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On-grid domestic battery storage

edited 30 November -1 at 1:00AM in Green & Ethical MoneySaving
1.8K replies 199.2K views
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  • Davo456Davo456 Forumite
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    So, I have a 3KwH solar array which I've happy with.

    Would something like this, make economic sense ?

    ok, its not as pretty as the Tesla ones, but I think I could mount it quite easily in the loft perhaps.

    I haven't found any real feedback on the company or the equipment on-line, and it does seem quite reasonably priced ? or is it too cheap to be any good ?
    Any feedback would be much appreciated.
  • Martyn1981Martyn1981 Forumite
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    Davo456 wrote: »
    So, I have a 3KwH solar array which I've happy with.

    Would something like this, make economic sense ?

    ok, its not as pretty as the Tesla ones, but I think I could mount it quite easily in the loft perhaps.

    I haven't found any real feedback on the company or the equipment on-line, and it does seem quite reasonably priced ? or is it too cheap to be any good ?
    Any feedback would be much appreciated.

    Hiya and welcome.

    Can I first caveat myself by being a teeny weeny bit rude, but as you are a new poster, can I just check you have nothing to do with this company?

    I'm only being cautious as I don't want to be tricked into appearing to endorse something .... but .... I also thought it looked quite interesting, so many thanks.

    I'll add the links:
    Home Switch
    AC Battery Storage Systems
    ME 3000SP Inverter Data sheet - see bottom of page

    This appears to be a DIY install with step by step instructions - no idea if this is easy or not.

    I also note the packages go up in price by the same cost as the battery unit, so I suppose you could add on later, rather than 'risk it all' at the start.

    Prices look good, eg 7.2kWh is roughly half the size and price of a Tesla PWII, before install costs. But whether it would payback is still questionable until prices fall in the future.

    Maybe one to watch, I'm really not sure myself, but certainly interesting, but I wouldn't want to be the first to jump! :undecided

    But thanks again, certainly an interesting read and interesting idea/prices.
    Mart. Cardiff. 5.58 kWp PV systems (3.58 ESE & 2.0 WNW)

    For general PV advice please see the PV FAQ thread on the Green & Ethical Board.
  • Davo456Davo456 Forumite
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    Hi Martyn,

    I can confirm I have nothing to do with this company, other than being amazed by the low price.
    And that's why I was thinking there was a catch!

    I was actually looking at DIY power walls made by 420+ 18650 cells - maybe that's just my engineer background shining through, when I saw someone mention the Hoemswitch LifePo batteries were cheap.

    I tried to find reviews, and also a forum where anyone else had discussed this and that's how I came across this thread.

    Spoke briefly to them yesterday, and they have sold around 1000 to date, and its expandable - so people have started with 2 batteries, and move to 5, one at a time.

    One thing I am curious of, the unit only seems to supply 13A back into the house fuse board - I'm sure that's what he said, so its not a way of running your house.

    With the 4.8kwh battery, 6000 cycles, I think it works out at about 7p/kwh which I think is close to what we pay now with EON for normal supply - I need to check this.

    Other thing I was amazed at, is you don't need to be MCS registered to do this. So a basic electrician with Part P should be able to do it for you,
  • Martyn1981Martyn1981 Forumite
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    Hello again.

    I've watched a few things on Youtube, but a lot goes over my head. This article has the story of a battery build using a written off Leaf batt, very yum yum!

    See from reply #20 August 17 2014

    Hadn't spotted the 6,000 cycle claim, that is interesting, but their warranty is 5yrs and links back to China. Doesn't mean it's no good, but I'd personally want to wait till the warranty was stronger, perhaps a bigger UK name. Seems harsh but you need the longevity to get your money back.

    I don't think it's 7p, as you can only use 90%, but 80% is probably a safer max (maybe less, by building in some redundancy by going a bit bigger again).

    So £2,274 / (6,000 x 4kWh) = 9.5p/kWh, ignoring lost interest etc. Or 7.5p/kWh for the 7.2kWh package.

    The limit on return is down to the inverter which is 3,000W AC, though it does say "1.5*Pnom ,10S; 1.2*Pnom ,30S"

    I'm not sure what that means, is it 4,500W for 10 seconds & 3,600W for 30 seconds?

    I'm wondering because a while back I mentioned that you may need DNO approval, which I couldn't understand, then it was pointed out to me, that if the battery/inverter can discharge more than 3.68kW, then theoretically you could export more than 3.68kW, hence the approval of the DNO ..... even though you don't want to export from the battery (unless being paid to do so?)


    I certainly think it's interesting and very promising for the future. My main concern is the warranty, and as it dawned on me a few posts back, the warranty may be an easier way to reach economic viability than falling prices, for example:

    I can save about £120pa from reduced leccy import savings and £30pa by then being able to switch to a no-standing-charge account. So a 10yr warranty gives me £1,500 to play with, but a 20yr warranty gives me £3,000 to play with, even though it may be the same battery, same cycles etc.

    More interesting, my personal example is based on 4kWh useable, so fits the 4.8kWh offering on the site. So we see that at £2.3k it doesn't work on 10yrs, but does work on 20yrs, using my rather unfair current mental rules.

    This is good fun!
    Mart. Cardiff. 5.58 kWp PV systems (3.58 ESE & 2.0 WNW)

    For general PV advice please see the PV FAQ thread on the Green & Ethical Board.
  • ASavvyBuyerASavvyBuyer Forumite
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    Martyn1981 wrote: »
    I can save about £120pa from reduced leccy import savings and £30pa by then being able to switch to a no-standing-charge account. So a 10yr warranty gives me £1,500 to play with, but a 20yr warranty gives me £3,000 to play with, even though it may be the same battery, same cycles etc.

    The Home Switch system looks interesting:
    Home Switch
    AC Battery Storage Systems

    Looking at the info on the 2.4kW model (for about £1.5k) I reckon we could save about £100/year on reduced leccy import (including the standing charge, as they tend to break even at around 1,000kWh/year, with the much higher unit rate for no standing charge tariffs).

    We would still need to import during the winter months, as our generation in low then, so not likely to reduce it even further, even with a bigger model.

    That works out as taking about 15 years to break even (assuming inflation & lost interest cancel each other out).

    So a 5 year warranty, and needing to pay for returning it to China if it fails in that time, does not seem to make it economically viable for us.

    Think it needs a longer warranty supported from the UK, or a much lower price to start making economic sense, for us.
    4kWp, W roof, 30° pitch, Solar Edge Inverter + Optimisers. South Wales Valleys, Installed Aug 2015. Octopus Agile Electric Tariff.
    Solic 200 Diverter, Toshiba Ultra High Efficiency Air Conditioner/Heat Pump, Kia Soul & Renault Zoe EV's.
  • theboylardtheboylard Forumite
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    Couple of bits in this piece concern me, but I'll wait for those that know way more than I do to comment?

    Questions economic benefit of home battery storage, or not as the case may be?
    4kWp, SSE, 16 x 250w EcoFuture BoB with retro-fitted SolarEdge P300 optimisers & SE3500 Inverter, in occasionally sunny Corby, Northants.
  • Martyn1981Martyn1981 Forumite
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    Electricity imported - 94kWh (123kWh in August 2016)
    Generated - 309kWh ( 326kWh in August 2016)
    Battery discharge - 93.91kWh
    ImmerSUN diversion - 47.64kWh (95kWh in August 2016)

    Bit of context - we were away on holiday or the first week of August, and then the kids were away from home for another 10 days, so probably our electricity and hot water demand were a bit lower than typical. Again shy of 100kWh/month, and if I average across the 9months of install so far I'm avoiding importing 73kWh/month. At current electricity import prices this battery will take at least 10 years to recover its costs - which is longer than the warrantied life-cycle of the batteries. Starting to feel like an expensive and futile experiment! Certainly feeling like a 4kWh battery isn't quite big enough for my daily usage, probably 6kWh would be a better size.

    Maybe I should look again at variable-rate tariffs and perhaps consider an additional night-time charge-up on an economy7-type cheap rate?

    for context, the battery here is an 8kwh lead acid, hence the short life expectancy, though the unit is fully upgradeable, so bigger and better batteries can be swppoed in at a later date.

    so 'taking one for the team' seems to apply here as we all learn from this experiment.
    Mart. Cardiff. 5.58 kWp PV systems (3.58 ESE & 2.0 WNW)

    For general PV advice please see the PV FAQ thread on the Green & Ethical Board.
  • Martyn1981Martyn1981 Forumite
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    STA points to ‘obvious flaws’ in battery degradation study
    The battery degradation model used in the study was developed after tests were carried out on LiNiCoAlO2/C6 18650-type cells, meaning a Lithium Nickel Cobalt Aluminum Oxide battery was used. The STA has stated this chemistry is not suitable to use in this application as it has a "low number of discharges", adding that its “short lifecycle and rapid degradation rate is well understood”.

    “For domestic solar PV applications, a battery that can discharge over 10,000 times is needed (like Lithium Phosphate or Lithium Titanate). Fundamentally the study seems to show us what the industry already knows - that choice of battery is vital and this is not a suitable battery for a PV installation,” the statement adds.

    personally i'm shocked at the marriage choice of a 4kwp system and a 2kwh battery.

    what little i've learnt so far suggests that oversizing the battery is sensible to reduce dod, rate of discharge, and to build in some spare capacity for later years as batt capacity falls. there's also an economy of scale issue too.

    to start with such a small battery seems to be asking for trouble.
    Mart. Cardiff. 5.58 kWp PV systems (3.58 ESE & 2.0 WNW)

    For general PV advice please see the PV FAQ thread on the Green & Ethical Board.
  • Martyn1981Martyn1981 Forumite
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    like buses, 3 posts come along at once.

    Suns, E3 / DC, Senec and LG Chem dominate German residential PV storage market
    Nearly two-thirds of all solar storage systems sold in Germany come from these four suppliers. According to EuPD Research, about 16,800 photovoltaic storage systems were sold in the country in the first half of the year. Falling prices and an attractive rooftop market are driving demand upwards.

    of interest to me is that the battery subsidy is actually quite small at 19pc for the period reported, and 16pc from 1st july.

    or looking at it another way, the grid benefits from large amounts of storage, but avoids 81pc to 84pc of the cost, and doesn't have to provide locations either.

    too simple, too obvious, and too cost-effective for a uk scheme perhaps?
    Mart. Cardiff. 5.58 kWp PV systems (3.58 ESE & 2.0 WNW)

    For general PV advice please see the PV FAQ thread on the Green & Ethical Board.
  • NigeWickNigeWick Forumite
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    theboylard wrote: »
    Couple of bits in this piece concern me
    How many batteries used in the research? Who funded it? Since Nissan have had their used Leaf battery for home storage scheme, they allegedly haven't had enough batteries from vehicles to cope with any demand. Then there's the research suggesting that V2G battery use increases the life of vehicle batteries.
    The mind of the bigot is like the pupil of the eye; the more light you pour upon it, the more it will contract.
    Oliver Wendell Holmes
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