Building a pocket bike with CA120-70 [8.6kW]

[zEEz]

I popped this thread up just to tell that some insane idea finally got me.
I decided to build an e-pocketbike too!
I found already the frame and I'm tinkering to provide a decent mount for a cloned 80-100 turnigy motor.
6kW should be plenty of power! I'm also adding hall sensors to the motor to be able to run it with a 12 mosfet Lyen controller with 4110 mosfets and the current limit maxed to 80-100 A.
Voltage will be 72V and provided initially with 3 packs of 6s lipos... turnigy as well.
Capacity is expected to provide only few minutes of fun, but it will be upgraded if needed!
have fun !

[Arlo1]

My money is on the 12 fet not lasting long!!! 45-50 amps from a 12fet is ok but even at those settings they get warm. If your controller gets warm meens the fets are getting warm and if they get warm their resistance goes up then the whole avalance thing starts realy fast!

[zEEz]

Hi!
As I understood from reading the forum people experiences ...
the problem is that most 12 fet controllers are sold with FAKE IRF fets ...
They show in the measurements an RdsON 3 to 4 times that of genuine IRF fets.

In my controller I upgraded the standard FAKE 4310 with original GENUINE IRFB4110.
This is lowering the RdsON of around 8 times .... hence the heat production too ...

by the way, I read stories of people running Lyen 12 fet at 120A and they are still alive ...

have fun!

[Arlo1]

Hi!
As I understood from reading the forum people experiences ...
the problem is that most 12 fet controllers are sold with FAKE IRF fets ...
They show in the measurements an RdsON 3 to 4 times that of genuine IRF fets.

In my controller I upgraded the standard FAKE 4310 with original GENUINE IRFB4110.
This is lowering the RdsON of around 8 times .... hence the heat production too ...

by the way, I read stories of people running Lyen 12 fet at 120A and they are still alive ...

have fun!

Yup I don't doubt you can get 100-120 amps from a 12fet but I built 4 12fet controllers with genuine IRFB4110 fets and they are much tougher then lyen controllers and they still get hot running easier to handle motors then yours. I have built 4 24fet controllers and a 18fet and have seen the limits on all of them! I will not run a controller that hot. I have blown over 100 genuine IRFB4110 mosfets on collossus and I have never blown any on any other motor other then once with shorted wires. Your motor is low inductance and resistance which means the controller will be first to go!

[zEEz]

Ouch, that is bad news, arlo ...
I'm not sure if I was clear enough about the motor: I'm not using
a CA120-70, but a clone of the Turnigy 80-100B with a kV of 120 ...
I would have expected it to be a reasonable load for a 12 mosfet ...
Do you think I'll blow everything?

ps. the motor winding resistance is around 32 milliohm ...
... so it is ten times the 1 mosfet RdsON ...

... while the MARS MOTOR ME0907 I would like to
use in the future for a standard size motorbike with
a 18-24 Mosfet controller has winding resistance of around 13 milliohm ...
... and the Inductance Phase to Phase is 0.10 Milli-Henry ...
... perhaps you can give me a hint on which controller to prefer
for an eventual modification ...

Thanx

[Arlo1]

The motor resistance will help. But a lot of the guys are getting controller resets and i belive its cause of the low inductance of these motors. I have a small collossus and its 75kv and it mesures 48uH at the low spot if you up the kv the inductance will be lower! I would say a 18 or 24 fet will be better for this motor if you want 80 or more amps! As for the mars im not to up to date on it.

[AussieJester]

Thuds been using re-built 12fet controllers with turnigy 80-100 motors, run on 66v they have been very reliable.

KiM

[Arlo1]

Thuds been using re-built 12fet controllers with turnigy 80-100 motors, run on 66v they have been very reliable.

KiM

Yes and he is not running the amps this high!

[zEEz]

Thanks guys!
having seen your comments, probably I'll stay on a more cautious position with the specs.
Indeed I'll want to get 6kW output for the pocketbike, but I suspect that in the beginning
anything above 3kW would suffice ...
I'll design the gear ratio to provide 70 kmph at around 6000 rpm.
It should be possible to start testing with 48V, at that point ...

So I'll get a feeling of what is going on and I'll decide what to do next ...

have fun!

[Arlo1]

3 kw on this will be insane!!! The original motor was proly ~.5 kw

[zEEz]

3 kw on this will be insane!!! The original motor was proly ~.5 kw

Hopefully !

But you see .. everything is relative ...

The petrol engine I took away is rated at around 3 ps and is supposed to bring the beast to a top speed of 70 kmph ...

The tuning petrol engine is around 5 ps and going up to 90 kmph ... .... perhaps those specs are a bit optimistic ...

The many chinese brushed e-pocketbike with power between 200 and 800 w are quoting 20 to 45 kmph ...

Several people on this forum and around has built e-pocketbikes with motors between 5 and 10 kW ... and they are still alive ... while being also very fast

From calculations, my e-minibike can have a final reduction between 1:5 and 1:10 (13 to 7 teeth motor sprocket)...
At 5000 rpm this is translating to 25 to 50 kmph (1:5) ...
Since the motor constant is around 120kV ... with just 48v I should be able to approach 60 kmph (1:5)
Of course the wise man would up the voltage to 60v or even 72v to be able to reach 80 kmph

have fun!

[hillzofvalp]

update? Also, could you link me to other good examples of pocket bike conversions on this forum? some friends and I are doing a couple pocket bike conversions.

[zEEz]

update? Also, could you link me to other good examples of pocket bike conversions on this forum? some friends and I are doing a couple pocket bike conversions.

here some serious ready stuff:

viewtopic.php?f=12&t=24125

then it is also mine -work in progress-:

viewtopic.php?f=12&t=32018

...

google is your friend!
have fun!