On-grid domestic battery storage

JKenH

mmmmikey wrote: »

p.s. as an afterthought if you want good advice on this, try


https://www.solarfixer.co.uk/


The guy that runs this business (Geoff) will do a good job at a reasonable price and not try and persuade you to do loads of unnecessary work. When he installed my PowerVault he did a bit of tidying up of the wiring for the solar installation and re-labelled everything properly and I was very happy with the work he did and the price he charged. He won't charge you any more than a regular electrician but has the technical skills and background to properly understand what needs doing.

Brilliant, that’s reasonably local to me. I am still thinking of getting a battery despite Mart’s recent comments. I don’t have much solar in the winter but I do have E7. Just waiting to get my DNO approval for the panels I’ve got - 15 months after installation - as I wouldn’t want to get a battery installed then find I was only allowed half my PV installation.

What made you go for the Powervault? Do you know if it is compatible with an IBoost?

If you don’t mind me asking, where are you based, mmmmikey?

1961Nick

JKenH wrote: »

Brilliant, that’s reasonably local to me. I am still thinking of getting a battery despite Mart’s recent comments. I don’t have much solar in the winter but I do have E7. Just waiting to get my DNO approval for the panels I’ve got - 15 months after installation - as I wouldn’t want to get a battery installed then find I was only allowed half my PV installation.

What made you go for the Powervault? Do you know if it is compatible with an IBoost?

If you don’t mind me asking, where are you based, mmmmikey?

Go for it Ken.....just think of all the additional spreadsheets you can create.:rotfl:

With enough batteries & the iBoost it's doubtful if you'd ever exceed 3.68 kWh export so some type of limiting device may suffice instead of the DNO approval?

https://www.powerflowenergy.com/solar-water-heating/export-module/

Perhaps you could ask that company that Mikey mentioned about export limiting?

mmmmikey

JKenH wrote: »

Brilliant, that’s reasonably local to me. I am still thinking of getting a battery despite Mart’s recent comments. I don’t have much solar in the winter but I do have E7. Just waiting to get my DNO approval for the panels I’ve got - 15 months after installation - as I wouldn’t want to get a battery installed then find I was only allowed half my PV installation.

What made you go for the Powervault? Do you know if it is compatible with an IBoost?

If you don’t mind me asking, where are you based, mmmmikey?

Hi Ken

I've posted a number of comments on the PowerVault on this thread:

https://forums.moneysavingexpert.com/discussion/6036084/edf-battery-offer

The grid services contract referred to in this thread was one of my main reasons for buying. It is quite an expensive solution compared with others, although the cost does include all the installation and excellent customer service, and to me it seems more future proof because of the frequency response capability I described in that thread.

Geoff at Solarfixer does installations for PowerVault but is not tied to them and also installs and repairs other kit, so worth having a chat through various options with him. Also, I found PowerVault very good for technical info pre and post sales, just give them a call with any questions, they're not unduly pushy.

As far as compatability with the iBoost is concerned, it is something they were going to have a look at to see if the iBoost and PowerVault can be set up so they don't compete with each other and I'm not sure where they got to with this. I had a Solic 200 which I had to operate manually which worked well but not ideal. I've just gone to metered export and I'm on an E7 tariff so get paid as much for selling spare solar as it costs me to buy it back overnight. This makes the Solic 200 redundant as I might as well heat the water overnight - i.e. the additonal cost is offset by the additonal export payment. It also means that I've just set up the PowerVault to fully charge overnight as again there' no real advantage to waiting for free solar. This makes it all very easy to manage - just set up the charging schedule and ignore - and also means you've always got a full battery. I reckon on getting 5 or 6 kWh per day out of my 4 kWh battery by charging it overnight, using a bit in the morning and through the day but recharing it with solar during the day, leaving me with a full battery for the evening.

To balance my enthusiasm a bit, I'd look at this more as a good way of saving the planet for little or no cost than as a money spinner, so may not appeal to a filthy denier like you ( nooooo - what have I said ) Seriously, I reckon on a fighting chance of breaking even with minimal net cost saving at best so if you go with this I'd do it on the grounds of reducing CO emissions or the fun of playing with it rather than as a pure money saving initiative. And, of course, you can have endless fun winding up other forumites about your green credentials

Probably worth pointing out that one of the advatnages or drawbacks of the PowerVault depending on your perspective is that it's very much geared up for remote management and support and there's not much for you to play with in terms of settings other than simple schedules. Doesn't stop you doing what I'm doing though and working out how to get the most out of it by adjusting your demand etc. but if you want something you can fine tune yourself you'd probably be better off looking elsewhere. The PowerVault is really aimed at the average, non-techie consumer and, IMHO, it does that very well.

I live in Navenby, south of Lincoln.

Keep us posted with your thoughts. I'm going out now to superglue myself to a lamp post as a protest against something to do with global warming - haven't decided what yet.....

mmmmikey

joefizz wrote: »

With your link inverter I could put a switch on half the pylontech batteries (split it into two feeds) and use those with the inverter in your link, that way it would still power the solar inverter and charge the other two pylontechs via the sofar inverter... or just get another sofar.. or... this is getting complicated ;-)

All sounds interesting, let us know how you get on. I get the bit about using the small inverter to create an artifical mains supply for your battery system to grid tie to, but how will you stop it overloading the small inverter if the main battery system can't cope? Also, my inverter/charger is really geared up for charging lead acid batteries and although the inverter will work with anything in the right voltage range I'm not sure how it would go on charging Lithium batteries.

Solarchaser

I think if you are going for a battery on straight out financial terms, its borderline even with shopping around for the best deal to get a break even in 10 years. Infact I'd say its highly unlikely.

The cheapest way to do it even now seems to be with a sofar me3000sp and pylontech batteries.
But if you go for 6kwh useable (7.2kwh) and use it fully every day, assuming a 13p/kwh charge then you can save 6x365x0.13 =£285 a year.
A quick glance at Ebay says that system will cost you £3k and that's Installing yourself , so over the 10 years it will cost you £150.
You could argue the batteries working that way will last 20 years, and so you could almost double your investment over the 20 years.

However, that's quite flawed, you dont generally get enough solar to charge the batteries in the winter.
My sofar which has been in for just shy of 11 months has done only 183 full battery cycles not the 330 odds you would expect if it had been cycling every day for 11 months.
Theres a caveat in there about micro cycles where it discharges a couple of kwh and then is recharged up to 100% again.
My system doesnt read that so I dont know how much of that the system is doing, i can only read total full cycles of the controlling battery, some days its doing alot of micro cycles, and some days none at all.

So you can set it to charge on e7. And so save 8p /kwh, but say you do that for the 150 darkest days of winter, you are only saving 6x150x0.08= £72
Plus the 183 days I've saved is 183x6x0.13 = £142 so a saving of £214

So after nearly a year of running batteries I cant see the breakeven being ten years, 15 or so seems logical I think.

So with all this said, I would obviously advise against batteries right?

On the contrary, I'd say if you are going batteries. go big.
I'm about to invest another few thousand to get my storage to around 22kwh, as that's what my house tends to use on an average day.

The new lux parallel systems will run the pylontech at 90% discharge in comparison with 80% discharge on the sofar.
And being parallel, they can cover 7.2kw of load, instead of the 3kw of the sofar.

Will it break even in 10 years? Not a chance, but it will give me a ton of satisfaction at not buying leccy at 13p pretty much ever.

This month isn't necessarily a great month to use, but I'm gonna anyway, this month I've exported over 200kwh, but bought 175kwh.
Theres no other way to justify my expenditure than just to say this sort of thing irritates me.
I mean at 13p, the total cost is only £22 odds, so hardly earth shattering, but it just irritates me.

Most of my solar is not fit, so I'm not getting paid for most of it, and so I want to self consume as much as possible.

My analysis is probably similar to many on here, and I know Mmmmikey has decided that he is going to use the export tariff to offset cost and charge overnight, and make the sun powered immersion redundant by also immersing overnight too, but I'm looking to self use, rather than *profit*, so I'm looking to move to using more of my solar rather than exporting it.

Or at least, that's my feeling today, I've flip flopped on this quite a few times, including recently calling ovo about the v2g trial.... mostly because I'm interested in using the v2g charger as a v2h charger after the trial, but also because they were advertising a high export tariff in the evenings for grid support.

However my leaf is a 15 plate and still under warranty. You can sign a letter to say you opt out of the warranty... but it's not just the battery warranty, it's the entire car warranty.

Also they are not really interested in large solar arrays, they ideally want to be at the 4kw array size.

Finally they want around 1000 people on the trial, so far they have less than 100, so goal posts may move.

Hope that helps someone

joefizz

mmmmikey wrote: »

but how will you stop it overloading the small inverter if the main battery system can't cope?

by probably invalidating the warranty ;-) If only there was a way to isolate the AC feed into the logic and control boards and keep that separate from the inverter output ac connection...

Solarchaser

Joe, could you not make solar part of the circuit supported by the eps from the sofar, so that it would see that as incoming mains and still power up the panels?

That what I was thinking of. And having a 100a contractor between the main meter and the consumer unit, so in the event of a power cut, the contractor fires and isolates the house, when mains is back on, it kills the contractor and normal service is resumed...

joefizz

Solarchaser wrote: »

Joe, could you not make solar part of the circuit supported by the eps from the sofar, so that it would see that as incoming mains and still power up the panels?

That what I was thinking of. And having a 100a contractor between the main meter and the consumer unit, so in the event of a power cut, the contractor fires and isolates the house, when mains is back on, it kills the contractor and normal service is resumed...

But that wouldnt also charge the sofar batteries. Thats the issue I had at the weekend, power went off early morning with batteries at about 50%. Everything ran ok on batteries and if Id isolated the sofar I could have probably run the solar output as well and saved draining the batteries as much but it wouldnt have charged the batteries plus theres the danger of what happens when the solar output is more than the load (could use an iboost or something to put excess into hot water tank).
I didnt go for the auto cutover route primarily due to the load concerns. The pv inverter may just shut down but Im not sure.



Would just be a lot neater if I could throw the house isolation switch and everything think the mains is on (off grid mode if you like). I know the pv inverter has an off grid mode, I just dont know if its 'user configurable' in the uk without resorting to reflashing the firmware, resetting a pcb jumper or getting the wire cutters out.

mmmmikey

Solarchaser wrote: »

So after nearly a year of running batteries I cant see the breakeven being ten years, 15 or so seems logical I think.

I have a very similar view - 12 to 15 years seems about right at today's prices, hence my comment of having a fighting chance but no certainty.

One great big unknown in all of this is what happens to tariff structures. Based on other posts folks have made here pointing to official data, it seems reasonable to assume that, over the next few years, average electricity prices will remain at about today's level, with the exception of "natural" inflation which is more or less balanced out by interest rates and the opportunity cost of lost interest on any savings used to buy the battery.

But - and it's a big but - there are a million or smart meters out there and like them or loath them it's a fair guess there are a lot more to come. This opens up the way for more and more time of use tariffs. Let's say instead of paying a flat rate of 13p per kWh you pay a rate between 5p and 20p per kWh depending on time of day. Given that energy company profits are effectively regulated this is likely to result in a bill that is about the same if you assume that average prices remain the same. Logically, you'd use the battery at a time when you were saving 20p per kWh, which makes the case much more attractive.

It's also by no means certain but not unreasonable to assume that you'll also end up on metered export which could well mean that you're in the same position that I am where you might as well charge the battery from the mains when power is cheap, meaning that, like me, you can squeeze more than one cycle per day out of the battery by using a combination of cheap night rate electricity and solar during the day to recharge the battery after your morning and daytime loads. Again, this has quite a big effect on the economics.

Clearly none of us know what's going to happen with any certainty, but my own best guess is that for the reasons outlined above I think the payback will be better rather than worse than predictions based on current pricing structures imply. To my way of thinking, it is unlikely that making a simple assumption based on flat rate tariffs will be a good one in the long run, but nevertheless is probably a reasonable place to start as it represents a realistic worst case.

Solarchaser

Mmmmikey I agree with everything you say there.
And if I'm moved to metered export at 5p and time of use at points is say 3p, then I'll be doing as you are, but while its borderline I want to self use as much as possible.

Joe, tbh we havent had a power cut in.... about 10 years I think, so I havent even wired up the eps on my sofar, but I assumed it would continue to charge the batteries if the solar was more than the load, I'm pretty sure I read that the lux will.