My brushless motor is getting very hot after few minutes running

Lightweight / Folding / Portable EVs - seats optional
Post Reply
zeroonea   10 mW

10 mW
Posts: 24
Joined: Oct 13 2017 7:17pm

My brushless motor is getting very hot after few minutes running

Post by zeroonea » Jan 04 2018 9:24am

My motor is outrunner brushless 6063 with 6S 40C battery. My ESC is 90A esc. Gear ratio is 12T/55T. I hear someone say it is undergeared or overgeared. What is undergeared and overgeared?

User avatar
parabellum   10 MW

10 MW
Posts: 2056
Joined: Nov 19 2010 9:55am
Location: Dominican Republic, north.

Re: My brushless motor is getting very hot after few minutes running

Post by parabellum » Jan 04 2018 4:06pm

In your case, it probably means, your motor does not reach enough rpm to work efficiently. What kv is your motor? What is your driven wheel diameter? What is your top speed?

zeroonea   10 mW

10 mW
Posts: 24
Joined: Oct 13 2017 7:17pm

Re: My brushless motor is getting very hot after few minutes running

Post by zeroonea » Jan 04 2018 7:35pm

280KV, wheel diameter is 20cm, I don't know my top speed... Can you explain what is undergeared and overgeared please?

billvon   1 MW

1 MW
Posts: 1808
Joined: Sep 16 2007 9:53pm
Location: san diego

Re: My brushless motor is getting very hot after few minutes running

Post by billvon » Jan 04 2018 8:00pm

zeroonea wrote:
Jan 04 2018 9:24am
My motor is outrunner brushless 6063 with 6S 40C battery. My ESC is 90A esc. Gear ratio is 12T/55T. I hear someone say it is undergeared or overgeared. What is undergeared and overgeared?
Undergeared or overgeared refers to a poor match between motor speed and desired vehicle speed.

Let's say your motor's constant is 60 RPM/V. That means for a 6S (~22V) battery you will get a "base speed" of 1320 RPM. Now you have to calculate what speed that means; to do that you have to know the gear ratio (.218 in your case) and the wheel diameter. For a 26" wheel that means 22mph.

Now, if you really wanted 10mph you are giving up some torque and not making a good match between your battery and your motor; you would be better off with a lower gear ratio, lower motor constant or a lower voltage. Likewise, if you really wanted 30mph you are going to have to phase-advance like crazy - that's not very efficient, and most controllers don't support it anyway. You'd again be better off with a different gear ratio, motor constant or battery voltage.
--bill von

zeroonea   10 mW

10 mW
Posts: 24
Joined: Oct 13 2017 7:17pm

Re: My brushless motor is getting very hot after few minutes running

Post by zeroonea » Jan 05 2018 12:08am

People say when motor very hot and ESC just warm. it is undergeared, so we should change the pinion to more teeth. Is it right?

User avatar
parabellum   10 MW

10 MW
Posts: 2056
Joined: Nov 19 2010 9:55am
Location: Dominican Republic, north.

Re: My brushless motor is getting very hot after few minutes running

Post by parabellum » Jan 05 2018 9:15am

My quick calc came to 6720rpm on motor at ~55km/h.
It is small motor, resulting system is underpowered and under geared, I would shut for ~ 10000rpm unloaded and gearing for 30km/h max.

Which is 9s battery and gearing 1:10.

zeroonea   10 mW

10 mW
Posts: 24
Joined: Oct 13 2017 7:17pm

Re: My brushless motor is getting very hot after few minutes running

Post by zeroonea » Jan 05 2018 10:31pm

My ESC just 6S, can you recommend gear for best performance and efficiency? I don't required it must run too fast

User avatar
parabellum   10 MW

10 MW
Posts: 2056
Joined: Nov 19 2010 9:55am
Location: Dominican Republic, north.

Re: My brushless motor is getting very hot after few minutes running

Post by parabellum » Jan 09 2018 3:58pm

zeroonea wrote:
Jan 05 2018 10:31pm
My ESC just 6S, can you recommend gear for best performance and efficiency? I don't required it must run too fast
Try to adjust gearing to the point where your top speed requirement matches top motor speed. For 30kmh 1:7 maybe.
P.S. It already accounts for 80% of no load rpm, where you motor delivers most of the torque. You will have ~152% of current torque available.

Post Reply