What I wish I understood before buying my hubmotor

Electric Motors and Controllers
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Ebikerbob@gmail.com   1 µW

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What I wish I understood before buying my hubmotor

Post by Ebikerbob@gmail.com » Apr 01 2018 6:27am

Don't buy a faster wind than your desired top speed or torque suffers terribly! I own two 1500w hubmotors and the 6t climbs off-road hills even at 48v that my 4t hubmotor cannot even at 72 volts and my controller overheats!
My top speed with both motors is not that different at about 35 amps and 72 volts! So if I understand this right, you need lots more amps for a 4t motor to match the torque of a 6t motor and that means more heat for my controller. Please enlighten me if I am wrong.

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amberwolf   100 GW

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Re: What I wish I understood before buying my hubmotor

Post by amberwolf » Apr 01 2018 11:33am

Depends on your controller, battery, wheel size, etc.

Check out the http://ebikes.ca/simulator to experiment with this

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circuit   100 kW

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Re: What I wish I understood before buying my hubmotor

Post by circuit » Apr 07 2018 2:03pm

Faster winding requires higher phase current. It does not necessarily mean higher power, if battery current is limited to same levels.
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sn0wchyld   1 MW

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Re: What I wish I understood before buying my hubmotor

Post by sn0wchyld » Apr 08 2018 8:25pm

Ebikerbob@gmail.com wrote:
Apr 01 2018 6:27am
Don't buy a faster wind than your desired top speed or torque suffers terribly! I own two 1500w hubmotors and the 6t climbs off-road hills even at 48v that my 4t hubmotor cannot even at 72 volts and my controller overheats!
My top speed with both motors is not that different at about 35 amps and 72 volts! So if I understand this right, you need lots more amps for a 4t motor to match the torque of a 6t motor and that means more heat for my controller. Please enlighten me if I am wrong.
for the same controller (at a given torque output), yes, it needs to put out more phase amps to the motor (this however wont require that much more battery amps). However if you match a controller to each motor, the higher speed wind will provide the same acceleration as the lower speed wind, with a higher top speed for a given voltage (though this may be limited by the power for both motor+controller+battery combo, rather than specifically a torque limitation). As far as the motor goes there's little to no difference in performance between different winds (all else, namely copper fill... being equal). there's a few threads on this issue already, so I wont blab on any more here.

The fact that your controller overheats at 72v suggests that it cant handle the phase amps required to make the 4t motor you have perform the same as your 6t, so its not so much a issue with the motors (assuming they both have the same copper fill) but with the controller you matched to the 4t. Back in the hey days of the HT/HS motors from cristalite, there were plenty of people running 4110 based controllers on the low turn HS model motors with a 24s (100V) battery, and plenty of corresponding blown controllers. I however had no issue running a HT model (higher turn count) motor with a 4110 based controller and 24s, as did a few others. This could be down to nothing more than the higher turn count motor being 'easier' to run from the controllers perspective - as you too find when running your low turn motor. You can run a controller closer to its limits with the 'easier' to run motor.

the OP is a worthwhile observation, but its more a case of 'be careful when selecting low turn motors to also match them with a suitably beefy controller, else your performance may be worse than a higher turn motor and a relatively weaker controller'.

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