Factory setting on SW900 display for P07 Parameter?

[rosewoodfarm]

I have a new e-bike that came with am SW900 display, but no instructions for it. I managed to find some info online and printed what the different parameters were about. I changed them to match this particular bike---but I accidentally changed the setting on P07--which the online instructions say NOT to mess with. This is for the "speed measuring magnet" parameter. Now I can't find any information to tell me what the default setting was to change it back. Can anyone tell me what the original factory setting was on the SW900 for parameter 07?

This is a Go Express 20" fat tire bike with a 500 watt Sandra fat tire specific rear hub motor, 48 v 10 ah high-capacity battery with 9 modes of cadence based pedal assist. It has a 12 magnet cadence sensor. If any other info is needed, please let me know.

 

[amberwolf]

Does it operate differently than before changing the setting? If not, I wouldn't worry about it.

Otherwise, there are a few posts that discuss the P07 setting:
https://endless-sphere.com/forums/search.php?keywords=p07&terms=all&author=&sc=1&sf=all&sr=posts&sk=t&sd=d&st=0&ch=300&t=0&submit=Search

which describe it as a poles-per-revolution setting usually used for reading the speed of a motor from it's hall sensor, sometimes for reading speed from a separate wheel sensor.

If your speed sensor is inside the motor, and it is a geared hub, it is very likely it uses magnets embedded in one of the side covers to trigger the sensor. If you gently hold a small magnet (like the inside-shirt strip of a namebadge) near the side cover of your hubmotor, and move it around from near the axle to near the outer edge of the cover, back and forth, around the cover, you'll likely find a spot where you can feel the magnet being pushed away or pulled on. That's where the magnet or circle of magnets is at. If you hold the magnet in place and gently slowly spin the motor you should feel a number of times that the magnet is pushed or pulled. If you count how many that is, and use that number in the P07, it will probably give you the right speed.

If the speed sensor actually reads the hall sensor in the motor itself, instead of a separate speed sensor in the hub, then you'll need to know how many magnets the motor has in it, *and* the gear ratio of the geared hub (if it's geared). Divide that number of magnets by two, and then multiply by the gear ratio, and that's probably the right number for P07.

 

[rosewoodfarm]

Thanks for the reply and for the link to other posts about the SW900.

1. To answer your question, it doesn't seem to ride any differently.

2. I don't think I'll need to do the (well explained) magnet test since the printout I found online about this model says it has a "12 magnet cadence sensor". So based on that, do you suggest I set it to "12"? (It has a geared hub motor.)

3. Another post suggested that a way to test if a person has chosen a correct P07 parameter value is to go on a ride of a known distance (using a GPS) and see if the readout provides the matching distance. If the readout is higher than the actual distance we would need to raise the value of P07, and if it's lower than the actual distance I would lower the value of P07.

So I think it's a decision that won't affect the performance of my bike. I can play around a bit with it until I find the correct setting by trial and error "distance tests".

 

[amberwolf]

2. I don't think I'll need to do the (well explained) magnet test since the printout I found online about this model says it has a "12 magnet cadence sensor". So based on that, do you suggest I set it to "12"? (It has a geared hub motor.)

No, the cadence sensor is just for your pedals, and has nothing to do with the speed sensor. It's just the little bit down by the pedasl on the frame, with the wire leading off, and the magnets are on a plastic ring stuck on the shaft the pedals are bolted to.

The speed sensor is on a wheel, either as a separate little "stick" or what3ver on the fork or stay of the frame near the wheel (usually spokes), with a wire leading off, and a magnet clamped to a spoke or glued/etc to a rim or hub, or else is built inside the hubmotor as previously described.

3. Another post suggested that a way to test if a person has chosen a correct P07 parameter value is to go on a ride of a known distance (using a GPS) and see if the readout provides the matching distance. If the readout is higher than the actual distance we would need to raise the value of P07, and if it's lower than the actual distance I would lower the value of P07.

If you have a phone wiht gps you can also just use a speedometer app (lots of free ones) and compare the speed directly to the displayed speed, and edit the P07 until they match. Less riding to get the same result, though potentially less accurate.

 

[Big_Truck]

I have just wired a SW900 to my controller so did not have any default information. The P07 setting seems to be used by the SW900 for reading out the speed and distance. Altering the setting has no influence on the operation of the motor.
Despite lots of info saying it should be 46/47 for a direct drive 26" wheel, mine is set at 48 after testing over a known distance and compared with a GPS speedo. As stated above, adjust it in increments over a distance or speed - if the displayed distance/speed is greater, increase P07 value, if it is smaller, reduce it. Eventually you will settle on a reasonably accurate value

I also note that my SW900 (which is fairly new) has an extra setting at P05, 2 for 9 PAS grades

HTH