Pedal assist magnet disc broken

[bootross]

Hi, first timer and new to e-bikes and have no idea with all things electrical, so please exercise some patience.

We bought a cheapy valk ladies step thru e-bike with rear hub 36v motor and pedal assist. The chain popped off in the rough stuff and I think that cracked the plastic disc behind the crank arm that houses the magnets for the pedal assist sensor. Either that or it got squashed when we loaded it onto a 3 - bike carrier hitch with another two bikes. Anyway, I couldn't find a direct plug-and-play replacement as all cheap generic online stuff has a different plug and wiring setup, but I ended up buying a cheap kit anyway because I only need the disc and not the wiring and cable connector back to the hub. I think the original disc had 5 or 6 magnets but I went with a 12 magnet replacement.

I have read a bit about the different cable connectors now and ours has the 9 pin julet connector, which I think contains wiring for the three phases of the motor plus a wire for the magnet 'hall' sensors? I couldn't find the same type of wiring connector and setup with any of the pedal assist sensor kits online. My queries are with all the generic replacement stuff I was looking at, the wiring appears to only have three wires, so how do they work if the three wires are for the phase and no other wiring which I thought are for the sensors? Also, what effect will swapping a 12 magnet disc onto our bike have when it only had 5 or 6 to begin with?

Thanks,

 

[E-HP]

Hi, first timer and new to e-bikes and have no idea with all things electrical, so please exercise some patience.

We bought a cheapy valk ladies step thru e-bike with rear hub 36v motor and pedal assist. The chain popped off in the rough stuff and I think that cracked the plastic disc behind the crank arm that houses the magnets for the pedal assist sensor. Either that or it got squashed when we loaded it onto a 3 - bike carrier hitch with another two bikes. Anyway, I couldn't find a direct plug-and-play replacement as all cheap generic online stuff has a different plug and wiring setup, but I ended up buying a cheap kit anyway because I only need the disc and not the wiring and cable connector back to the hub. I think the original disc had 5 or 6 magnets but I went with a 12 magnet replacement.

I have read a bit about the different cable connectors now and ours has the 9 pin julet connector, which I think contains wiring for the three phases of the motor plus a wire for the magnet 'hall' sensors? I couldn't find the same type of wiring connector and setup with any of the pedal assist sensor kits online. My queries are with all the generic replacement stuff I was looking at, the wiring appears to only have three wires, so how do they work if the three wires are for the phase and no other wiring which I thought are for the sensors? Also, what effect will swapping a 12 magnet disc onto our bike have when it only had 5 or 6 to begin with?

Thanks,

A picture of your PAS unit, bottom bracket, and the connector would be helpful.

I think I followed your detailed description, but got sort of mixed up when you described the motor connector. There are several types of connectors used, but generally there are only a few used for PAS,
the JST style:

and the HiGo/Julet water resistant style:

Similarly motor connectors use a few common connectors, including versions of the above. I'm assuming you mentioned the motor connector to help describe the connector you need for the PAS sensor?

If you're looking for a PAS unit that uses the HiGo/Julet style of connector, you have a few options including the one piece style (if you have a Shimano style bottom bracket)

Or the two piece style you seem to be describing

You can search on Google or Amazon, etc. for PAS HiGo and find what you need. NOTE that these come in drive side and non-drive side versions, so yours may be drive side, since you mentioned the chain. Even if you just got a replacement disc, you need to make sure it's the made for the correct side.

 

[bootross]

A picture of your PAS unit, bottom bracket, and the connector would be helpful.

I think I followed your detailed description, but got sort of mixed up when you described the motor connector. There are several types of connectors used, but generally there are only a few used for PAS,
the JST style:

and the HiGo/Julet water resistant style:

Similarly motor connectors use a few common connectors, including versions of the above. I'm assuming you mentioned the motor connector to help describe the connector you need for the PAS sensor?

If you're looking for a PAS unit that uses the HiGo/Julet style of connector, you have a few options including the one piece style (if you have a Shimano style bottom bracket)

Or the two piece style you seem to be describing

You can search on Google or Amazon, etc. for PAS HiGo and find what you need. NOTE that these come in drive side and non-drive side versions, so yours may be drive side, since you mentioned the chain. Even if you just got a replacement disc, you need to make sure it's the made for the correct side.

Thanks E, attached are photos of the 9 pin connector and the magnet disc with the sector missing. I have ordered the two piece style PAS kit you have a photo of above just to get the disc out of it, but with that connector, it only has 3 pins which I can't work out and won't be able to use with my existing wiring back to the hub anyway.

 

[fill]

Hi the pas sensor is not intended to connect to the hub motor via that 9 pin connector but is intended to connect directly to the controller box with its own dedicated 3 wire connection. The controller will also have a 9pin socket to connect to the hub.

systems using the julet 'waterproof' connecting plugs/sockets generally employ a 4 into 1 or 5 into 1 cable to connect the peripheral sensors and display to the controller.

 

[Mclewis1]

Fully agree with what fill said ...

I think if you look more closely (and it can be difficult to follow wires in and around the bottom bracket area without turning the bike over) that there is a different wire from the cadence sensor going back to the controller. The 9 pin connector shown isn't likely to be also handling the cadence sensor's connectivity unless the Valk bike uses a really bizarre custom wiring harness (very unlikely due to costs).

The 3 pin connections from the cadence sensor will be GND, +5v, and the sensor signal (which is likely to be from a simple hall sensor). The sensor signal line will produce a pulse as each magnet passes by the sensor.

Assuming that the Valk's controller is a pretty standard Asian product, replacing the 6 magnet disk/ring with a 12 magnet ring should work assuming as HP mentioned that the direction/side preference is followed. You'll need to pay close attention to the position of sensor with respect to the magnets as the 12 may be arranged in a slightly different diameter circle.

With a 12 magnet ring you should see the motor assist come on a little bit quicker from a start. The controller will now obviously be seeing twice as many pulses per pedal revolution but unless there is some controller logic looking to ramp up the power at higher pedal rpms (which is unlikely on a lower end controller setup) it shouldn't matter and should generally feel the same as it did before (unfortunately more like a power on/off switch as you start pedaling).

 

[bootross]

Fully agree with what fill said ...

I think if you look more closely (and it can be difficult to follow wires in and around the bottom bracket area without turning the bike over) that there is a different wire from the cadence sensor going back to the controller. The 9 pin connector shown isn't likely to be also handling the cadence sensor's connectivity unless the Valk bike uses a really bizarre custom wiring harness (very unlikely due to costs).

The 3 pin connections from the cadence sensor will be GND, +5v, and the sensor signal (which is likely to be from a simple hall sensor). The sensor signal line will produce a pulse as each magnet passes by the sensor.

Assuming that the Valk's controller is a pretty standard Asian product, replacing the 6 magnet disk/ring with a 12 magnet ring should work assuming as HP mentioned that the direction/side preference is followed. You'll need to pay close attention to the position of sensor with respect to the magnets as the 12 may be arranged in a slightly different diameter circle.

With a 12 magnet ring you should see the motor assist come on a little bit quicker from a start. The controller will now obviously be seeing twice as many pulses per pedal revolution but unless there is some controller logic looking to ramp up the power at higher pedal rpms (which is unlikely on a lower end controller setup) it shouldn't matter and should generally feel the same as it did before (unfortunately more like a power on/off switch as you start pedaling).

Far out, it's like you were both right there .... literally got my wires crossed on this one and with the bike on its stand and me just sitting on the ground next to it and not knowing anything about them, I've traced the rear hub motor to controller circuit and wire and taken photos of that line and 9 pin plug and not the one I'm actually after, which is the PAS to controller line. Having a proper second go with the bike laid over, I can now see the PAS line is bundled up with the motor line under the bottom bracket but then both run up inside the frame behind the battery via a removable cover plate on the bottom of the frame just next to the bottom bracket. Removing that plate revealed all and I do indeed have the two piece setup with same julet style 3 pin connector shown in E-HP's post above and as you're thinking. The julet plug setup doesn't seem to be anywhere near as common online as ones with the JST connector but I've at least found the right kit for AUD$30 which is ok but will be likely be down $12 because I've already ordered the wrong JST plug kit just to get the magnet disc out of it. And as you said, if the disc diameter doesn't match with my pickup, then it won't work anyway and I'll have to wait until the second correct kit arrives. Anyway, thanks again everyone for your assistance and getting things back on the right track.

 

[E-HP]

And as you said, if the disc diameter doesn't match with my pickup, then it won't work anyway and I'll have to wait until the second correct kit arrives. Anyway, thanks again everyone for your assistance and getting things back on the right track.

I couldn't see the actual sensor pickup in the pics, but there are a couple of styles used with the magnetic disc type of PAS. One is like the one I previously posted, with a ring that is used with certain bottom brackets, which also fixes the distance to only work with discs with that radius. The other common type doesn't use a ring, but mounts on the seat tube, sometimes with a zip tie and sometimes with a clamp mount. Those can be aligned to different disc diameters because you can adjust the mounting location. If yours mounts in a manner that you can adjust, it may still work with the larger diameter disc.

Amazon.com

 

[bootross]

I couldn't see the actual sensor pickup in the pics, but there are a couple of styles used with the magnetic disc type of PAS. One is like the one I previously posted, with a ring that is used with certain bottom brackets, which also fixes the distance to only work with discs with that radius. The other common type doesn't use a ring, but mounts on the seat tube, sometimes with a zip tie and sometimes with a clamp mount. Those can be aligned to different disc diameters because you can adjust the mounting location. If yours mounts in a manner that you can adjust, it may still work with the larger diameter disc.

Amazon.com

Yes, mine is the shiny metal ring type in your previous post, so will only work with discs that have the right diameter for it. Looks like the above kit you posted just now with removable disc and sensor that you can position pretty much where-ever you need was designed to avoid having to take the crank off if you crack the disc or wiring, so it makes replacement less of a hassle. I could probably have bought that kit seeing it looks like it gives you a choice of connectors.

 

[E-HP]

The split disc type is pretty convenient, as you pointed out. I like the single piece style mounted on the non-drive side, because you don't have the alignment issue. Note that going from drive side to non-drive side, or vice versa, usually require changing a parameter in the controller, but won't be an issue if you're sticking with the drive side.

 

[bootross]

The split disc type is pretty convenient, as you pointed out. I like the single piece style mounted on the non-drive side, because you don't have the alignment issue. Note that going from drive side to non-drive side, or vice versa, usually require changing a parameter in the controller, but won't be an issue if you're sticking with the drive side.

Uh-oh, what is the alignment issue you speak of? I was really hoping the second kit would be straight plug and play and not too fiddly now that the connector should fit my existing wiring.

 

[E-HP]

Uh-oh, what is the alignment issue you speak of? I was really hoping the second kit would be straight plug and play and not too fiddly now that the connector should fit my existing wiring.

Not a big deal, just a onetime setup. The magnets and the sensor just need to be aligned and close enough for the sensor to detect the magnet.

 

[bootross]

haha, learning as I go. Bought a cheapy tool online to press the crank arm off, worked fine. The broken disc slid off. Now I find the shiny ring that mounts the magnet pickup is clamped behind the axle nut or whatever you call it. Pretty sure I need a shimano 20 spline bottom bracket tool to get that undone to slide the mounting ring off. Bit of a mission ...

 

[fill]

As long as your new sensor is different and is not intended to be clamped by the bottom bracket retaining ring, just leave the old one where it is and fit the new one..

 

[docw009]

haha, learning as I go. Bought a cheapy tool online to press the crank arm off, worked fine. The broken disc slid off. Now I find the shiny ring that mounts the magnet pickup is clamped behind the axle nut or whatever you call it. Pretty sure I need a shimano 20 spline bottom bracket tool to get that undone to slide the mounting ring off. Bit of a mission ...

You have a couple of choices. One is to buy the Shimano tool and get the BB off. Another is to buy the one-piece sensor. However, you have to make sure there is enough gap between the pedal arm and BB for it to fit. I've encountered bikes where that gap was too narrow..



The final one is to not spend any money and waste a few hours fashioning a DIY bracket for the sensor. Sometimes easy. Sometimes a PITA.

I now own the BB tool, and it's a lot less time to mount these sensors.


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