Pedelec response curve - cheapo kit

D

docdelete

1 mW
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Jan 8, 2019
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Hi - forgive me if this has been covered, I've searched a few times and couldn't see anything of help...

Anyway, a while back I fitted up my wife's cheap MTB with a cheap rear hub kit - one of the typically low-priced ones from eBay - 36v 250w - the kind with the controller limiter than can be left disconnected. Cost? £120.

Okay, we didn't expect much but it's generally a useful piece of kit. What would be nice is a more gradual /pedelec/ response. It takes many revolutions and quite a few mph before the assistance comes in, and then it seems to start at a high level. So her riding experience, especially with non-electric cyclists, needs a 'speed-up and then coast' approach. Also, as a consequence, she's getting lazy and keeping the bike in top gear, using the throttle to start off. The upshot is (ahem) muscle-wastage and high battery consumption ;)

Long story short: is there some hack I can perform to the magnetic pedal sensor, or a respected, reasonably-priced, generic controller I can swap in? Programmable isn't what I'm particularly looking for unless it's relatively painless and low-cost. This is not a mission-critical enhancement, and any cash may be better spent on a Tongsheng at a later date.

Thanks all!
 
Count the magnets in the crank sensor plate. If it's a small number (less than 6) you can try replacing the plate with one with a dozen or so magnets, or just adding some to the existing plate. That should get the pedelec to engage sooner. It likely won't do anything about the assist power level, though.
 
LeftieBiker said:
Count the magnets in the crank sensor plate. If it's a small number (less than 6) you can try replacing the plate with one with a dozen or so magnets, or just adding some to the existing plate. That should get the pedelec to engage sooner. It likely won't do anything about the assist power level, though.
Click to expand...

That sounds like the simplest choice, engaging sooner would be worth trying. Thanks!
 
FWIW, the "cheap" PAS kits I've experienced so far are not controlled by the PAS, just engaged by it. Meaning, it doesn't matter how fast you pedal, you don't get any more or less assist out of it than whatever is set in the PAS level you've picked on the display (if it has one).

It's just on, if you're pedalling faster than the engagement limit, and off, if you're not.

Changing the magnet ring for one that has as many magnets as possible will probably improve the amount of time it takes to engage it, but it won't change the amount of assist you get out of it or give you any control over it, if it is this type of PAS kit.


The only way to fix that is to change to a different kind of controller that does actually control assist based on speed of pedaling (cadence), or torque, or both.


Or using something like the Cycle Analyst v3 that you connect the PAS sensor to (instead of to the controller), and the throttle output of the CA to the throttle input of the controller, and setup the CA to give you the cadence-to-throttle amounts that you need. However, this requires the controller have a throttle input that does not require the PAS input to be active in order to operate (because it won't be getting any PAS input anymore).
 
Thanks - that also makes a lot of sense, and is borne out by our experience - it's a fixed level of whoooosh from the assist.

The kit we have doesn't require the PAS sensor to function. I know because when I recently serviced the BB I forgot to reconnect it and the unit still fired up under throttle control.

CAv3 would be the way to go if I wanted to improve the kit, but it's likely I'll just stick with the magnet trick for now, and save the money towards a better build down the line.

Top advice, thanks again.
 
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