UK legal rear hub 48 volt kit?

[Woosh]

I can't see any speed sensor,

Hub motors can have internal speed sensor.

 

[Nealh]

So, assuming that the motor is marked as 250w, as stated in EAPC rules below, can anyone see any reason why this kit won't be suitable for my needs?
I have sent a message to the vendor to ask what markings are on the motor.

Electric Bicycle E Bike Motor Conversion Kit 26" Rear Wheel

It's not legal, another one of them cheap 1KW Chinese D/D kits. The power drive of motors/kits aren't allowed to be switchable this one uses a switching cable embedded in the controller although it is 250w legal in one sense it can be changed to 1KW, It has a double mode so is sheep in wolf's clothing.
The motor is wound for 28mph and fast riding so is probably about 400rpm or more, at 250w and 16mph it will be so inefficient and power will be transferred in to heat.

 

[Nealh]

Internal speed sensor hubs have the 9 wire motor cables with the white one used for this.

 

[anotherkiwi]

Any 36V kit geared hub with a 36/48 V controller and a 48 V battery would be legal as long as the motor is engraved "250 W".

 

[Danidl]

And a technical question about the kit in post #19. I can't see any speed sensor, so how does the controller know what speed the wheel is going, to cut off the power at the legal speed?

.... It doesn't need one. The controller has a clock and electronic switches which switches the DC current into the three sets of coils in the motor in a specific sequence and rate. It doesn't need to know from the motor what speed it is going at, because it is doing the driving. The speed of the clock in the controller sets the rotation speed.

 

[Fordulike]

Right, I understand that hub motor has the function to send a signal to the controller to set the speed, but I still can't get my head around how it knows how fast the actual bike is going depending on the wheel size. Is each controller programmed for one wheel size only? I'm only talking about the kits that don't have the LCD display.

 

[Woosh]

you set the wheel size in the LCD.

 

[Fordulike]

you set the wheel size in the LCD.

So, the one in the listing, which doesn't have a LCD display, would have already been pre-programmed for a 26" wheel?

 

[Fordulike]

It's not legal, another one of them cheap 1KW Chinese D/D kits. The power drive of motors/kits aren't allowed to be switchable this one uses a switching cable embedded in the controller although it is 250w legal in one sense it can be changed to 1KW, It has a double mode so is sheep in wolf's clothing.
The motor is wound for 28mph and fast riding so is probably about 400rpm or more, at 250w and 16mph it will be so inefficient and power will be transferred in to heat.

How about if I pull the switching wire cable inside the controller casing and leave it connected inside the sealed casing? Then it's not easily switchable on the fly by the rider.

Not worried about the efficiency!

 

[Woosh]

So, the one in the listing, which doesn't have a LCD display, would have already been pre-programmed for a 26" wheel?

without the LCD, it can't display speed and apply restriction.

 

[Danidl]

Right, I understand that hub motor has the function to send a signal to the controller to set the speed, but I still can't get my head around how it knows how fast the actual bike is going depending on the wheel size. Is each controller programmed for one wheel size only? I'm only talking about the kits that don't have the LCD display.

.. the controller generates current for the motor at a specific frequency. The motor tries to attain this frequency , subject to load limitations, . The frequency determines the road speed depending on the diameter of the wheel and whatever internal gearing there is in the hub motor. In bikes with an LCD display panel, a service menu can/ may be selected which allows the shop or the user to send the appropriate parameters to the microcontroller in the controller, . The LCD panel is a human machine interface , just like the monitor and keyboard on a computer . Its primary purpose is to communicate not control. Most of the operational intelligence resides in the controller.
If you set the controller with the parameters appropriate to a small diameter wheel and actually had a large wheel fitted, it will make the bike have a higher top speed.

 

[Fordulike]

without the LCD, it can't display speed and apply restriction.

Mmmmm, I'm just wondering if the controller in the listing just lowers the current to the motor in 250w mode, and naturally tops out at 16mph.

If I'm correct, the law requires it to cut off the power totally at that speed (well 15.5mph)

 

[Woosh]

Mmmmm, I'm just wondering if the controller in the listing, just lowers the current to the motor in 250w mode and naturally tops out at 16mph.

If I'm correct, the law requires it to cut off the power at that speed.

on those small SWX motors, the legality depends on the motor's winding.
i usually go for 180 rpm on 26" wheels,
the current drops as speed increases, eventually becomes useless at over 16mph. You don't break any law.

 

[Nealh]

on those small SWX motors, the legality depends on the motor's winding.
i usually go for 180 rpm on 26" wheels,
the current drops as speed increases, eventually becomes useless at over 16mph. You don't break any law.

The hub in the listing isn't a geared hub, it's a gearless D/D.

 

[awol]

PSWPower.com, 20a Sine wave.

Just had a look and it says stronger mosfets but was wondering if this is basically a BMSBattery S06S? If I solder the shunt up to 20a on my S06S it got so hot the label writing melted off.

Can you limit the max amps using the LCD? Reason I ask is I notice they also do a 17a version and was thinking of getting the 20a and limiting it for general use but have the option of upping it to 20a if I wanted to test other motors.

 

[Nealh]

The controller is a Kunteng, don't know who makes the S series from BMSB as never had one to play with.
I have the lcd2 so amps aren't adjustable by lcd as the 5 assists give different Torque in each level, though possible other lcd options could be adjustable.

 

[Fordulike]

Right, just to clarify. If I get a 250w rated hub motor, couple that with a programmable 48v controller, set it for 15.5mph max speed, then that is totally legal in the eyes of UK law?

 

[Deleted member 4366]

Right, just to clarify. If I get a 250w rated hub motor, couple that with a programmable 48v controller, set it for 15.5mph max speed, then that is totally legal in the eyes of UK law?

Yes. That's a good way to get more torque from a 250w motor. You need to be mindful of the motor's maximum rpm. if you're going to limit it to legal speeds, you want a 36v one with a speed around 200 rpm or a 48v one with a speed of about 230 rpm (maybe 260 rpm highest). There's no downside to using a 36v motor at 48v as long as it has the right speed.

 

[Fordulike]

Yes. That's a good way to get more torque from a 250w motor. You need to be mindful of the motor's maximum rpm. if you're going to limit it to legal speeds, you want a 36v one with a speed around 200 rpm or a 48v one with a speed of about 230 rpm (maybe 260 rpm highest). There's no downside to using a 36v motor at 48v as long as it has the right speed.

Thanks Dave. I did toy with the idea of using a buck converter, but none appear to be able to supply enough amps. I think I'll have to go the programmable controller and 250w motor route.

 

[Deleted member 4366]

Just use a normal KT controller. You can set the speed in the LCD. I'm sure that's enough. Do you already have a motor in mind?