On the SpeakEV forum, apparently it's not such a terminal problem, if an older (losing value) EV's battery loses too much capacity - good used ones from a crashed car are available on ebay, costs £1500 to install - and fitting a higher capacity later-model battery while you're at it.
I'm saying this because the old one still has value, indeed the good ones are offered alternatively as a domestic battery. Deterioration doesn't matter so much for domestic - just add another one. There'll be a Youtube about it.

For me the Jury is out for the moment with balcony solar and associated batteries. There are technical hurdles to overcome to ensure safety. An electricians view.

https://www.youtube.com/watch?v=Tq3Vr8pOUoc

Main issue is how they work when the grid goes down and the balcony system is sending juice the other way. What you could consider is a standalone power station of which I have 2 small ones I charge overnight on cheap tariff. I do not know about what is involved with connecting a ESS battery to micro inverter systems. But you could charge a PowerStation during a sunny day instead of sending surplus to the grid. I have one next to the TV which is permanently plugged in which I can also use with power tools when I am out of reach of power points. As mentioned in posting from the beginning of the year I lost my Delios inverter to a failure (Delios gone bust) and bought into a replacement that would work with my BMZ battery. The BMS locked it out I could not unlock it as BMZ has also gone into receivership. I am hoping this week I will be up and running with new batteries totalling 36Kw nearly finished the install. Just to show how cheap batteries have become my 36kW is cheaper than what the 10kW BMZ was 5 years ago.
A friend bought a 20kW battery pack reclaimed from an EV write off from a supplier and had it installed. When he realised how easy it was he has since made up his own battery packs from write off EV's and buys BMS chips off eBay. Batteries need a profiled charging regime and I do not think that using generic BMS will get the best out of a particular battery pack, He is however very practical and I personally would not venture down that road. I forget how big a size of pack he has now but it will be several tens of kW.

You could splash out and install a Tessla battery system a neighbour is taking up an offer from Octopus which includes a second slave battery at big discount. You also get UPS but check that out.

Posted By: djhI presume when you talk about 36kW you mean 36 kWh?

Correct each unit of 12 kWh can deliver 5kWmaking 15kW in total but there are other restrictions like the inverter at 6 kW and existing wiring from the inverter to the consumer unit which stands at 32A. However I will be able to increase this to 40A as the inverter has a greater tolerance to voltage drop than the previous one.

Posted By: djhDIY used batteries are illegal (i.e. not in accordance with regulations - do you know different?)

As far as I am aware, and it certainly was the case 5 years ago batteries are not certified in the same way as inverters and solar panels are, which need to be declared in DNO applications and that appear on the approved list.
There is no such list for batteries

Far from DIY batteries being potentially illegal which I do not believe they are currently not, my concern would be a potential insurance problem in the event of an incident resulting in an insurance claim. A reason why I would not consider a DIY made up battery.

Posted By: djhI know about large batteries, as I said. I'm specifically interested in the new small ones.

What size were you considering?

Have you asked Ai ? Here is an example.

https://iask.ai/q/UK-4kW-solar-microinverter-battery-recommendation-ivifh9o

Posted By: WillInAberdeenBy the new small batteries, you mean the ~1kWh ones that come packaged for householders to 'plug in' ?

Yes, those are the ones.

Afaict there are two kinds of users, the two kinds of product are not interchangeable:

- the off grid types such as motorhomes and outdoors power tool users (1kWh replaces a 12V leisure battery) - those have a small inverter and a couple of sockets built in, charged from PV or grid, but not certified for grid export

- to reduce clipping losses for a German -style balcony 1200W panel arrays connected to an 800W grid tie (plug in) micro inverter that doesn't get paid for exports but also doesn't have an export clamp meter. 1kWh is enough to shift the clipping loss into the evening period. No ability to charge from the grid.

I definitely want the ability to grid connect, but I am looking at examples that can charge from the grid e.g. https://www.ankersolix.com/eu/products/a17c2?s_1=A17C23Z1&o_c=eu or https://uk.ecoflow.com/products/delta-2-portable-power-station?variant=43099247608000 (the second definitely appears to be aimed at the UK).

One use case is to reduce or eliminate my grid usage during the 'peak' hours (16:00-19:00 or so), charging overnight in winter and from PV in summer.

In principle plug-in batteries and PV can be safe, but they are not yet legal in UK, so imports are 'grey market ' and caution advised, many fires reported to be caused by 'grey market ' imported e-bike batteries. No market-leading brands clear yet, as the plugin battery market doesn't officially exist in UK.

Govt has declared it will make them legal. The laws in question seem to be G98/99/100 which are made by the distribution operators, and the wiring regs BS7671 which are referenced from English building regs and the devolved nation equivalents. The UK government doesn't seem to have much direct authority over the wiring regs so IDK how quickly/easily they will change them.

ETA: the wiring regs are updated roughly every 2-3 years and by chance the latest update 4 was a few weeks ago. It seems to make plug in generation more difficult (required to be on supply side of RCDs not load side, batteries to be outdoors, etc). IDK how/when this can be changed.

https://electrical.theiet.org/wiring-matters/years/2024/102-september-2024/the-impact-of-amendment-42026-on-the-18th-edition-of-the-iet-wiring-regulations/

Further ETA: the link above to the IET journal was in 2024 when they had identified, debated and drafted the changes and were putting them out to consultation. It's now 2026 and they've just been enacted. That's how slowly it is to change electrical industry regs.

Yes, I'm asking if anybody knows what the up-to-date legal position is, and what the timescale is if they're not legal yet. I think your reference is somewhat out-of-date, and there have been at least two changes since with another one to come. I know there's a load of fuss about bidirectional RCDs at the moment.

On a related but different subject I belive the BUS grant for air-air heat pumps is now law, so I went to the MCS site to find an installer near me to find:

"Air-to-Air Heat Pumps

"There are currently no installers certified for this technology.

"Air-to-air heat pumps are a new technology that will be available to installers later this year.
"Please check back soon for updates." !!

Thanks.

Posted By: WillInAberdeenAlso the plug-in-to-export Euro batteries are limited to 800W output to the home.

Yes, and that seems sensible to me; I expect some similar rule here. You wouldn't want unexpected major power injection into a ring main.

Plug in Solar and Batteries (combined output) are limited to 800W in Europe - the rules around what will be allowed in the UK are still to be defined!

ED Miliband and the UK press jumped the gun on the announcement before checking if it could work in the UK.

The UK ring main circuit is unique in Europe; other countries use radial circuits with a higher current carrying potential (4mm cables instead of 2.5mm) so are safer with PIS.

European plugs/sockets (type E or F in EU parlance or the newer CEE 7/7 which combines both grounding types) are also rated to 16amps continuous (due to better heat dissipation by design), wheras UK fittings are 13a PEAK.

That is a pretty major difference in fire safety and the reason for official UK EV 'granny chargers' having a thermister in the plug to control overheating (this only protects the plug, not the socket and wiring, but that is a whole other subject...)

Plus we still have a lot of older houses on re-wirable fuses and other outdated technology that are not as safe.

Then factor in all the non-compliant Chinese crap that will flood the market on fleabay/amazoon and the uneducated masses who will merrily plug in extra panels/batteries to any available socket (or extension leads!) and we have a recipe for a summer of house fires ahead.

There are a whole host of reasons why I consider plug-in solar to be a less than ideal option in the UK - but then I would say that as an ex PV installer...

@sgt_woulds. A normal UK ring circuit has 2 x 2.5mm cables which I guess has a greater current carrying capacity than an EU radial wired in 1 x 4mm cable??

If capped at 800watt output, a plug in solar unit is only going to push out circa 3 amps. Thatseems to be well within the rating of a 13amp plug/socket.

Biggest risk I can see with plug in solar is panels being dropped from a high rise block!

@philedge, in a ring main the ampage is cut in half betrween the two cable paths which is why we can use 2.5mm.

This was dreamed up in the 50's to help deal with material shortages, as much as any technical advantage.


@WillinAberdeen, the issue is less about circuit protection for the size of cables but more about fault detection and maintenance of the existing cables. Schuko plugs, sockets, and wiring are designed for 16a CONTINUOUS load. The cabling and sockets in a UK ring main are designed for 13a PEAK.


A 13amp socket is only allowed on a 32amp ring main because our plugs have 13amp fuses. (If you were to fit European/Schuko sockets in to a UK ring main, the whole circuit would need to be downrated to 16amp due to the unfused plugs that could be used)


With PV (or battery) dual supply, issues arrise when you plug a high load (E.g. an EV) in the same circuit as PIS.
Any generation goeas striaght to the load. Any protective detection device at the consumer unit will not 'see' the full ampage going to the plugged in device which - it is being supplied by the sun, not the national grid.

There are all sorts of electro-mechanical reasons why connections on 4mm cable are better than 2.5mm - this is important, as the nature of variable PV generation works neutrals loose over time, even on 'traditional' systems. It is why (IMPO) any PV installation shoild have bi-annual maintenance checks at a minimum.

When was the last time you had the electrics in your house checked? Every house I've moved into, the first thing I do after unpacking is pop the plates off every socket and light switch. It is rare not to find loose connections, pinched sheethes, etc, even on new build homes, let alone in a 60 year old house after generations of DIY 'upgrades'. All hidden behind a nice looking plaster wall.

There are plenty of examples to be found with an interweb search, and plenty more if you talk to an electrician.

Whether using 4mm or 2.5mm cables, the main issue with PIS and batteries is user ignorance. The point is that this is not just about what you plug in, it is about the state of your home wiring too - the stuff you cant see.


E.g. A proper EV granny charger plug should have a fuse and a thermister to limit plug heat, but again, what you order off TEMU might only look fine on the surface.

Even compliant granny chargers already cause hidden scorching damage to sockets (which are not rated for 10a continous loads for 8 hours plus - and also do not give off warning smells like the pre-1990's ones used to)

What if the PIS wis plugged into a double socket with the car? (I'm sure you can think of other examples!
Nothing exceeds mankinds seemingly boundless capacity for stupidity)

What if its a long ring circuit, with lots of high load items (plug in stove oven, microwave, kettle, car charger, porn server, etc, etc), all switched on at the same time. Each load is cumulative even if they are only drawing less than 10 amps each.

Without PIS that high cumulative draw will be detected by the mcb. With P-I-S it could be be 'situation normal' whilst the cables or arcing connections, or overstressed sockets burn out in the walls.

So people are using salvaged EV batteries as domestic.
https://www.ebay.co.uk/itm/363935804948?mkcid=16&mkevt=1&mkrid=711-127632-2357-0&ssspo=99q_olKrSsW&sssrc=4429486&ssuid=st4EeeKJQrm&stype=1&var=&widget_ver=artemis&media=COPY
@ £2.2K (make an offer) is the high capacity 42kWh final version of BMW i3; the 22kWh first version should cost a great deal less, but asking prices are all over the place.

Posted By: fostertomSo people are using salvaged EV batteries as domestic.

It's being sold as a replacement battery for an i3, not advertised at all for domestic use?

@WillInAberdeen you are missing my point, but it could be I'm not explaining my issue correctly.

My issue isn't with a single panel plugged in by someone who knows what to look for in a well maintained house.

The issue is with the general leval of stupidity/ignorance that can be applied by the masses in a typical older UK home.

Most homeowners cannot/wont fit a 16amp roof mounted system themselves. (However I have seen it done, with the inverter wired into a 13amp plug by someone who's brother 'knew what they were doing'...)

If you can pick up a 'balcony' kit with a plug on it from ALDI for around £50 anyone can have a go, and merrily plug in as many as they want. Anyone with an EV will want to charge it from the sun.

They won't read instructions telling them not to plug in more than 800w of pannels - most of those instructions will be in pictograms or Chinglish at best. And a plug does not need instructions for any living person born after WW2.

No-one has been able to plug a generator into their house before. Their only experience is with items that draw power - and they rely on all the little safety devices and wiring regs that have kept them safe over generations without any thought or imput required from them. And they still regularly manage to start electrical fires!

For a multiple PIS 'installation', the MCB WILL NOT see high draws as PV generation in the circuit will flow direct to the highest load. Each panel and micro inverter will be from a different manufacturer and won't communicate to maintain safety either.

(Hopefully they will at least cut out if voltage reaches above 266 volts due to multiple inverter ramping, but for something bought on Ali Express I wouldn't stake my life on it - and I have seen this occassionaly IRL even with reputable micro inverters)


Modern people get their knowledge from social media and do not apply critical thinking to any subject if an influencer can do that for them (most of them wouldn't even look at a site like this - communicating politely with real people is so last century :-) ).

They probably already think that PIS is allowed in the UK because they've seen the clickbait header...

Posted By: djhI'm asking if anybody knows what the up-to-date legal position is, and what the timescale is if they're not legal yet.

There's a chance that there may be something included in the Energy Independence Bill announced a couple of days ago, but if so it would probably only be some legislation allow the Government to make rules under secondary legislation at a future date, which likely wouldn't be any time soon.

Posted By: WillInAberdeen2.5mm2 is very common for radial socket circuits in NL and Germany in my experience living there.

2.5mm² and 1.5mm² are normal here in France too. Unlike UK radials they're limited to a certain number of sockets, not to a certain floor area.

Posted By: WillInAberdeenTheir 2.5mm2 radial circuit uses the exact same 16A MCBs that we see in UK for 2.5mm2 radials, it's a European Norm design.

AIUI standard domestic UK MCBs / RCBOs only cut the live pole of a circuit. In Europe (or at least France) they cut live and neutral to provide full circuit isolation with a 3mm contact gap*. Though there must still be older properties that use fuses.

*bonus: no need for switched connection units / isolators for fixed appliances.

Posted By: djhWhat I believe is that they are subject to the same anti-islanding provision as everything else. They only ever send power back the other way when there is mains voltage present where they're sending the power.

I seem to recall that that can be defeated by plugging in a second balcony solar panel; they each detect mains voltage from the other. Of course there should only be one, but...

Posted By: djhBiggest risk I can see with plug in solar is panels being dropped from a high rise block!

+1.

>>> defeated by plugging in a second balcony solar panel; they each detect mains voltage from the other.


I'd heard that one too but a few of the usual YouTubers tested it and it didn't work. Plug in solar uses a microinverter with a PLL to follow the frequency of the mains and stay at 50Hz. If you plug two microinverters into each other, neither generates a reliable 50Hz frequency so they quickly drift away from 50Hz and trip on over frequency.

It's no different from if you have 16 panels and a bunch of microinverters on your roof, if the mains goes off they all trip.

Posted By: djhActually it wasn't me that said that. @philedge did

Sorry!

Posted By: WillInAberdeen>>> defeated by plugging in a second balcony solar panel; they each detect mains voltage from the other.

I'd heard that one too but a few of the usual YouTubers tested it and it didn't work.

One less to worry about then :)