Multiple Tesla Charger's on One Circuit

[flstcgranucci]

We currently have a Tesla charger for my wife's M3 installed in our garage and I purchased another for my "soon to come" MLYR but it looks like I have run out of room on our breaker panel to run another circuit. Upgrading that panel would require permits and plans and lots of money I've heard that there is a way to connect two chargers on the same circuit and have a few questions. Since two cars will be charging during super off peak hours at the same time, will it take twice as long to get them charged and is it easy to configure the chargers for power sharing? If I can, upgrading the amperage on the breaker to charge two cars at once seeing that the M3 only charges a max of 31 amps do the trick?

I am by all means not an electrician so please be kind LOL

 

[ChrisMPK]

You should provide more info such as the breaker rating of your current charger and pictures of your panel. My first thought is: You don't need two chargers. Just alternate nights that you charge your vehicles (assuming the cord will reach all parking spots). It is possible to connect two gen3 chargers via wifi and share a single feed, but this may not be ideal for you. Installing a sub panel, two chargers on separate circuits at lower ratings would also be an option.

 

[jcanoe]

Yes, if two Tesla vehicles are charging at the same time using 2 Tesla Wall Connectors on the same circuit then the amperage would be reduced, so that the total amperage did not exceed the allowed maximum for the circuit. The time to charge would be longer, expect it to take twice as long to charge both vehicles at least until one vehicle completes charging. Then the second vehicle would continue charging but at the maximum charging rate for the vehicle and the circuit.

Example: A 240V, 50A circuit will support charging at up to 40A. If you have two Tesla vehicles charging, assuming they are charging at the same rate, then each would be limited to a maximum of 20A while both are charging. I believe you can limit each vehicle to a different maximum when both are charging as long as the total does not exceed the maximum for the circuit. So you could set the Model 3 to charge at 16A, maximum, and the Model Y to charge at 24A maximum when both vehicles are charging. If the Model 3 completes charging first, (perhaps because you don't drive the Model 3 as many miles per day or you have the maximum charge level of the Model 3 set lower than the Model Y), then the Model Y would continue charging at 40A until charging was completed or the end of the off-peak rate period.

 

[brkaus]

We have 3 EVs on a single WC.

Would like to add more WCs, but cost.

Clearly depends on miles driven per day.

If you are adding another WC, it would likely require a permit no matter how you do it.

 

[lzolman]

On a related note: We currently have our original V2 wall connector for our '18 M3, and I've bought a V3 to put next to our new MSLR. I want to just tap off the same circuit the V2 charger is using, and we'd be responsible for simply never running more than one at a time.
Is this a trivial installation for the electrician (just extend the conduit between the units), or are there additional issues we should be aware of? Thanks!

 

[flstcgranucci]

We have set up and are currently using two V3 chargers and have power sharing enabled. Its kinda nice too. And yes, when both cars are charging, the AMP's drop, but its pretty intelligent as when one car finishes, the remaining car will automatically ramp up to finish the second car.

 

[lzolman]

You mean this functionality is already in the wall connectors? Sorry, don't know about that. I'm actually planning to head by the Peabody Service Center and get clarity from them before the electrician is scheduled to arrive this afternoon. If the chargers can self-regulate like that it would be awesome.

 

[flstcgranucci]

You mean this functionality is already in the wall connectors? Sorry, don't know about that. I'm actually planning to head by the Peabody Service Center and get clarity from them before the electrician is scheduled to arrive this afternoon. If the chargers can self-regulate like that it would be awesome.

Yes, but only on the V3's.

 

[Rocky_H]

You mean this functionality is already in the wall connectors? Sorry, don't know about that. I'm actually planning to head by the Peabody Service Center and get clarity from them before the electrician is scheduled to arrive this afternoon. If the chargers can self-regulate like that it would be awesome.

Yes, but only within the same version of wall connectors. The version 2 wall connectors (the older bigger ones) could share between them, with a wired control signal. You had to run a little twisted pair wire between the units to let them communicate. On the version 3 wall connectors (the new smaller ones with the white faceplate), they use wi-fi connectivity, and can wirelessly communicate to manage sharing the connection. They do need to be run from a subpanel, though, so each has its own breaker. But it's still effectively sharing: For example, you run one main line of 50A to the subpanel, and then a 50A breaker for each, and set them up so they will make sure the total amps stays within that limit of the main circuit.

On a related note: We currently have our original V2 wall connector for our '18 M3, and I've bought a V3 to put next to our new MSLR. I want to just tap off the same circuit the V2 charger is using, and we'd be responsible for simply never running more than one at a time.

Can't share between V2 and V3 ones.

Is this a trivial installation for the electrician (just extend the conduit between the units), or are there additional issues we should be aware of? Thanks!

An electrician shouldn't do that at all, because that is a violation of code. Electric car charging equipment is required to be each one on its own dedicated circuit unless it has this kind of communication load sharing system running, and you can't do that mixed between the V2 and V3 wall connector types.

 

[roblab]

Most of this can be handled by starting and ending at different times so that you're not charging two cars at once. You can have two cars on the same circuit, but start charging one at 10PM and the second one at 3AM. Or some such. This is why Teslas can be programmed to start at different times.

I also set up my cars to charge at lower speeds so they don't overload a circuit, also programmable.

 

[jcanoe]

With the latest revision to the national electrical code (NEC) any new electrical circuit for charging plug-in hybrid or electric vehicles must be a dedicated circuit. The only exception is when multiple electric vehicle service equipment (EVSE) support, are configured for automatic load balancing.

 

[lzolman]

Thanks, very helpful. So this is what I'm now thinking: put in a subpanel and have the line from the main panel go into the subpanel instead of to the old V2 charger (it's a long run, which is why I'm trying to avoid having to run another circuit all the way back to the main panel). Then hook each of the two chargers up to the subpanel so that they each have a breaker.

I was told today at the Tesla SC that wall connectors only last 5-6 years? I hadn't heard that and I'm not sure I believe it, but for the time being we plan to only run one charger at a time, so they don't need to communicate. When the V2 needs to be replaced, then I get a V3 and then they can load balance to their heart's content if needed.

Make sense?

 

[flstcgranucci]

This is what our setup looks like

 

[jcanoe]

So this is what I'm now thinking: put in a subpanel and have the line from the main panel go into the subpanel instead of to the old V2 charger (it's a long run, which is why I'm trying to avoid having to run another circuit all the way back to the main panel). Then hook each of the two chargers up to the subpanel so that they each have a breaker.

I was told today at the Tesla SC that wall connectors only last 5-6 years? I hadn't heard that and I'm not sure I believe it, but for the time being we plan to only run one charger at a time, so they don't need to communicate. When the V2 needs to be replaced, then I get a V3 and then they can load balance to their heart's content if needed.

That would be the correct way to wire two Wall Connectors; using a sub panel and a separate circuit breaker for each Wall Connector unit. Unless you are using (2) Gen2 Wall Connectors or (2) Gen3 Wall Connectors you cannot use the automatic load balancing. Depending on the circuit breaker and rating of the wire that originally went to the Gen2 Wall Connector, that would now go to the sub panel you would have to manually limit each Wall Connector to no more than half of the 80% limit for the circuit. I.e. if the circuit was originally rated for 100A then you can safely set each Wall Connector to charge at a maximum of 40A.

The EVSE units do wear out; from age and usage. There is no way to say how long the Tesla Wall Connector will last. The industry standard warranty for EVSE is 3 years (not sure about Tesla's warranty.) At the outside limit probably 10 years; the use of lead-free solder in most modern electronics definitely affects the life of the equipment.

 

[lzolman]

You should provide more info such as the breaker rating of your current charger and pictures of your panel. My first thought is: You don't need two chargers. Just alternate nights that you charge your vehicles (assuming the cord will reach all parking spots). It is possible to connect two gen3 chargers via wifi and share a single feed, but this may not be ideal for you. Installing a sub panel, two chargers on separate circuits at lower ratings would also be an option.

Yes, we've been charging both cars off the single gen-2 (on the wall between the bays) but there's not a lot of clearance between the rear of the MS and the garage bay door, so that has been causing some issues and I just want a dedicated wall unit next to the MS's port.