Swift Xootr E-Conversion

[Jeremy]

That is a nice wattmeter you have put together Jeremy. Am interested in what you mean by a 'torque driven controller'?

The little black box controls the bike power and does things like automatically shut off the battery if the bike is left for a few minutes without significant current being drawn (saves accidentally leaving the bike switched on and killing the battery!). It also keeps track of total Ah used from the battery, and stores this every time the bike is switched off, so that if you use the bike a few times between being charged the "fuel gauge" display always shows the remaining battery capacity. The next version will have an RFID tag reader to provide security and stop anyone just turning the bike on with the on/off button.

The controller I'm currently building uses a variation on Field Oriented Control, a method of providing more accurate control of the motor than the simple 6 step commutation that ordinary ebike controllers use. This measures the phase current in each motor phase, very quickly, and the throttle controls this phase current directly. The result is that the throttle works rather like that on a car or motorcycle and controls the motor output torque fairly directly, rather than the motor speed.

I'm hoping that this will remove some of the mid-speed jerkiness that results from using a speed throttle control. There are other fixes for this, like using a two or three speed switch with the controller, to vary the throttle range, but I've always wanted to see what true torque control would feel like, as I have a suspicion it may feel more natural.

 

[hech]

Brilliant, well done!

 

[hech]

Do you know what the 3 speed switch limits - voltage, current, phase amps and will all lyen's controllers have this feature even if it is not wired up?

 

[Jeremy]

Do you know what the 3 speed switch limits - voltage, current, phase amps and will all lyen's controllers have this feature even if it is not wired up?

The 3 speed switch limits the maximum speed, so sets an upper limit on the controller output voltage. The effect (when set to a speed lower than 100% on the switch) is to expand the throttle range, so throttle 0% to 100% may, for example, give 0% to 30% in the low speed setting, or 0% to 60% in the mid speed setting. This feature is on all Xiechang controllers, including the versions that Ed Lyen sells (it's also on the much cheaper version of the same controller available from e-crazyman on ebay, for example).

To use the speed setting means programming the desired maximum speeds for each switch setting using the "parameter designer" or "XPD" software (both freely available) and then wiring up a switch to select between low, medium or fast speeds. If the wires aren't brought out of the controller case (often they aren't) then the board needs to be removed from the case and wires attached to pads X1, X2 and 0V. Connecting X1 to 0V sets low speed, connecting X2 to 0V sets high speed. With neither X1 or X2 connected to ground then the medium speed is selected. This means a single pole, two way, centre off switch can be used with the switch sequence being "low", "medium" and "high". With no speed switch connected these controllers default to the programmed medium speed (which Ed Lyen usually sets to 100%).

 

[jhruk]

Thanks Jerry. Yes it does shift - 60V driving the highest speed version of the Q100 makes for a fairly fast bike, but also, unfortunately, makes the throttle response rather jerky, almost just on/off at modest speeds. The next stage is to replace the xiechang controller and power control stuff in the silver box with a proper torque driven controller, which I hope will give a smoother response than the speed throttle that most ebikes have.

I have a Q85 motor with a ku63 controller in a 20” Dahon folder and although I only run it a 36v I’ve also had the jerky throttle problem. As my larger wheeled bikes don’t seem to suffer from this I’d put it down to flex in the long handlepost making smooth throttle movement more difficult. In an attempt to lessen this I changed to a half throttle and have found this does make some improvement, body movements not being transferred to throttle movement quite so easily.

I’ve often thought some sort of smoothing of the throttle signal might help as well and would be very interested in any solution you come up with.

 

[Jeremy]

The Wuxi Xichen Micro-Electronic Co controllers (variously badged as KU, Greentime, Hua Tong etc) all have a three speed switch capability, too. BMS Battery sell the switch to add this functionality, I believe. The effect of selecting a lower speed on the switch is to smooth out the throttle, by reducing its sensitivity to small movements, so worth doing when you're not riding at maximum speed.

 

[jerrysimon]

As a quick update I have been riding this bike a lot more now the weather has improved. The Goldant motor seems to be performing well. This is in fact my fastest conversion I have done despite the small motor. I quickly get up to 18-19mph with assistance and now I have fitted a whopping 56T chain ring its really comfortable to ride. I find I have to pay more attention when riding and take extra care when other pedestrians and sedate riders are on the paths. In this configuration the bike is both lovely to ride with assistance switched off or on. I am hoping to use it a lot in the summer with minimal use of the assistance and being "relatively cheap" I will be able to lock it up in town without too much fear of it being stolen.

The fold is never going to win any awards, buts it fine for stowing in my office or the car if need be. The big apple tires make it really comfortable to ride whilst having minimal effect on rolling resistance.

The Brompton is still the king of the fold for shopping etc.

Regards

Jerry