Focbox - stuttering when accelerating from slow speeds in FOC mode?

This might be a shot in the dark but is your receiver or its wires close to the phase wires going to the motor?

I had an issue with my board once where if I accelerate up a steep hill it would cut out a little, My receiver wires wrapped over the phase wires and when there was a large amp flow it would make the receiver cut out. Rearranged the layout then it was all good.

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TBH I dont think its the issue in this case. Its more of a sensor wire issue or a bad FOC mode. Im wondering if I should try to reinstall the firmware? My gut feeling says there is a motor issue but so often, software makes you think you have a hardware issue!

i think we have exactly the same problem. bldc motor detection fails at default values but when i up the duty cycle to around 0.09 detection is successful. no problems with normal acceleration from a dead stop but if i hammer the throttle when im cruising at lets say 15kph it makes a massive stutter. with fairly quick acceleration theres no problem what so ever but if i push it too hard i feel its coming :smiley: no problems with braking. this happens both in FOC and BLDC. ive sent my motor for replacement due to another problem but i ll see if the new one makes the same thing. i can narrow down the problem by using another focbox i have and making another phase wire extensions. so motor, cables and focbox is what i can swap other than that i dunno whats wrong with it. edit: forgot to mention i did a motor detection in bldc tool and detection was successful every time i did it but when i upgraded the fw so i can use it with vesc tool detection failed with default parameters. sadly i did not test it on the road to tell if bldc tool vs vesc tool makes any difference. because on the bench theres no problem with hard acceleration it only happens when theres a load

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Yip, sounds spot on to me. Same issue! Mine is fine to smash throttle after about 10mph but anything below it stutters and shuts of till i release trigger and reapply gently. Keep me informed and ill do the same to you!

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All right, my new motor is on itā€™s way to me I ll report back. When I get it I wonā€™t change anything to see if the motor was the problem and go on from there. Iā€™m suspecting it was a tiny strand touching inside the motor or I have a cold solder joint in my extensions but thatā€™s highly unlikely as I inspected each one of them when I was making them.

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I should also add that on the bench, even with belt on, its completly fine to smash the throttle. Iā€™ve even tried holding the wheel with a towel to simulate load and its fine. Its clearly not enough load to replicate the issue.

Lol I tried exactly the same thing same result

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@lrdesigns has a point. 10-15 mph is too high to be sensor related, the motor detection worked fine, and you guys donā€™t get a fault code. The only other thing that I can think of that can cause this crap without throwing a fault is the receiver.
The fact that the problemā€™s gone after a certain speed suggests that it happens at high motor current or fast changes of the motor current. After a certain speed, the battery current becomes the bottle neck instead of the motor current.

Rearranging is one way to improve it, but a ferrite ring around the PPM cables is also a good idea.

I have another receiver also got a gt2b remote going to use itā€™s receiver too see if that makes any difference. Expecting the new motor next week so I can test these options

Yeah, I could try moving receiver but I know itā€™s pretty far from phase wiresā€¦ I think. The issue isnā€™t at 10-15 mph, itā€™s at speeds lower than that. 0-10 mph where if you squeeze trigger gradually, you could get to 25mph no issue but if you squeeze hard from 0mph it jumps to 2 or 3 mph then stutters and stalls. If you squeeze hard at 15 itā€™s got no issues.

Thatā€™s my point. Squeezing hard at low speeds means high motor current. At high speed the battery max limits the motor current, which would explain why the problem goes away at high speeds.

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UPDATE:

So, I moved the reciever and placed it far from any major current and it made no difference unfortunately.

It also got me thinking about my description of the error in more detailā€¦ It actually stutters from very little throttle from the get go. 1 or 2 mph its ok then around 3mph it just fails, stutters and you have to release throttle and start again, teasing it up to around 10mph where its got enough momemtum to allow full throttle (or indeed where its past the sensors use).

It feels like a car engine thats being flooded with petrol, causing misfires. You have to tease it with power till you get momentum, then its fine. Any other ideas welcome. I have a feeling, if I had another sensored motor to test, itā€™d be fine. I only have a non sensored Hobbyking 6374 SK3 150KV and its not worth swapping over.

Ok, What would allow a motor, battery and FOCBOX all to work perfectly when using BLDC mode but stutter when accellerating from very slow speeds in FOC mode??

Youā€™d say sensorsā€¦ right!? But sensors pass the hall sensor test in BLDC mode and give all green in FOC mode in Vesc Tool.
Stumped!

Can you try FOC mode with sensored turned off in vesc tool and unplugged?

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Ive quickly tried FOC mode ā€˜sensorlessā€™ and it was no different. I used Perimetr (iPhone app) to load a pre-saved version I had so I have now tried what you suggested however, I didnt open the enclosure and remove the sensor plug. I dunno if that would have made a difference!?

Anyway, unfortunatly the problem continues.

Yeah un-plugging the sensors shouldnā€™t make a difference, its just nice to be 100% sure you have illiminated a potentiality issue.

So weird, it seems like a sensor issue as it goes away after you pic up speed and get into the sensor-less speed range.

So you fixed the battery, and is the over heating issue also gone? Maybe change your tittle to focbox slow speed stuttering in FOC mode.

But it works in BLDC mode just fine?

This leads me to 3 possible causes, bad sensors, bad motor or software issue.

If it works in BLDC there seems like there is no reason not to work in FOC except for a software issue. This might be a pain in the a** but maybe erase all settings and try a different firmware???

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Yeah, I was thinking reinstall the firmware. Cant bear the thought of going through it all again haha. BLDC is fine. No overheating (well, in the relativly short test run of a mile or two). Iā€™ll get a good run on it today in BLDC and see if its actually not overheating.

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Update,

So, Im back to only charging to 60%. That means Ive blown another connection and a set of 4 18650s are most likley doomedā€¦ another Ā£20 wasted never mind the rebuilding effort. The nickel strips Iā€™m using are relativley thick and posed no issue before I was having other issues.

The motor gets warm in BLDC mode when ridden for a mile or two. It also becomes very hard to move (Its pretty impossible to roll the board when not applying power to motor - after a mile or two or riding). Focbox is hitting 83deg C after just a couple of miles.

So, heres my guessā€¦

The motor is to blame for everything. The FOCbox overheats because the motor is ā€˜stickingā€™ and requires extra strain to turn. The nickel strips are breaking like a fuse, due to the extra constant amps its needing to draw to turn the bad motor.

I dunno. My Metr app didnt save the data today so I cant see the stats but it felt like the last time its was only charging to 60% and nobody on here mentioned anything about the stats of the motor the last time I shared that data.

I know Ive got the amps set high for the battry but at 80A I dont think its excessive. Maybe I just need to rebuild batt and double up on all strips.

Still, doenst explain the cogging in FOC even when battery was mended last time.

Are you sure FOC is working properly? Mine was good for 40 miles then the sensor board went out on meā€¦also, where are you?

It is getting hot as hell here in alabama and when I was riding harder, my temps would climb into thermal throttling range pretty quickly. @deckoz also mentioned some demagnatization on the motors at these higher temps. Even magnets swapping poles causing lock up.

Obviously not your battery problem, but something to think about in these warm summer months.

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Cheer, Nah Im in Ireland and although this week is in the 80s, its abnormally hot.

This has been going on a while and its been pretty crap weather untill this week. Id hate to think the FOCBOX is potentially bad. I guess Iā€™ll fix battery (AGAIN!) and then swop out the Alien Power Sys motor Ive in there and put in the SK3 150kv Iā€™ve got sitting in a box. If the same issues happen again, itā€™ll be the foxbox.