Proper Kill Switch

[vwhammer]

Getting down to the nitty gritty bits of my E bike build and am having trouble sorting out a good way to connect/disconnect and/or shut down my bike without big electrical arcs and cooking switches.
I have been searching and reading for about a week now and every time I find what I think is a solution the person or company is no longer making the bits needed or it turns out to not be precisely what I am looking for.

It seems strange there are no readily available parts for this seemingly important item.

Anyway what I am looking for is an elegant way that I can mount a simple push button within easy reach that will safely disconnect the battery from the system.
By elegant I mean not just a simple high VDC, high current breaker or big clunky switch.
I would like a nice push button that activates the rest of the circuit to make the magic happen.
The rest of that circuit would be located in my battery/controller enclosure that I am building.

I am running a dual motor dual controller set up and neither of my controllers have a proper power switch.

In total the max load should be about 45 amps at 48 volts.

I guess I also need the diagram for this switch to be laid out in relatively plain english.
I would like to think I am not a moron but I am also not an EE so the acronyms and industry terms tend to lose me sometimes.

I did find a couple threads on here covering something similar but one ("Smart Switch") the guy no longer makes parts for.
https://endless-sphere.com/forums/viewtopic.php?f=31&t=32135&hilit=Smart+Switch
And the other on I could not really follow with everyone's suggestions to make it better and I am not sure if it is exactly what I am looking for.
https://endless-sphere.com/forums/viewtopic.php?f=3&t=40142&hilit=inrush

I have a couple different methods to make PCBs at work and there is equipment and assistance to do surface mount and through mount components.
I just need to know what it looks like and all the bits to get and I can run it by some friends at work to get the assembly sorted.
Anyone care to give me a little nudge in the right direction?
I am sort of leaning towards the item in the second thread if that can do what I want and I can sort out exactly what components I need based on all the suggestions.

In the mean time I will continue reading.

 

[Joachim]

Electric car parts shops have nice push butons but i dont know how they build up inside.

I,have a simpel socket key between the positieve lead of the battery to the controller,pull the socket out and the system shut down compleet.

 

[John in CR]

If they're brushless motors/controllers, all that's required is a simple low current key switch on the line that powers the controller's MCU. Typically there's a separate wire for that switch. Then all you need for proper safety is a good fuse near the battery.

Contactors and heavy duty high current switches are a carryover from the old days of brushed motors, where numerous failures including a simple controller failure could result in a runaway condition only stoppable by cutting mains power. With brushless rigs, the motor absolutely cannot run without the controller brain sending the correct ordered alternating pulses to the motor. That current supply is under 0.1A, so almost any switch can handle it. It use motorcycle key switches, which are small, cheap, durable, and give you the added security of having a key that locks in place when on. They can also handle significantly more current, so you can tie the pack voltage supply to your DC/DC converter for lights and accessories to the same switch.

In addition to being able to switch the controller(s) off with a switch placed in easy reach in an emergency, a mandatory ebike safety feature is an ebrake switch that cuts power from the controller (and activates regen braking if you have it) when you squeeze the brake handle.

I run up to 27kw from dual controllers on my ebike and have regen braking, so I have the low current lines that power up the controllers attached in parallel to my key switch. I have one ebrake switch going to the rear brake handle, and the other ebrake switch wired to a horn button. That gives me regen braking force of either or both controllers, which is nice on long mountain descents, because the force of just one is sufficient to suppress speed, plus I can alternate between the 2 to prevent heat buildup in either.

 

[icecube57]

I would try and find a jet ski kill switch. It depends on what you are going after. You can kill the main power or shunt down the MCU in the controller. They have the big red key switches ..breaker type switch. You could use a magnetic reed switch and have a like a magnetic ring on your finger or something that would cause it to latch. Ive seen people experiment with RFID and FOBs. I would like to see a reed switch type system that will only allow full power if both hands are on the handlebars.

 

[Joachim]

I was thinking to make the same switch as the brake/ebrake and put this in the seat :lol: you can only drive the bike when you have a seat on the bike..

 

[slowhands]

I guess "proper kill switch" means you don't trust the electronic on/off.

The simplest is just a jumper wire that you insert/remove. I'd have two, one for each controller, since 25A is easy but 45A is harder. I'd just use two 30A car fuses in a pair of fuse holders. Put em in to go, pull out to kill.

More elegant is a relay and switch. You will need a small switch (keyswitch?) to control the coil of high current relay or "contactor" capable of handling your maximum battery power of 50 amps. You need to find a relay with the coil voltage close to matching your battery voltage (24v, 36v, 48v, etc.), or you need to drop down the battery voltage to the switch and coil. There is a lot of telco equipment running 48v, so that's available as surplus if you know where to look, though 24v and 12v are much more common. You can put two 24v 25A relay coils in series for use with a 48v battery, then use the contacts separately. Or a 48v DPDT 25A relay should handle the current using both poles. Online you can find these in electronic surplus houses.
http://www.surplussales.com/relays/REcontacts-1.html
http://www.allelectronics.com/make-a-store/category/500/relays/1.html

In a pinch, at your local auto parts store there are very inexpensive transfer relays for RVs that will handle the current, but they only have 12v coils. They are for transferring battery power to a camper battery when the ignition is on, typically. They use a 12v coil though, so you must adapt to that. Amazon has a 12v 80A transfer relay that would do:
http://www.amazon.com/Stinger-SGP38-80-AMP-Battery-Isolator/dp/B001HC6UJ0/ref=sr_1_1?s=automotive&ie=UTF8&qid=1440771229&sr=1-1&keywords=STINGER+SGP38+80++relay

Alternatively a scooter power relay would do and they are easy to find. And make sure you always turn off the switch when not in use, or you will kill your battery overnight, energizing the relay coil (my kid forgets this on his scooter all the time, sheesh).
http://www.electricscooterparts.com/relays.html

 

[dnmun]

you can turn off the battery by putting a small DIP switch in the circuit current of the BMS to turn off the BMS.

 

[SlowCo]

you can turn off the battery by putting a small DIP switch in the circuit current of the BMS to turn off the BMS.

I saw this comment and hope you could elaborate on that. Where in the circuit would that small switch have to be?
I have a BMS with a small switch in my battery pack but if I switch that to the off position I still measure 44V (56V when "on") at the output.

This is the thread where youve helped before: https://endless-sphere.com/forums/viewtopic.php?f=14&t=66456

Photo's:





Apologies for the hijack...

 

[d8veh]

If you have a BMS, you already have a switch that can switch off the battery. That's what a BMS does.

When you can still measure voltage with the switch on your battery, does your bike still work. Normally, you can still measure some volts on the output wires with the BMS switched off, but it's only charge, you can't draw any current

 

[vwhammer]

Perhaps kill switch was the wrong term to use.
What I am more concerned about is eliminating the sparks that one gets when plugging or unplugging the battery as not to destroy connectors and such.
At least from what I have read that appears to be a problem.
If it is not an issue then I am not too worried about it.

However, I would like a switch that disconnects the battery in an emergency situation.
Preferably this would just be a handy button that can be easily accessed in an instant.

 

[John in CR]

You need a pre-charge resistor circuit to avoid the spark which gets worse the higher the voltage. On my bikes the batteries always stay aboard and connected, so I manually use a resistor to charge the controllers' capacitors before making the second battery mains connection. The caps are already charged when I turn on the low current carrying key switch, so there's no arc to scar those contacts.

 

[vwhammer]

Yes. I believe that is what I am looking for and I believe that is what is in the second link in my original post.
So if I build one of those then everything should be good to go.
I should be able to set up everything I want.

 

[d8veh]

The BMS does switch the battery off in an emergency situation. As I said before, that's its function. Why do you want another switch when you already have one?

 

[dnmun]

you can turn off the battery by putting a small DIP switch in the circuit current of the BMS to turn off the BMS.

I saw this comment and hope you could elaborate on that. Where in the circuit would that small switch have to be?
I have a BMS with a small switch in my battery pack but if I switch that to the off position I still measure 44V (56V when "on") at the output.

This is the thread where youve helped before: https://endless-sphere.com/forums/viewtopic.php?f=14&t=66456

Photo's:

View attachment 1



Apologies for the hijack...

did you even look at the picture you posted? the switch to turn the BMS on and off is already in place in the lower right corner. that will turn off the battery and stop the spark when connecting to the controller.

 

[vwhammer]

The BMS does switch the battery off in an emergency situation. As I said before, that's its function. Why do you want another switch when you already have one?

I have not actually purchased my battery yet.
I am looking at a pack from luna cycle and if it has the switch that I can access then everything will be good.

 

[SlowCo]

you can turn off the battery by putting a small DIP switch in the circuit current of the BMS to turn off the BMS.

I saw this comment and hope you could elaborate on that. Where in the circuit would that small switch have to be?
I have a BMS with a small switch in my battery pack but if I switch that to the off position I still measure 44V (56V when "on") at the output.

This is the thread where youve helped before: https://endless-sphere.com/forums/viewtopic.php?f=14&t=66456

Photo's:

View attachment 1



Apologies for the hijack...

did you even look at the picture you posted? the switch to turn the BMS on and off is already in place in the lower right corner. that will turn off the battery and stop the spark when connecting to the controller.

Yes I did and even posted the second picture ("Small BMS switch.jpg") with the switch in close up. And as I stated, when I turn that off I can still measure 44V on the output of the pack. That's why I'm curious if the battery pack is actually "off" in that state?

 

[dnmun]

put a resistor across the output and see if there is still voltage there. if there is still voltage with a resistor across the output then your output mosfets are shorted.

 

[ecycler]

It sounds like something like this is what you are seeking. It works great in electric skateboards and based on your power requirements is in spec for your application:

http://diyelectricskateboard.com/product/on-off-high-voltage-anti-spark-power-switch-2-14s/

It consistently sees more than 50 amps climbing some steep pulls around these parts.

 

[vwhammer]

Hmmm yes that does appear to be what I am going for.
I may give it a whirl.

 

[d8veh]

You don't need that if your switch is working.

With everything connected, switch off the switch on the battery. Can you still operate your bike? No, problem solved!

You can measure voltage with the switch off, but no current can flow, so no spark when you connect. You won't be able to measure any voltage when you connect it to your controller. It'll go immediately to 0v.

 

[vwhammer]

Not sure if my battery from luna cycles has a switch. (Have not received it yet)
They send their batteries with an XT90 connector with some kind of spark resistor in it.
From the pics it does not look like there is access to the BMS or a switch.

 

[d8veh]

Have you a link for your battery, so that we can see what it is?

 

[vwhammer]

This is the one I bought.

http://lunacycle.com/batteries/48v-samsung-18650-battery-pack-10ah/

 

[dnmun]

then open the battery up and pull the BMS out where it can be cooled in the air and then add the switch to it.

 

[vwhammer]

Is it as simple as adding a switch to the BMS?