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How does... or how will V2H for emergency backup work?

4.6K views 43 replies 18 participants last post by  p7wang  
#1 ·
A recent post on a poor man's V2H setup got me wonder how V2H works. And how easy this would be for an emergency backup situation.

Googling around I see GM will gladly sell you some $13K system (need professional install they say) with a battery, smart hub,..... Isn't the EV already the battery? The minimum system seems to be pushing $7k for a $1700 smart bidirectional charger (EVSE) and some $5K management hub that does stuff I don't quite understand and also claims to have a small battery in it. So three batteries now??

Other companies seem to be pushing other expensive system where when your EV is plugged in it monitors household power use. It can then add power to the house or charge the EV when cheaper. Needs to have current monitors on the feeds, etc.... Hook up to your solar system or backfeed the grid. Blah Blah Blah.

Why? I just want something where when power goes out I can plug the car into the generator inlet and backfeed my panel via it's interlocked breaker.

So, do current (or future) V2H enabled EV's actually use the existing on board charger, or add an onboard inverter, to send AC back down wire feeding the EVSE? Or do they send DC direct from the battery to a separate inverter? Sending 400V DC back sounds like the NEC would flip out. If it sends AC back down the line I would need some type of "transfer switch" so not to route the car generated AC current back into the circuit breaker feeding the car.

I guess with something like an F150 I could plug into the 7.2Kw plug on the truck, but I want the full 11.5Kw or 19.2Kw the car can provide other wise its not worth the cost/effort.

Thanks
Jim M.
 
#2 ·
AFAIK there's no practical way to get a full 11.5kW out of the Bolt. But how often does your power go out, and do you really need to power all - or most - of the house during the outage?

During outages I've used a 1500w (peak) inverter and extension cord a couple times from my Bolt EUV to power refrigerator, internet and a few lights. Best to keep power draw under 1000 watts. Depending on initial state of charge of the car, that setup could last several days.
 
#5 ·
Yes I know the Bolt will never support V2H so this is really a forward looking thought/question.

So maybe I'm spoiled or something but when power goes out if I'm going through the "trouble" of plugging in the care or pulling out the generator I want to be comfortable. It seems that when power goes out my wife is always getting ready to take a shower, or has laundry running, etc. 1500W will not cut it. Hair dryers are 1800W. Coffee pot will pull 1000w on top of the base load (yes we can boil water).

I have well water and electric hot water so I need 240V. My 5500 generator is about the minimum I can get by with. 7500 watt would allow me to run the dryer when those extended multiday outages happen. 10K would be nice so I could run the A/C, however the last outage a few weeks ago we moved in to the camping trailer overnight since that A/C unit only draws 1500w so I can wait on getting a bigger generator.

In the not too distance future house will have electric ranges/ovens so more power will be needed to cook. And electric heat so even more power. Thats why I'd like to get the 48A/11.5Kw back feed a common in stall would support.
 
#4 ·
The current GM EVs are supposed to have V2H.

They are basically a generator backup. The $18K install includes an ABT. Automatic bus transfer box.

Almost what you read on Powerwall is same. Just a moving battery.
 
#6 ·
The current GM EVs are supposed to have V2H.

They are basically a generator backup. The $18K install includes an ABT. Automatic bus transfer box.

Almost what you read on Powerwall is same. Just a moving battery.
The Problem is I'm sure GM is way more interested in selling you the money making "generac like system" instead of the much cheaper "portable generator" system.
 
#11 ·
Wild guess. If you want to tap directly into your 400 volt or 800 volt EV battery you are gonna need in-car software that can sense when the EV is not DC fast charging but still responds to requests to access to the raw battery output so that the appropriate contactor will close. The software also needs to sense that a suitable inverter is connected so that the hot DC terminals on the charging port are never exposed. The AC charging connection for CCS seems pretty straightforward, but since the same pins are used for both AC and DC on NACS it might be quite a bit trickier to implement. Clearly the software that controls the contactor on current EV’s that do not support vehicle-to-X (very few do) does not permit hot DC terminals when the EV is not DC fast charging for obvious safety reasons. I am pretty sure that when you dig down into the details that some other requirements will surface, as well. The point that I am attempting to make is that it ain’t gonna happen on your Bolt because it is pretty obvious by now that we Bolt owners have been orphaned by GM as far as adding any new features is concerned.
 
#15 ·
Not for the Bolt and I'm not interested in trying to tap the 400V battery directly myself. GM says all their new EV's will be V2H capable so they already put the hooks in to tap the main battery. What I'm trying to figure out is if 240V AC is generated by the car. I don't see the need in my case to deal with the $7K minimal system that will "connect to selected circuits" in the house. I don't need it to monitor the house for power failures, or to pull excess solar to the car. I just what to know if using the car as a portable backup generator is/will be possible.
 
#16 ·
hey there, i'm no expert but from what i understand most current v2h setups do use the onboard inverter to send AC back through the charging port. the expensive systems you mentioned are probably overkill for basic emergency backup. maybe look into simpler transfer switch setups?
 
#17 ·
You need to think of your backup picture differently. You need an inverter and battery buffer capable of serving back your home's load, at that point you need your car charging the batteries. Ideally you want it to be a DC to DC operation where efficient, but that gets complicated.

If you want ideal? People toss around twice your daily kWh usage as backup, which is insane, sure if you live in West Hollywood and have a $30 million home. In Texas on a summer day that could easily be 120kWh of battery you're asking for, on a smallish house.

Stuff is getting cheaper, here's a kit with an inverter for 62kWh for only $21k.

My F150 is still the best power exporter and it can only do 10kW through its inverter system in only a backup situation. That to me isn't worth putting money into. I have a 32A receptacle off the tail. 32A can serve 184kWh / day which far exceeds my house usage (and the truck's 135kWh pack!)

For me? In the end an Enphase solar system feeding its limited power back in a backup situation combined with 32A from a transfer switch off the Lightning is luxury I didn't have before and way more than enough for "critical loads". We go kinda nutso about backup electricity but not everywhere is TX. Here in NY, no ones heat runs without electricity. Every house on my block has been up since the 30s, some people are in there 80s, I'm a multi generational family myself, I never heard of anyone's pipes freezing.

If in 100 years the grid hasn't failed on that level, what in the **** are we all preparing ourselves for?
 
#26 ·
You need to think of your backup picture differently. You need an inverter and battery buffer capable of serving back your home's load, at that point you need your car charging the batteries. Ideally you want it to be a DC to DC operation where efficient, but that gets complicated.

If you want ideal? People toss around twice your daily kWh usage as backup, which is insane, sure if you live in West Hollywood and have a $30 million home. In Texas on a summer day that could easily be 120kWh of battery you're asking for, on a smallish house.

Stuff is getting cheaper, here's a kit with an inverter for 62kWh for only $21k.

My F150 is still the best power exporter and it can only do 10kW through its inverter system in only a backup situation. That to me isn't worth putting money into. I have a 32A receptacle off the tail. 32A can serve 184kWh / day which far exceeds my house usage (and the truck's 135kWh pack!)

For me? In the end an Enphase solar system feeding its limited power back in a backup situation combined with 32A from a transfer switch off the Lightning is luxury I didn't have before and way more than enough for "critical loads". We go kinda nutso about backup electricity but not everywhere is TX. Here in NY, no ones heat runs without electricity. Every house on my block has been up since the 30s, some people are in there 80s, I'm a multi generational family myself, I never heard of anyone's pipes freezing.

If in 100 years the grid hasn't failed on that level, what in the **** are we all preparing ourselves for?
The 7.2K the Ford puts out its tail is better than I got (5.5 generator) but not enough peak for the "future" house with all electric appliances. I'd like 10-11K. While I'll always have a pickup for the foreseeable future and maybe GM will get on board with this. Does the Silverado EV have such a plug?

The hope was that with V2H, or maybe just V2L there was a simple way to get more power. See DAH's post below. I don't see myself going all in on these crazy micro grid based systems for the 2-5 time a year I need backup power. When I retire I'll need to move to a red state who will not be banning gas generators I guess.
 
#19 ·
We'll see how these utility programs develop. They're paying people up to $4 / kWh delivered in California. If I dump 60% of my F150 in those conditions 10 times a year, that's $3,240. If that happens over 10 years, that's $32,240.

That just seems like an insane rate to me but I guess I don't know the economics of not needing to fire up emergency measures to meet peak demand.

I think it's clear if you can get by with NEM arrangements, that's the clear faster payback, but man $4 / kWh if that's the way things are going for selling back power begins to change math, quickly.
 
#21 ·
I don't know how to gauge where home batteries will go. Seems to be some belief out there that it's going to follow EV demand. If EV demand stays low, all these companies with multi-billion in investments need to find a way to sell product to stay alive, even at a loss.

I also don't know what the above means! $75/kWh? $50/kWh? Don't know! What happens when we resume the EV revolution? Don't know!

It's a commodity whose demand should outstrip supply, but instead we have volatility for intrinsic, complex reasons which can't all be considered at once.
 
#22 ·
Googling around I see GM will gladly sell you some $13K system (need professional install they say) with a battery, smart hub,..... Isn't the EV already the battery? The minimum system seems to be pushing $7k for a $1700 smart bidirectional charger (EVSE) and some $5K management hub that does stuff I don't quite understand and also claims to have a small battery in it. So three batteries now??
Ignoring the arguments around cost and necessity....

The GM system creates a microgrid in your house isolated from the utility grid (as required by code). The bi-directional charger output supports:
Image

The inverter supports 10kw from the car:
Image

Here's the whole thing:
Image

Not shown is "future" support for AC solar into the hub.

As an example, the Chevy Equinox EV has an 85kwh battery which is about the capacity of 6 Tesla powerwall batteries which would cost (at least?) $44k. For less than $44k you can get 85kwh of backup battery and a free car.
 
#23 ·
This is not a real thing that anyone is ever going to do until they can do 100A, 200A and 400A. Who is putting in that kind of money to have 9.6kW pipeline to house? Your stats also indicate like 19,000W which has to be wrong since their press releases all said 9.6kW, that "max" must be for inrush or something. (or theory land for later)

Also why would they need anything special for AC-AC coupling? They're serving 9.6kW, a Sol Ark or whatever "adult" inverter is going to have to come in and manage it all, since, you know, this is $15,000 worth of equipment for OEM-specific backup, not a real, leading edge solution for the industry.

Poke around the Lighnting forums and it's "so, transfer switch." Because it's evreything you're listing for 9.6kW when you have 7.6kW inverter off the tail anyways.

All of these companies should be investing in open standards and onboard inverters. No one in their right mind is going to sign themselves up for limiting themselves to GM-derived vehicles for the rest of their lives. They should learn from the Lightning example.

Standards, not stupid. This is stupid. Maybe looked good on an earnings call or something but not practical hardware Americans are going to invest in.
 
#25 ·
Me too. I'm surprised I spent $2500 just to have Internet, heat, refrigerator & TV for the few hours or a couple days without power. Any longer than that frequently, solar & Tesla is probably worth having.
 
#29 ·
I have rooftop solar with a SolarEdge inverter and an LG 16KWh whole house battery. I do not have a critical load panel; everything still has access to power when the grid is down. I am aware that my available power is not infinite and that I need to manage things carefully if the grid is down. And that the margin of error is much smaller in winter. I have had the system for about two years now and it has carried me through every outage I have had so far, without any particular pain and suffering. Also, note that I am in a wheelchair and have a residential elevator. It needs 220v and the house battery supports it just fine.

When I selected that 16KWh battery, I did not worry too much about needing more. I figured that long term, I would have a more generous amount of backup power in my next EV. I still think so. And frankly, given the low frequency of need, I would never invest in DC to DC equipment to move that power. Say the inverters running DC to AC and back are super inefficient and I lose 50 KWh of power during ann outage. Best case, I recharge from solar and there is no marginal cost. Worst case I have to take the car to the DCFC and pay top dollar to fill it back up, it’s still only $30 or $40. Hardly worth investing thousands to save that amount.

So what I am saying is, buy the minimum equipment. As long as it’s safe it’s fine.
 
#30 ·
I DIY installed 16 x 400W PV panels (6.4kW), an EG4 6000XP (6kW) All-in-One (AIO) inverter and two EG4 WallMount batteries (28.5kWh total). Did it all by myself, with the exception of hauling the 45 lb panels to the roof. I'm 68.

$15k, all in.

The DIY solar market is thriving, and there's a great forum that helped a lot:


Do note that I'm a retired EE, and have pretty extensive experience with residential wiring.

YMMV

Be safe.
 
#43 ·
There's nothing stopping you from doing this with DIY resources. Utilities interact with the various smart systems attached to the inverters and it doesn't know what the battery storage is, only what is being reported by the "smart inverter."

In practicality you could have 120kWh of EG4 LiFePo4 batteries for dirt cheap attached to a Sol Ark and as long as the utility interacts with the Sol Ark specifically (many do) then you have no problems.

In theory you can do this with "Cadillac systems" like Enphase as well. The AC Combiner box can take I believe 40A (intended to be a generator) from any source. People are using this capacity to add third party batteries to Enphase systems. Provided Enphase will allow it (they probably don't, since they want to push 5Ps) the system controller at that point can dump the power to the grid when asked.

Edit: Ugh, I just undermined my forked discussion idea didn't I?
 
#35 ·
I DIY installed 16 x 400W PV panels (6.4kW), an EG4 6000XP (6kW) All-in-One (AIO) inverter and two EG4 WallMount batteries (28.5kWh total). Did it all by myself, with the exception of hauling the 45 lb panels to the roof. I'm 68.

$15k, all in.

The DIY solar market is thriving, and there's a great forum that helped a lot:


Do note that I'm a retired EE, and have pretty extensive experience with residential wiring.

YMMV

Be safe.
I DIY installed 16 x 400W PV panels (6.4kW), an EG4 6000XP (6kW) All-in-One (AIO) inverter and two EG4 WallMount batteries (28.5kWh total). Did it all by myself, with the exception of hauling the 45 lb panels to the roof. I'm 68.

$15k, all in.

The DIY solar market is thriving, and there's a great forum that helped a lot:


Do note that I'm a retired EE, and have pretty extensive experience with residential wiring.

YMMV

Be safe.
my compliments
 
#38 ·
RacerX00 said, "They're paying people up to $4 / kWh delivered in California."

SAY WHAT?!? WHERE?! WHO?
I have solar, and Pacific Graft and Extortion doesn't even pay me the going rate of 36 to 64 CENTS per KW!! Where the **** did you get $4???🤔🤔