Help! Bafang RM G020 speed and PAS errors

Achle29

Finding my (electric) wheels
Jul 4, 2021
5
0
Hi.....some time ago I bought a good 2nd hand Benelli Achle 29"....my old legs needed a bit of help. Recently, the rear hub motor packed in (Bafang 36v, 250W) and, after finding that virtually NO e-bikes were in stock, I opted for a replacement hub motor. I got a Bafang 36v 250W G020 and had it fitted. Yes...it works, but not too well. My old 800S display (that only ever showed the PAS setting and the battery indicator, the speed and odometer showed "zero") suddenly sprang to life but gives erroneous speed figures - I surely can NOT pedal at 99 mph - and only the 1 setting on PAS gives any power....and not very much. Tried the obvious settings on the display (wheel diam etc) but no joy.
Reading your website I wondered about C and P advanced settings, but can not get them on my display.
Is there a display out there that will communicate with the controller and let me see which settings need to be adjusted?
Not sure, if like mid drive units, the controller/motor can be connected to my laptop either.
Yes....my bike works, but it is nowhere near as good as it was before the new motor was fitted......help.....summer is here and my auld legs are getting worn to a frazzle.....
 

vfr400

Esteemed Pedelecer
Jun 12, 2011
9,822
3,931
Basildon
It sounds like you have 6 speed sensor magnets in the motor instead of one. If you can't find a setting to change it, you'd need to use an external wheel magnet speed sensor, which you'd have to splice in to the wiring. You can pick up a 5v and ground from the PAS, Throttle or hall wires. The signal wire then has to go to the white wire in the motor cable that obviously needs to be cut from the motor, otherwise you get 6 +1 pulses per revolution of the wheel instead of one pulse.

The high speed calculated comes from having 6 times too many pulses from the sensor. That will cut off the power at 2.6 mph instead of 15.5 mph unless you can release the speed limit in the settings.
 

Achle29

Finding my (electric) wheels
Jul 4, 2021
5
0
Oh lordy...that sounds a bit beyond my capabilities. Many thanks for the reply, but not sure I'm really ready to start cutting wires yet. I was hoping that there would be a compatible display that allow alterations to the data settings.....but maybe not. I've also been in touch with Benelli for ideas and am keeping my fingers crossed.
 

Woosh

Trade Member
May 19, 2012
16,398
14,101
Southend on Sea
wooshbikes.co.uk
I was hoping that there would be a compatible display that allow alterations to the data settings..
if you can open the motor's lid, remove 5 magnets leaving just one.
 

Achle29

Finding my (electric) wheels
Jul 4, 2021
5
0
Thanks, I might look into this. I can see that it would reduce the erroneous speeds on the display by cutting the number of magnetic pulses, but would it cure the problem with my PAS setting?
 

Woosh

Trade Member
May 19, 2012
16,398
14,101
Southend on Sea
wooshbikes.co.uk
Thanks, I might look into this. I can see that it would reduce the erroneous speeds on the display by cutting the number of magnetic pulses, but would it cure the problem with my PAS setting?
Correct your speed sensor first then deal with the PAS sensor next if it still malfunctions.
 
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Achle29

Finding my (electric) wheels
Jul 4, 2021
5
0
Correct your speed sensor first then deal with the PAS sensor next if it still malfunctions.
So, I now discover that the motor housing is secured with Torx pin security bolts. Waiting for a set of relevant keys/drivers then I can open it up and see where the magnet sensors are positioned and consider removing some or most of them.
 

Achle29

Finding my (electric) wheels
Jul 4, 2021
5
0
Some time ago, I removed the Torx security bolts on the motor housing but can not see any magnets or anything that could look like a speed sensor. One thing that helped was to go into the controller settings and set the wheel diameter to 16". This has allowed the PAS system to work, and now it runs up to, and cuts off at, 12 mph. Much better but not brilliant. Has anyone found a way to bypass or reprogram the controller speed limiter. ?