Help with Pedal Assist settings

[yossarian5891]

Hi, new here!

Recently installed a new e-bike front motor kit from Yose Power. I've set it up so I'm only using the pedal assist. Everything seems to be set up working great. The controller is integrated into the battery base. The LCD is a KD21C display. The front motor is 250w.

I'm a bit confused about the pedal assist settings so was hoping someone could clear my thoughts up! (And maybe help understand if I could get what I want...)

I've left the settings mostly default, they're all fine. I've changed the assist setting to 0-3. I like quickly being able to change from no assist for tight careful manoeuvring, to some assist on the flat, to 2 for the up hills. Haven't even needed the highest setting, maybe when I feel super lazy.

In changing the assist you can alter the ratios, between 0-100, and an AC/or UC at the max whatever that means. My assumption was this is a % of assist provided up to 25kph. But this isn't what I feel when I'm riding so I'm a bit confused by how these ratios work.

For example, (and my assumption was), if I had level 1 = 20, I would get 50 watts of power up to 25kph, if level 2 = 60, I would get 150 watts up to 25kph.

In practice I have left the settings for 0-3 the same as the level 2/4/5 on the 0-5 setting. So level 1 ratio = 50, and level 2 ratio = 75, and level 3 ratio = 95. This seems fine as it's a copy paste of what felt most useful on the 0-5 setting assist.

But what I feel when I'm riding with the 0-3 assist levels setup as above, (and have the watt setting on the LCD to follow the output), is that on level 1 assist the assist is strong up to about 16kph and then tails off, this is fine as I can manage close to 25kph on my own steam thereafter. At higher end of that speed the display is showing 0 watts, but it feels like there is some assist to ~20kph. On level 2 assist it gives loads of assist up to 25kph, great for going up hills etc. Each time the assist kicks in strong, it says it's providing up to ~200 watts on the display. If I soft pedal in assist level 1, it will output 200 watts and then drag me along at ~16kph.

I guess my question is, is this normal for Pedal assist to function like this? Or is there a way of setting it to provide what I what, i.e. 50 watts on a lower setting, and 150 watts on a higher setting? Is it maybe some weird controller? Is the Assist ratio, a ratio of speed, not power output of the motor?

Sorry for so many rambling questions! I'm a bit confused. All in all I'm happy, and if this is just how it works, I can live with the quirks of that. It basically does what I intended it to do. And I hope that was all clear!

NB having written this all out, I've just realised the assist ratio maybe of the speed given a 32kph max. I could test that out, as then level 3 at 95 should assist me to ~30kph. I have the speed limit set at 25kph, but I could see if that theory works. But again, I don't understand by it isn't a ratio of power, unless the display lies!

 

[Nealh]

I'm not familiar with the KD21C and controller but think they are Lishui brand.
I believe the system is a mix of speed control with some options of setting the power ratios. One gets a different max speed in each assist level, the power will drop off to nothing near the optimum speed but may still give 10/20 watts of low power.
The PAS system is a simple rotation cadence system, it only needs a simple crank rotation and even if one pedals with a very high cadence won't get any more power. One will simply reach the cut off quicker and exert more energy for fitness.

I have similar systems on my bikes but they use current control for the PAS which is more user friendly and one can decide on the actual power delivery. I get max speed to cut off in each PAS level.

For ultimate riding and control then Torque drive systems may offer a better ride.

Of the three systems used the speed control ones are least favoured given a choice.

 

[yossarian5891]

Thanks for the reply. You are correct that it is a Lishui brand controller. I found a better quality manual, although it doesn't really clear up my question. Although the manual seems to imply it's a % of power in the appendix. But I'm convinced, just as you say, it's in relation to speed.

I understand the kit I chose was pretty low cost, so I'm not expecting much to be honest. To be fair I'm a reasonably strong cyclist, and chose the kit for delivering, as reregistering as an e-bike means more delivery options, so I wasn't basing my decision around the most practical kit. But the assist is super helpful in getting up the hills quickly, and I'm happy to keep my fitness up as much as possible.

I can totally see how see how torque assist would be the most desirable option.

Being a bit worried about the kit quality, I filled anything exposed in the controller, and gaps to the controller with epoxy. I've read largely that the biggest failure is water ingress, so I hope this helps with longevity. But I also wanted lower assist settings so I didn't stress out the motor/battery with high torque/high currents. Hopefully that's a sensible decision in the long run...

As an alternative, there's an option in the manual to reduce the peak current (I think) which at default is 15A called "Controller over-current cut". Would it be sensible to drop this to ~12A to reduce that 'surgey' feeling of the assist, and maybe it'll peak at ~150 watts. I wouldn't damage anything by reducing this value right?

 

[Nealh]

One can try to see if the bike feels better and if the surging less noticeable.

I use KT current control the difference is night and day compared to Lishui.
The KT has five current power settings in the std firmware of 13, 20, 33 50 & 100% of the max current, one can use 20,22 & 25a controllers with a 250w hub for a bit more oomph in PAS1 without needing higher power levels, these can e saved for hillier terrain riding. PAS 1 is tame and gives nice low power with max speed if one wants it by pedalling a little harder.
If one is techy knowledgeable then there is OSF out there to make whole sale changes to both makes of controller to totally re-programme them.

 

[yossarian5891]

Well. Playing around and reducing the pedal assist further (to 35/70/95) has helped a lot. PAS1 now feels a bit of low speed torque but not excessive, but the feeling is a lot more natural with gentle assist up to the speed limit. I also reduced the current slightly, which may or may not have helped. Then setting 2 is great for heading up hill a bit faster.

I think you're right. The assist seems a combination of power reduction and a speed limit. Thanks for the help. I'll keep those options in mind for the future.

 

[Nealh]

I think PAS1 should always be a very low power option with cadence type speed controllers, it takes quite a few users by surprise as they don't like the initial surging and can be off putting. Esp for leisure riders who are in a group or amble along.
2 - 3a of current is plenty of current for low power to give a gentle shove in the back.

 

[Bobbo1260]

I personally found the 0-5 setting too aggressive so have changed mine to 0-9 with the power settings starting at 20 for PAS 1 and increasing by 10 for each of the next 8 PAS modes ending at 99 for PAS 9.
This means more pressing of the +/- button to change the PAS throughout its range but the increase or decrease of the power band is more gentle. PAS 1 is hardly noticeable but handy for me as I ride my trike on paths and in shopping centres where it only gets up to a legal 4mph. PAS 2 when hitting a gentle incline which again in minimal. Generally I use PAS 3 which gets me up to about 6/7 mph on the flat which is fast enough on a trike on a road where avoiding pot holes with 3 wheels is an acquired and needed skill.
If setting the PAS at 0-7 start at 14 and increase in increments of 14 or to what suits you preference.