Can I use my EV as a battery on wheels to power my off-grid home?

Dear Bryce,
 
Thank you very much for your articles on bi-directional charging.
 
This is probably as much a comment as a question, but here goes.
 
I am building an adaptable house for one person in the upper Blue Mountains west of Sydney, to last
me for about 30 years until I die (fingers crossed).  As you probably know the climate there is cool
temperate, and significantly cooler and less humid than Sydney (Smogney).  My block is at 1,030
metres above sea level.  (Before anyone asks, it will be built far in excess of current bushfire
protection standards.  “Future-proofing” is my middle name.)
 
The plan is to have it finished around Christmas 2023.  Famous last words!
 
It will be a PassivHaus and off grid (though suburban).  The roof will have a generous covering of
solar panels.  It’s north facing and not shaded, because that was one of the criteria I had when
looking for land.  All I know is that solar panels have come down in price and continue to do so, more
so than batteries, so it will probably make sense for me to have as many PV panels as possible.
 
The difficult part is that the upper Blue Mountains region is prone to long periods (i.e. days on end) of
mist.  This is good for a whole lot of reasons but definitely not for PV electricity generation.  My aim is
to use an EV battery to top up the house battery/batteries when they get low.  Effectively I should, if
the house batteries get low, be able to go a short distance (eg Katoomba shops) and charge the car
up, and bring the electricity home to top up the house batteries.  I’m retired so I can use electricity
directly off the roof during the day for things like the washing machine, substantially avoiding the
physical inefficiencies of having to store it for use at night.
 
All fine in theory, but there’s not much to choose from in Australia’s EV market at the
moment. Hopefully our EV dam is about to break.
 
A common response to the situation I’ve described is that I shouldn’t go off grid, and use the grid to
top up the house batteries on the occasions they get low.  That’s logical and cheaper as far as I know,
but I’m committed to giving fossil fuels (from utilities, governments and car manufacturers) the
finger, emphatically, permanently and with indescribable satisfaction.  I’m therefore resigned to
paying more as a capital expense, but hope to run the house for peanuts.  I don’t want a generator as
backup, and being a suburban location I probably wouldn’t get permission for one anyway.
 
This plan makes even more sense when you realise (I understand) that EV batteries have 4 or 5 times
the capacity of a typical house battery.  Given that on average cars are said to spend about 90% of
their time sitting in the garage (certainly mine will), not using them for V2H or V2G is an inexplicable
and criminal waste of resources.  In addition, not being able to use the EV battery for V2H (I’ve ruled
out the Nissan Leaf for a number of reasons) means I will have to buy more house batteries to last
me over the long misty periods.
 
I’m monitoring the pending introduction of the Subaru Solterra as that ticks most of my boxes,
although if it has CHAdeMO it’s not great, close to obsolete in fact.  It may be that I should just get
any old car (or keep my current ICE car) to last me till about 2027 when there will be better choice

and the charging technology is more mature and cheaper, and buy more house batteries in the
meanwhile.  Sad, but that’s the predicament Australia is in.
 
Yours in anger and frustration!
 
John.

Hi John

I hear your pain re the delay in V2X for the winner of the Plug War between the two DC
charging systems/plugs – CHAdeMO and CCS. (V2X by the way means vehicle to ‘something’, i.e.
getting power out from the battery instead of just charging it).

It really feels like CCS are dragging out the process. However, developing the earlier CHAdeMO V2X capability was also not particularly
fast, it just got in first. CHAdeMO was designed with it in mind back in 2009, but only became a
standard in 2014. CCS sadly wasn’t designed with it in mind so they are late to the party… but by
doing so, they should at least be better at it given technology has moved on a lot since 2009: the
CHAdeMO V2X capacity is best described as ‘clunky’.

The delay in CCS having it has a lot to do with ensuring there is one agreed set of standards for CCS
to communicate with the car, V2X unit in the house (which will enable the safe supply of power from
the EV to the switchboard) and to/from the grid. However, given CharIN (the CCS controlling
consortium) is bigger than the EU in terms of large auto and charging industry players and works on
achieving consensus before moving forward, they can seem slower moving than a Greenland glacier
at times ….

In your situation, a V2H car would be ideal to act as a large battery back-up to an off grid system.
Unfortunately, it’s unlikely that the manufacturers will even offer V2H (vehicle to home) or V2G
(vehicle to grid) capability from a CCS equipped car for at least another 12 months … then the
equipment manufacturers have to build/test their units … and then the various electric supply
authorities have to agree to let them be connected.

In addition, here in Australia COAG (Council of Australian Governments) here have agreed to not
return to the issue of V2G connectivity until 2025, so it is going to be a while before we can install
CCS V2H systems here.

You also can’t easily build your own V2H system for connecting a CCS EV via the switchboard as
there are no CCS V2H/G cars yet – plus the supply authorities would be unlikely to let you use it
unless considerable expense has been made to get an engineer to design and sign it off as safe: the
Wiring Rules (AS/NZS 3000) apply to all 240/415V AC systems, on or off the grid.

Also: the V2L that is currently available in CCS cars is via the AC socket. V2H/G for CCS I believe is
going to be through the DC pins, so we are waiting on the draft standards being accepted: mind-you,
many test units are in the development or testing phases. As I keep saying though, none will be
approved to buy and install here until at least 2025/6, so your 2027 timeline is definitely the most
likely for getting reasonably priced V2X connection boxes.

In the meantime: being off-grid, you will still need to have a stationary battery system to power you
at nights and when your EV is away. It is only the size of that stationary battery that would differ if
you have a bidirectional capable EV.

Seems to me then therefore you have four options:

1. Stay off-grid from the start, but install a bigger stationary battery with the intention to sell-
   off part of it when the CCS capable EV arrives;
2. Stay off grid but only install the final (small) stationary battery in readiness for the EV to bethe main back-up, be very frugal in your electricity usage in the meantime before a CCS V2Hcar is available … and be prepared for the odd black-out;
3. Install the final (small) stationary battery, but temporarily connect the grid until CCS V2H cars become available – means you are unlikely to use the grid much, but it will be your back-up for two to three years. (Oh, and when your CCS V2X car arrives, enjoy the disconnection party. 😉
4. Install the final (small) stationary battery and buy a V2L capable CCS car now, plus a 240V to 24/48V DC inverter (depending on the stationary battery system’s voltage) for charging the stationary battery. As examples, an Ioniq 5 that would give you up to 15A V2L of back-up for the inverter and 10A from a BYD Atto 3. That way, the battery would supply the house as per normal at night/misty days, but you have an available 240V supply (from the car) to charge the home battery if needed. No complicated electronics required!

As I often say in my public talks: looking back at historical transitions, they seem almost instantaneous and very directed, but when you're in the middle of one – they can seem very slow and determined to go down the wrong path at times. CCS V2X systems are on the way, but they won’t be available tomorrow.

Hope that helps John?

Cheers

Bryce