AC relay for car charger?

[Togg]

I'm looking for suggestions for a good power relay to buy to help limit when our cars can charge.

Basically I'm looking for at least a 240V / 60A relay that can be switched with low voltage, like 12V. It will hook between our 50A electric service panel breaker and our NEMA 14-50 220V car charger outlet, and be controlled by a ELK M1 home automation & security controller which can tell it when to turn on and off.

Here is one option, if a little pricy: https://www.mouser.com/ProductDetail/Carlo-Gavazzi/RGC1A60D60KGU?qs=xZ/P%2Ba9zWqZa21w2CLj5Xg==

Reason: Our power time-of-usage tripples our electric cost after 4:00 PM, so I want to program my house computer to disable the car after 4pm, and then re-enable it again when the sun is up.

I imagane that I only need to switch one leg on and off, but switching both legs would probably be better. Probably an electronic (triac) switch is better than a mechanical one, but there are magnetic latching switches also available, like this one: IM601 32A 40A 60A 5V 6V Magnetic Latching EV EVSE Relay for Electric Vehicle Charger

Anyone have any experience in hooking up such a relay, and have any suggestions as to which is the best way to go?

(The best would be if the Tesla cars would be smart enough to allow us to input our electric time of use rates and have the car limit themselves depending on user preferences, but we're not there yet, ... hello Elon, are you listening.)

 

[israndy]

You can simply write a little Python script that will do that. I have a hot tub that pulls almost as much as the Tesla and I don't have THAT much solar, so when the tub comes on I want the Tesla (and our other EV and space heaters) to turn off. I wrote a little script (TesSense) that pulls the free solar figure from my Sense Energy Monitor and if there is any it will wake my Tesla and start it charging (if it's full or unplugged the car'll go back to sleep), but when the Hot Tub (or Microwave, or Nespresso, or Dishwasher) come on the cars and the space heaters will kick off.

The Tesla even has the ability to charge at any rate from 48 amps down to zero. So I will read the free solar and adjust the Tesla. Only if the Tesla is already off will I pull the space heaters. Turns out it's pretty easy to write crud in Python and the APIs for Sense and Tesla and Kasa (the energy monitors I have on the space heaters and the other EV) are pretty fool proof (I'm the fool that proved it).

Making a script that responds to TOU and Solar should be even easier. I don't know if there is an ELK 1 API out there, but if it can control a relay perhaps it can trigger software too.

 

[ATPMSD]

Why not use Scheduled Charging or Scheduled Departure that is built into the car?

 

[israndy]

I would have suggested just that except I assumed he had solar because of this statement:

I want to program my house computer to disable the car after 4pm, and then re-enable it again when the sun is up.

 

[Togg]

Why not use Scheduled Charging or Scheduled Departure that is built into the car?

Have you tried it yourself? How do I set my electricity time of use rates and times in it?

 

[Togg]

You can simply write a little Python script that will do that. I have a hot tub that pulls almost as much as the Tesla and I don't have THAT much solar, so when the tub comes on I want the Tesla (and our other EV and space heaters) to turn off. I wrote a little script (TesSense) that pulls the free solar figure from my Sense Energy Monitor and if there is any it will wake my Tesla and start it charging (if it's full or unplugged the car'll go back to sleep), but when the Hot Tub (or Microwave, or Nespresso, or Dishwasher) come on the cars and the space heaters will kick off.

The Tesla even has the ability to charge at any rate from 48 amps down to zero. So I will read the free solar and adjust the Tesla. Only if the Tesla is already off will I pull the space heaters. Turns out it's pretty easy to write crud in Python and the APIs for Sense and Tesla and Kasa (the energy monitors I have on the space heaters and the other EV) are pretty fool proof (I'm the fool that proved it).

Making a script that responds to TOU and Solar should be even easier. I don't know if there is an ELK 1 API out there, but if it can control a relay perhaps it can trigger software too.

"will wake my Tesla and start it charging"?? Ok, but how exactly do I tell a Tesla to turn charging on and off?

 

[israndy]

It's done programmatically, but you can also do it from your phone. The same API that Tesla's app uses can be used by other programs. I got sick of no one writing such a program so I sat down two months ago and started reading the TeslaPy API page at Github. I downloaded the example code and made changes that made sense to me and saw what they did to the running of the example code. Slowly taught myself Python Programming. I wouldn't say the app I wrote for myself is done, I make changes every day. But I have been posting the results on my Github repository under the name TesSense.

If all you need is a timer for your car that's SUPER simple to write, but you can also respond to solar generation. I have a Sense Energy Monitor that ALSO has an API written for it and I took that example code and figured out my free solar and then made the app turn my car's charger on when there was extra and off when there wasn't. Eventually I learned you can set the RATE at which the car charges and so as the sun goes down I keep setting the charge rate 1 amp lower until there's nothing left, then I turn it off for the night and we do it all again tomorrow.

Eventually I figured out all the bugs I was putting in my code so it doesn't crash overnight, and added features so it will also show when I am at a Supercharger or just that I am not at home, this way if the app is running while I am charging elsewhere I don't limit the charge to my free solar at home.

Now I wanna get a little Raspberry Pi that runs the app all the time so I can do things with my main computer like let it sleep at night or drive with me to the cabin and not impact the functionality of the app running.

 

[Jeepxj]

i'd suggest using a 120v coil contactor and use a smart plug with an internal schedule or IFTT/alexa

ex:

YC-CN-603-2 YuCo CN-PBC603-120V Definite Purpose CONTACTOR 60AMP 3POLE 120VCOIL 60 FLA 75 RES - - Amazon.com

YC-CN-603-2 YuCo CN-PBC603-120V Definite Purpose CONTACTOR 60AMP 3POLE 120VCOIL 60 FLA 75 RES - - Amazon.com

www.amazon.com

https://www.amazon.com/Sonoff-Monitoring-Certified-Assistant-Supporting/dp/B08GKGS197

 

[mswlogo]

If you are using UMC you only need 40A not 60A. The relays are typically 24V. With such long duty cycle I would not use a Relay (that needs to be energized for the whole charge). But a get a Bistable Switch that can be programmed to flip to either state and does not require power to stay in either state. You definitely do not need 3 pole. 2pole would be fine.

But if you can do this by scripting Tesla side or buy a smarter charger that’s more flexible programmable it would be a much cleaner and more robust.

Adding the relay / switch is just adding another point of failure. It’s also not “smooth”. You are basically going to setup a programmed power failure every night. Not a good idea.

 

[Togg]

If you are using UMC you only need 40A not 60A.

Was planning ahead, as future vehicles might draw more. There is a J1772 version that draws more I think.

get a Bistable Switch that can be programmed to flip to either state and does not require power to stay in either state.

Yes if I don't take the software approach, I'm looking at going that way. There are a number of different bi-stable relays I've found. None I'm in love with just yet because they all are a little harder to control including default initialization.

But if you can do this by scripting Tesla side or buy a smarter charger that’s more flexible programmable it would be a much cleaner and more robust.

I like this but it seems that the Tesla API is a reverse engineered one, and that means it might change in the future, even become unusable. I wish Tesla would open up this API and stand behind it. So that was part of the reason I was even considering a relay. I might just have to mull it over because neither way is optimal.

Adding the relay / switch is just adding another point of failure. It’s also not “smooth”.

Here, I don't know what you mean by 'smooth'. Do you mean switching things when the voltage wave is zero vs at a random time. I hear you on this. But I don't think this will hurt anything, except perhaps relay contacts.

You are basically going to setup a programmed power failure every night. Not a good idea.

Help me understand why this seems like not a good idea to you? We unplug powered on stuff all of the time. Yes it does put a bit of a spike on the line. Any other reason you suggesting this is a not good idea?

 

[ATPMSD]

Another “software” option

Save on your electric bill

Optiwatt integrates your exact electricity rates so you can save on EV charging and HVAC. Automatically use electricity off-peak and earn rebates in utility programs.

getoptiwatt.com

 

[mswlogo]

Was planning ahead, as future vehicles might draw more. There is a J1772 version that draws more I think.

Yes if I don't take the software approach, I'm looking at going that way. There are a number of different bi-stable relays I've found. None I'm in love with just yet because they all are a little harder to control including default initialization.

I like this but it seems that the Tesla API is a reverse engineered one, and that means it might change in the future, even become unusable. I wish Tesla would open up this API and stand behind it. So that was part of the reason I was even considering a relay. I might just have to mull it over because neither way is optimal.

Here, I don't know what you mean by 'smooth'. Do you mean switching things when the voltage wave is zero vs at a random time. I hear you on this. But I don't think this will hurt anything, except perhaps relay contacts.

Help me understand why this seems like not a good idea to you? We unplug powered on stuff all of the time. Yes it does put a bit of a spike on the line. Any other reason you suggesting this is a not good idea?

When you normally finish charging the car will ramp things down orderly. It may also plan out some balancing near the end. Some claim it always balances.

Cutting power is harsh. Components are not designed for that to be the normal usage path. It might not hurt anything but I don’t think it’s a good thing to do routinely.

I have no proof of that.

 

[Togg]

Another “software” option

Save on your electric bill

Optiwatt integrates your exact electricity rates so you can save on EV charging and HVAC. Automatically use electricity off-peak and earn rebates in utility programs.

getoptiwatt.com

Interesting. I like it but...

How do we deal with key privacy?

Are we going to be giving our car keys to them? Is that a good idea? Do we just 'trust' them? Why is it that this is free? What do they get out of the deal? Humm?

Maybe I'm just an old kodger, but I'm not so hot on private software (i.e. i didn't see anywhere that this is an open-source project) holding the keys to my car.

 

[Togg]

I suppose the other option, is to just wait for Tesla to fix this TOU (Time of Usage) management issue, as they really must at some point, if only because other car vendors will also fix it. (I guess I'm just getting impatient with this, as I think Tesla should have fixed this important issue long ago, e.g. rather than adding more useless console games over and over.)

I also plan on more solar, and in particular dedicated car solar (i.e. not grid-tied). And I think an important part of that is like what Randy Spencer is doing in matching the car draw to the solar power availability. From our experience that is very important to get to work to help cut electric expenses. So kudos to you Randy!

 

[Watts_Up]

Cutting power is harsh. Components are not designed for that to be the normal usage path. It might not hurt anything but I don’t think it’s a good thing to do routinely.

I have no proof of that.

This DCC EV Switch just turns on and off EV charging using a relay when the total load excess a giving setting value.
It doesn't communicate with the car to stop charging before de-energizing the EV charger.
I hope this would not create any damage.

DCC-9 EVEMS for Electric Vehicle Charging in Condos and Apartments

DCC-9 EVEMS device used for apartment and condo electric vehicle charging installations. Used for direct energy billing. Think apartments, condos, duplexes.

dccelectric.com

 

[ATPMSD]

Interesting. I like it but...

How do we deal with key privacy?

Are we going to be giving our car keys to them? Is that a good idea? Do we just 'trust' them? Why is it that this is free? What do they get out of the deal? Humm?

Maybe I'm just an old kodger, but I'm not so hot on private software (i.e. i didn't see anywhere that this is an open-source project) holding the keys to my car.

There are many apps that people use with their Tesla’s and each requires you grant the app access to do its job. Each allows you to revoke your access or, if you wish, you can just change your Tesla password.