Preparing for bi-directional charging

[ohseedee]

So I was in similar situation and put some thoughts into this. Then some action early this month (trenching 18" deep for 2 conduits for ~40 feet, pulling a ton of beefy cables, etc)

My conclusion was that I pulled a 15A line from my garage to my basement (where my main panel lives). I put this to the garage end: https://a.co/d/a2cbJ2A and a normal 15A GFCI outlet in the basement (wit ha 15A breaker in between them). This is not hooked to the main panel directly, I had a separate small box for the 15A breaker between the GFCI outlet and the wires coming from the garage.

The idea is that this will connect to the Rivian outlet and will power a DC charger for a "solar generator" and I will use the solar generator inverter's 240V output to feed my main panel thru an interlock.

1) There are a few reasons why I did this way, most notable is that I do not depend on V2H equipment (charger should support it, vehicle should support it and more importantly there must be transfer switch associated to it, etc).

2) Second most important reason is that the average power usage of my house -with usual stuff on- is about 400W (of course cooking, laundry will increase it but those are not constant loads) so a solar generator about 3~4 kW should serve as a buffer between my DC charging from the R1T and my house usage.
In this scenario I use the R1T's battery to steadily charge the solar generator (with a 600W DC supply, easy for 15A 120V).
And this system (solar generator -> DC charger -> power extension cable -> R1T bed) is super portable and future proof in a sense I can change my charger infrastructure, I can change my EV, etc, still I have a system working (also see next point )

3) I also have an inverter generator running on my house NG line so I can always swap from the solar generator to a "real" generator if needed.

Note: I had no direct line from my main panel to my garage for the EVSE so I used 4AWG wires (in a sperate conduit from the 15A ones running in the same trench I made) to feed a new subpanel in my garage that is used for the EVSE. Plus I hooked all my electricity at my garage to this new subpanel (the original circuit from my main panel to the garage had a lot of stuff hooked to it at my house before going to the garage. So now I put the extra load off from the garage circuit).
So technically I can reverse the things and use this feeder line for V2H but then I loose my dedicated line from the main panel to this new subpanel. Never the less I left it as an option for the future.

Long story short: I did not want to run two 4AWG or conduits that long (due to cost) so I opted for one beefy run to use an EVSE from main panel and a much cheaper smaller run for the 15A 120V as an alternative "V2H"

I created a similar setup. But I also wanted to make sure the "investment" was not just for emergencies but also something that I could take advantage of daily and for other ad-hoc uses. I have the solar generator connected to some outdoor powered stuff that runs all day (e.g. fountain) and I typically get about 3kW of daily solar power out of it (about $0.75 worth of electricity at my rates). I also built it to be portable, so I can unplug it from the diy solar array and take it camping and leverage the 2.4kW battery capacity (basically a custom ecoflow). I like the idea of V2H, but it's crazy expensive and I hate the idea of investing in something that never (or almost never) gets used. I've not had a power outage is over a year and never more than 16 hours at a time. This setup will keep everything I need running except for AC.

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[docwhiz]

I created a similar setup. But I also wanted to make sure the "investment" was not just for emergencies but also something that I could take advantage of daily and for other ad-hoc uses. I have the solar generator connected to some outdoor powered stuff that runs all day (e.g. fountain) and I typically get about 3kW of daily solar power out of it (about $0.75 worth of electricity at my rates). I also built it to be portable, so I can unplug it from the diy solar array and take it camping and leverage the 2.4kW battery capacity (basically a custom ecoflow). I like the idea of V2H, but it's crazy expensive and I hate the idea of investing in something that never (or almost never) gets used. I've not had a power outage is over a year and never more than 16 hours at a time. This setup will keep everything I need running except for AC.

Most of the V2H setups are crazy expensive especially when you consider they only are for occasional use.
I like the idea of using a "solar generator" with a simple generator transfer switch to the house for emergencies. This can be trickle charged with solar or car battery if available.
Until we can participate in a virtual power plant, the expensive V2H setups just don't make sense.

 

[ttphhi]

Running higher than necessary capacity wiring to allow for upgrading makes sense. I guess the question is where the hardware that allows for switching inputs to the house lives. If it’s built into the charger, it seems like you’d want the charger between the house and the main line, but I guess it makes more sense to have the hardware to switch over right at the main panel anyway, so it should probably be safe to put in the wiring now, and plan to add a new charger when a bi-directional one is available.

Not sure how it is in your area but our electrical utility wouldn't let you put the connection between the house and main (assuming you mean the utility when you say "main").

 

[josh0]

Not sure how it is in your area but our electrical utility wouldn't let you put the connection between the house and main (assuming you mean the utility when you say "main").

The utility, yeah. But you have to be able to put something between your house and the utility, otherwise it wouldn’t be possible to have a transfer switch to power your home from a backup generator/battery. You have to be able to sever the connection to the utility to avoid feeding power back into their lines during an outage, and obviously that has to happen between your house and the utility. This is, as far as I’m aware, a common requirement more or less everywhere, in the US and abroad (a friend in Australia dealt with this when installing a solar system).

It’s entirely possible that I’m just using the wrong words to describe what I mean, this is far from my area of expertise.

 

[ttphhi]

I think we're saying the same thing. This always has to happen between the utility meter and the house.

I really am looking forward to V2H though. I've put off adding another Powerwall to my house hoping that I'll be able to use that giant battery in my EV's instead (plus getting the satisfaction of not adding to Elon's coffers).

 

[josh0]

As long as it just has to be between the meter and the house, I’m pretty sure we’re good! The meter is on a pole by the road, about 500 feet away from the house! ?

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