Controller for Bafang SWX01

[Alan Quay]

Hi all,

Last week I picked this motor up cheap from eBay, and now I need a controller for it.

My questions are:

1. Is it worth going for torque simulation sine wave controller? Perhaps the s06s or the s12s?

2. How far can one of these motors be pushed? Should I stick with a 250 watt controller, or can I go a bit more?

3. I note that Bmsbattery now have bottle batteries with integrated controllers. Anyone had experience of these? They look to be a neat solution.

You thoughts would be appreciated.

 

[averhamdave]

I've run 1000w+ through one of these - and stripped the gears after a few miles of rough pot holed street riding.

The 250w number is notional only anyway, they are good for 600w peak and more. (36v battery off the charger is 40v+ and 15 amp current setting on the controller equates to 600w and is no big deal.)

Unless you understand the detail you'd probably be best to tell BMS what you have and are trying to achieve and let them advise on compatible parts.

Bottle batteries with inbuilt controllers have their place in making for neat installations - as long as you don't need high current deliveries.

 

[averhamdave]

Oh and you need to know the spec of your motor - what voltage it was wound for and what it's rpm is at that voltage.

I ran a 36v unit at 48v for quite a while, gave comfortable 25mph but the nylon gear drive is the weak spot.

 

[Deleted member 4366]

I don't know whether you noticed, but the motor has a stub on the brake side. My guess is that it makes the motor 150mm wide. If you pull the innards out, you may be able to cut that stub off to get it down to 135mm. have you tried it in a frame yet? If not, you should try it first.

Which controller you get depends on what you want. The motor will run fairly safely at 20 amps 36v, but if it's a 24v one it might get hot when hill-climbing. You need to power it up and measure the speed to find out whether its 24v or 36v, not that it matters. The 9FET controllers tend to take about 22 amps, which might be a bit high, si I'd get a 6FET one and solder the shunt for a bit more oomph.

Ihave one of the torque simulation controllers, but I don't use that feature. I prefer it in the old-fashioned speed control mode for the PAS, which works like a sort of cruise control. The torque simulation gives power control, which to me is not so logical, but more like normal cycling.

I haven't opened a BMSBattery bottle battery with an integrated controller, but I have other ones, which have sealed controllers to waterproof them because the compartment in which it sits isn't sealed, and it gets the spray from the front wheel. This makes current adjustment impossible, so you're stuck with the standard 15 (if you're lucky) amps.

 

[Alan Quay]

Thanks guys. I will connect it up and see what results I get.

D8veh, I hadn't considered that it could be 150mm, I will check that later and report back back.

 

[Alan Quay]

....I hadn't considered that it could be 150mm, I will check that later and report back back.

....but it is. As ever, eagle eyed D8veh is spot on.

Hmm, that's gonna be a problem, since my drop out are for 135mm, as I suspect are most other MTB's.

What bit are you suggesting can be chopped off D8veh?

 

[Deleted member 4366]

You have to take the side cover off the motor. Normally the axle and motor gubbins comes out with it leaving an empty hub. If you can get at the screws, you don't need to remove the free-wheel, but you need to remove the nuts from the other side. When you have a bare hub, you should be able to saw off that spigot, but check that the bearing is inboard of it. Finish off with a file/Dremel/angle grinder. The axle will hopefully have flats for the drop-outs that run right through the spigot. If not, you'll have to carefully file them further. The axle is probably hardened, so you'll need a Dremel or angle grinder to grind it. If you're unsure, pull it apart and take some photos.

Another option is to stretch your frame. If you lay it on the ground, put one foot on the bottom side and give the other a good jerk, it'll move. You shouldn't move it more than once because it work-hardens.

 

[Alan Quay]

Great, I think I'll have a go at that, cheers D8veh.
Might have to wait until the stitches are out from my knee - had a little tumble testing the new cruiser last weekend. Result: 7 Stitches.

 

[Alan Quay]

Ok, so I looked a bit closer, and disassembly was not required. Chucked it in the vice, and chopped that spigot off saving about 13mm.

The wheel needs to be dished to bring it back to the middle, but with my trusty 2lb percussive adjuster I reckon it'll fit.