Using an EV for backup power in case of power outage

[chucchinchilla]

@chucchinchilla If you want to set up to use a 240V source as backup power during a power outage, install a transfer switch or other approved solution. Using a 240V outlet to send power into your house during a power outage without a proper cut-off switch (called in interlock) is called "backfeeding" and is extremely unsafe and almost certainly illegal.

Look two posts up where I said the following..

So when I wired my home to charge our EV, I simply had a 240V outlet installed next to our driveway. We then plug an L2 charger into that and use it, with the idea being over time that L2 charger will change but the outlet/wiring will remain. So in order to enable home backup, could I have that 240V outlet first connect into a manual transfer switch that then plugs into the main electrical panel? From there it would simply be a case of either plugging my Anker power station into the 240V outlet or some future bidirectional EV charger, is that right?

..am I missing something here because that's exactly what I said?

 

[BeerParty]

Look two posts up where I said the following..

..am I missing something here because that's exactly what I said?

You cannot use an outlet connected to the transfer switch to send power to the other outlets of a transfer switch. A transfer switch has a dedicated inlet for sending power into it, you must use that. If you wire up a 30amp outlet on the transfer switch for charging your EV, and then use a male-to-male extension cord (usually called a "suicide cord") to send power into the transfer switch from a generator, it will either not work or damage the transfer switch.

The power inlet on transfer switches is designed so that the power from a generator will always be physically isolated from the main power lines. The outlets are not. The same thing I said about backfeeding directly into a house applies even if the outlet is connected to a transfer switch.

 

[N Wilson]

You cannot use an outlet connected to the transfer switch to send power to the other outlets of a transfer switch. A transfer switch has a dedicated inlet for sending power into it, you must use that. If you wire up a 30amp outlet on the transfer switch for charging your EV, and then use a male-to-male extension cord (usually called a "suicide cord") to send power into the transfer switch from a generator, it will either not work or damage the transfer switch.

The power inlet on transfer switches is designed so that the power from a generator will always be physically isolated from the main power lines. The outlets are not. The same thing I said about backfeeding directly into a house applies even if the outlet is connected to a transfer switch.

This.

https://www.homedepot.com/p/Reliance-Controls-30-Amp-Power-Inlet-Box-PB30/202213702

Here's an example of a generator inlet box. This is what my electrician installed on my house, and what you need to plug a generator or 240V output from an EV into. This box is then wired to your transfer switch as @BeerParty described.

 

[SpaceEVDriver]

Look two posts up where I said the following..

So when I wired my home to charge our EV, I simply had a 240V outlet installed next to our driveway. We then plug an L2 charger into that and use it, with the idea being over time that L2 charger will change but the outlet/wiring will remain. So in order to enable home backup, could I have that 240V outlet first connect into a manual transfer switch that then plugs into the main electrical panel? From there it would simply be a case of either plugging my Anker power station into the 240V outlet or some future bidirectional EV charger, is that right?

..am I missing something here because that's exactly what I said?

You must have an input that's on the same logical side as the main grid input such that there can only be one of those two inputs active at any time. The grid input must not be connected if the generator input is connected. It must be "physically impossible" to have both connected at the same time.

You cannot achieve that and also have power available to anything plugged into that inlet port when the grid is connected.

This line drawing shows what has to happen. The interlock/transfer switch is between the 200A grid and the 30A generator inlet. If one is connected, the other is not. And there must be a break-before-make situation so that it's not possible to even momentarily have the two connected at the same time.

And this is what a manual interlock looks like when installed on a service entrance panel. When the main breaker can be turned on, the generator breaker cannot be turned on.

 

[MountainDad]

If you are adding batteries to your solar system and have a EV with V2L, you can skip the generator. The batteries would work just like my Delta Pro 3 does, and you can use the V2L to charge up the batteries when they get low.

Can only skip the generator if the batteries are in a climate controlled enclosure or have auxiliary heaters. I have an insulated garage, but it's not climate controlled. And if you get a big enough snowstorm or a week of cloudy weather you're not recharging your batteries sufficiently, and so you WILL need a generator.

 

[Mousehunter]

Not that Scout is doing it - but have seen some videos on home DC V2G (and a bit of V2H) systems. While I am sure there are plenty of issues, it gets around any vehicle charger limitations. While it has limited value to most people when charging, as AC charging can still charge the vehicle overnight, it might be nice in a backup situation - getting closer to the output of a backup generator.

 

[chucchinchilla]

This is some really good info thanks guys. Rest assured however it's installed I will be using a professional electrician and not doing it myself! Also I would imagine by the time we get around to doing this in a couple of years (once we have a vehicle that supports this), there will be more knowledge/products/etc. on the subject. Actually I bet within 10 years V2H support will be part of a "standard" home charge setup people have installed at home.