How can I connect a thumb operated key switch / kill switch?

[shenzhen_ex]

I want to make "kill switches" for both controllers on my 2WD and i think the key switch is a solution.

My thumb switches have 2 wires each. Can I just connect one wire to the orange "key switch" wire (see image below) and the other to the full 48v battery +? My concern is that the switch may not be rated for 48V. What about the door lock wire, whatever the he11 that is.

BTW.. Thanks ES for helping me with my project!

 

[wesnewell]

Splice your key switches into the orange key lock wire. DO NOT try and run main power wires through them. If you don't understand what this means, ask.

 

[dogman dan]

Yes, battery to switch, then to the orange wire.

Even a very cheap key switch will work fine, because when the contact is made, it will not draw enough amps to spark and weld the switch. It's just a tiny current to power up a part of the controller that does not have big amps flowing. So even though you may be using a 12v switch, it won't matter that it's getting 48v.

Not like the main wires, that run full amps, and have the big spark connecting up. Those need to be connected with plugs rated for big amps, or large contactors.

 

[teklektik]

There are a couple of popular strategies for kill switches:

1. Use the controller 'ignition' wire as you propose here to disable the controller logic and prevent motor rotation. No contactor.
2. Use a contactor to cut the power completely - very effective but requires expense/space/power for the contactor.

From this other thread you already have a contactor with a separate push-to-kill switch.

You are doing several strategies at once: you have three switches to 'kill' the bike - the big central one that requires releasing the grips or flipping BOTH thumb switches to completely kill both controllers. Too much - in an emergency situation, you should be able to kill power with a single kill switch that is easy and natural to reach - preferably without releasing your grip.

If you are going to keep the contactor, I would recommend that you eliminate the big push-to-kill switch and use only one of your thumb switches as a kill switch to replace it. Use no switches on the controller 'ignition' (keyswitch) wires - just jumper them. The contactor coil current should be low and the switch should work okay at 48v. You could also put the thumb switch in series with the big central push-to-kill switch, but I'm not sure I see a good reason....

You might also wire the two thumb switches in series (since you seem to have two throttles) so either one will kill the contactor/bike if you are riding one-handed (there is always a switch in thumb's reach).

 

[shenzhen_ex]

Splice your key switches into the orange key lock wire. DO NOT try and run main power wires through them. If you don't understand what this means, ask.

I believe I understand. I wont put the key switches between the source and load. I will create a parallel connection. Thanks for the warning.

 

[shenzhen_ex]

If you are going to keep the contactor, I would recommend that you eliminate the big push-to-kill switch and use only one of your thumb switches as a kill switch to replace it. Use no switches on the controller 'ignition' (keyswitch) wires - just jumper them. The contactor coil current should be low and the switch should work okay at 48v. You could also put the thumb switch in series with the big central push-to-kill switch, but I'm not sure I see a good reason....

The entire battery box, with contactor attached is removable (see image below). I only need to disconnect the 50A anderson to separate the box from the bike. I was hoping to avoid switches going to the box that would add to the disconnect steps.

You might also wire the two thumb switches in series (since you seem to have two throttles) so either one will kill the contactor/bike if you are riding one-handed (there is always a switch in thumb's reach).

I can see your point clearly, however i want to be able to turn off an individual controller and keep the other running. For example I may just run with front wheel if the rear malfunctions.

.... if you are riding one-handed.....

With my DH forks and a huge battery strapped on them, do you think I will be able to do that?

 

[shenzhen_ex]

Yes, battery to switch, then to the orange wire.

OK...that is what I am going to do! Thanks man.

Even a very cheap key switch will work fine, because when the contact is made, it will not draw enough amps to spark and weld the switch. It's just a tiny current to power up a part of the controller that does not have big amps flowing. So even though you may be using a 12v switch, it won't matter that it's getting 48v..

The concept quoted above is very helpful!
My switches were 96 cents each, so they are cheap. Of course everything eBike related is cheap here.

 

[teklektik]

If you are going to keep the contactor, I would recommend that you eliminate the big push-to-kill switch and use only one of your thumb switches as a kill switch to replace it. Use no switches on the controller 'ignition' (keyswitch) wires - just jumper them. The contactor coil current should be low and the switch should work okay at 48v. You could also put the thumb switch in series with the big central push-to-kill switch, but I'm not sure I see a good reason....

The entire battery box, with contactor attached is removable (see image below). I only need to disconnect the 50A anderson to separate the box from the bike. I was hoping to avoid switches going to the box that would add to the disconnect steps.

If you are using Andersons, just add an extra connector for the coil to the battery pair to make a triple. No extra connection steps. My point here was that you have decided to use a contactor but are only using it as a sort of complicated on/off switch. This device is typically incorporated to implement the kill switch - if you are not using it for that purpose, a simple high-amps switch or magnetic circuit breaker would likely have been a simplifying choice. If you are going to keep it, it will arguably give better kill switch functionality than messing with the controller 'keyswitch' wires.

You might also wire the two thumb switches in series (since you seem to have two throttles) so either one will kill the contactor/bike if you are riding one-handed (there is always a switch in thumb's reach).

I can see your point clearly, however i want to be able to turn off an individual controller and keep the other running. For example I may just run with front wheel if the rear malfunctions.

I appreciate the desire for that functionality - I have it on my 2WD - however, a kill switch and a limp-home-motor-selection switch may both turn motors on and off but the basic problems they address are quite different. In the end it's your decision, but I believe you should have a single kill switch on the throttle grip and separate motor selection switches elsewhere - you will seldom use them so they could actually be back with the controllers - there is no reason to use up high-profile handlebar space for a seldom-used failure mode switches. In case of a runaway, the last thing I would want is to be flipping multiple switches while trying to hold on and control the bike.... but that's just me.

.... if you are riding one-handed.....

With my DH forks and a huge battery strapped on them, do you think I will be able to do that?

Perhaps you might be running one motor and just supporting your other hand by the heel on the throttle to give it a rest - I honestly don't know. Your design requires you throw both thumb switches, but two throttles opens the possibility that one hand may be not well positioned to hit the second kill switch. I was throwing out an option to give you some extra safety since you have the switches available and have decided to go with two throttles. If you feel this is not a consideration, then don't do it!

 

[shenzhen_ex]

.......... I was throwing out an option to give you some extra safety since you have the switches available and have decided to go with two throttles. If you feel this is not a consideration, then don't do it!

One thing I can say for sure is that your "2WD Electric Yuba Mundo Build" is amazing and lends tons of credibility to your recommendations for both electrical and fabrication. I looked through your build thread and consider it an inspirational model. For a while there I was actually thinking of stealing your Deflopilator concept, but i think my front wheel will never leave the ground.

However, I do want to be able to enable and disable motors individually from the handlebars. Not just for limp home, but also for temperature control, traction, range, experiments, etc. Maybe i need more switches .

I have a question about the need for kill switches to stop a "runaway condition". My 2 motors are 48V 500W and my 2 controllers are rated for 500W 30A, don't you think I can stop them with my hydraulic 203mm disks?

 

[wesnewell]

Splice your key switches into the orange key lock wire. DO NOT try and run main power wires through them. If you don't understand what this means, ask.

I believe I understand. I wont put the key switches between the source and load. I will create a parallel connection. Thanks for the warning.

Like this.

 

[teklektik]

Thanks for the kind words about the Mundo build - it's a big horse of a cargo bike, but it's a pleasure to ride.

However, I do want to be able to enable and disable motors individually from the handlebars. Not just for limp home, but also for temperature control, traction, range, experiments, etc. Maybe i need more switches .

Some back story: My initial build used the controller 'ignition' (keyswitch) signals to enable/disable the controllers to switch between one/two motor operation on the fly. I killed a number of controllers, even when only switching with zero throttle. At the time I was using Xlyte analog controllers which gave very smooth BMC motor control, but which were a pretty old design (and were known for spontaneous death anyway). In the end, I re-wired the motor switches to clamp the throttle lines to zero volts instead. This suppresses operation of the controller but leaves it running without the nasty startup/shutdown effects - I switch one/two motor operation all the time on fly and have never had another problem. Sadly, this was an empirical fix that remedied the symptom - I never did really ferret out the cause of the failures when using the ignition wires (although theories abound). I subsequently switched to Infineon controllers as a plug-and-play replacement for the Xlytes, but left the throttle-clamp wiring the same.

Anyhow - that was a long way of saying that I'm not sure if you will have problems switching the controllers on/off with the ignition wires on the fly - this is not an approach I would pursue again (but that's not based on any technical argument). It seems from your questions (which are all good, BTW) that electrical stuff is not presently one of your strengths. We always do best playing on our strengths, so maybe in this case simpler is better and going with what you have planned is a reasonable start - you can see how it goes. In any case, you can always just leave one throttle backed off as an alternative to switches. I have a single throttle and like the one/two motor control on my left hand and a single kill switch on my right on the throttle - but again - personal preference.

I have a question about the need for kill switches to stop a "runaway condition". My 2 motors are 48V 500W and my 2 controllers are rated for 500W 30A, don't you think I can stop them with my hydraulic 203mm disks?

Well - this is a main reason for the kill switch - to address all manner of Bad Things with certainty and finality. There is no reason to theorize about or try to foresee different particular scenarios if you have a means to kill the bike easily. In the end, when you need to kill it, you will be startled and won't have a split second to think - the best solution is something that will work with little more than muscle memory.

That said - ebrakes can address what may arguably be the single biggest cause of runaways - a broken/intermittent throttle ground connection. If you have ebrake sensors on your hydros, it would make your proposed braking strategy effective in the most likely failure situation - braking would be a natural response to the situation and would kill the motors as well... If you don't have ebrakes, perhaps pursuing them would be a better alternative than mucking with more complicated motor switching just now.

 

[d8veh]

A couple of ideas. You can have a kill switch and a motor selection switch. It's still two switches, but the functions are separate. It's useful to be able to switch off your battery completely either temporarily or permanently.

Motor selection switch:
Use a three position switch. Connect each 48v key/ignition wire to the outer poles and the two returns to the middle pole. The switch three positions will give one motor, the other or both. For anybody that doesn't have ignition wires, you can do the same to the brake switch connectors. If you already have the brake switches connected, you can connect it in paralllel.

Kill-switch:
A kill switch is useful as your main battery switch if you want a plug-and-play battery. I often use the red switch that you get on those thumb throttles with LEDs, but you can use any switch. You need to make this little board, which is very easy, and doesn't require any special equipment other than a soldering iron and drill. It uses a bank of FETs to completely isolate the battery. I use these switches on all my bikes, and they work very well even with knockoff cheap Chinese 4110s. Its lightweight, very small, and doesn't consume any power when off, and no significant power when on: