How to wire a key switch properly? (for main power)

Hey there! This is actually my first time posting! I build Electric-Assist Tricycles. They currently draw up to 50A continuous at 36V.

I have been using automotive switches (and before that, e-scooter switches) for my 'frankentrikes' (www.frankentrikes.com).

My current rated 12V 35A automotive switch just fried. It took 4 years--which is pretty great--but I'm not sure if I'm going to be able to get another one of those, as that model has be discontinued.

I'm aware that electric golf carts generally use 50A solenoids. In theory, that's a better match for my trike methinks.

I can't really conceptualize how to install it however. I 'get' that there is an ordinary key switch activating the solenoid (or 'contacter') but I'm going mad trying to understand how it all gets wired into my vehicle.

Do I get a 12V or a 36V solenoid/contacter? I mean, most switches are rated at 12V (I have a DC-DC 36 to 12 step down converter), but main power is 36V.

Soo....which do I get? I see 12V 200A solenoids, which would probably do the trick, but I also see 36V 50A contacters/solenoids.

With my current key switch, it is brutally easy, just wire it in-line with the red wire (+) that comes out of the battery, so that it interrupts the main power. Works great until I blow it up, which always happens eventually.

But with two components, what do I do? Do the 2 large ports get connected in-line with the (+) red wire out of the battery? No, that wouldn't make any sense! Would instead the small ports get connected in-line with the (+) red wire out of the DC step down power to 12V? Well that's great, but then the main power stays on in order to do that, draining the battery! This is crazy! It's so easy with a heavy duty key switch and now I'm sooo confused.

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I have another option, which is to use a master disconnect like you see on a Caterpillar or something; the problem there being that the keys are generic! One Caterpillar key fits all of the same switches! It's super frustrating that I haven't found a single master disconnect that has ordinary keys like you would want for your personal vehicle. I have a Pollak in house that would take the heat.

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I am also looking at remote switches, but the problem will be the same perhaps as with the solenoid/contacter dilemma, in terms of where to connect the power so that it works! I have one of those in house also.

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Could anyone offer any guidance on how to wire a solenoid? or maybe some knowledge of some top secret master disconnects that have personal keys? Thanks so much!

sfiii said:

This is actually my first time posting!

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No, it' isn't. You've posted twice before, about four years ago, the first time n another key switch thread:
https://endless-sphere.com/forums/viewtopic.php?f=3&t=15585&p=1049805#p1049805

I can't really conceptualize how to install it however. I 'get' that there is an ordinary key switch activating the solenoid (or 'contacter') but I'm going mad trying to understand how it all gets wired into my vehicle.

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There's a number of threads around ES that contain wiring diagrams with contactors, relays, etc., to show you how this works if you need pictures. I don't have links, but you can find them in a search relatively easily, though it might take some time.

But it's very simple. The contactor or relay has two parts. The coil, which is controlled by the switch, runs on a separate voltage than the contacts. This can be any voltage, you have to get the contactor with the right "coil voltage" for your setup. If your switch is using 12v, then you get one with a 12v coil. If 36v, then you get one with a 36v coil.

The contacts are controlled by the coil. If the coil has enough voltage on it, current in it pulls the contacts closed, letting current flow thru the contacts. If you have a 36v battery system for the motors, then the contacts must be rated for 36v *or more*. It must also be rated for *at least* the maximum peak amount of current the motor system will pull from the battery. If the contacts are not rated for at least that voltage and at least that current, then if something happens that causes the contactor to turn off under that load, it may continue to arc current thru the contacts and damage them, perhaps welding them together, or just arcing and heating until things melt or catch on fire. Not a likely thing, but it can happen.

The coil is wired so one end goes to the ground of the switch's power supply. The other end goes to one side of the switch. The other side of the switch goes to the positive of the switch's power supply.

THe contacts are wired so one of them goes to the main motor battery positive. The other one goes to the main motor controller positive. The main controller negative goes to the main battery negative directly.

This means when you turn the switch on, the coil turns the contacts on, and the motor controller gets power.

Do I get a 12V or a 36V solenoid/contacter?

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Solenoids are just a coil with a pushrod or other mechanical device that perform a mechanical action when you put a current thru the coil.

Contactors (and relays) are what you want, as they are a similar device that uses the mechanical action to move a set of contacts (switch) to create an electrical path.

most switches are rated at 12V

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No, there are many voltage ranges for switches. If anything, you might say that "most" switches are rated at 115-130VAC, or perhaps 230VAC, because there are so many light switches in buildings of all kinds across the world.

You can go to Mouser, Digikey, Farnell, etc., and look thru all the many many many kinds of switches to see their voltage and other ratings, if you're curious.

amberwolf Oh my goodness, I didn't remember posting before, and about the same problem, and now there are so many wonderful replies to that thread which I will now review! When I wrote 'most switches', I mean't 'most automotive and scooter key switches.' I see a few on the market that are 24V but never 36V. I only see master disconnect switches with generic keys at 36V and higher. I have looked in the DigiKey catalog and saw nothing that met my needs, at least not in a straightforward fashion.

I have melted down a number of escooter and automotive key switches over the past 13 years. They always last for awhile before dying in an instantaneous manner. The last one, rated at 12V 35A, was an automotive switch that lasted 4.5 years! (since the last post on endless sphere, apparently). This is likely because I am shunting 36V 50A through the switch and overloading the switch, (though one wonders why it didn't happen sooner if that is the case).

Thanks for explaining how I need a contactor/relay rather than a solenoid. I believe you, but am confused by how I will see an item called a 'solenoid' on one website and then the precise same component is called a 'contacter' on another website! It makes it hard to know what to buy. I also I think got misled by electric golf carts, which use solenoids. I was mistakenly assuming that I could use the same tech as a golf cart but perhaps you are correct that I need to specifically search for a 'relay.'

I searched for threads on endless sphere for 'switch' or 'key switch' and got an overwhelming number of unrelated threads as results so thanks for understanding my reason for this original post (being fooolishly unaware of my 2015 post).

Just as an update, I was able to locate on my shelves a remote switch rated at up to 48V 53A continuous designed by Christopher Wiggins at Glide Cruisers. I got it installed and working (as most of the wiring is already done by him) and will be testing it to see if I can get a better performance out of it than my previous experiments. It appears to use a remote switch connected to a cube on the main power circuit which I assume is the relay. Short term, my crisis is averted but, longterm, everything that is posted may become relevant to this project or someone else's project now or in the future.

Thank you again for your response, amberwolf!

sfiii said:

The last one, rated at 12V 35A, was an automotive switch that lasted 4.5 years! (since the last post on endless sphere, apparently). This is likely because I am shunting 36V 50A through the switch and overloading the switch,

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The usual problem, if not switching under load, is the arc from the too-high voltage burning the contacts. eventually damaging them beyond the ability to make contact, *or* welding them together so they won't break contact anymore.

Switches that move their contacts in a circular or linear fashion, wiping them across each other, will last longer in this type of misuse than ones that simply open and close them like pinching your fingers together...but they'll eventually still fail.

I'm using a battery isolator / cutoff switch, from harbor freight, on my 14s "52v" (58v full) pack on the SB Cruiser trike, and it gets operated multiple times a day, every day, been using it at least a couple years now, maybe three. No failure yet...but no guarantees, either, cuz it is designed for 12v. It didn't have a current rating on it, AFACR, but it would have to be able to handle the hundreds of amps of starter current on a car, at least for a few seconds at a time. So it handles the 60-100A+ I throw at it regularly at startup from a stop, and the 20-30A continuous for cruising, so far at least.

I believe you, but am confused by how I will see an item called a 'solenoid' on one website and then the precise same component is called a 'contacter' on another website!

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That just means they're misusing the term "solenoid"; technically the contactor and the relay *are* solenoids but they re not *just* solenoids...they do contain one, though.

To be sure you're getting what you need, look at the pictures; a pure solenoid just has two connection points. A contactor or relay will have at least four (or more). Two will be smaller, those are the coil, and the larger ones are the high-current connections that are switched.

I also I think got misled by electric golf carts, which use solenoids. I was mistakenly assuming that I could use the same tech as a golf cart but perhaps you are correct that I need to specifically search for a 'relay.'

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It should be the same technology. You probably don't need one as hefty as the golf carts use, as those often use much higher currents, so they're pretty large.

It sounds like the terms are just being misused by people that dont' know what they really mean. :/ Sometimes that happens for a long enough time that it just becomes permanently wrongly used.

I searched for threads on endless sphere for 'switch' or 'key switch' and got an overwhelming number of unrelated threads as results so thanks for understanding my reason for this original post (being fooolishly unaware of my 2015 post).

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Yeah, it's hard to find the gems in the tailings pile.

Here's some searches that may have more relevant results, hopefully:
https://endless-sphere.com/forums/search.php?keywords=key*++switch*&terms=all&author=&sc=1&sf=titleonly&sr=topics&sk=t&sd=d&st=0&ch=300&t=0&submit=Search

And this one finds an RFID keyswitch thread that isnt' related but might be interesting / useful:
https://endless-sphere.com/forums/search.php?keywords=keyswitch&terms=all&author=&sc=1&sf=titleonly&sr=topics&sk=t&sd=d&st=0&ch=300&t=0&submit=Search

Which cutoff switch are you using from Harbor Freight? Just curious. And what are you running at? What's your top Amps output?

The 'solenoids' I have been looking at have 4 connectors.

I actually think I DO need what golf carts are using. And the run of the mill ones are actually not so big. My trike is pretty big, so they look small by comparison {

Thanks for the thread links, amberwolf! I will look at those too. Someday, one switch system will emerge victorious! Will it be the slick one I have just installed? Stay tuned!

sfiii said:

Which cutoff switch are you using from Harbor Freight?

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Some version of this one (mine didn't come with the little cap, but otherwise it is very similar).
https://www.harborfreight.com/Battery-Cutoff-Switch-63425.html

And what are you running at? What's your top Amps output?

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Rather than retyping, I'll just quote my previous post and highlight it:

amberwolf said:

I'm using a battery isolator / cutoff switch, from harbor freight, on my 14s "52v" (58v full) pack on the SB Cruiser trike, and it gets operated multiple times a day, every day, been using it at least a couple years now, maybe three. No failure yet...but no guarantees, either, cuz it is designed for 12v. It didn't have a current rating on it, AFACR, but it would have to be able to handle the hundreds of amps of starter current on a car, at least for a few seconds at a time. So it handles the 60-100A+ I throw at it regularly at startup from a stop, and the 20-30A continuous for cruising, so far at least.

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The 'solenoids' I have been looking at have 4 connectors.

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Then they are probably really contactors / relays. (BTW, often, contactors are sealed to be weatherproof and to be filled with a neutral gas, or a vacuum, so arcs extinguish easier.

I actually think I DO need what golf carts are using. And the run of the mill ones are actually not so big. My trike is pretty big, so they look small by comparison {

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You should post pics and stuff. (if you attach them directly to the post, then anyone that can see the post can see the pics).

You can see mine over in the SB Cruiser thread; the latest "version" is at the end of the thread, there's relatively recent pics at the top of the first post though.

amberwolf, as you can tell, I clearly have no idea how to do this forum thing correctly! { I have seen those isolater switches everywhere, but I'm designing a product, not just a one-off, so I can't imagine this sort of a clunky generic key being a selling point for future buyers. If anyone can spend $5 and get a key that will enable them to steal any 15K$ electric tricycle, not good.

I just discovered that when I called CarQuest directly, they could order me a replacement switch BWD CS200! They are no longer in stock, but still being manufactured apparently. They are rated at 12V 35A, but I was punishing this switch with 36V 40-45A continuous for over 4 years without a hiccup. I recommend this switch for DIY electric vehicles that will run under 40A. They are cheap and very easy to direct wire in; just make sure you put rubber caps over the nuts so that they cannot arc to each other or the frame (and so they stay dry where it counts). Mine was protected from rain but not from splashing water but that didn't seem to be a problem. If I recall correctly, this switch even got dunked in salt water and survived for another year after that!

I used connectors to wire the switch in, so that it is easy to 'hotwire' the vehicle to get home. (by simply removing the switch from the circuit)

I don't know how to post pics here, but there are plenty on my website, frankentrikes.com . I just repaired the red trike, which is still my personal vehicle, but also a research vehicle for future prototyping and manufacture. If you mean specific pics, well, a photo cannot transmit the vile smell of a fried switch!

That's really cool, that some contacters are weatherproof and filled with noble gasses! I still might explore the golf cart angle at some point...

Most ebikes just have the battery always connected to the controller and only switch the low current "key" or "ignition" line. If you want to store the bike for a long time, unplug the controller.

fechter, I have two controllers and they are hard to reach. Some have switches so one wouldn't even need to unplug them. I also don't store it for a long time, I drive it nearly every day. But yes, all advice would be appropriate to a less complicated set-up

In case anyone is interested, LockMasters just pointed me in the direction of a different Pollak switch than I was already aware of, 31-499, which is the same size as a standard automotive switch but rated to 40A continuous! That's beefy, folks.

If you have a large enough vehicle to care, Pollak also makes a monster switch 51-916, actually rated to 36V DC and 180A continuous! It is just really big and heavy and, on my vehicle, awkward to stash anywhere.

Would an SSR relay be something you would consider? I use one on my 52 volt LI-Ion system that has worked well for me. It's rated 6 to up to 60 volts DC, and up to 120 amps. It comes with a lighted push on/off switch. (I like lights!) But you could use a low voltage, low amp locking keyed switch in it's place. The relay makes/breaks the negative or ground wire connection to the battery, the red wire goes straight thru. The switch has it's own low voltage 4 wire harness. (2 wires for LED, 2 wires for the switch) Switching and LED power provided by the relay assembly. Switch push button glowing blue, lower right...







See it HERE...



Regards,
T.C.

TommyCat, yeah I saw that item on a similarly-themed thread. People complained about it not being weatherproof, but that sounds like a not-insurmountable problem. Thanks for explaining what the little wires do. If the remote switch I just installed fails (or i lose the only remote {: o ), that might be next in line.

Alright, if you don't want something bulky, and even at the super high price of the trikes it's too expensive to get the "right" part, then I'd go with a double cutoff.

First, the primary would be just the "keyswitch" or "ignition" line on the controller. You can use a very "small" (low current) keyswitch, of any kind, that suits your trike's visual style, location/mounting, budget, weather-proofing needs, etc. This switch is wired between the battery voltage to the controller, and the "KSI" (keyswitch / ignition) line from the controller. All it does is turn off power to the "brain" of the controller, by cutting power to the entire low voltage side. Power to the FETs is still present, but there's very little power drain because they're not being driven by anything. This would be the "security" part of the system, since the key would be unique, or at least not that common.

Then you can use whatever kind of battery cutoff you prefer, for those times you need to disconnect the battery from the system. (or rather, whenever your customers do; their needs aren't always going to be the same as yours, and they might need to leave it for a significant time unattended).

For instance, if you don't want to take any significant mounting space "in the open", you can just use a relatively easy-to-unplug but still secure battery connector, like the Anderson SB-50 or SB-75, which can be bolted down to the trike on the controller side, and a T-handle on the battery side, so if needed a user can just pull the handle to disconnect the battery. It can't be plugged in backwards, so replugging is safe for the user, and the Andersons are designed with 'sacrifical tips" on the contacts, so that the spark one gets from plugging into a controller with big capacitors doesn't damage the contact surface itself.

Or, you can use the battery cutoff like I use, mounted on the battery box itself, etc.

Or, if the battery has a BMS, you could use a BMS with an "enable" line, and put a switch on that. it can even be a keyswitch for security. Works basically like the controller KSI line, so only a small switch at very low current is needed.

Plenty of other options, too.