Speed Limiter on PCB: I'm clueless

Hello guys!

I've been surfing the board for a while and wanted to congratulate you first for the endless source of information.

I bought my first ebike a few days ago. Nothing too fancy, just a 250w 36v model.

I really want to get rid of the speed limiter so I did a little research and changed the P08 setting in the trip computer from 25 to 30km/h. Unfortunately, nothing happened.

Then I searched for alternatives: The ebike hasn't an external speed sensor, it appears to be inbuilt or maybe some sort of regulator within the hub. So the trick to place the sensor somewhere else is not possible.

Then I got to the controller: Unfortunately it doesn't have a cable that I could unplug and get rid of the limiter.

So this is when I think you guys might have an answer. Do you think it's possible to modify something from the PCB to disable the speed limiter?

Please have a look at the photos attached.

Any idea would be helpful.

Cheers!

Here you have the links to the images in case you may want to have a closer look.

https://ibb.co/cbMvby
https://ibb.co/hDXOUJ
https://ibb.co/hgDaby
https://ibb.co/hPQA9J

Hey there,

Normaly there's a shunt on the PCB somewere, it pumps current trough the shunt, then reads back the voltage difference. Based on the difference in voltage it can calculate the amount of amps you're pulling through the controller, it them limits the amps if needed.

A 'solution' to the limiting is to add some solder to the shunt, as it gets bigger the voltage 'drop' gets less, and the controller thinks you're pulling less current.

The above is just my understanding, i'm sure it's not fully electrical correct.

I cannot see the shunt in the pictures you've posted, but maybe you can find it somewere hidden on the PCB. It looks like this: https://i.imgur.com/FtA7Rzv.png

Remember that by pulling more current trough the controller it might break down faster or just burn out completely..

Tim

AFAICS, he's looking to remove the speed limit, not the current limit.

The shunts don't do anything to monitor or limit speed, only current.



As far as removing any speed limit, if there's no separate sensor, and it's using one of the phase-hall sensors to monitor speed, then your only options to remove the limit are:

reprogram the controller, if it's programmable. That usually requires software (that isn't usually available) from the manufacturer.

If there is a speed limit jumper wire (found on some scooters, not often on bikes with LCDs), disconnecting that might do it, depending on the limitation of the programming of the controller.

Replacing the controller (and LCD) with one that has no limit, or is settable in the LCD (for real, whereas the one you have appears not to be).


Note also that to go faster requires more power, so a 250w system is only going to go so fast before it simply couldn't propel you any faster even with no limitations.

You can use simulators like http://ebikes.ca/simulator with various motors/controllers/batteries to see what it might take to reach the speed you want, and maintain it without overheating anything.


FWIW, if it is just that your system cant' supply enoughpower to go any faster, then what homescape suggests might work--but it also will be harder on your battery pack, aging it faster and causing it to perform less well and get shorter range, and it also has a risk of damaging the controller and motor from overheating.

If you did want to do this, you can't quite do it like he suggests, because you don't have a shunt wire, you have a shunt resistor (the big rectangle with R005 on it). You'd ahve to replace that with a lower resistance shunt, or parallel another one to it, etc.

Thanks guys! You are really friendly.

Unfortunately it seems there's no easy way out of this. I can't find a jumper anywhere in the PCB, so the programming option might be the only one, and that totally exceeds my possibilities.

I'm going to try to disconnect the LCD to see if I can reset it and insist by modifying the P08 setting again.

Thanks again!

Hello guys, me again.

I did some experiment today with the ebike. I tried to trick the controller by setting a smaller wheel size in the LCD as suggested by others.

To my surprise it did not work.

I maxed the throttle for a while and the speed was still limited. The speed limiter is set to 25km/h. After modifying the wheel size in the LCD, the speed limiter kicked in at 14km/h (the actual 25km/h).

So I guess the speed limiter is built within the motor hub. Something I never thought possible.

Have you ever heard of something like that??

No, but it's certainly possible for the system to have a separate "calculation" for the speed limit and the speedometer reading.

In that case, it would ignore the wheel size and other settings, and assume you have whatever wheel size it was programmed with originally, and calculate speed based on motor RPM and that size, and use whatever speed limit it has built in, ignoring any setting by the user.

The speedometer would still operate based on user settings.


I don't know that your system works this way, but it would explain what you see.


Also, are your tests done with the driven wheel off the ground, or while riding, or both?

If the results are different between the two, (faster off ground) then the speed limitng is probably working via setting, and it's just power limited.

Thanks mate!

I'll keep experimenting. If I have news, I'll let you know.