Rc Twin Mid Drive
- Thread starter Joe90
- Start date
Doctorbass
100 GW
Nice work Joe!
I likethe battery design. It look like you choosed to leave some room between cells for better cooling. How was the cell tab soldering?
Did you managed to keep cells cold and not overheat the tabs to join copper to them?
I like the current share attention tou took care of with the triangular copper shape!
Also 12 miliohm is very good !
20Wh/km is reasonable value at 40km/h for that bike.
Doc
I likethe battery design. It look like you choosed to leave some room between cells for better cooling. How was the cell tab soldering?
Did you managed to keep cells cold and not overheat the tabs to join copper to them?
I like the current share attention tou took care of with the triangular copper shape!
Also 12 miliohm is very good !
20Wh/km is reasonable value at 40km/h for that bike.
Doc
The space between cell is to ''shape'' the pack to fit inside the bag.
It was too high and I had some lenght left so by spacing them I was able to reduce high at the expense of lenght.
A side benefit help cooling. But maybe I dont need cooling since I draw a fraction of what those cell are capable.
I draw less than 1A each. It's easy for those batteries.
I did practice soldering batteries and it took some !
I did find on practice cell that if they get overheated the increase internal resistance.
After some try I was able to keep internal resistance to initial spec.
I was able to hold my finger on the solder right after the solder. So I guess that the surface temperature was about 60-70 Celcius.
Also I have soldered a pack 2 years ago that is still performing at 95%
I cannot be sure that I did no damage. but I cannot garanty that's as good as spot weld.
Efficiency is not good but I did forget about this while I did the bike. I wanted to experiment with VESC and have a better handling bike. Hub motor is hard on rim even more with a hard tail.
A good hub motor have some serious assets.
70lbs finished weight
It was too high and I had some lenght left so by spacing them I was able to reduce high at the expense of lenght.
A side benefit help cooling. But maybe I dont need cooling since I draw a fraction of what those cell are capable.
I draw less than 1A each. It's easy for those batteries.
I did practice soldering batteries and it took some !
I did find on practice cell that if they get overheated the increase internal resistance.
After some try I was able to keep internal resistance to initial spec.
I was able to hold my finger on the solder right after the solder. So I guess that the surface temperature was about 60-70 Celcius.
Also I have soldered a pack 2 years ago that is still performing at 95%
I cannot be sure that I did no damage. but I cannot garanty that's as good as spot weld.
Efficiency is not good but I did forget about this while I did the bike. I wanted to experiment with VESC and have a better handling bike. Hub motor is hard on rim even more with a hard tail.
A good hub motor have some serious assets.
70lbs finished weight
Awesome! Love this project, I'm designing something similar using a pair of rc motors and contemplating using the VESC controller as well. I've got some questions for you, if you don't mind?
You appear to be using two SK3 6374 motors, but what kv are they? Any trouble with running these at 12s on the VESCs so far?
You list a 12.24:1 ratio as the reduction, is this the total reduction to the rear wheel? How would you rate the acceleration? Is the actual top speed 60kph (37mph)?
What are you using for motor current, battery current and absolute current settings in BLDC-tool? Seen any faults? Any overheating issues?
What are you using for a throttle and how are interfacing that with the VESCs?
I'm sure I've got a million more questions for you as well! Nice job, I hope you'll treat us with some video? It'd be great to see a BLDC mode vs FOC mode sound comparison!
You appear to be using two SK3 6374 motors, but what kv are they? Any trouble with running these at 12s on the VESCs so far?
You list a 12.24:1 ratio as the reduction, is this the total reduction to the rear wheel? How would you rate the acceleration? Is the actual top speed 60kph (37mph)?
What are you using for motor current, battery current and absolute current settings in BLDC-tool? Seen any faults? Any overheating issues?
What are you using for a throttle and how are interfacing that with the VESCs?
I'm sure I've got a million more questions for you as well! Nice job, I hope you'll treat us with some video? It'd be great to see a BLDC mode vs FOC mode sound comparison!
I am running SK3 6374 149kv.
you can go with 162 or 192 kv. There is enough torque for that.
Acceleration may suffer. I am contemplating 192kv but I cant recommend it since I dont have experience with this setup.
They run great on VESC and 12S
I top out at 80A phase current before running faults on abs max of 150A.(spikes)
There is a option and corresponding firmware with 0.0005 ohms shunts that can read up to 320A but will have less precision. The fet are rated 240A
With this option I think that you may be able to run 120A phase but that need to be tested.
Batt current is not a problem, it will never go above phase current. I can be used to help a weak battery. say limit things at 50A batt but still have 80A phase to accelerate.
I run BLCD mode as FOC seem to be more difficult to run at high power especially with 12S
The acceleration is brisk, almost motorcycle feeling. front feel light but no wheelee by itself.
Certainly fun accelerating out of the curves.
Yes top speed is 60-62 km/h on a fully charged battery. It tapers down to 52-54km/h at the end of charge.
Good enough for a bicycle, you may want more if yours is fully suspended
It run ok with only 1 motor. nothing overheat.
For cooling I use a small computer fan that run on the 5V power supply of one of the VESC not overheating issues with that.
Test done in march with up to 5 celcius outside. 90A phases 50C board temp when it cut from too much current under acceleration. still some margin left on cooling here.
Throttle: I use the PWM output of the cycle analyst with 1000ms/sec ramping to smooth things. No ramp it's too direct, harsh. But it's a personal thing for this.
I run VESC PPM option current with brake no reverse. so part of the throttle travel is regen. It's like one pedal drive on new electric cars.
No problems for reading split PWM signal from Cycle analyst on VESC. You can try using CAN bus for a nicer solution.
I recommend that you brace your reduction box well, belt pull a lot and 1 milimeter of flex from pull misalign pulleys, make belt jump and wear costly belt.
This said I dont have too much problems with this.
First stage is perfect
Second stage flex under acceleration but it's ok steady state. This is only 4000W
I need to add a brace to make things perfect.
you can go with 162 or 192 kv. There is enough torque for that.
Acceleration may suffer. I am contemplating 192kv but I cant recommend it since I dont have experience with this setup.
They run great on VESC and 12S
I top out at 80A phase current before running faults on abs max of 150A.(spikes)
There is a option and corresponding firmware with 0.0005 ohms shunts that can read up to 320A but will have less precision. The fet are rated 240A
With this option I think that you may be able to run 120A phase but that need to be tested.
Batt current is not a problem, it will never go above phase current. I can be used to help a weak battery. say limit things at 50A batt but still have 80A phase to accelerate.
I run BLCD mode as FOC seem to be more difficult to run at high power especially with 12S
The acceleration is brisk, almost motorcycle feeling. front feel light but no wheelee by itself.
Certainly fun accelerating out of the curves.
Yes top speed is 60-62 km/h on a fully charged battery. It tapers down to 52-54km/h at the end of charge.
Good enough for a bicycle, you may want more if yours is fully suspended
It run ok with only 1 motor. nothing overheat.
For cooling I use a small computer fan that run on the 5V power supply of one of the VESC not overheating issues with that.
Test done in march with up to 5 celcius outside. 90A phases 50C board temp when it cut from too much current under acceleration. still some margin left on cooling here.
Throttle: I use the PWM output of the cycle analyst with 1000ms/sec ramping to smooth things. No ramp it's too direct, harsh. But it's a personal thing for this.
I run VESC PPM option current with brake no reverse. so part of the throttle travel is regen. It's like one pedal drive on new electric cars.
No problems for reading split PWM signal from Cycle analyst on VESC. You can try using CAN bus for a nicer solution.
I recommend that you brace your reduction box well, belt pull a lot and 1 milimeter of flex from pull misalign pulleys, make belt jump and wear costly belt.
This said I dont have too much problems with this.
First stage is perfect
Second stage flex under acceleration but it's ok steady state. This is only 4000W
I need to add a brace to make things perfect.
My reduction is lasercut and I welded bracket to the frame 100$
I think that you would have to do something similar to lightningrod.
The drive, is not that cheap but is really small, 150$
Motor is 75 $
Maybe 300$ worth of bearings, pulleys, shaft and belts.
Plus bolts, nuts and wiring. maybe 100$
A hubwheel is way easier to install and quieter.
On the other side I can put any wheel I want and if there is a flat, no biggie to repair, it's like a simple bike.
Pot holes are handled better too. This is why I did it and also to learn to solder surface mount the ESC component.
Range is similar, but hub have a slight advantage because there is no losses in the reductions unit.
Maybe the best compromise is a single stage reduction with approx 60kv 3-4kg motor.
Not too much losses from reduction, light wheel, light motor.
This is my next experiment.
I think that you would have to do something similar to lightningrod.
The drive, is not that cheap but is really small, 150$
Motor is 75 $
Maybe 300$ worth of bearings, pulleys, shaft and belts.
Plus bolts, nuts and wiring. maybe 100$
A hubwheel is way easier to install and quieter.
On the other side I can put any wheel I want and if there is a flat, no biggie to repair, it's like a simple bike.
Pot holes are handled better too. This is why I did it and also to learn to solder surface mount the ESC component.
Range is similar, but hub have a slight advantage because there is no losses in the reductions unit.
Maybe the best compromise is a single stage reduction with approx 60kv 3-4kg motor.
Not too much losses from reduction, light wheel, light motor.
This is my next experiment.
Wheazel
10 kW
Very nice work!
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