Using a car as battery storage

[Square Feet]

I'm very much at the research stage here, but I know that I want my future build to be as off-grid as possible. If I can make it completely off-grid for electric then this would make me very happy. I drive an old Nissan Leaf electric car with similar specs to the one in the link below (for anyone reading this after the eBay link has expired I will summarise it as having a 24Kwh battery with 9 bars of health out of the original 12. It's a scrap vehicle in the listing but the battery is fine. It's £2.5k fixed price). I know this isn't exactly how these things work, but for the sake of argument let's say it has c.18Kwh of battery storage (24/12*9), perhaps 15Kwh to ensure it isn't depleted down too far. This is more capacity than the 13.5Kwh Tesla Powerwall 2.0s, which cost in excess of £7k.  

 

https://www.ebay.co.uk/itm/175949367105?hash=item28f7664741:g:M10AAOSwRZJlIq~M

 

Years ago I had a girlfriend who lived off-grid and powered her house with a small solar array and a fairly substantial wind turbine. She stored her excess in some old forklift batteries but I don't think these were really working very well. On still, foggy days she basically had very little power and couldn't run a washing machine etc. She also used a back burner to heat water as there wouldn't have been enough power to run an immersion.  So I know that winter is a difficult time for off-grid power generation, particularly if you aren't able to install a wind turbine for planning reasons. I know that using the batteries from scrapped EV's for PV storage is a common enough route, but my question is more about using my current on-the-road car for additional battery storage. 

 

So let's say I squeeze as much solar capacity on to my roof as I possibly can but I am denied planning for a wind turbine. Then let's say that even with an old EV battery for storage I am just not able to keep up with demand over the winter. My idea is that in these circumstances I take my car to a public EV charger and top it up to the max and drive home and use this to boost my storage battery back up again. Admittedly not exactly fit-and-forget, but not that much of a hardship either. The cost wouldn't be overly punitive as I live in Scotland which has publicly-owned chargers which are kept at a fair price. For example near me I can rapid charge at 35p/Kwh or slow charge at 16p/Kwh. 

 

I plan on building a garage to store the battery in so there wouldn't be issues around space. I am mostly concerned about the effect of this plan on the health of my own car battery if it gets depleted and recharged a lot, but I suppose my real question is - would this work?  Would I be likely to be able to keep up with demand in practical terms?  I don't mind making a special trip to a (hopefully nearby!) public charger once a week but once a day would be a pain. I have absolutely no idea what sort of demand a 175sqm passive standard house would have, nor what I could generate from solar over the winter. I could go on a massive internet deep dive to try and figure this out, but I wondered if anyone here had those sort of figures to hand from their real-world experience. I also thought thrashing it out in here might be useful for anyone else reading it later on.

Cheers

 

[Dillsue]

There's a similar thread in the PV section about sizing off grid systems so have a read.

 

I don't believe your Leaf supports exporting from the car to external load so you'd likely be looking at modding the car to get access to the battery. I think it's the 40kwh version from 2017/2018 that support export???

[JohnMo]

2 minutes ago, Dillsue said:

don't believe your Leaf supports exporting from the car to external load

All Nissan Leaf models support it, and always have, but getting a charger in the UK that supports it, is different story.

[Square Feet]

Yeah my understanding was that the Leaf does support it, but I didn't know there was an issue with the charger connection. 

I plan on changing my car to an E-NV200 van later on which would have a 40Kwh battery, but I don't have the funds for that just yet.

I also meant to say that I can't really apply my current electricity usage to this as I use gas for heating and hot water. I don't want to have any gas in my new house.

Edited October 24, 2023 by Square Feet

[Square Feet]

I found this pdf which relates to using the Leaf as a battery to power a home that is connected to the grid. It's basically used as a way to exploit lower tariffs over night - the battery is charged then and discharged during the day when the tariff is higher. It can also be used to power the house when the grid power source is disrupted and there's no reason it shouldn't apply to the use I have suggested - basically replacing a genny in an off-grid setup. 

 

https://www-asia.nissan-cdn.net/content/dam/Nissan/th/news/nissan-introduces-blue-switch-program-to-asean-region-th/EN-Factsheet Nissan LEAF V2H.pdf

 

I've looked at my home electricity consumption and it seems to be about 3.28kwh per day.  That is with gas being used for heating, hob cooking and hot water. So figuring out how much I would need for a passive-standard house is a bit of a shot in the dark for me.  Three times maybe? 10kwh a day?  The MHRV shouldn't use much. The trouble is that there are then additional variables to be introduced as usage will be higher in winter while solar generation is lower. I've put a scribble of a graph of this below.

In winter I will be home more, have more lights on, use a tumble drier and maybe need some electric heating. Meanwhile my solar generation will be a lot lower - perhaps 12 times lower than in summer.  I want to be able to charge my car from the solar wherever possible and happily car usage would correlate to some extent with generation - I will probably use the car more in the summer to go out and about.  I haven't added the car into the calculations as it's really just a bonus to be able to dump some into the car as-and-when.  

The bar graph shows output from a 4kw solar array in southern Scotland. It basically shows that an array of that size wouldn't meet my current demand in Nov, Dec or Jan. It's a bit of a blunt instrument though, so I would love to hear real-world figures if anyone has them. 

 

Edited October 24, 2023 by Square Feet

[Dillsue]

3 hours ago, JohnMo said:

All Nissan Leaf models support it, and always have, but getting a charger in the UK that supports it, is different story.

Is that all UK models? Do you have a reference for that? I've been looking at maybe using V2X in the future and all I can see for the leaf is post 17/18 models that support it in the UK

[Kelvasco]

Hello,

 

It's a great idea. I've put a few discussion points/options below but happy to discuss further.

 

1. Not all Nissan Leaf's are suitable. Only though with Chademo 1.0, those with Chademo 0.9 are not V2G capable. The fastest way to tell is the interior color. If you have a grey dash and grey carpets then it's a Japanese-built 24kHhr model with Chademo 0.9. If it's a black dash, black carpet then it's a UK-built 24kWHr with Chademo 1.0.

2. You'll need either a Wallbox Quasar or Indra V2G. Many of the UK trials are ending at the moment so look on eBay and Facebook for used versions. Expect to pay £1,500 for it (excluding fitting). Quasar is the better option if you can get it, just make sure you get proof of "ownership" from the trial it was on (normally Ovo Energy or Octopus).

3. If you use the above option then you'll need a way to auto disconnect and also provide a neutral base which the Quasar can't do (sometimes called "islanding mode").

4. The best option, if you don't use the car, is to remove the battery from the car and connect directly to a DC-coupled inverter with islanding support. There is a GitHub by a person called Dala-EV that goes into detail if needed. This also enables you to have a higher power output if needed (Quasar is limited to 7kW, Dala method can go up to 22kW 3 phase quite easily).

 

I'm in the middle of a similar development. I'm going with option 1+2 using a Gen 2 40kWhr Nissan Leaf + a Quasar but I'm on-grid and don't have the neutral/islanding issues. I'm also planning on adding 2 other batteries to our system using method 4 within a 10ft container. But that's mainly because I have access to cheap used vehicle batteries and want a scalable solution.

 

Thanks 

[mike2016]

The car batteries aren't meant to be fully charged and discharged regularly (daily) although slow charging will help longevity. Home Batteries use LFP which is designed for this usage / profile. Only recently we've seen these enter the EV market. The key hinge point is that your car has to be in situ for the house to use it. You can buy ex leaf batteries separately to get the cheaper capacity or purchase an Ecoflow battery that accepts dual fuel, Solar PV or Propane which will help in Winter. Your space heating loads will be much lower in a passive house than your hot water requirement, that's going to be the biggest energy load. Then you can look at off peak charging / loading of the battery / sunamp or Tepeo ZEB boiler to time shift your usage to the cheapest period. 

[Square Feet]

4 hours ago, Kelvasco said:

Hello,

 

It's a great idea. I've put a few discussion points/options below but happy to discuss further.

 

1. Not all Nissan Leaf's are suitable. Only though with Chademo 1.0, those with Chademo 0.9 are not V2G capable. The fastest way to tell is the interior color. If you have a grey dash and grey carpets then it's a Japanese-built 24kHhr model with Chademo 0.9. If it's a black dash, black carpet then it's a UK-built 24kWHr with Chademo 1.0.

 

Black interior on mine so all good there, thanks.

4 hours ago, Kelvasco said:

 

2. You'll need either a Wallbox Quasar or Indra V2G. Many of the UK trials are ending at the moment so look on eBay and Facebook for used versions. Expect to pay £1,500 for it (excluding fitting). Quasar is the better option if you can get it, just make sure you get proof of "ownership" from the trial it was on (normally Ovo Energy or Octopus).

 

I had actually found both those products in an internet deep dive this afternoon, but I can't find any second hand. I will keep an eye out though. 

 

4 hours ago, Kelvasco said:

4. The best option, if you don't use the car, is to remove the battery from the car and connect directly to a DC-coupled inverter with islanding support. There is a GitHub by a person called Dala-EV that goes into detail if needed. This also enables you to have a higher power output if needed (Quasar is limited to 7kW, Dala method can go up to 22kW 3 phase quite easily).

Yeah, the plan would be to do this with one battery for regular storage - I can't see the point in paying for leccy at night if I have been generating excess during the day.  The plan to also use the car is in case this just isn't enough ie during winter - so I can go out and get charge to bring back with me and add to the system.

 

I found this guy on YouTube who has made some sort of hook up to use his imeev in the same way (also uses chademo).  He is a wee bit bonkers though - he made a lamp out of a pickle by sending a current through it, so it does come with a bit of a caveat.  Cheers for your help - it's good to know I am not the only one thinking along these lines here.

 

Edited October 24, 2023 by Square Feet

[Square Feet]

4 hours ago, mike2016 said:

 you can look at off peak charging / loading of the battery / sunamp or Tepeo ZEB boiler to time shift your usage to the cheapest period. 

Nice one thanks. I will check those out. Not having hot water is my biggest fear!

[Dillsue]

35 minutes ago, Square Feet said:

I had actually found both those products in an internet deep dive this afternoon, but I can't find any second hand. I will keep an eye out though. 

Bear in mind that, AFAIK, both those bi directional chargers are grid tied so should shut down when the grid goes down and wouldn't work in an off grid set up, if that's what you're after.

 

 

[RobLe]

I have some experience in a few areas here:

We have a Nissan leaf, been on the OVO V2G Indra trial for 3 years, and now a V2H trial for 1 year.  You could indeed charge the car up elsewhere, and then run it as V2H back at home to bolster a home battery.  The Indra V2H box does not generate a grid - it has a CT clamp which it nulls by pushing in more power to an existing grid.  So with our V2H box & a Nissan leaf you'd need a home battery system which was islanding to generate the local grid in the first place.  When the car is connected, this home batt system can be programmed to pull power in, and the car will oblige if it can, to top it up.

 

We have an elec only home which is almost enerphit, with a 2.5kW gshp providing heating and DHW.  There's 4 people living there, with "normal" lifestyles, so using 3500kWh/year(stuff) + 2000kWh/year(heating+DHW) + 1500kWh/year(elec car going places) - 3600kWh/year(PV).

 

My only issue with what you want is that modern lifestyles amounts to a lot of power; maybe you are more frugal - that would make it much easier!  We do have 4kWp of PV, so we could be self sufficient in summer, but definitely not in winter - for us, a cold winters day would consume 10kWh(stuff.. telly/fridge/laptops..modern stuff...) + 10kWh(heating+DHW) + 4kWh (car) - 2kWh(PV).  So we import 22kWh for the day - which is probably more than our old 30kWh Leaf can fit in it these days.  An honest appraisal of your energy demand is needed I think.

 

Good luck!

[Square Feet]

13 hours ago, RobLe said:

An honest appraisal of your energy demand is needed I think.

Thanks Rob. I am not under any illusions and am very much looking to establish whether it is possible rather than proposing it as a finished plan, so thanks for your stats - those are very useful. I am indeed very frugal with leccy and gas, but a lot of the point of wanting a passive house with PV is so that I don't have to watch the pennies quite so closely in future and can live in a bit more comfort.  The figure of 3.28 Kwh/day is genuine as it comes from a year's worth of leccy readings for my 150sqm double-upper flat that has terrible insulation in the upstairs part as it's basically a shed dropped onto the roof. Because I am in a flat I can't charge my car at home so those figures aren't included. I live alone but with my son here on uni holidays. We both use computers, TV, nintendo etc but all our lightbulbs are led and I turn them off behind me wherever I go. Our shower is run from the tank and only uses electric to pump it, not heat it so that makes a big difference I think. I use the airfryer as much as I can and avoid running the 'big oven' wherever possible. 

 

I suppose the whole point of wanting to do without grid leccy is that I hate paying the standing charge and being beholden to price fluctuations. It would also make quite a few cheaper remote plots viable if I didn't have to pay for a connection which is why I am going into this in detail at such an early stage (don't have a plot yet!)

 

It may well be that I will have to get a grid connection for the house but I am viewing this as a two-stage project where I move onto the plot and live in basic accommodation above a self-built garage at first. I would put solar on the roof of the garage and house the battery inside. This way I would hopefully have enough power to live (frugally!) and power all the tools, lights etc of the main build. And if I didn't then I could nip out in the car and juice up so that work didn't have to stop on site because I had run out of power. From what you are saying this plan would be workable I think.

[Square Feet]

.... and I could power the garage build like this..... You can't pull high voltage that way but it would be enough to charge tool batteries overnight, run a few lights and so on.

 

[Carrerahill]

On 24/10/2023 at 12:51, Square Feet said:

I'm very much at the research stage here, but I know that I want my future build to be as off-grid as possible. If I can make it completely off-grid for electric then this would make me very happy. I drive an old Nissan Leaf electric car with similar specs to the one in the link below (for anyone reading this after the eBay link has expired I will summarise it as having a 24Kwh battery with 9 bars of health out of the original 12. It's a scrap vehicle in the listing but the battery is fine. It's £2.5k fixed price). I know this isn't exactly how these things work, but for the sake of argument let's say it has c.18Kwh of battery storage (24/12*9), perhaps 15Kwh to ensure it isn't depleted down too far. This is more capacity than the 13.5Kwh Tesla Powerwall 2.0s, which cost in excess of £7k.  

 

https://www.ebay.co.uk/itm/175949367105?hash=item28f7664741:g:M10AAOSwRZJlIq~M

 

Years ago I had a girlfriend who lived off-grid and powered her house with a small solar array and a fairly substantial wind turbine. She stored her excess in some old forklift batteries but I don't think these were really working very well. On still, foggy days she basically had very little power and couldn't run a washing machine etc. She also used a back burner to heat water as there wouldn't have been enough power to run an immersion.  So I know that winter is a difficult time for off-grid power generation, particularly if you aren't able to install a wind turbine for planning reasons. I know that using the batteries from scrapped EV's for PV storage is a common enough route, but my question is more about using my current on-the-road car for additional battery storage. 

 

So let's say I squeeze as much solar capacity on to my roof as I possibly can but I am denied planning for a wind turbine. Then let's say that even with an old EV battery for storage I am just not able to keep up with demand over the winter. My idea is that in these circumstances I take my car to a public EV charger and top it up to the max and drive home and use this to boost my storage battery back up again. Admittedly not exactly fit-and-forget, but not that much of a hardship either. The cost wouldn't be overly punitive as I live in Scotland which has publicly-owned chargers which are kept at a fair price. For example near me I can rapid charge at 35p/Kwh or slow charge at 16p/Kwh. 

 

I plan on building a garage to store the battery in so there wouldn't be issues around space. I am mostly concerned about the effect of this plan on the health of my own car battery if it gets depleted and recharged a lot, but I suppose my real question is - would this work?  Would I be likely to be able to keep up with demand in practical terms?  I don't mind making a special trip to a (hopefully nearby!) public charger once a week but once a day would be a pain. I have absolutely no idea what sort of demand a 175sqm passive standard house would have, nor what I could generate from solar over the winter. I could go on a massive internet deep dive to try and figure this out, but I wondered if anyone here had those sort of figures to hand from their real-world experience. I also thought thrashing it out in here might be useful for anyone else reading it later on.

Cheers

 

If you do this, get a hybrid inverter with a AC input, this can be grid, or, as I plan, a generator for the worst winter days. I know of a chap not far from Glasgow who bought a plot with no power, SPEN wanted silly money, he went off-grid, he has PV, storage and a generator, he reckons he uses about 50litres of diesel a year max and it only kicks in during the worst winter days - as PV pane efficiency increases he expects to come off the generator once he renews one of his arrays in 5-6 years. 

 

 

[Alan Ambrose]

>>> He is a wee bit bonkers though - he made a lamp out of a pickle by sending a current through it

 

Someone has to nudge us all into using pickles to their full capacity...onion? cucumber?

[Square Feet]

 

34 minutes ago, Alan Ambrose said:

>>> He is a wee bit bonkers though - he made a lamp out of a pickle by sending a current through it

 

Someone has to nudge us all into using pickles to their full capacity...onion? cucumber?

Here you go.... 

 

[Square Feet]

1 hour ago, Carrerahill said:

If you do this, get a hybrid inverter with a AC input, this can be grid, or, as I plan, a generator for the worst winter days. I know of a chap not far from Glasgow who bought a plot with no power, SPEN wanted silly money, he went off-grid, he has PV, storage and a generator, he reckons he uses about 50litres of diesel a year max and it only kicks in during the worst winter days - as PV pane efficiency increases he expects to come off the generator once he renews one of his arrays in 5-6 years. 

 

 

That's really interesting thanks.  I could live with that - it's not ideal but would be ok in the interim. Nice one, cheers.

[Dillsue]

The posts above using a Leaf for V2H/G both use a Quasar or Indra unit which seem in short supply second hand and aren't available new. Anyone aware of any other units to hook up a Leaf without modding the car? Ideally grid tied but I think that's not yet legit outside of the official trials??

[S2D2]

3 minutes ago, Dillsue said:

The posts above using a Leaf for V2H/G both use a Quasar or Indra unit which seem in short supply second hand and aren't available new. Anyone aware of any other units to hook up a Leaf without modding the car? Ideally grid tied but I think that's not yet legit outside of the official trials??

I looked recently but all the manufacturers just have notification list sign ups rather than launch dates.

[Kelvasco]

1 hour ago, Dillsue said:

The posts above using a Leaf for V2H/G both use a Quasar or Indra unit which seem in short supply second hand and aren't available new. Anyone aware of any other units to hook up a Leaf without modding the car? Ideally grid tied but I think that's not yet legit outside of the official trials??

Unfortunately, no, all of the current suppliers no longer make the V2G units as Chaedmo is a dead standard in EU/NA and both Wallbox and Indra now make CCS2 versions (which don't work with the Leaf). The best bet is used unfortunately, I've been tracking it though and there seems to one come up on average every 6 weeks based on the last 1 year of tracking (average prices between £1,400->£1,500)

[RobLe]

We're likely to sell our V2H unit at some point.  It's always worked fine for us, it's got several settings available on the Indra Portal - unfortunately I think this portal is only available in the trial and I doubt you could persuade them to allow it off grid - they don't generally even offer 2nd hand unit support.  I think the unit will carry on working in that mode; but it might want to "phone home" at some point - it normally connects over the internet.  I've tried it several times without the internet - I've never known it not work like that, but it may get upset eventually, who knows.

 

The most likely useful setting for Square Feet would be  "Load match" the whole time - with a CT on a grid forming inverter, then the car will push or pull up to 4kW (it is a 6kW unit, ours is locked to 4kW for dno reasons) in or out of a grid forming hybrid inverter system.  Eg a Sunsynk inverter + battery system creating a grid, the car bolstering it if there - Sunsynk could then manually be triggered to pull power from the car. While I can't see why it wouldn't work, until somebody tried you'd never be sure the inverters didn't get upset.  The grid forming stuff would cost anything from rock bottom £6k (3.6kW + 15kWh(see Seplos Mason EVE 280 kits) + 4kWp PV, all DIY) upwards - personally if space I'd go for a bigger unit and loads more PV.  You can always parallel up Sunsynks - other inverters are available.  As suggested above, a genny would get you out of trouble!

[Dillsue]

4 hours ago, Kelvasco said:

Unfortunately, no, all of the current suppliers no longer make the V2G units as Chaedmo is a dead standard in EU/NA and both Wallbox and Indra now make CCS2 versions (which don't work with the Leaf). The best bet is used unfortunately, I've been tracking it though and there seems to one come up on average every 6 weeks based on the last 1 year of tracking (average prices between £1,400->£1,500)

Assuming V2G/H gets approved and publicly available in the next year or 2, are you saying Leafs will be a non starter with no compatible bi directional chargers available? I'm guessing there'd be a market to sell Chademo units into??

[Kelvasco]

On 26/10/2023 at 16:59, Dillsue said:

Assuming V2G/H gets approved and publicly available in the next year or 2, are you saying Leafs will be a non starter with no compatible bi directional chargers available? I'm guessing there'd be a market to sell Chademo units into??

 

Correct, the market for Chademo units (V2G that is) is basically disappearing very quickly. But if you want to have V2G at home then a used Leaf + a used charger is quite a competitive offering.

[Square Feet]

This isn't quite what I was looking for as it's basically battery to house, but it's done with a Leaf battery and is quite interesting.