Do you really need 15kW? AC coupled inverters are 3-3.6kW and hybrids not much more than 5kW.

If you’re pulling 15kW, you’re going to need a big battery otherwise you’re going to drain it pretty quickly.

 

Sunsynk have just released 16kW single phase hybrid inverter which has 48 kW pass through, I'm buying the 8.8kW version. With a 3kW inverter if you put the kettle on it will switch to AC bypass, all your load will come from grid not battery. With a higher capacity inverter this does not happen. Going to start with one 15 kW battery and get another later.

 

Remind me, there is some allowance for 'micro' grid tied inverters, that you can just plug into a socket, is that correct?

And second question, do smart meters run backwards if you generate rather than use power?

 

No. They measure import and export separately.

 

Similar to what I’m doing just I’m doing it with VW golf hybrid modules.

Will be about £1500 for 8.8kWh

 

Just to confirm, you are dismantling the VW hybrid packs and using the modules with another BMS? Or have you hacked the VW controls?

 

Where are you getting inverter ? How safe is it ? How many cells do you need for 15kwh pack and how many of the battery boxes ?

Looks like potential to cause a big fire !

 

Lifepo4 is much more stable than other chemistries. The Catl cells are what I have in my Peugeot. 16 cells are needed for the battery. It all goes into one box. Does weigh 120kg when finished. I currently use around 12 kWh hours a day. Charging and discharging the battery between 10% and 90% gives me 12kWh of useable battery. Therefore all my consumption is at 7.5p and not 40p.

 

Have you received and built it ? The 320 cells don't seem to be in stock . Where did you get your inverter ? How long does delivery take ? It's interesting but no warranty support or come back you can get a circa 10kwh battery from UK supplier for £3200 and not have to build it. Not sure it's worth risk.

 

The inverter is from the UK. I'm about to order both. Batteries will take two months to get here. I've done a lot of DC battery stuff on boats. I regularly have a 48v Lifepo4 between my legs in the rain, on the ebike I built.

 

I've seen some tear downs of ready made battery packs and the quality is way below the DIY kit listed above. Also you don't have control over what cells they use. It is in their interest to use the cheapest possible. Repair is almost impossible with ready made kits. Stuff is often welded and glued in place. There are many complaints about failed Pylontech, the most popular ready made battery, warranty claims.

 

Batteries make more sense than solar as long as cheap rate available and day rate is current level or higher. Certainly at current solar pricing.

 

Interesting in hearing how you got on with this - did you order everything?

Where did you get the Sunsynk inverter from in the UK out of interest?

 

Where did you get the Sunsynk inverter from in the UK out of interest?

ITS Technologies sell them. Also Dragons Breath Solar (but very overpriced from there and also won't sell unless you order some of their very overpriced batteries with it).

 

Docan are one of the few reliable battery suppliers on Alibaba

If you prefer to buy from the UK, Fogstar are reasonably priced - especially if you use the wholesale site. Saves the hassle - I seem to remember they've got new stock coming in the middle of October. They will also top balance the cells for a small charge so you can avoid having to buy a big PSU you will use once and waiting a week whilst you do it.

The case is nothing special - you could skip it, make something out of ply and buy a bms separately.

 

If you prefer to buy from the UK, Fogstar are reasonably priced - especially if you use the wholesale site. Saves the hassle - I seem to remember they've got new stock coming in the middle of October. They will also top balance the cells for a small charge so you can avoid having to buy a big PSU you will use once and waiting a week whilst you do it.

Been following a few threads on these Seplos units and EVE cells, debating whether to jump in or go Pylontech etc.

Noticed Fogstar have a 15% off today - NOVEMBER4 - so it brings the 16 cells to 1700+VAT which is not hugely more expensive than getting them from Alibaba suppliers, so I've decided to go for it.

 

I'm very interested in buying a battery system to store off-peak energy which can be used during the day. I think I would need about a 25 kwh battery to have sufficient capacity with a bit of headroom. I'm also not interested in getting solar.

On another thread, there was a lot of talk about the need to inform the electricity board if you have an inverter over 3.7kw. OP - did you decide you could comply with that regulation as I think on another thread you were concerned it might be difficult to get approval?

 

I'm very interested in buying a battery system to store off-peak energy which can be used during the day. I think I would need about a 25 kwh battery to have sufficient capacity with a bit of headroom. I'm also not interested in getting solar.

On another thread, there was a lot of talk about the need to inform the electricity board if you have an inverter over 3.7kw. OP - did you decide you could comply with that regulation as I think on another thread you were concerned it might be difficult to get approval?

I'm not the OP but it was a very easy process to get approval for my 5.5kW inverter. I made the application to the DNO myself and the approval came back in less than 24 hours.
25kWh is a huge system. You don't need "headroom" it's actually more cost effective to slightly undersize. No point paying for capacity you will never use.
I've installed 15kWh and haven't used a full charge yet, lowest SOC I've got to is 21%, but I'm usually at 40-odd when it starts charging will increase a little in winter.
Like you I don't have solar, this is just charging at cheap overnight rates.

 

If you want 25kwh you may need parallel systems - you’ll struggle to fully charge 25kwh on 4-5hrs off peak

 

You could be right, as this is a topic I'm only just starting to learn about. When I charge my car, it gets 6.6kw so 4 hours off-peak charging should be sufficient to charge a 25kwh battery. Which is why I was interested if the inverter in a home battery storage system used to charge the battery was the same as the inverter used to discharging it. As, if it was much less powerful than 6.6kw, it wouldn't be sufficient.

 

...I looked at buying UK ready built batteries. Cheapest I could find were £1600 for 5.1kW. Then looked at Alibaba, managed to find good quality 5.1kW ones from a reliable manufacturer for £1000 tax and shipping included. I was about to buy these when I came across the Seplos 48v 280 to 300ah self build kit for $600 taxes and shipping included. You can buy 16 48v 300ah Lifepo4 cells for $1600, shipping and tax is $350, add another $100 for credit card fees. The total cost of a self built 48v 300ah 15kW battery including case, BMS, 400A fuse and cells is £2300. The total build time is around 3 hours and very hard to get wrong. The BMS will communicate with most inverters. If th

I'm based in the UK too, and I'm looking at battery storage, but I'm wondering about the prices you have quoted for a self build.

This chap below has made quite a few videos and has taken apart most of the popular 'server rack' batteries. His conclusion seems to be that the difference in cost between building your own battery pack and buying an assembled server rack with BMS etc is now minimal, once you compare cells on a like-for-like basis And whilst the prices below are for the US it seems for high quality Lifepo4 cells in a server rack you are paying around $300/kwh. So probably around £300/kwh once here in the UK. Whereas, if I understand your quoted prices correctly, you're estimating the total price of your assembled pack will be less than half that price per kwh. Just wondering if I'm missing something?

ETA : Just added a youtube link from a chap in the US who seems focused on the cheapest possible self-build battery systems - he also used Docan cells (and he is quoting prices per Ah and prices from 2021 whereas I assume current prices are higher), but his prices for the Docan cells would look to be around $150/kwh and that is before shipping, tax and any inflation since last year).

2nd ETA : Looks like Docan are now selling cells in the 'server rack' form factor (link below). Based on another thread for import to the US, a 20kwh battery of 4 would costs as follows:

Item value: 1280*4= USD 5120
Shipping cost: USD 948
Total: USD 6068
Alibaba trade assurance fee: USD 134
Totally: USD 6202

Assuming import costs to the UK are similiar, it would make the cost per KWH still about £300/kwh.

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On my boat I have 5kw of solar and 46kwh of batteries currently they are devided into 36kwh @ 72 volts for electric drive and 10kwh @ 24 volts for domestic use. Shortly I am trying an experiment, I will put all solar onto the drive batteries and use a 72v to 24v 1kw converter to charge the domestic bank. its in an effort to reduce switching panels from one to the other. Winter can be tight on power so this will give me a bigger capacity. I do have a 6kw generator as backup but dont like to use it.
Batteries are all Valance and are LifePo4s with an addition of something

 

My batteries from Fogstar have arrived, Seplos BMS/case arrives mid-jan, time after Christmas to try to top balance them in readiness.

Still trying to decide whether to go with Solis AC Inverter @3kW, (£720) or Sunsynk Hybrid @5Kw (£1200).

 

Still trying to decide whether to go with Solis AC Inverter @3kW, (£720) or Sunsynk Hybrid @5Kw (£1200).

Batteries took 2+ weeks to balance - but done now.

I've been let down by CEF on Sunsynk inverter and now being told end of Feb, which also might come and go.

I'm tempting to go back to cheap option of Solis AC 3kw, and look to sell and switch out after a year or so of use when I know what I might want.

For reference, I will have Solar on a non-hybrid Solis which I can't change now to hybrid now, so this is an additional inverter. I liked the idea of Sunsynk hybrid to enable full charge on Octopus Go, especially if I go to 30kWh of battery in future. The Sunsynk also seems more capable in terms of software. Is there anything I can/can't do with an AC inverter vs a hybrid? Any views welcome to help me choose one or other...or any other brand (easily in stock) should I consider?

 

Seplos Battery case arrived from China via DPD, very solid.

I decided on the Sunsynk hybrid 5kW, partly as it seems like you can monitor it better (@robert79 posts), partly as I am not sure how much I will want to expand this system with an additional battery to 30kWh. We currently use around 10kWh/day but we haven't done our full refurb yet and can see that increasing even without electrical loads like heat pumps/electric DHW. 5kW will at least give us more scope for 4 hrs Octopus Go period.

Next job, top balance cells before assembling Seplos box, and in parallel install the Sunsynk with electrician so it's ready for battery connection.

 

5kW will at least give us more scope for 4 hrs Octopus Go period.

Does it definitely charge at 5kW? Hybrids are often marketed at the combined solar and battery discharge power.

Worth keeping in mind if you go over 3.5kw inverter you will need DNO consent unless you are off grid only.

You need DNO consent to connect any power generating equipment. The 3.5 (actually 3.68kW) limit is just a different process between G98 and G99.

 

I am getting Sunsynk 8kw Inverter and 15kw battery installed 23rd / 24th. Feb..it's well regarded kit the inverters and batteries have a 10 year warranty. It's also has integration with octopus tarrifs agile etc apparently.

Worth keeping in mind if you go over 3.5kw inverter you will need DNO consent unless you are off grid only.

 

Have you done a payback calc? And have you got solar? Am really tempted by this.

 

Solar is being installed with it. 16 x400w pure black panels all have Tigo optimisers. It's a 6.4kw system. I am also going to add another 4 panels to garage in pretty short order either 4 more 400w matching panels of could fit four 540w panels on there. I need to talk to installers to see if that's possible with the optimisers or if it's better for system performance to stick to all 400w panels. I think the optimisers are good for 25% variation in panel generation but I don't know enough about this stuff really.

Yes there is a payback calculation. Really it depends where the energy prices go but also how much of my heating I move onto electric. I already started using IR heating panels pretty extensively this winter they work very well.

It will probably be a heat pump of some sort eventually or a combination.

Also moving hot water heating to the immersion on the mega flow. At current gas costs that save around £750 a year with my system boiler heating it. If you did all your hot water on solar - unlikely but large proportion with rest off peak electric.

At current prices and consumption would be 6 - 7 years payback. With all water heating / more electric heating would be less than that.

At pre Ukraine war prices payback would be - never or a long long time. So I guess it depends where energy prices go. There is more to it than payback though. There is islanding, self sufficiency and it's a good thing to do environmentally. It's also going to give a decent bump to my house EPC it's not an energy efficient property I have done most of what can be done cost effective wise improvements anyway. At the minimum it will make the house more attractive to a buyer with the EPC improvement/ free / cheap energy.

As someone said in another thread you don't buy a kitchen and expect there to be a pay back and you don't need a new kitchen you just want one. I am comfortable with the economics of it.

 

Yes the installers did ours it took three months to come through. They are taking longer than normal currently. In our area anyway.

 

Thanks

 

I've been speaking to Seplos, as I was looking at buying 5 more boxes for my warehouse this time, interesting quote on fully assembled packs:

About 48V 280Ah battery packs,we have two types:
DIY 48V 280Ah battery packs we have 200A BMS(assembled battery packs,it's with GFB grade A cells)=2700USD/pcs
①we will provide 10 years warranty
②we will provide manufacturers full testing spreadsheet with matching serial numbers for each cells


DIY 48V 280Ah battery packs we have 200A BMS(assembled battery packs,it's with A- cells)=2000USD/pcs
we will provide 5 years warranty

The latter one is tempting, CATL cellls I guess Grade B in reality. These would not ship DDP well for consumer purchase, but if shipped by sea then not a huge amount - I estimate about $200 extra per unit door to door. I'd have to pay VAT and duty, but that's fine for the business as I can claim back. £1800+VAT for a pre-assembled 15kWh battery seems good.

 

A you tube battery/ inverter reviewer I follow reviewed b cells .He seemed to think most have been heavily used and are from EVs, vans etc and have been cycled 50% of their life capacity already at least. Hence common distortion commonly seen on these cells. He was saying calendar degradation will kill batteries before cycling does though probably. He has a 30kw battery storage using b cells rack he charges off solar and uses to charge his EVs.

I am interested to see how you get on no doubt these things are cheap. I guess at these prices they don't have to last long. Post some pics when you have it built and installed.

Assembled boxes is preferable to self assembly. They are offering a 10 year warranty but is it worth anything really with no UK based operations?

 

Just fit an Eddi? Interested to see how your battery pack does post some pics !

This guy has built one of these and building another getting rid of his pylontech batteries

Page 4 | My experience with the Selpos Mason DIY kit

Page 4 | My Seplos kit arrived last week and I've put it all together with some Xuba 280ah cells. I thought I would give some insight and some picture...

renewableheatinghub.co.uk

 

Just fit an Eddi? Interested to see how your battery pack does post some pics !

Well, an Eddi costs money Seriously, I haven't got it all installed yet so can decide later, and the Flux tariff we've all discussed throws a different light on it all anyway, so the approach might change.

This guy has built one of these and building another getting rid of his pylontech batteries

Page 4 | My experience with the Selpos Mason DIY kit

Page 4 | My Seplos kit arrived last week and I've put it all together with some Xuba 280ah cells. I thought I would give some insight and some picture...

renewableheatinghub.co.uk

Yes, that's one of the guys I've been following, along with the Off Grid Garage guy in Australia. Lots of info, but a pretty much all over the place.

I'll take some pics of the battery and inverter when I put it together in the garage hopefully next week.

 

The thing with Eddi is once setup you forget about it. You could probably setup some sort of timer yourself for when there is reliable excess production. It just sits in background a d does everything for you. I thought about managing myself. Looking at people who have gone down this route they all ended up installing an Eddi. For the money it's not worth the hassle.

By all accounts you get free hot water with a decent sized array most of the year our system boiler is no efficient for heating the water it's cost £600 - £700 a year at current gas prices. So Eddi will ay for itself in a year