Help! Motor cutting out and speed on screen incorrect

[pajtaz]

I would be inclined to fit a different PAS on the RHS and use 8 or 10 pole version, if that doesn't work better use a KT from another source.
Ofkeet or C&N on Aliexpress sell 9 fet ones 22 or 25a max or buy from PSWPower or Topbikekit.

Why do you still think it could be PAS? There is no intermittent cutting out due to PAS signal and when it does cut out, many times it seems to be related to sudden demand in power like a wind gust hitting me. I will see what I can find for 8 or 10 pole PAS and I will check the magnets again. They might be slightly off center but if it works for most of the time, that shouldn't be the problem. Main problem I have with PAS is that I have a Hollowtech BB so only certain ones fit and I do not want to remove the crankset to install the magnets. So I opted for the split ring one and that one just happens to be 12 pole. It was the only one that would fit. I can try buying one of the other split ring ones that can't fit then drilling through and then finding a way to attach it to the inner chainring.

So what is it with the controller that would cause this? I already have 20A 6 FET KT controller from PSWPower. It is the largest one they had that is sine wave. The other 9 FET ones are square wave and from what I gathered researching, I don't want that with this motor. I will look what is out there.

What do you think is happening with the controller to cause this? Let's say I don't change my pedaling and there is a sudden gust of wind. Does that mean that motor will demand more current to maintain the same speed at that moment? How would the controller respond? Why is the motor then reducing in power - is the controller not able to respond that quickly to a sudden demand in current or is it something else? Maybe there is a problem with PAS signal such that controller cuts out very quickly but why would there be a problem with PAS signal due to wind gusts?

Another time this cutting out will happen is when I am shifting gears to higher gear. It doesn't happen all the time but it is somewhat connected. Am I changing my pedaling ever so slightly that it is causing the PAS to delay the signal and therefore the controller cuts off power? Or is it something related to power demand again?

 

[Nealh]

The change from 12 to a 10 pole PAS disc worked for me, I was experiencing some intermittent pick up with my Akiema and 6 fet controller. No matter what I tried to configure with settings didn't make much difference I drilled out my new PAS ring to fit over the Hollowtech.
For the controller I started to suffer with thermal cut outs on my longer runs up to 100 miles/160km eventually the 6 fet ran far to hot (so hot I couldn't hold it) esp when climbing in higher PAS mode, so opted for a 9 fet model which runs cooler with more fets. I have two 9 fet controllers both are sensored sinewave one is 11/22a and one 12/25a.

It also may be some of the intermittent cut out may be due to BACK EMF within the motor causing back resistance, to technical for the likes of me to understand fully. I have read about it but for me it is gobbledygook stuff, saturation of amps/voltage to the windings/coil afaict is the issue and seems to cause momentary powerloss. I can only guess that the effect of having the wind at your back giving more watts/force to pedal turn the motor faster may cause power saturation in the hub.
Others with more mechanical knowledge of electrical physics might be able to explain better but some may baffle you more then when you started to ask the question.

 

[pajtaz]

Nealh, you were right. It was the PAS. Holy crap, this was such a silly thing.

First thing I noticed is that I installed the sensor incorrectly. Magnet is fine but sensor should have been installed against the frame but I had it over the bottom bracket cable guide. The sensor comes with its own cable guide and a cover. So I had to first remove the cable guide, put the sensor against the frame where cable guide was, put sensor cable guide over it, run the cables for derailleurs then install the cover and tighten everything. It should have still worked anyway because the sensor was still at an ok level with respect to magnets but I should have installed it properly. I obviously had a brain fart when I installed it first because I didn't get why the sensor came with two parts and one of the looked like the cable guide. Duh! But hey, it happens.

Then I started testing. This sensor lights up all the time unless it is sensing a magnet. Once the magnet passes, the light goes off. I noticed that even though the sensor was fairly close to the magnet, the light was flickering a lot. It was obvious it was not sensing the magnets well enough. Once I pushed it so it's basically touching the magnet ring and then tested it, it finally had nice clean evenly spaced signals. I counted all the signals and watched them to make sure they are clean. I finally had clean 12 signals.

I tightened everything back up, had to re-adjust the rear derailleur because of the new cable guide and took it out for a quick test ride. I rode maybe 2km but had no cut outs. The real test will be tomorrow riding to work but I think I fixed it. The only thing I can think that can cause problems is if the magnet ring moves. I am not sure if this happens when strong wind blows or when I go over bumps but the magnet seems to be strongly attached to the chainring with magnetic force. I have now ridden over 250 km with the magnet ring attached like this and when I looked at it today, it seemed to be in the exact same place as when I put it. I was hoping to attach it more rigidly but if it hasn't fallen off so far, it must be adequate.

Man, I am so relieved. I had worked myself up worrying that it is the controller or the motor but at the end you were correct, it was the PAS. It's very sensitive and it must be super close to the magnet ring. If it all goes well tomorrow, I will make a new post describing the bike and the kit installation and all of the problems.

Thank you for helping out. I appreciate it, and I hope I can pay it back some day.

 

[Nealh]

Phew. Good to here all is well.
PAS set up is the all and be all for correct motor running on hub bikes, persistence is the name of the game.