Difference between 250w vs 350w Bafang 8Fun hub motor

[tapash]

As the title says, what is the difference between these 2?

 

[Deleted member 4366]

It depends which one you're talking about. There's more than ten different 250w motors and about five different 350w ones. The main difference is that some are rated at 250w, so legal and others rated at 350w, which is not legal in the UK. You can get ones rated at 250w that produce more power than the 350w ones.

 

[trex]

100W. Joking aside, there are two factors that you can use to gauge the raw power of the motor: its diameter and its gear reduction ratio. The BPM for example has 180mm diameter, the SWX like on your Metro 120mm. The BPM can deliver roughly 50% more power than your SWX without overheating. The gear reduction ratio is important for hill climbing, the higher the better. SWX has 4.4 reduction, the BPM 5. Recently, I test rode the Q128H from bmsbattery.com. I think it's the same motor made by Aikema, 128SX. The Q128H has 128mm diameter but a reduction ratio of about 11. The Q128H weighs about 3kgs and delivers about the same power as the BPM albeit more slowly (the BPM can delivery an astonishing amount of power on startup) so it would suit lighter weight riders.

 

[mike killay]

Getting complicated here.
OP asks about Bafang 8 Fun motor. Replies are about BPM, SWX etc.

 

[trex]

SWXes are 8-Fun 250W, BPMs are 8-Fun 350W.
They have new models now, revised versions of the above:
http://www.szbaf.com/en/components.html

 

[Neil5403]

Is the 8FUN CST HT C02 a 250w or 350w motor ?

 

[Deleted member 4366]

Is the 8FUN CST HT C02 a 250w or 350w motor ?

Yes.

 

[Neil5403]

Yes.

Yes.

Care to elaborate?

 

[LeighPing]

Is the 8FUN CST HT C02 a 250w or 350w motor ?

Yes.

Care to elaborate?

It depends which one you're talking about. There's more than ten different 250w motors and about five different 350w ones. The main difference is that some are rated at 250w, so legal and others rated at 350w, which is not legal in the UK. You can get ones rated at 250w that produce more power than the 350w ones.

@Neil5403 it gets complicated at times mate.

 

[D8ve]

Power is controlled by the controller.
Run higher voltage and current it's higher power.
So it's both.
The original motor test specs had a difference. A manufacturer rated the motor at the highest power it could handle and not burn out at. So they could sell a powerful motor.the test proved it could cope.

The bike law lets them rate a 1,000 watt motor as 250 watts. They make one motor and rebadge it for multiple markets.
And sell it as legal. The 8 fun motors can mostly handle over 500 and even as high as 1,500 watts but reduced life happens at extremes.

 

[Neil5403]

It does sound complicated..
In a nutshell is the 8fun CST HT02 250w motor sold in the Oxy kit able to produce more power and speed than a 'standard' 250w setup? E.G my Halfords Carreras crossfire e-bike..

 

[D8ve]

Yes the oxidrive is ABLE to deliver more than A standard 250,i.e. Carrera.
But you need to be nice to D8veh to get the best out of it. And a standard 250 Could also be more powerful than the oxidrive if it was tweaked.
Remember too that higher power makes for slightly higher speed but much reduced range. Is it worth it?

 

[Deleted member 4366]

It does sound complicated..
In a nutshell is the 8fun CST HT02 250w motor sold in the Oxy kit able to produce more power and speed than a 'standard' 250w setup? E.G my Halfords Carreras crossfire e-bike..

It's not the motor that decides how much power you get. It's the battery and controller. The bigger the motor, the more power it can take. That's pretty simple, but has nothing to do with how much power it produces.

The same motor can be run at 24v, 36v or 48v. At 48v, it will make double the power it would at 24v, using a controller with the same maximum current.

Next, comes winding speed. Often, the same motors are sold with different speeds. A low-speed one will make significantly more torque at low speed than the equivalent high-speed one and the high-speed one will make more torque in the mid range.

Then there's internal gearing. The faster the rotor spins, the more torque and power the motor can produce. Nearly all geared hub-motors used to have standard 5:1 internal gearing. Now, there's 8:1. 12:1 and more, plus a few in between. Wheel size also changes the speed at which the rotor spins in the same way.

Therefore, we have current, voltage, winding speed, reduction ratio, wheel size and battery that affect how much power (torque) you get at any point in time. This is where all the myths about hub-motors not being able to climb come from. Some combinations can blitz your average Bosch bike in a climbing contest, others would look very sad. Most of the people who say crank-drives are better have never tried hub-motors designed for climbing.

Back to your question: The Oxygen and Oxydrive systems are designed for mid-range grunt, so they can sustain relatively high speed cruising. I haven't ridden your bike, nor tested it's system, so I have no idea of the winding speed, controller current or reduction ratio. if you or anybody else could provide that info, I could convert that into a real-world comparison.

 

[Neil5403]

Thanks for that. It is far from simple !!
I have a Specialised Crosstrail Hybrid with 700c wheels and am looking for a kit that is 'legal' to the eye but has the ability to occasionally do approx 20mph with pedal assist. My current Carrera has a range of about 30-35 miles with my mixed riding, so as long as it can match that, then I am happy.
The Oxydrive kit is a rear 8fun CST HT02 250w, with a Panasonic 36v 14ah battery. Doesn't say spec of intergral controller. Will that suit me 'out of the box' or will it need 'tweaking'.

 

[Deleted member 4366]

The Oxydrive kit is a rear 8fun CST HT02 250w, with a Panasonic 36v 14ah battery. Doesn't say spec of intergral controller. Will that suit me 'out of the box' or will it need 'tweaking'.

How heavy are you?
What sort of hills do you encounter?

 

[Neil5403]

I am not small. 6'4 and 115kgs
Not big hills just the odd one here and there !!
I manage 30+ miles out of my Halfords Carrera e-bike.

 

[Deleted member 4366]

Have a word with Woosh. I think they run their kit with slightly more current, which would be better for a heavy person.

 

[redcup1999]

It does sound complicated..
In a nutshell is the 8fun CST HT02 250w motor sold in the Oxy kit able to produce more power and speed than a 'standard' 250w setup? E.G my Halfords Carreras crossfire e-bike..

Are you looking for something with more oomph than a Crossfire-E?
If so, be aware that the Suntour Crossfire-E already has a fairly powerful motor / controller combination, so you need to be picky in selecting something that has noticeably better performance.

My Crossfire-E has similar performance to my Bafang SWX08 (essentially a slightly less powerful BPM) powered ebike and cuts out assistance at 16.5mph (as reported by Garmin).

 

[Neil5403]

Thanks for that. What does BPM mean?

 

[LeighPing]

Thanks for that. What does BPM mean?

Big Powerful Motor.