'250w' hub motor - what will it really take?

[iangreenhalgh]

Hi folks

I picked up a front hub motor from a Raleigh Velo XC bike and as with all bikes sold in the UK, it's rated at a supposed 250w. It's a 36v motor but I have no idea who made it or it's specs.

The bike it was intended for was fitted with a puny 8ah battery, so I'm wondering how many amps this motor will actually take?

I have a Yiyun 36V controller I could use but it is rated for 28A max, which I'm concerned could be too much for this little motor.

Anyone know anything about this motor? Raleigh seem to have fitted it to a wide range of bikes.

 

[motomech]

It looks a little crude compared to the current crop of geared mini motors, but I suppose it would fall in line to the others in power handling. The basic rule of thumb is, "up to double the rating". Maybe 600 watts if it is never allowed to fall below half the no-load motor speed when climbing. Since you don't know the specs(try and research), suffice to say, never let it fall below half the top speed(Probably around 10 mph).
So you want a controller rated around 15 Amps. If you order one, you should get one with at least the simple 3-speed limiter LED display w/ PAS.
The battery really doesn't have much to do with this discussion except it's Volt rating and possibly a limit on dis-charge rating.
You should post on pedelecsuk to see if anyone else knows the motor.
Bottom line is, go ahead and use it w/ an appropriate controller. If it dies, you aren't out much
I'm just trying to figure where the cable exits the motor.

 

[dogman dan]

Well, to start with, much depends on the load. What I mean is,, the more you weigh, the more that thing will suffer if you hit it with 28 amps. But if you are more like 150 pounds, it won't actually ever pull all 28 amps long enough to matter.

But if you weigh 250, and give it max amps up a steel hill 4 miles long,, it will smoke it. 20 amps continuous going slow will roast it.

 

[iangreenhalgh]

Actually, I weigh 320, this bike wouldn't be for me.

Today, running on the flat at full throttle, I was pulling 30A and consuming a peak of 1190W on my MTB with Chinese '1000w' hub motor and a 12s8p battery built from Samsung 26F cells. Dunno how fast I was going, haven't fitted a speedo yet. My controller says it is 28A max but it tops out at 30.6A according to my watt meter.

 

[Cowardlyduck]

Actually you can get away with it if you cool it well enough.

I added oil and heat-sinks (not shown in this pic) to my '250W' hub motor and have been able to run it up to 750W without too many issue's. I've had to replace the gears once (after previously running 1000W+) and the hall sensors once.

I also tow a kids bike trailer around with it, so it is clearly able to handle a bit of load ok.

All that being said, I was towing the kids around the backyard the other day and got the motor shell up to 75C...now it looks like I might have another blown hall sensor.

Anyway, full details on my motor/mods here:
https://endless-sphere.com/forums/viewtopic.php?f=3&t=53322&start=25#p1168020

If you already have the '250W' motor and have no other plans for it, I say fill it with oil and see what it can handle.

Cheers

 

[iangreenhalgh]

Interesting stuff! I'll put my thinking cap on, cheers guys.

 

[d8veh]

How much power it can take depends on lot on how you use it. At 320lbs, it's going to struggle whatever you do. For a 220lb rider, it would be OK at 36v and 20A, or 48v and 15A if you wanted a higher cruising speed. You could go maybe 1o% higher than that if you're sensible in the way you use it, like only using high power at high speed.

 

[Cowardlyduck]

My modified '250W' motor has been hauling about 290lbs + the bike itself, so total system weight is right around 320lbs.

I also discovered that it's not toast as mentioned above, just an intermittent issue with my controller that occasionally makes it seem like a hall sensor has blown in the motor.

Cheers