@prjohn V2G would be ideal, sadly its not really available yet. However I have seen the new ID3 from VW if you get a model this year will have V2G and V2H enabled - however the problem remains you cant use it yet. Everything is still in trial phase/stage.

@batalto I believe Nissan is doing it at present via the Leaf.

@prjohn The Leaf has v2g and I would buy one just to experiment with. 

However, the biggest problem is the hardware in the house is very complex and the only available charger I’ve seen is the wall box quasar at £10k, unless you got it free in a pilot area. 

I can see the potential for using your car battery in this way invalidating your warranty if used to excess. 

@mattengineer I honestly think car batteries would be fine for a house. The loads a house would give them pale in comparison to driving. The peak load of an accelerating car would be far more than any home might need at peak. I've seen a number of Leaf and Tesla car batteries pulled out to be used in homes because they don't work anymore in the cars - just look on youtube if you want to see some.

@batalto It wasn’t so much peak load it was more additional cycling on the battery unit in leased vehicles, where you paying a mileage rate which is designed to be a proxy for wear and therefore residual value. I know cap hpi are looking at new standards for how the health of batteries are assessed. 

Have you had any luck finding an inverter charger at 100amps? 

A lot of information here for V2G.there is also a link to octopus regarding the trials.

https://www.nissan.co.uk/range/electric-cars-technology/v2g.html

Posted by: @mattengineer

@batalto It wasn’t so much peak load it was more additional cycling on the battery unit in leased vehicles, where you paying a mileage rate which is designed to be a proxy for wear and therefore residual value. I know cap hpi are looking at new standards for how the health of batteries are assessed. 

Have you had any luck finding an inverter charger at 100amps? 

The Nissan Leaf battery guarantee is still valid for all the trials. 8 year guaranteed replacement if the battery drops below a particular level based on model.

The V2H trials which are following on from V2G may be better for some people depending on usage and tariff

The folks over at diysolarforum.com are getting quotes for $1300-1800 (delivered, variously to US, EU, etc) for ~10kWh of LiFePO4 cells from China, depending on the exact grade of cells and the trustworthiness of the supplier.  Enclosure, BMS, charger and inverter are then your problem (but not massively complicated, just buy the right bits)

I was gradually starting to build a system, but without solar everything currently being on a flat tariff means there's not much point.

Posted by: @mattengineer

Have you had any luck finding an inverter charger at 100amps? 

Sofar has bigger units than the 3kW version, or you can double up. But 16A per phase (ie 3kW single phase) is the limit of the UK G98 certification, by which means you tell your DNO that a grid-connected inverter is present.  Above 16A you get into G99 territory which needs DNO pre-approval - and they can say no if your local grid isn't up to it. An alternative is to fit a limit device that prevents feeding back into the grid (at all or more than 16A) - you can consume power locally but don't expect the DNO to take it if you have too much.  That would seem to be better for a battery setup where, unlike solar, you don't have an urgent need to dump power right now - you can keep it in the battery for later.

Posted by: @batalto

@mattengineer I honestly think car batteries would be fine for a house. The loads a house would give them pale in comparison to driving. The peak load of an accelerating car would be far more than any home might need at peak. I've seen a number of Leaf and Tesla car batteries pulled out to be used in homes because they don't work anymore in the cars - just look on youtube if you want to see some.

Car batteries do work satisfactorily as storage in a domestic setting. Eaton developed just such a battery system in 2017.

However, there are practical and ethical reasons why many people won't want to go down this route:

Practical: EV batteries usually employ LiMNC chemistry. Each cell has a nominal 3.7v and the battery is optimised to supply lots of current fast. That's what's required to accelerate a car. The downside of this approach is battery life, which tends to be about ¼ that of the main alternative cells using LiFePO4 chemistry (3.2v). Householders are more interested in a storage investment which lasts a similar length of time as PV solar panels. They don't require high current to run anything!

Ethical: LiMNC cells use cobalt; The cell chemistry is Lithium Manganese Nickle Cobalt. The world supply of cobalt is largely deposited in Congo. Workers extract it whilst operating under conditions akin to modern slavery, with little regard for safety. The 'mine owners' receive funds which are then used to buy arms and protect their personal interests. Schools, hospitals and the rule of law don't feature highly amongst their priorities.

Hi Everyone. We've just had a quote for £7,500 for a 10Kwhr Solar Edge Energy Bank.

Two questions. Does this seem to be a decent enough quote, & is it worth it? I'll try to answer the second question, but I could really do with your advice on the first.

I already have a Solar Edge PV system, & during the recent sunny week here in the UK in March, we were giving away 15Kwhr per day back to the grid. I'm on a "Welcome to British Gas" variable tariff: This week it's £0.20208 per Kwhr, Standing Charge of £0.2646, but next week it'll be £0.27092 per Kwhr with a standing charge of £0.48913 instead.

I realise that trying to work out the maths for this is an exercise in futility, as the battery will provide more that 10Kwhr per day! I base that assumption on the fact that there are times during daylight hours when we are cooking/washing/cleaning when our usage is higher than our solar can cover. A battery would iron out those peaks, then recharge itself again in time for the night. Given that, I'm going to estimate that it would give me an extra 13Kwhr per day. I'm also going to estimate that that means that I would be essentially self-sufficient & off-grid for more than half the year. I know that I could (possibly) change over to Octopus, get a cheap night time tariff, & charge it up at night, but I'm not on that hypothetical yet. My calculations are based on my energy consumption over the past few months. My ASHP may be more efficient next winter (covered in other threads), but £7,500 is a big wad of cash...

So, very estimated worst case scenario with battery:

Annual Standing Charge:                    £180
2 months at 1,400 Kwhr each             £760
2 months at 1,300 Kwhr each             £700
4 months at 700 Kwhr each                £760
4 months free
                                        Total:   ~£2,400 per annum

and estimated worst case scenario without battery:

Annual Standing Charge:                    £180
4 months at 1,400 Kwhr each           £1,520
4 months at 900 Kwhr each                £975
4 months at 450 Kwhr each                £490
                                        Total:   ~£3,165 per annum

Gives me a potential saving of around £765 per year. OK, that's not to be sneezed at, but it almost exactly works out as taking 10 years to pay back the initial £7,500 cost. On the plus side, this estimate uses current prices for the next 10 years, & we can assume that they are only ever going to increase. So, maybe payback in six to ten years, if I cough up £7,500 right now.

If my ASHP behaves exactly as I hope that it will next winter, & if my solar is fab this year, then my electricity consumption is even less. That would bump the payback date back to well over a decade.

Amazingly, I have a lead time to install of around a month on that quote, so if the national electricity supply does go completely pear shaped, it may all appear to be a much more viable option.

What do you think...?

@justinsb in my view, that's too much on 10kwh of storage. £750 per kwh of storage. You should be aiming for more like £250.

I would set my ceiling on Pylontechs (as I already have them) from Ebay, plus install - £5k for 10kwh. This is basically a slightly smaller version of what I have, 10kwh vs my install of 14.6kwh.