Electric kart


100 W
Apr 4, 2015
Took a Tony kart without motor and installed batterys and electric motor.
Motor: GM 10kw 48V and 100kv I think.
Battery: 16x 60Ah Winston
Controller: GM VEC500 48V

Motor speed with wheels of ground was 4700rpm. Rear wheel size is 11" :) and theoretically top speed should be 81km/h.

First day in the track had a 15 teeth motor spocket and 45 teeth rear spoket, this made a 3 times reduction of motor speed and 3x increase of torque.
Max speed on the track was 73km/h, so motor rpm was 4300. Current was limited to 200A on controller. As the speed was not enough spockets were replaced :)

Next try was with 18 teeth motor spocket and 36 teeth rear spocket, this made a 2 times reduction, and with 4300rpm max speed should be 112km/h.
But actually max speed was 93km/h so motor speed was only 3600rpm. Result of this test was that motor controller overheated after 12km of racing (12 laps).
Max current was increased from 200A to 250A also, but it overheated even with 200A. Motor was only slightly warm.
Video on that day: [youtube]https://youtu.be/ypJ3Iw4WwiQ[/youtube]

Installed a big heatsink beneath controller with active cooling to keep the controller heat down, but have not had time to test it.
Heatsink size compared to controller: Controller.jpg and here installed with coolers: ExtraCooling.jpg
Also increased rear spocket size to 40 teeth, so right now I have 2,2x reduction and should get the same 93km/h with 4000rpm but have more power for accelerating.
Are waiting for analogger to be delivered so I could see my motor and controller temperature compared to current.

It seems that 48V is not enough :) Was thinking of adding 4 more elements to increase voltage to 60V. I know that controller can handle it, as it is universal from 48V to 110V.
But how can 100kv motor handle 60V, it makes the maximum rpm to 6000 without load? With load and 4700rmp is good enough to me.
That thing looks quick, 93km/h is fast to me. What top speed do you think is ideal? How does it compare to the gas karts in terms of acceleration?
Rotax Max with 23kw engine got 110km/h in the same track and their lap (964 meters long) time was 10sec faster.
I hope to brake 100km/h barrier :) But I do not think it is possible with my current 48V setup.
if I were you I'd be thinking about running 96v

the increased rev range means you could change your cogs again, so you have 110kph top speed (or whatever you need)

but also increase acceleration

but that all depends on your motor/controller working with the extra power without overheating

200amps at 48v is 9.6kw

200amps at 96v is 19.2kw - so you only need to run 100 amps for same power at motor
Was racing with 9hp hobby karts last week and it is faster that reqular 9hp, but slower than tuned 9hp kart.
But this 10 laps rised one more problem, it seems that controller was reducing current because motor temp.
In VEC500 controller software there are 3 settings for motor temp: level 1 120 degrees celcius, level 2 130 degrees and shutdown 150 degrees.
It seems that GM HPM10 has very poor cooling because from outside motor temp was only 33 degrees of celcius.
Starting from 7th lap current was lowered from 250A to 220A and then after 1,5 more laps to 200A.
I managed to use 27Ah with ~12km (10 laps + 1 cooldown lap), it makes 2,25Ah per lap.
RaceRender and analogger together make very good analys tool :D

Meanwhile I have opened controller and there are 75V fet's inside :cry: so I will add only 4 cells to total 60V.
I have now installed 4 more cells to my 16S pack and have now 20S pack. I have driven over 50km with it and controller is working ok with 58V and 225A.
Was again racing with hobby karts last week against 9hp tuned version. And I still have a motor overheating problem :(
I lowered battery current to 225A because of voltage rise from 48V to 60V.
Here is a video https://youtu.be/c6om_p3X9xI of one race where controller reduced battery current from 225A to 163A and loosing 3kw was enough to let gas powered kart to pass us.
Then after 1,5 laps motor somehow cooled down a little and controller gave back the power but in the end we braked to heavily and made a spin. It seems I need front brakes also.
Controller temp is under control because of this big heatsink behind it (its 30 degrees). Do not look lower temp gauge, because it is motor outside temp not inside.
There is now forced airflow to the motor. Fan motor is 48V/45w and capable of 270 l/s of airflow.
I designed the scope so that when driving it directs outside air also to the motor.
Here is picture of my vision:
And here is actual output:
View attachment 1
There is also protective aluminium web on top of the blades:

It added about 3kg to the weight, so I need to loose 3kg :)
I am going to start the same project than you... And now I am looking for the motor...

GM also have water cooling system for this motor, did you consider this type of cooling?
They go pretty hard for a few laps with enough controller. Then you gotta back it off or you cook them. I was feeding mine 660A phase current on a bicycle that went pretty hard.
Will try to install forced cooling to blow air inside of motor because cooling motor outside did not help at all :evil:
1. Make holes in both side of cable box.
2. install intake scoop to mount two fans.
3. Red thing in middle of the wires is for redirecting air inside motor and not directly throught cablebox.
4. install output scoop so I can put some metal filter there (so that small particles do not enter from there)

I hope that I can push 27 l/s through the motor, because there are very little space in the motor (1,3 liters of air in my calculations).
Can someone calculate how much heat can be removed with this?
Was racing with this motor mod and now I think that the controller is my bottleneck.
Because after just one lap max battery current went from 290A to 240A and were there till the end of race (13 ~800m laps).
I have a multimeter showing motor windings thermostat ohms in the weel (GM has two of them and I'm using the spare one) and it showed 750ohm, it should be 70-80 degrees of celsius only.
And also at the 10th of lap controller was shutting itself down like when I did not have cooling for it. So it seems that 45 degrees in heatsink is maximum for my controller.
In this video lower temp is controller heatsink and upper temp is air temperature coming from motor. Outside temp was 20 degrees on that day.
https://youtu.be/GgJ4wN15At4 Controller disabling output current is when current went to 0A after I pass kart nr 19. Then I had to release throttle and current came back and went away multiple times until to the end of race.
My plan is to get at the end of August Sevcon 72V Gen4 Size6 controller and see what I can get out of that motor then.
Right now 14kw is the max my controller can input to the motor and that is to little for a 149kg + 86kg of mass.

Installed front brakes last week and braking improved like 100% :D
Some fun in the track also https://youtu.be/a1wnrENzBK0
It is average 2,5Ah per 1km lap. Right now in 10th of lap my controller overheats. But batterys should last 20 laps it makes 50Ah and after that there is 10Ah left in the batterys but voltage drop is too large to race anymore :)
Average races are 10-15 laps so I have to much Ah and wasting weight that way.
Finally 100km/h in a race track, just for a moment though :D

Video also: https://youtu.be/0pyk49RWJSM
Swap those Winson cells for some RCLipo to cut a bunch of weight.
That will instantly improve your acceleration, speed and cornering = much reduced lap times.
If you upped the voltage at the same time, (more rpm range), you could increase the gear ratio and reduce the current draw to help the motor stay cooler too.
Do you know how to set up the chassis to suit the track/ tires etc ?
There are many adjustments on a kart that can have a huge effect on lap times.
Really nice Kart you have there.

Regarding RC lipos: Maybe have a look at the Hobbyking Turnigy Multistar lipos. They seem to be getting quite popular lately in the RC community. They don't have the highest C-Rating but they are available in large capacities (for rc lipos) and are lightweight and cheap.

Only drawback I can see is that lipos can burn like crazy if something goes wrong ...
It was busy winter, building my new 100V 4kwh battery pack.
But now kart has new controller also and is driving way faster.
Have not had time to go to the track jet :(