10-08-2017, 08:45 PM.

        • max_volt
          max_volt commented
          Editing a comment
          Which begs the question of what quality are the magnets? Would the electrical parts fry before any loss of magnetism?
          Here is a video that takes it all the the nth degree(pun intended)
          https://youtu.be/e03rMDmJzLE

        #5
        Other ideas for reducing heat would be (a) accelerating more slowly, (b) keeping the number of tire liners and the amount of tire slime to a minimum and (c) installing/using tall gears and maximizing human power.

        Comment


          #6
          I don't know why people would drill a hole (for a nipple) in order to put in ferrofluid. Wouldn't metal shavings get into the motor? It seems to me that one should remove the side cover in order to put in ferrofluid.

          Comment


            #7
            I assembled a hubmotor bike this summer just to see what they were like, used Statoraid and a set of Hubsinks. 48V hub, powering it with 52V Shark battery. Rode it really hard in quite a bit of 100 degree heat days powering up steep hills and couldn't get it to where I couldn't hold my hand on it. The hill I live on is about a mile long and fairly steep, riding bottom to top WOT it stays pretty cool.

            Riding across town with lots of WOT and then max throttle up my hill-same thing, it stays cool, barely even warm. I'm guessing it might heat up some if I was lugging it and carrying a bunch of weight. I might mention I'm cyclist weight myself, only 125-130 lbs, I'm sure this has something to do with it too.

            added: opened up the hub to add the ferrofluid, it was kind of a fun project.
            Last edited by Zippy; 10-08-2017, 09:26 PM.

            Comment


            • commuter ebikes
              commuter ebikes commented
              Editing a comment
              Did you have to press in the wheel bearing again after removing the side cover?

            • Zippy
              Zippy commented
              Editing a comment
              No, it was just a matter of pulling the little bolts with an Allen key and sticking three thin flathead screwdrivers in there (marking them with tape so as not to press them in too far), a little gentle pressure and it just popped open. Squirted the Statoraid inside and the cover went back on just as easily. This was a 9C clone type hubmotor by the way.

              I've found the hubmotor to be a lot of fun, it's fast on flat ground (35ish mph) pulls hills real well especially if you keep your speed up. Of course the BBSHD is on a whole other level as far as torque and ability to work with the gears to move weight up steep hills and I have a feeling a 230 lb person might have a completely different experience with my hubmotor trying to tackle big hills.

            #8
            Battery getting hot?
            I use this temperature display with probe. The probe should be attached to the side of the pack preferably on the cells or close as possible. Battery will get hot fast when it is beliw the nominal volts.
            Eg. 52v battery is 58.8v fully charged and will get hot "faster" during WOT when the volts fall below 52v.
            38•C on a normal day is a good battery temperature.
            Above 43•C is the hazardous zone. Never charge a battery that is over 38•C (if you can help it)

            Comment


            • Zippy
              Zippy commented
              Editing a comment
              Good tip there on voltage/battery temps, never knew that.

            #9
            If I know I am going on a long ride, I will travel at reduced speeds. This really keeps temps down.

            Comment


              #10
              I like to monitor my Ebike heat after a 5 mile ride. Then I will take a 10 mile ride. And then a 15 mile ride. Etc..... I like to learn about the throttling and speed of my new Ebike without the use of gauges because what if my gauges don't work one day? I just want my expensive Ebike to last forever. It's really important that my Ebike is reliable every day at any power level.

              Comment


                #11
                Amps/Watts, keep it realistic to the motor rating. Burst above rating is OK for short durations but maintain "continuous" power at or below the rating of the motor. If 1000W rated motor, laws of physics for upright bicycle works out to around 30MPH on level paved road through calm wind.

                New riders alway benefit learning from a power meter until they understand operational envelope of a system under various loads and conditions. Once learned, riding without any meter input is much more predictable and reliable.

                Comment


                  #12
                  Originally posted by Ebike1 View Post
                  Battery getting hot?
                  I use this temperature display with probe. The probe should be attached to the side of the pack preferably on the cells or close as possible. Battery will get hot fast when it is beliw the nominal volts.
                  Eg. 52v battery is 58.8v fully charged and will get hot "faster" during WOT when the volts fall below 52v.
                  38•C on a normal day is a good battery temperature.
                  Above 43•C is the hazardous zone. Never charge a battery that is over 38•C (if you can help it)
                  That device looks like one of the 12 volt units on eBay? How do you power it on your ebike?
                  Robert

                  Comment


                  • max_volt
                    max_volt commented
                    Editing a comment
                    I believe that uses internal button batteries.

                  #13
                  Ya, don't own a hub motor.. Mine is a electric motor connected to the chair directly. The controlled hook to motor and gives two speeds controlled by the throttle. The motor does get hot though, claims a man on YouTube. Most electric motors are covered, but this is open, probably for cooling purposes. I spent on the scooter bike, nearly $400 + $50 in safety equipment. It does have a safety warning of motor might get hot when rode. My motor is 36 volts and 500 watts.

                  Comment


                    #14
                    The Magic Pie 5's windings and hall sensors are expected to survive up to 150c...with possible magnet damage at 200c.


                    Quote from GMChina...For MP5, there isn't any temperature sensor for the motor, because mostly the motor can't reach such high temperature. But there is temperature sensor in the controller to cut off the power when the controller temperature is too high to protect the controller.

                    Riding at required regulation wattage and limited top speed keeps my Pie cool and happy.


                    See my completed Magic Pie V5 rear hub motor E-Bike build HERE.

                    Comment


                      #15
                      Yes, I agree, if rode correctly and no modifications, a motor can last along time. A lot modify and try to make faster but in doing so, may make the machine where one would have to register it. Tires too, wear quicker and may not hold up to such speeds.

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