TESLA transfer switch/portable generator

Status
Not open for further replies.
G

Greg1707

Senior Member
Location
Alexandria, VA
Occupation
Business owner Electrical contractor
I have a customer that wants to setup a transfer switch for his Tesla charger. He wants to have the option of charging his Tesla with his 6,500 watt portable generator.
Any thoughts on this?
 
Most car chargers that want/need a fast charge need a 50A or 60A circuit. The 6500W would only be around 27A. That wouldn't be much better than a 120V charger. Is the customer just wanting a way to charge during a power outage?
 
I installed a 14-30R on the output side of a 10kW LP Generac. Turns a Tesla into a dual fuel vehicle ;).

In reality it is backup in case of a long term grid outage when a big whole house genset is not available.
 
Little Bill said:
Most car chargers that want/need a fast charge need a 50A or 60A circuit. The 6500W would only be around 27A. That wouldn't be much better than a 120V charger.
Click to expand...
A 120V EVSE is typically set to 12A maximum current, so 1,440W into the EV. Having a 24A/240V 5,760W EVSE that could run on a generator would be a big step up in charging speed.

Cheers, Wayne
 
Can the generator deliver that much power at start up would be the only question. EV chargers don't start slow. They negotiate how much current they will deliver with the EV, and then they deliver it.

There are 16A / 240V EV chargers, and before plopping down the coin on a 24A version, I'd make sure it works at all.
 
tallgirl said:
Can the generator deliver that much power at start up would be the only question. EV chargers don't start slow. They negotiate how much current they will deliver with the EV, and then they deliver it.

There are 16A / 240V EV chargers, and before plopping down the coin on a 24A version, I'd make sure it works at all.
Click to expand...
My old boss’s daughter has a Tesla she bought after I installed a 22 kw whole house generator, generator ran everything fine until then. They lost power, generator kept tripping out, I asked if the Tesla was was plugged in, and trying to charge, she said it was plugged in, but wasn’t set to charge. After a while of troubleshooting, told her to unplug it, generator worked fine after that.
 
With a Tesla you can adjust the power amp draw to the source. So yes when charging from a generator source and draw need to be matched.
 
Greg1707 said:
I have a customer that wants to setup a transfer switch for his Tesla charger. He wants to have the option of charging his Tesla with his 6,500 watt portable generator.
Any thoughts on this?
Click to expand...
this is the definition of of "Irony".
 
DanS26 said:
With a Tesla you can adjust the power amp draw to the source. So yes when charging from a generator source and draw need to be matched.
Click to expand...
Can it be set to less than what the EVSE "advertises" as its highest rate?

There's already automatic negotiation between the two. The J1772 "interface", as it were, supports a wide range of currents and voltages. If it's possible to set a lower current, that would be a solution. Start with 16A @ 240V. If the generator is stable after a minute or two, manually increase it to 24A, or whatever higher, intermediate, currents there.
 
tallgirl said:
Can it be set to less than what the EVSE "advertises" as its highest rate?
Click to expand...
Yes, the EVSE advertises the maximum charging current it can provide, then the car charges at whatever rate it wants (often tapering a little as it nears 100%). And with a Tesla you can tell it on the dash (at least) to limit charging to a lower rate.

Of course protocol compliance requires not charging higher than the advertised rate, but I don't think there's any mechanism to actually prevent a misbehaving car from doing that.

Cheers, Wayne
 
I don't think the idea makes any sense without a larger generator. Since nobody has spelled it all out yet...

It's unclear if we are talking about a Tesla wall charger or using the Tesla cord with a receptacle. I'm inclined to assume it's the wall charger because why wouldn't you just plug the cord directly into the generator? But in either case, if the usual on-grid setup delivers more power than the generator it's going to be inconvenient for the owner in a way the transfer switch is unlikely to solve.

The wall charger has an internal amp setting that the installer is supposed to set to agree with the circuit and breaker that it's installed with. If that amp setting is greater than the generator rating then the generator circuit breaker will probably trip after a while. Same if the cord is used on a 40 or 50 amp receptacle. The cord knows which plug adapter is connected to it and draws the amps accordingly. So running off the generator would require a separate 30A plug to be installed, which makes no sense to be on a transfer switch.

Perhaps if we had more clarity on the generator setup and what other loads it's powering, the idea would be more clear.
 
retirede said:
Most EV owners would like to power their home from the car during a power outage. This person has it backwards!
Click to expand...
I had battery-backed solar with way more storage capacity than my EV back in the day. Since it also made power during the day, being able to charge my EV from a non-grid source was a better solution.

I do think the trend towards massive batteries in EVs will change that equation.
 
tallgirl said:
I had battery-backed solar with way more storage capacity than my EV back in the day. Since it also made power during the day, being able to charge my EV from a non-grid source was a better solution.

I do think the trend towards massive batteries in EVs will change that equation.
Click to expand...

But if you lost grid power at night, I wouldn’t think you’d normally use the house battery to charge the car and risk a dark house.
 
Status
Not open for further replies.
Top