Field/Flux Weakening & Boost Button Fardriver Controler

[72V]

I have recently finished converting a YZ85 to electric. However, I am having an issue achieving my goal of 70-75mph for a top speed. Im using the qs138 v3 70h motor and a 72530 controller. My battery is Amorge 72v 350a sustained and 450a peak. I am running a 17t front and 35t rear. This is the largest front sprocket and smallest rear sprocket that I could find online to fit the motor shaft and wheel hubs that I am running. When the bike is on the stand, the highest RPMs that I can hit is around 4700 according to the graph readout on the Fardriver app. I have read about field weakening, and that people are achieving nearly double the RPMs with this. I have played around with the settings on the app called "Weak Response" with values ranging from 1-7. I have tried all of these settings while the bike was on the stand and none of them seem to make any difference If anyone has any suggestions to try, that would be greatly appreciated.

my next question is regarding the "boost button. I have this hooked up to one of the momentary switches on my handlebars. The input also controls cruise control. The cruise control function does work, however, Im not getting any kind of noticeable "boost". Perhaps I'm not using this feature correctly?

 

[gromike]

Thanks for the pic. Kind of like emoto porn. Beautiful bike.
What speed can you get to? And at what amps/watts?

 

[dominik h]

I have seen 6300rpm form the QS138 70H V3 with field weakening and 72V battery. While I was testing with no load.
Have you raised the ratios in speed in the higher regions?
Please post screenhots from your settings.

For an effect on boost you have to set higher values in
Custom max line current
Custom max phase current
then in your normal settings.

 

[72V]

Thanks for the pic. Kind of like emoto porn. Beautiful bike.
What speed can you get to? And at what amps/watts?

Thanks man, I've been looking at different decals for it. But this plain look is starting to grow on me lol.

With the current gearing and settings, it tops out at 54mph with GPS.

 

[72V]

I have seen 6300rpm form the QS138 70H V3 with field weakening and 72V battery. While I was testing with no load.
Have you raised the ratios in speed in the higher regions?
Please post screenhots from your settings.

For an effect on boost you have to set higher values in
Custom max line current
Custom max phase current
then in your normal settings.

Hi Dominik, I have tried raising all the speed ratios to 100%. However, I have recently changed them at the advice of a guy on Facebook to see if that would help achieve field weakening. My max line current is 350A, and Max phase curr 530A. And the light bulb just went off in regards to why my boost isn't working after reading your post. I have Max boost set to 350a line and 530a phase also lol. Which is the maximum that my controller can handle. So that makes sense as to why it doesn't seem to make any difference. Im going to run out to the garage to take some screenshots and upload them in a few minutes.

 

[dominik h]

Does the phone app display MTPA or weak at full speed on the graph page?

 

[72V]

Im pretty sure it says MTPA in the middle of the screen on the graph page. I will have to run back out and double-check, but thats what I see on old screenshots.

 

[72V]

I have seen 6300rpm form the QS138 70H V3 with field weakening and 72V battery. While I was testing with no load.
Have you raised the ratios in speed in the higher regions?
Please post screenhots from your settings.

For an effect on boost you have to set higher values in
Custom max line current
Custom max phase current
then in your normal settings.

Here are all my current settings.

 

[72V]

Here are all my current settings.


View attachment 360008

View attachment 360009


View attachment 360010

However, I just changed the ratios in speed to these settings yesterday. Before that I had them all maxed out to 100% just to see if it changed anything.

 

[72V]

Does the phone app display MTPA or weak at full speed on the graph page?

it says MTPA.

 

[dominik h]

You are in low gear and the motor is not running.
Mine shows MTPA even when I'm not connected to the controller
Near max rpm the Display should Show "weak".

 

[72V]

Does the phone app display MTPA or weak at full speed on the graph page?

Just to clarify, the "weak response" setting is what controls the field weakening right? And what setting would be the highest setting 1-7? I was also wondering what "weak character" does.

 

[dominik h]

Weak response 0 is the highest value you can set. 7 is no feald weakening.
Please also make Screenshot from the other settings and from the Front Page of the app

 

[72V]

You are in low gear and the motor is not running.
Mine shows MTPA even when I'm not connected to the controller
Near max rpm the Display should Show "weak".

Yeah, the bike is most likely still in low gear. It started raining when I got home on it last night and had to ride through wet grass with slick tires to get back to the shop so I put it low.

 

[dominik h]

Weak Charakter should only be reduced when the motor is jittering, according to the manual

 

[72V]

The front page as in the "simple mode" I think they call it?

 

[dominik h]

Yes, there are also possibilities to reduce max current and max rpm

 

[72V]

So what would be the normal setting then if you went by the manual and didn't have jittering... 0?

 

[72V]

Yes, there are also possibilities to reduce max current and max rpm

Ok, one sec. ill send them.

 

[dominik h]

We tested the weakening field with no load on rollers. Or how are the red barrels under the rear wheel called.

 

[dominik h]

Weak Charakter fast
Weak response 0
Should get you the highest rpm, if there are not other parameters limiting the rpm

 

[72V]

Weak response 0 is the highest value you can set. 7 is no feald weakening.
Please also make Screenshot from the other settings and from the Front Page of the app

Here are the other screen shots.

 

[72V]

Weak Charakter fast
Weak response 0
Should get you the highest rpm, if there are not other parameters limiting the rpm

I just ran the bike on the stand again 3 times with with weak response set to 0, 3, and 6. Its topping out at 5200 for each run. This is 700RPM faster than the last time I tried this. I'm not sure what the difference is. Also, my battery is only 70% right now. The last time I tried this it was 100% charge.

 

[72V]

We tested the weakening field with no load on rollers. Or how are the red barrels under the rear wheel called.
View attachment 360019

That's a really cool setup. I was just letting the wheel free spin while off the ground on the stand when I tested mine.

 

[72V]

I just ran the bike on the stand again 3 times with with weak response set to 0, 3, and 6. Its topping out at 5200 for each run. This is 700RPM faster than the last time I tried this. I'm not sure what the difference is. Also, my battery is only 70% right now. The last time I tried this it was 100% charge.

Also I noticed it changed to "weak" where it says MTPA when the RPMs got up around 4k