250 watt motor and 18max current controller?

E

Electricmover

New Member
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Europe
I have a 250 watt nominal front hub motor. I have a 48 volt battery and the controller that seems to work best with the wires is a 18max current controller that I have. Would this work or would it fry the motor in a winter barbecue?

I am thinking short bursts it could probably be fine now in winter right? If careful it won't fry, if gearing down in up-slopes ? Or is this a stupid idea. Maybe I should lower to max current controller of 15a?

Motor and controller is in these images.
 

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Chances are it will be fine. The motor is rated for 250 watt continuous, but should be able to burst higher for short periods. If it has a temperature sensor and the controller supports that feature, it will shutdown the motor before it overheats on a long climb.
 
That sounds like a bit too much power to me?

A fully charged 48V battery is 54.6V
That's almost 1000 watts at 18 amps.

Your display settings may allow you to turn down the maximum power.
Otherwise be real careful giving it over 900 watts.

Temperature sensors in motors are very rare, and a motor can overheat and burn out in less than a minute.

Just be really careful and keep putting your hand on the motor to see how hot it is.
Your first test ride is the most important.
Check the motor temperature every couple of minutes at first to see what it takes to get it hot.
 
PCeBiker said:
That sounds like a bit too much power to me?

A fully charged 48V battery is 54.6V
That's almost 1000 watts at 18 amps.

Your display settings may allow you to turn down the maximum power.
Otherwise be real careful giving it over 900 watts.

Temperature sensors in motors are very rare, and a motor can overheat and burn out in less than a minute.

Just be really careful and keep putting your hand on the motor to see how hot it is.
Your first test ride is the most important.
Check the motor temperature every couple of minutes at first to see what it takes to get it hot.
Click to expand...
I have a kt-lcd3 and a sw900 lying around. Anyone knows if one of them supports this feature of turning down the max current?
 
Electricmover said:
I have a kt-lcd3 and a sw900 lying around. Anyone knows if one of them supports this feature of turning down the max current?
Click to expand...

Your kt-lcd3 allows you to adjust your maximum power,..

Screenshot_20260101_095104_Adobe Acrobat.jpg



Here's a link to the owners manual.
(The display will show you the motor temperature, but you normally have to install the temperature sensor in the motor yourself)




As a general reference, motors can usually handle double their rated power continuously without overheating, so 500 watts at 36 volts is ~13.9 amps, and 500 watts at 48 volts is ~10 amps.

If it were me, I'd cut the power in half (C5=3 9amps) and see how it goes.
If it's too gutless, turn the power up a notch and try it again.

I didn't want to worry about cooking my motor, so I cut my power in half so I could ride full throttle without worrying about it.
 
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RunForTheHills said:
Grin sells that motor, and at least their version comes with a thermister. They do warn that allowing too much phase current can strip the gears. https://ebikes.ca/product-info/grin-kits/bafang-g310-g311.html
Click to expand...

Yeah Grin sells good stuff but you'll need the Cycle Analyst to go with their motor to read the motor temperature data.

As far as I know, to use the "Motor Temperature" readout on the KT display, you not only need a temperature sensor in your motor, you also need to wire it all the way up and into the display and solder the wires directly on to the circuit board inside.

The KT wiring harness doesn't have the extra wire for the motor temperature sensor, so it has to be completely installed separately.

@Electricmover that Grin link is great!!
They show you all the ways that the motor can fail.

Knowing how it can 💩out, helps you to know how to run it hard without it breaking or 🔥ing up. 😁
 
I run a 25A KT sinewave controller with a 48V battery into this little Q100H 250W motor. It's rider restraint that keeps it from melting. I use it with an LCD3 display. It might show 1200 W briefly on a hill, but it would be foolish run it at high levels sustained . That's 25A peak anyway. KT expects you to run it at 12 A which is 500-600W,

P1110451.JPG
By the way, displays are specific to the controller brand, I doubt an LCD3 or SW900 work with the controller in your picture. I have turned down the current in KT displays to allow the bike to run around 100-120 watts in level 1. That's so I can go slower and not out run my wife in PAS 1.
 
So I have made it move now at least. With an external throttle. Had to clip of the cables there a bit to get it onto the controller. It is not generic throttle to jhrak so different interface/hookup there at the cables.

Anyway, now it is moving. I am pressing full throttle all the time in the video so no interruptions with lighter press from the thumb. But kind of sounds a bit "weird". Like with "bursts". Any idea if this sounds normal or if the sound should be exactly the same at full throttle all the time? Not with bursts like this?

www.veed.io

ow's Video - Jan 1, 2026

www.veed.io www.veed.io
See vid.
 
Electricmover said:
You just basically paste that thing onto the motor? To check temp.
Click to expand...

Yeah, its a sticker.
Like the kind for an aquarium, but it's for a coffee kettle so it reads temperatures that would cook regular 🐟 🐠 lol
 

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Electricmover said:
So I have made it move now at least. With an external throttle. Had to clip of the cables there a bit to get it onto the controller. It is not generic throttle to jhrak so different interface/hookup there at the cables.

Anyway, now it is moving. I am pressing full throttle all the time in the video so no interruptions with lighter press from the thumb. But kind of sounds a bit "weird". Like with "bursts". Any idea if this sounds normal or if the sound should be exactly the same at full throttle all the time? Not with bursts like this?

www.veed.io

ow's Video - Jan 1, 2026

www.veed.io www.veed.io
See vid.
Click to expand...
Phase wires / hall sensors are not in the right order. You have to try different combos until you get it right. Don't do it at full throttle.
 
RunForTheHills said:
Phase wires / hall sensors are not in the right order.
Click to expand...

The three Fat Phase wires are color matched and paired with the same color hal sensor wire, so when you swap a Phase wire you swap the same color hal sensor wire along with it.

The guy in the video didn't do that and had to do a lot of trial and error.
You can damage your hal sensors if they aren't paired properly.

There's four hal sensors in my motor.
Three Phase monitors, and a Speed magnet monitor.
 

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PCeBiker said:
The three Fat Phase wires are color matched and paired with the same color hal sensor wire, so when you swap a Phase wire you swap the same color hal sensor wire along with it.

The guy in the video didn't do that and had to do a lot of trial and error.
You can damage your hal sensors if they aren't paired properly.
Click to expand...
I'll be honest, I didn't actually watch the video. I just grabbed the first one that looked like it covered the subject. At any rate, it isn't rocket science.
 
RunForTheHills said:
Maybe this link will work better, although he does test the order of the phase wires and hall sensors separately.
Click to expand...

Yeah, that might be necessary for proprietary equipment.

They do s*it like mismatched wire colors to sell you their own replacement parts.
 
Aha yeah that whole thing with testing hall sensors and stuff is a real headache. Been doing it once before :)

This controller has two self learning/intelligence connectors that are put into each other to make it work. Do you guys think it will be enough to check a few different matches with these two and it will understand automatically how the halls have been wired and make the bike work? Or does it have to be done like in the video above. Manually in other words?

I remember using a self learning line another time and I think it kind of understood how the halls were wired by itself or something ? But I might remember this incorrectly..

By the way I feel like I should use a torque arm as well? Or do you guys not use torque arms on such small motors? Since it is a front motor I feel like my face might thank me :)
But the thing is the dropout is a bit weird as well. 10mm. m10 I think. Closest I found was this one below. Do you think it will do the job. I ordered the one called 10x14x5: https://www.aliexpress.com/item/100...o.order_list.order_list_main.5.21ef1802dBjObF
PCeBiker said:
If that were my motor, I'd take it apart and grease it, especially if I was planning on super-charging it. 😁

View attachment 204128


Wipe off the clumps so they don't get flung off into were they shouldn't go,..

View attachment 204129


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Click to expand...
Lithium grease for example right?
 
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