250w gear motor. what amp limit not to kill the gears.

brumbrum

100 kW
Joined
Oct 30, 2010
Messages
1,383
Location
Wales U.K
Hi everyone.
I'm a new member and first time question asker so please don't slam me! I'm in the UK and am suffering from hardcore e-bike regulations. I am currently trying to bend the UK rules by being as incognito as i can with my set-up.
I have two 250watt geared 'mini' motors. I also have a 54v 20ah lithium-ion pack. The controllers i use are amp controllable/adjustable.
Question: What would be a safe continuous and peak amp setting and speed limit for each of the two motors without stripping the nylon gears?

Thanks BrumBrum :)
 
Depends on the motor.

I'd say take it a few amps above normal, not much more.
Most geared motors are already unreliable over a long period of time on their stock settings !
 
If you ever find yourself in a finacial position where your play-budget is substantially increased, your best performance bet is to give the motor some gears.

You can take some type of motor that passes inspection, and mount it so that it drives the Bottom-Bracket, which will give the motor the use of the bikes existing gear-set on the back wheel. Or, you can have a separate drive-line where a motor drives a chain/belt to an independent freewheel on the right side of the rear wheel.

The other thing you can do is to have parallel/series voltage switching. One example would be to have two 24V battery packs that operate in parallel for long range, but they can be temporarily swutched over to a series connection to provide 48V for a burst of higher top-speed (when nobody is looking, and you appear to be pedaling furiously).

For reasons that would take a long time to explain, RC outrunner motors are very power-dense. Everyone I show the 63mm motors to, are very skeptical that they can provide 1-HP continuous (750W) and 2-HP temporary-peak power (1500W). They are the size of a coffee cup, and if they were labeled withan official-looking 250W @ 24V sticker, everyone unfamiliar with them would believe it, and the battery would measure at 24V with a meter.

Just a few thoughts, best of luck...
 
spinningmagnets said:
For reasons that would take a long time to explain, RC outrunner motors are very power-dense. Everyone I show the 63mm motors to, are very skeptical that they can provide 1-HP continuous (750W) and 2-HP temporary-peak power (1500W). They are the size of a coffee cup, and if they were labeled withan official-looking 250W @ 24V sticker, everyone unfamiliar with them would believe it, and the battery would measure at 24V with a meter.

Just a few thoughts, best of luck...

Those only work if you are wallet-dense too... :mrgreen: j/k
Actually you have a really good idea there. RC motors look weak and sound weak too since they spin to such high RPMs to generate the same amount of power.

But they do generate a lot of noise compared to hubs..
 
brumbrum said:
Hi everyone.
I'm a new member and first time question asker so please don't slam me! I'm in the UK and am suffering from hardcore e-bike regulations. I am currently trying to bend the UK rules by being as incognito as i can with my set-up.
I have two 250watt geared 'mini' motors. I also have a 54v 20ah lithium-ion pack. The controllers i use are amp controllable/adjustable.
Question: What would be a safe continuous and peak amp setting and speed limit for each of the two motors without stripping the nylon gears?

Thanks BrumBrum :)

What motors are these? Bafang QWSX perhaps, or Tongxin, or what?

See
http://endless-sphere.com/forums/viewtopic.php?f=3&t=20736&p=385320&hilit=butter#p385320
Several reports of 36v20A and 48v20A being fine.
 
try cell-man.. he has some quality replacement gears... i have a puma motor...stripped original nylons in less than 200 miles.. swithched to bmc green... no problems in 1800 miles... also have a bafang.. changed one nylon to steel.. agein no problems for aboiut 1600 miles :mrgreen:
 
Thanks for all the replies, there are obviously lots of opinions. The motors are not Bafangs, they are Golden Motor 902 Prokit motors. i already run a very successful front and rear 'magic pie' bike which is great and runs without any problems so please do not start warnig me about the company's reputation :wink:

Kriskros, does the metal gear make the motor much louder? and where can i get them?

Is there any more information on adding a steel gear? or a how to guide on the ES forum?
 
jbond said:
brumbrum said:
See
http://endless-sphere.com/forums/viewtopic.php?f=3&t=20736&p=385320&hilit=butter#p385320
Several reports of 36v20A and 48v20A being fine.

Thanks ever so much for the link :)

The golden motor 'magic controllers' are programable via a USB cable to PC so i can actually turn down the continuous and peak amp settings. i believe these controllers are only about 20A even though they are rated higher. When setting up the motors i will be able to program the controllers and then compare/test with the readings of a watt meter.
 
cell_man is Paul.
http://endless-sphere.com/forums/memberlist.php?mode=viewprofile&u=14820


FWIW, no one can give you an absolute safe wattage for geared motors, and it's all a trade off against relaibility, cost, speed etc
Personally I'd say 1200-1800W depending on the motor type, usage, rider weight, temperature etc etc.
 
Gregory said:
cell_man is Paul.
http://endless-sphere.com/forums/memberlist.php?mode=viewprofile&u=14820


FWIW, no one can give you an absolute safe wattage for geared motors, and it's all a trade off against relaibility, cost, speed etc
Personally I'd say 1200-1800W depending on the motor type, usage, rider weight, temperature etc etc.

Thanks for pointing me in the right direction for Paul. :) 1200W :shock: that sounds an awful lot for a 250w rated motor. Reliabilty being most important, i will also ride this freewheeling motored bike with constant light to moderate pedalling 8)
 
brumbrum said:
Thanks for all the replies, there are obviously lots of opinions. The motors are not Bafangs, they are Golden Motor 902 Prokit motors. i already run a very successful front and rear 'magic pie' bike which is great and runs without any problems so please do not start warnig me about the company's reputation :wink:

Kriskros, does the metal gear make the motor much louder? and where can i get them?

Is there any more information on adding a steel gear? or a how to guide on the ES forum?
the steel gear was a little noisy at fist but quieted down after about 3-400 miles....i got mine from ebikes.sf [ ilya an ES member] there are some earlier reports on bafang[250 watt motor running 72v 20amp with one steel gear]
 
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