Brake sensor question

Ponder44

New member
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Mar 10, 2024
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Scotland
Hi guys I have a question about my Bafang 500watt mid drive .I purchased my 500 watt e-bike kit about 5 years ago and fitted it to my old faithfull Merida bike which has v brakes so the mechanical brake lever sensors were used . best purchase ever never had any problems and done about 3000 miles . Decided to change the kit to a Boardman bike which has hydraulic brakes and suspension .All went well and I ordered new hydraulic brake sensors which when I plugged them in don’t work .The mechanical ones work ok but the hydraulic ones don’t work ,can’t understand why as they plug in fine they just don’t seem compatible with the kit ,any ideas what could be wrong .thanks in advance .
 
Seems weird. I would guess the pins for the cut offs on your new brakes don't match with the pins from your bike's wiring harness
 
Thanks for quick reply. Yes does seem weird they were purchased on eBay and seller said these were for mid drive bafang only and the pins in the connectors look the same .one is three pin male and other is 3 pin female so can’t understand why there’s a problem.
 
This is a photo of the sensor cable plug the orange one ,and the double cable I’m plugging them Into they seem okay.
 

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By doesn't work do you mean that the motor won't turn on when the sensor cable is plugged in? If thats the case the answer may be that the small round magnet which was or should have included with the sensor must virtually touch the sensor in order to power the motor. The magnet must be up against the sensor which keeps the circuit open. Once I get mine set properly I use a product available here called JB weld to securely hold both the sensor and the magnet. The little bit of two way tape provided is fine to start off but personally I like the sensor and magnet to be more secure. If they don't sell JB weld in Scotland it's just a 2 part epoxy.
 
By does not work I mean when sensors are plugged in the motor still runs , my guess is it should not run until the magnet touches the end of the sensor, but the motor runs all the time whether the magnets are touching the sensors or not .Think I will just have to run the bike without them as I have a gear sensor fitted which works perfect and IT comes off the same part of the harness.Might not matter about sensors as I don’t brake while pedalling anyway. All very strange lol.
 
Also I don’t want to order anymore in case there is a problem with them
When they come ,the eBay seller gave me a full refund when I told him so that was really good of him .
 
They make a couple different brake sensors.

A normally closed & a normally open sensor. Or in other words a normally on or normally off sensor.
 
Yes worth a try although there is 3 pins on my sensor it would be worth a try moving the plug round to see if it made a difference as I still have the sensors as the eBay seller told me just to keep them he didn’t want them back.might be difficult removing the plastic ridge without damaging the pins though . Maybe a fine tip on a soldering iron would be best. Thanks for the suggestion.
 
Yes worth a try although there is 3 pins on my sensor it would be worth a try moving the plug round to see if it made a difference as I still have the sensors as the eBay seller told me just to keep them he didn’t want them back.might be difficult removing the plastic ridge without damaging the pins though . Maybe a fine tip on a soldering iron would

I read through some of the comments. You'll need to be careful if you decide to cut the guide off the connector. Some people bent or broke the pins.
 
Yes worth a try although there is 3 pins on my sensor it would be worth a try moving the plug round to see if it made a difference as I still have the sensors as the eBay seller told me just to keep them he didn’t want them back.might be difficult removing the plastic ridge without damaging the pins though . Maybe a fine tip on a soldering iron would be best. Thanks for the suggestion.
Before trying that you shoud verify which pin is 5v and which one is ground. In your photo (notch facing up) 5v should be on the left and gnd on the right, if these 2 are inverted there is no rotation that will give you the correct result. To test (power on) you can use pieces of 24AWG wire and a voltmeter.
 
Yes maybe you’re right I could have the hassle of cutting the guide off and still be no farther forward, think I will just leave well alone I have connected the mechanical lever on the bars just in case I need to stop the motor while gear changing but at the moment all seems ok ,but I haven’t really used the bike yet as just finished the transfer of the E kit and it’s been winter here and just coming to spring now
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so will be using it soon. Thanks everyone for the suggestions and comments.
 
Oops, with notch facing up 5v should be on the right and ground on the left on the cable from the motor. Sorry about that.

Since you still have the sensors and the mechanical levers are correctly wired, you could cut the cables and splice them together, red to red, black to black and white to white, or whatever's the color of the third wire. Use silicone self fusing tape instead of vinyl electrical tape for a waterproof seal.
 
Since you still have the sensors and the mechanical levers are correctly wired, you could cut the cables and splice them together, red to red, black to black and white to white, or whatever's the color of the third wire. Use silicone self fusing tape instead of vinyl electrical tape for a waterproof seal.
and for even better connections use these ( https://www.amazon.com/Solder-Seal-Connectors/s?k=Solder+Seal+Connectors ) then the silicone self fusing tape instead of vinylelectrical tape...
 
Links to Amazon may include affiliate code. If you click on an Amazon link and make a purchase, this forum may earn a small commission.
I'm curious about the silver colored brake lever under the regular brake lever on the left side
 
You really don't need brake sensors. I haven't put them on any of our e-bikes and I really don't see the need. I have ridden motorcycles for most of my life and there is no such thing on a motorcycle. You let off the throttle and hit the brakes at the same time pull the clutch lever. Likewise on a bike you stop pedaling first. I never keep pedaling while using the brake because why would you.

One other nice thing about not having them is cleaner handle bars. I coil up the control wires coming from the motor and have them in a small pouch or it goes in the battery bag I then use an extension cable for the display so that there is only one thin wire going from the motor to the display.
 

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Where I live brake sensors are required in case of a runaway situation. That could be a stuck throttle (which has happened to me when winter riding in the woods after a wipeout) or possibly some other type of electrical malfunction. They are a safety system and I have met rider's here who don't use them. That goes to personal choice.
I also have owned and ridden many motorcycles and you are right, the throttle is spring loaded and there is always the clutch.
Where I find the brake sensors useful is on my rides down tight singletrack trails. When coming to a turn on the trails I ride if you stop pedaling shortly before a turn there is a short lag before the motor cuts out. Enough so that a couple of my newbie friends stuffed their bikes off the trail and into the bushes. Just lightly touching the brake lever enough to trigger the sensor instantly cuts motor power, you make the turn and resume pedaling. Not an issue on street riding generally of course.
 
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