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Votol EM200 Contactor Wiring—Key Switch Voltage?

HoboBob

1 µW
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Sep 18, 2023
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4
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SC, USA
Hi All!

New to the forum and working on refining an EV Kart I recently put together, but have some questions regarding wiring in a contactor and how to do so correctly. Couple build overview specs:

  • QS138 90H motor
  • Votol EM200 controller
  • 72v 240a battery

There is no DC/DC converter on this build so I am needed to switch the contractor using full pack voltage. Where my confusion is coming into place is am I needing to use a key switch that is rated for 72v DC? Finding a small rocker switch rated for this is proving difficult so it has me questioning my path in accomplishing this. I'm attaching some wiring diagrams I've come across that mostly reference the 48v TopKart system, but the theory behind my build is similar.

Additionally, if anyone is familiar with the EM200, is it the E-Lock wire I can use as the key switch? I haven't brought out the multimeter to test this yet, but if anyone happens to know.

Thank you!
 

Attachments

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There is no DC/DC converter on this build so I am needed to switch the contractor using full pack voltage. Where my confusion is coming into place is am I needing to use a key switch that is rated for 72v DC? Finding a small rocker switch rated for this is proving difficult so it has me questioning my path in accomplishing this.
To be sure, are you also using a contactor with a 72v coil? If not, you don't want to switch battery power to it. In that event we can work out a different solution.

If it is a 72v coil, and you need a 72v switch, a quick google for "mouser 72v rocker switch" provides this link
to a few, along with other places like Digikey and so on. You'll want to verify the ratings for the switches to be sure they'll handle the required current, etc, and fit in your application physically.





Additionally, if anyone is familiar with the EM200, is it the E-Lock wire I can use as the key switch? I haven't brought out the multimeter to test this yet, but if anyone happens to know.
The names used for the KSI (keyswitch / ignition) wire vary, but almost universally the way they work is to be connected to battery power to provide that to the controllers internal LVPS that makes 5v, etc to power the MCU/brains/etc. So if that's where the E-lock wire goes, then that's what you can use to connect it up.

Some use "lock" wires as an antitheft mechanism, and what it does is turn on a motor drive mode that actively fights rotation of the wheel, usually active, when grounded and when unconnected, the mode is disabled. Specifics vary between controllers, so the manual would be your best place to verify this, despite the usually-poor wording and translations in them. :(

There are a few big Votol threads around here, at least one of which includes some discussion of this IIRC.
probably this one
or this one
 
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The contactor is separate from the components you've already listed. Can you provide a link to your contactor?

The activation coil is usually either 12v or pack voltage. If it's 12v, you'll find a wealth of available automotive switches that would work.

If it's pack voltage, 72v for you, I have advice, take it with a grain of salt please. I use a contactor with a 72v coil. I use a small toggle switch rated for 120vac @ 5a, similar to this one, though not the exact one I use. I have no issues with it, because the current used to flip the coil is .015a in my case, at max 82v, so my switch is working. Should I be using this switch in a manner for which it's not specifically rated? Perhaps not.
 
To be sure, are you also using a contactor with a 72v coil? If not, you don't want to switch battery power to it. In that event we can work out a different solution.

If it is a 72v coil, and you need a 72v switch, a quick google for "mouser 72v rocker switch" provides this link
to a few, along with other places like Digikey and so on. You'll want to verify the ratings for the switches to be sure they'll handle the required current, etc, and fit in your application physically.

The names used for the KSI (keyswitch / ignition) wire vary, but almost universally the way they work is to be connected to battery power to provide that to the controllers internal LVPS that makes 5v, etc to power the MCU/brains/etc. So if that's where the E-lock wire goes, then that's what you can use to connect it up.

Some use "lock" wires as an antitheft mechanism, and what it does is turn on a motor drive mode that actively fights rotation of the wheel, usually active, when grounded and when unconnected, the mode is disabled. Specifics vary between controllers, so the manual would be your best place to verify this, despite the usually-poor wording and translations in them. :(

There are a few big Votol threads around here, at least one of which includes some discussion of this IIRC.
probably this one
or this one

Thanks for all the links, Amberwolf! I did come across those rockers on Mouser, but the sparse selection furthered my concern I was way off-basis here. I'll have to pop into some of those Votol threads! I did some quick reading in there before posting but maybe need to spend more time.

The contactor is separate from the components you've already listed. Can you provide a link to your contactor?

The activation coil is usually either 12v or pack voltage. If it's 12v, you'll find a wealth of available automotive switches that would work.

If it's pack voltage, 72v for you, I have advice, take it with a grain of salt please. I use a contactor with a 72v coil. I use a small toggle switch rated for 120vac @ 5a, similar to this one, though not the exact one I use. I have no issues with it, because the current used to flip the coil is .015a in my case, at max 82v, so my switch is working. Should I be using this switch in a manner for which it's not specifically rated? Perhaps not.

My apologies, I should have specified this in my original post—I do not have a contactor I am set on using. I have a 48v coil contactor on hand, but I was planning on using a Tyco EV200 or other rated contactor to avoid using a DC/DC if possible.
 
With a 48v coil you could drive it from 72v if you use a dropping resistor in series with the coil to limit the current. Measure the coil resistance, then use ohm's law and some algebra (sorry, i'm terrible at math that requires making my own formula) to determine the necessary series resistance. Then use the current thru the resistor and the voltage developed across it to determine the watts it has to dissipate to get one of the right physical size. There is a thread somewhere where I helped work this out for someone else in a similar situation, IIRC, but can't remember who it was. :oops:
 
Thanks for all the links, Amberwolf! I did come across those rockers on Mouser, but the sparse selection furthered my concern I was way off-basis here. I'll have to pop into some of those Votol threads! I did some quick reading in there before posting but maybe need to spend more time.



My apologies, I should have specified this in my original post—I do not have a contactor I am set on using. I have a 48v coil contactor on hand, but I was planning on using a Tyco EV200 or other rated contactor to avoid using a DC/DC if possible.

72v contactor, 72v coil, no dc/dc needed. This is the one I use, with the abbovve mentioned toggle
 
Couple build overview specs:
  • QS138 90H motor
  • Votol EM200 controller
  • 72v 240a battery
BMS?
Additionally, if anyone is familiar with the EM200, is it the E-Lock wire I can use as the key switch? I haven't brought out the multimeter to test this yet, but if anyone happens to know.
Yes. Votol literature commonly labels the controller power supply as “e-lock”. Supply pack voltage to it and the controller will power up. Draw should be <20mA.

I’d propose a different approach though.

Just shut down the BMS instead of using a contactor.

Keyswitches are failure prone, inconvenient, and insecure. Have you considered a hidden switch or plug/socket arrangement?

If you insist on a key switch, have you considered instead wiring it to enable/disable the BMS?

If you do this the switch sees no voltage or current, and emergency shutdown is taken care of, making a contactor redundant.

Having to turn a key in an emergency is not ideal though, I’d suggest a more practical and ergonomic kill switch than a keyswitch, but you can have both in series if you insist on having a keyswitch.

For the kill switch you can use a 1/4” phono stereo socket wired in the vehicle dash, with the male plug attached to a projecting element so that you can yank it out as needed. I keep the plug attached to my keyring, which is appropriate since it is the “key”.
 
BMS?

Yes. Votol literature commonly labels the controller power supply as “e-lock”. Supply pack voltage to it and the controller will power up. Draw should be <20mA.

I’d propose a different approach though.

Just shut down the BMS instead of using a contactor.

Keyswitches are failure prone, inconvenient, and insecure. Have you considered a hidden switch or plug/socket arrangement?

If you insist on a key switch, have you considered instead wiring it to enable/disable the BMS?

If you do this the switch sees no voltage or current, and emergency shutdown is taken care of, making a contactor redundant.

Having to turn a key in an emergency is not ideal though, I’d suggest a more practical and ergonomic kill switch than a keyswitch, but you can have both in series if you insist on having a keyswitch.

For the kill switch you can use a 1/4” phono stereo socket wired in the vehicle dash, with the male plug attached to a projecting element so that you can yank it out as needed. I keep the plug attached to my keyring, which is appropriate since it is the “key”.

Thank you for the confirmation! I have the e-lock wired straight to pack voltage for now and did not wire in a switch for testing purposes, so I will do that.

ANT BMS on removable battery. Don't want to wire anything directly to that BMS as the system is meant to be hot-swappable at the track. I am interested in having two redundant points at which I can break the pack—the big red button emergency disconnect that will break pack voltage in emergency and the keyswitch rocker as a more friendly on/off for the contactor—so like you said, both switches in series. Being a kart, not a lot of room to work with so the more lightweight the solution could be, the better.
 
That makes sense. Although I’d still argue in favour of a BMS disabling solution, since the contactor adds bulk, and hot swappability isn’t much hindered by having an extra plug/socket from the BMS to disconnect in addition to the positive and negative battery leads.

I haven’t looked into ANT BMS. I started buying JB ones as soon as I saw they had the integrated enable/disable functionality that I wanted, which saved having to find alternative ways to de-power them such as by hacking power traces.
 
If the BMS is a contactor-based type, that's a good solution, but if it is a FET based type, then the typical failure mode of FETs is stuck-on, and then you can't shut it off. Contactors can weld shut (stuck on) too, but it's not nearly as common a problem for properly sized contactors--even properly sized FETs can be blown or damaged by improper gate drive or lack of protections against little voltage spikes, etc.
 
Yes, but still not a valid reason to install a contactor IMO.

If you’re concerned about BMS failure, a simpler, cheaper, more reliable, and less (power) lossy solution is to have a short circuiting switch to deliberately trip the circuit breaker (or fuse) on the battery positive. In a cart you could use a stomp pedal switch.

I think it’s unnecessary though. What are the odds of all the required system failures occurring in the correct sequence for it to be a real concern.

I don’t know what emergency situation other people are conceiving, but for me it’s a controller failure that results in uncontrolled acceleration.

(I discount throttle failures, because there’s already defence against them incorporated into controllers, in addition to the upstream system shutdown options available to you).

So the situation is, your controller is in runaway acceleration, and the brake lever isn’t shutting it off.

Terribly unlucky I’d say. So you flick the switch to shut down the controller.

Even more bad luck, the controller won’t shut down. So, while making a mental note to never buy another of these wretched controllers, you casually pull the pin on the BMS.

Oh no, BMS won’t shut down either! Truly you are a cursed individual.

I shouldn’t be facetious regarding valid safety concerns, and I apologise for that, but I just don’t see it ever happening.

Plus, you have two independent powerful hydraulic brakes to mitigate the situation. And helmets and body armour if it still ends in an ugly fashion.
 
Wanted to loop back here and give some closure!

I went with a Tyco 72v coil contactor to eliminate the need for a DC-DC converter. Found a 72v DC-rated rocker switch on Mouser for the keyswitch, which was in fact the "E-Lock" on the EM200.

Still trying to figure out a resistor for a precharge setup if anyone has any tips on choosing the right value; can't find any literature on the capetance of the EM200. But in the meantime I'll scale down the starting amps of the battery from the BMS and we're closer than when we started!

Thanks for the help @glennb and @amberwolf !
 
hi. i have recieved today the 200-2 votol controller and i am almost sure i read somehwere that it is internal contactor which is energized when connecting elock (purple+grey wire) to positive. that no need for external contactor but i am not sure about that.
havenot you read anything indicating that?
 
Not many votol disassenbly pics, but I don't recall a contactor inside any of the few pics I've seen. But I don't know if any of them are the same model you have.
 
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