Help choosing motor for pit bike converions

ehseki · Jul 3, 2021

Hello,
I recently purchased a 125cc pit bike rolling chassis and was looking to convert it to electric. I have a KLS7218S kelly controller and two 36 volt lithium-ion packs which I plan to run in parallel for a combined total of 72 volts. However, I am having trouble picking a motor and was wondering if anyone had any recommendations. My budget for the motor is around $200. I am hoping for around 40 mph.

SlowCo · Jul 4, 2021

You'll have to connect the batteries in series (not parallel) to get 72V.
As for a motor that will fit and get you that speed for that price maybe look at these:
https://nl.aliexpress.com/item/4000....store_pc_groupList.8148356.12.76c76307XIFjb0

ehseki · Jul 4, 2021

SlowCo said:
You'll have to connect the batteries in series (not parallel) to get 72V.
As for a motor that will fit and get you that speed for that price maybe look at these:
https://nl.aliexpress.com/item/4000....store_pc_groupList.8148356.12.76c76307XIFjb0

Yeah, I meant series my mistake. Thanks for the recommendation

hugok · Jul 5, 2021

This might be out of your budget but I would go for http://www.cnqsmotor.com/en/article_read/QS%20120%202kW%2072V60KPH%20Mid%20drive%20motor%20with%20428%20sprocket%20driven/900.html

It the first one is too expensive you could look at this one:
http://www.cnqsmotor.com/en/article_read/QS%201kW%2090%2072V55KPH%20Mid%20drive%20motor%20with%20old%20appearance/899.html

Both these motors can be pushed way above specification.

SlowCo · Jul 5, 2021

hugok said:
Both these motors can be pushed way above specification.

QS motors were also my first thought but I suspect that the 36V battery packs can't supply the amount of amps that those motors can handle...

hugok · Jul 5, 2021

What kind of packs do you use?

You could always limit the max current in the motor controller to what the battery can handle. In case you get better batteries its nice to already have a motor that can handle it.

ehseki · Jul 6, 2021

hugok said:
What kind of packs do you use?

You could always limit the max current in the motor controller to what the battery can handle. In case you get better batteries its nice to already have a motor that can handle it.

my packs are custom 10s 8p. I was planning on doing 40 amps continuous with an 80 amp peak. (80 amps is the max current the packs can supply)

ehseki · Jul 6, 2021

hugok said:
This might be out of your budget but I would go for http://www.cnqsmotor.com/en/article_read/QS%20120%202kW%2072V60KPH%20Mid%20drive%20motor%20with%20428%20sprocket%20driven/900.html

It the first one is too expensive you could look at this one:
http://www.cnqsmotor.com/en/article_read/QS%201kW%2090%2072V55KPH%20Mid%20drive%20motor%20with%20old%20appearance/899.html

Both these motors can be pushed way above specification.

Oh I have seen people use the qs 120 but never the QS 1kW in similar sized project. I will do some research on the qs 1kw and based on advertised torque I may end up purchasing this one.

Help choosing motor for pit bike converions

ehseki

1 µW

SlowCo

1 MW

ehseki

1 µW

hugok

1 W

SlowCo

1 MW

hugok

1 W

ehseki

1 µW

ehseki

1 µW

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