Throttle jerking on Bafang question please?

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Shedster   1 mW

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Throttle jerking on Bafang question please?

Post by Shedster » Jan 06 2021 11:57am

Hi, not been on here a while, but I've recently got sucked into adding motors to pushbikes... I've currently done my first, a Voilamart hub motor in a non-suspension bike, which works great and whizzes along on the flat roads a treat, but now I want something for the trails and with some hill-climbing ability. So I've just picked up a full suspension bike, and I'm going to add a Bafang 48v 750w mid-drive.

So far so straightforward, but I don't want to run any pedal assist, what I really like about the hub drive is I can use the motor and/or pedal as much or as little as I want (I have a full-twist throttle so it reminds me of all my motorbikes), so basically I'm in control with no electronics interfering. But I've been reading various threads about the later Bafang mid-drives being very inconsistent with the throttle, kinda jerky on and off, even apparently with PAS at zero, and obviously I want as smooth a power delivery as possible.

Does anyone have any helpful advice or experience to share please? Is this still a problem with a new BBS02 (the threads I saw were from 2017). And does anyone do a decent full twist throttle to go with this motor please?

I do understand it may be possible to reprogramme the controller, but I'd very much prefer not to get involved in that, I'm not computer savvy (I don't even have a smart phone...). I just want to fit the kit, twist the throttle, pedal as much or as little as I like, and razz off into the sunset... ;-)

Thanks in advance.... :thumb:
It will be alright in the end. And if it isn't alright, it isn't the end yet...

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amberwolf   100 GW

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Re: Throttle jerking on Bafang question please?

Post by amberwolf » Jan 06 2021 2:29pm

It's unclear, but have you already added the drive, and are you having a problem with it?

If not, I would recommend against messing with it, because altering settings or flashing firmware always has the chance of bricking it, and then you either replace the whole drive unit or open it up and replace the controller (which risks breaking other parts in the disassembly/reassembly process).

Regarding the throttle issues, the known solutions are in the big thread(s) discussing the problem(s), so if you read those threads, you already read the solutions, where they exist. ;)

As for which throttle itself to use, that depends on your specific preferences for grip and action style, etc. There arent' any "really good" ones out there, that are single-unit types, that have all the features in one unit, and durability, reliability, waterproofing, adjustability, etc. Almost all of them are cheap plastic things that generally work well enough for most people, so there's not much out there that's different from any other option.

There are some very expensive ones that are a little better, but they're not much (if any) more durable, etc.

The "best" option for customizability to your own specific preferences is to use a cable-style throttle control on the bars (grip, thumb, toggle, etc) of the type that physically suits you, and then use a cable-operated-throttle of the hall or potentiometer type, to provide the signal to the controller. Make sure that the mechanical pull unit (grip, etc) has at least the same amount of cable pull as the COT unit itself, or you won't be able to get the full output range from the COT, and so the controller won't respond with the full speed / power range.

A Hall-type COT works best with units like the BBSxx series; to use a Potentiometer (pot) type you'd need to add some external passive electronics (resistors or potentiometers); there are threads on how to do that if you need to.

Alternately, you can use the Cycle Analyst v3 to "adjust" the output range of a COT unit (or any other throttle) to match the input range of a particular controller, to eliminate electrical deadzones (where moving the throttle does change the output voltage but doesn't change the controller behavior for parts of the rotation range).

That's what I do for the SB Cruiser, to use a metal durable ATV thumb throttle on the bars to control a COT (presently "temporarily" mounted on the steerer tiller tube) to run the controllers as needed...and the CAv3 also takes my PAS input and converts it to a throttle signal so I can control the motors by pedalling, even without having to be in a gear that puts any load or strain on my joints.

This thread shows how to do it with a brake lever for variable regen braking (for controllers that support that on DD hubmotors) but the same principles apply to a throttle:

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