EV batteries as battery storage?

[Gareth J]

So, I'm teetering on the edge of changing my car. It's getting tired but it's on the cards. I think an EV would suit us but, tending only to spend a few thousand on a car, the jump in investment is not an easy one to make!

However, with the extra PV arriving soon, I thought it might be more easy to justify if I could use any potential car as a battery storage device too. I can imagine a setup where you could get an AC battery inverter, like you'd use for a normal battery system and hook it up to the car batteries....but I can't see many options or examples of people doing this themselves online. Do car manufacturers make this sort of thing impossible or nigh on impossible? Read a post about using the cars cigarette lighter to power a fridge in a power cut but that's not what I'm thinking. I want there to be a pair of big dangerous terminals at X00V DC that I could wire in a giant plug to that'd connect to a battery inverter.

An electric car might as well be earning it's keep while sat in the garage.

[Stinsy]

What you’re talking about is V2G/V2H.

The easy bit is charging your car from excess solar. Zappi (or similar) charging points can vary the charge-rate to reflect how much your solar is generating. This is where it ends for most people. Many people drive enough that the car uses more electric than they can put in it from solar alone, so they don’t need to go any further.

The difficult bit is taking electric from the car and using it to power your house. There was a trial involving ChaDeMo Leafs. It was great for those on the trial, primarily because they got a £10k charger fitted to their house for free and they had their power company negotiating with the DNO on their behalf.

There are a few domestic V2G chargers for CCS in development but they’ll be expensive, currently they all require 3-phase and they’re a few years off.

You can bodge together something that uses the car’s onboard DC:DC converter and a Y&H style “plug in” grid tie inverter, but there are a few technical hurdles to overcome, you’d be in breach of the wiring regs, and the efficiency would be dire. Worthwhile only if you’re filling up on free electric at Tesco or your workplace.

[Joeboy]

As I park on the drive it's no problem to run a lead to the car for V2L.and run the washing machine or tumble dryer off of the car. This preserves the soc of the home stack if need be. Have not had to do this but handy to have. More so is the 73kWh storage that the battery represents for excess PV.

V2L is not exclusive to the Ioniq 5, maybe worth a search to see what aligns best with your needs?

[Tinbum]

Their are 2 or 3 manufactures that do it at the moment, can't remember which other than Hyundai, but I don't know up to what current.

[Joeboy]

I5 is 3.6kW, MG do it too and the Ford Lightning has a massive 9.6kW discharge rate. There may be others..

The above are simple plug n play V2L.

[Gareth J]

Thanks for the replies, great to get a handle on all the V2X acronyms and terminology for googling.

What I don't get is why you can't use an off the shelf battery-PV-house/grid inverter (or a hybrid inverter) to hook up a car battery to the house and use it as you would a stack of pylontech batteries.... Are there some electrical vehicle management shenanigans that get in the way of such things? Why does it need to specifically be a bi-directional vehicle charger? I can't seem to see anyone doing this, there must be some barriers. In an ideal world, the charging port could be used but I wouldn't be against having a second, appropriately protected and rated socket in the car that allowed connection to a normal battery inverter.

Wasn't really thinking of using the onboard DC- 240vAC supplies some vehicles have.

This confusion might be because my understanding of cars is a bit antiquated, am used to ones you can take apart, modify, tinker with; electronically through CANbus as well as with spanners and hammers. Maybe there are just too many obstacles to do that now.

[nowty]

Thanks for the replies, great to get a handle on all the V2X acronyms and terminology for googling.

What I don't get is why you can't use an off the shelf battery-PV-house/grid inverter (or a hybrid inverter) to hook up a car battery to the house and use it as you would a stack of pylontech batteries.... Are there some electrical vehicle management shenanigans that get in the way of such things?

Yes, there are some electrical vehicle management shenanigans that get in the way of such things, but for good reason. Just think how dangerous it would be is you could easily tap into circa 400v of DC with a 70kWh battery pack behind it. And even if there is a protection fuse in the car its going to be a f'ing big one considering the rapid charge rates they can achieve.

There is a set of comms protocols that has to communicate to the car to access the DC side of things. As a test I just put my voltage multimeter on the CCS pins of the car and there is no voltage.

[Gareth J]

Thanks for the replies, great to get a handle on all the V2X acronyms and terminology for googling.

What I don't get is why you can't use an off the shelf battery-PV-house/grid inverter (or a hybrid inverter) to hook up a car battery to the house and use it as you would a stack of pylontech batteries.... Are there some electrical vehicle management shenanigans that get in the way of such things?

Yes, there are some electrical vehicle management shenanigans that get in the way of such things, but for good reason. Just think how dangerous it would be is you could easily tap into circa 400v of DC with a 70kWh battery pack behind it. And even if there is a protection fuse in the car its going to be a f'ing big one considering the rapid charge rates they can achieve.

There is a set of comms protocols that has to communicate to the car to access the DC side of things. As a test I just put my voltage multimeter on the CCS pins of the car and there is no voltage.

Kind of imagined that would be the case. And I suspect that ferreting out terminals to make my own input/output cable would result in some other kind of tamper induced wobbly.

[Gareth J]

https://www.speakev.com/threads/ev-batt ... 461/page-3

Yea, I don't know enough about this topic to be even contemplating it as an idea!

[Swwils]

It's very common in Japan.

UK will lag behind due to our relatively small market and corresponding slower electrical market.

Most EV can do it already, but it's not allowed or the options aren't installed on the veichle themselves. Manufacturers will want to know about effects on battery lease and/or warranty claims etc.

Ironically home storage is meant to be one of the "retirement" uses for older cells that have already seen their useful lifetime in an EV and thus be comparatively cheaper. But I think everyone has been pleasantly surprised by the relatively low degradation rate seen even in EV use when the battery is properly managed.