DIY Battery/Solar installation..

Malt_Vinegar

Malt_Vinegar

Malt_Vinegar

Don
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CliffsNotes - I am looking to build a battery system for my house, then perhaps add a solar array to it later, but I want to do it DIY.. As much as possible....


Background - I have had a couple of Solar quotes recently, and am not impressed with the "Value" they provide. Upon looking up the costs of the parts alone, there does seem be a very significant mark-up being charged, and Labour costs seem somewhat crazy for the work actually being done. Which means that pay-back times are 2-3 times longer than if you were to DIY the system.

We typically use about 8000-10000 kwh in a year, which I think puts us in quite a heavy user bracket.

So, with that in mind, I am planning a DIY option with an Inverter and Battery first with a DIY install. Then later when I have the system up and running, add solar power once I have got things running properly. I can then use a night rate to charge my battery, and use this during the day to offset some of my electricity costs, before then topping this up with solar if I do add it eventually, or add a second battery. This will all depend on how things are going with usage after the first battery is in and I have some data on how it is affecting any overall usage/bills.

I wish to use a battery kit like this:
www.fogstar.co.uk

SEPLOS Mason 280 and x16 Grade B Envision 305Ah Battery Bundle

Our Seplos Mason battery bundle contains everything you will need to create a DIY 48V 14.3kWh battery. As part of this bundle you’ll receive a SEPLOS Mason 280 kit and 16 Grade B Envision 305Ah LiFePO4 cells with the SEPLOS Grade B Busbars.
www.fogstar.co.uk www.fogstar.co.uk
Which should give me over a 15kwh battery for about £1500.

I believe that I will then need a 5Kw Hybrid inverter, which I am shopping for currently. (I am budgeting as close to £1000 for the inverter+parts+sparky final connection/sign-off)

So, all in costs for the initial system would be around £2500, and the closest systems I can find online are all upwards for £7000 for similar systems without solar. So, pay-back would be much sooner!

Has anyone else got experience with this?

It seems that MCS is not needed for solar installations anymore to qualify for being paid for excess, which is great, so I will look to do that once(if) I go solar, and will also do the G99 (as its over the 3.6 limit for G98) application to the DNO myself before the installation starts, and after I know the manufacturer/models and specs of all the kit I intend to use.

As far as I can tell, the only part of the work that HAS to be done by an electrician is the final connection to the board, provided I follow Part P for anything I do, it should not be an issue! I did the wiring for a shed in my old place, followed part-P and got it all inspected/signed off/final connections done by a sparky, and paid him some moolah to do this.


It does seem that DIY for solar/battery is becoming a lot more common, and the MCS accreditation (now correctly!) not being enforced on applications to providers for feed in rates should mean it is a lot more accessible provided you are willing to do the paperwork!
 
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Also watching for the domestic batteries; I'm in a townhouse with other dwellings above me, so solar is out, but I do have cheaper overnight power - so the temptation to get a home battery to run more daytime stuff on the night rate is incredibly high.
 
A friend of mine set something up himself but used 2nd user forklift truck batteries (They had loads of space - farmers) I must find out how the project went. Interested in something like this myself, but cant afford loads of space.
 
Inverter prices seem to be all over the place, but I am thinking something like this:
batterygroup.co.uk

Fox H1 5kW Hybrid Inverter G2 - FE-H1-5.0-G2

Fox H1 High Voltage 5,000W Single Phase Hybrid Inverter with Dual MPPT - FE-H1-5.0-G2 The Fox H1 5kW Single Phase Hybrid Inverter is a high…
batterygroup.co.uk batterygroup.co.uk
With the extra costs of hardware and signoff. may need to up the budget a little bit for that kit!
 
Just a note in regards export. I believe it is still true that Octopus (running a trial) are the only ones who will pay export without MCS cert.

The suppliers seem to have taken MCS as a shortcut in that it provides proof of complying with ISO17065. Ie they just shortcut it.
The ISO is whats actually required to comply with the requirements for SEG that OFGEM specify.

This could be out of date, its an ever evolving thing.
 
Malt_Vinegar said:
Inverter prices seem to be all over the place, but I am thinking something like this:
batterygroup.co.uk

Fox H1 5kW Hybrid Inverter G2 - FE-H1-5.0-G2

Fox H1 High Voltage 5,000W Single Phase Hybrid Inverter with Dual MPPT - FE-H1-5.0-G2 The Fox H1 5kW Single Phase Hybrid Inverter is a high…
batterygroup.co.uk batterygroup.co.uk
With the extra costs of hardware and signoff. may need to up the budget a little bit for that kit!
Click to expand...

That inverter and the pack you've linked aren't compatible (your pack is 48v and the inverter wants 80v - 480v), also it seems limited to 40 amps on the battery connection so to achieve 5kW charge/discharge from battery you'd need a pack around 125v. (Someone with more knowledge might find other things with the spec though, i'm not that knowledgable having only started looking into it recently)

I'm assuming you need full whack on importing to battery given your usage is around 25kWh a day, and you've speced a 14kWh pack. So it'll be emptied everyday and to fill it at night on the cheapest rates you'd need a good 3 hours at full pelt.

Personally I can't get the maths to add up for my situation even on a self install battery only. It would take nearly 10 years payback since we only use about 12kWh a day at an average cost of about 14-15p per Kwh. Factoring in purchasing at 7.5p thats only saving a £1 a day. At the 10 year point I think you need to factor in replacement of most of the parts. I'd be better off just banging the capital instead into S&S for a 6% return
 
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Gammawolf said:
That inverter and the pack you've linked aren't compatible (your pack is 48v and the inverter wants 80v - 480v), also it seems limited to 40 amps on the battery connection so to achieve 5kW charge/discharge from battery you'd need a pack around 125v. (Someone with more knowledge might find other things with the spec though, i'm not that knowledgable having only started looking into it recently)

Personally I can't get the maths to add up for my situation even on a self install battery only. It would take nearly 10 years payback since we only use about 12kWh a day at an average cost of about 14-15p per Kwh. Factoring in purchasing at 7.5p thats only saving a £1 a day. At the 10 year point I think you need to factor in replacement of most of the parts. I'd be better off just banging the capital instead into S&S for a 6% return
Click to expand...

Thanks! I am still just shopping around for ideas, prices, and not done any specific checks yet, but I will always check specs before I pull the trigger :D
 
Gammawolf said:
That inverter and the pack you've linked aren't compatible (your pack is 48v and the inverter wants 80v - 480v), also it seems limited to 40 amps on the battery connection so to achieve 5kW charge/discharge from battery you'd need a pack around 125v. (Someone with more knowledge might find other things with the spec though, i'm not that knowledgable having only started looking into it recently)

Personally I can't get the maths to add up for my situation even on a self install battery only. It would take nearly 10 years payback since we only use about 12kWh a day at an average cost of about 14-15p per Kwh. Factoring in purchasing at 7.5p thats only saving a £1 a day. At the 10 year point I think you need to factor in replacement of most of the parts. I'd be better off just banging the capital instead into S&S for a 6% return
Click to expand...

Have you calculated what you'd get paid for exporting? I'm all electric at home, cooking and water, run an ev (15k miles PA so charging almost every day). Last month my electric bill was £160 income / profit.
 
Gammawolf said:
That inverter and the pack you've linked aren't compatible (your pack is 48v and the inverter wants 80v - 480v), also it seems limited to 40 amps on the battery connection so to achieve 5kW charge/discharge from battery you'd need a pack around 125v. (Someone with more knowledge might find other things with the spec though, i'm not that knowledgable having only started looking into it recently)

I'm assuming you need full whack on importing to battery given your usage is around 25kWh a day, and you've speced a 14kWh pack. So it'll be emptied everyday and to fill it at night on the cheapest rates you'd need a good 3 hours at full pelt.

Personally I can't get the maths to add up for my situation even on a self install battery only. It would take nearly 10 years payback since we only use about 12kWh a day at an average cost of about 14-15p per Kwh. Factoring in purchasing at 7.5p thats only saving a £1 a day. At the 10 year point I think you need to factor in replacement of most of the parts. I'd be better off just banging the capital instead into S&S for a 6% return
Click to expand...

Where are you getting 14-15p average elec price from?

@Malt_Vinegar make sure you check the DOD as well. The useable will be lower than the pack capacity, not sure if you know this, don't think I saw you mention it.
 
john_smith said:
Have you calculated what you'd get paid for exporting? I'm all electric at home, cooking and water, run an ev (15k miles PA so charging almost every day). Last month my electric bill was £160 income / profit.
Click to expand...

That's different though, the thread is mainly about a battery only system, which i've also thought about hence a summary of those calcs. Export plays such a minor part due to the thin margins left after buying it. Then you have sizing issues on batteries and inverter trying to save/dump into the grid at favourable times while keeping capacity for yourself.. ofc the calculation is totally different when you include a generation element throughout the day at 15p.

Mercenary Keyboard Warrior said:
Where are you getting 14-15p average elec price from?

@Malt_Vinegar make sure you check the DOD as well. The useable will be lower than the pack capacity, not sure if you know this, don't think I saw you mention it.
Click to expand...
I'm on agile with no solar/battery and thats what i've been achieving on my bills. Last month was 13p but that was unusually low, its usually 14-15

SKuE9ar.png
 
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ok, I am on agile as well and mine was 9p import and 15p export
I don't overly game it but because I have panels, I use grid when its <15p so I export more at 15p

Edit, just realised I forgot to take into account powerups, when I get free power, thats charged and then credited back later.
So the 9p units included powerups, which are always in day and typically can have costs above 15 even.
The credits for June powerups (my bill is 1st to end of month) was just under £15.
 
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@Malt_Vinegar take a look at my build thread if you want to see what's possible.

Ronski's Solar & battery DIY build with whole house backup

We already have 4kw of solar on our house roof, which was installed in December 2015, this is comprised of 16 panels witha Solaredge inverter and optimisers, and uses the best two roof's of the house. As some of you might be aware on the solar thread I've been looking into getting an additional...
forums.overclockers.co.uk forums.overclockers.co.uk

You'll want a hybrid inverter that's 48v nominal, which is roughly 42v to 56v. You also need to consider how flexible you want it to be, how easy it is to program to charge at certain times, to force discharge etc. Over the winter I earned £200 from saving sessions, last year my gas & electric bill was minus £400, this year it currently stands at £71 in total for gas, electric and standing charges. Rates are lower now so I won't be as profitable as last year. Oh, I also have a load of solar.

Another thing to consider, especially for a battery only system is how quick you can charge the batteries, I have 29kWh of storage and 8 kW inverter, so in the 3 hour flux window can only charge 24 kWh of energy or there about.

PS. I thoroughly recommend Victron, but you'll need a bigger budget.

Mercenary Keyboard Warrior said:
@Malt_Vinegar make sure you check the DOD as well. The useable will be lower than the pack capacity, not sure if you know this, don't think I saw you mention it.
Click to expand...

These batteries can be 100%, but its not worth it, there is so little stored energy at the upper and lower limits its just not worth stressing the cells for it. But its up to the user to set the limits in the inverter and the BMS. Cell voltages can range between a minimum of 2.5v up to a maximum of 3.65v, which for a 16 cell pack gives 40v to 58.4v operating range.

I have mine set to stop using the battery at 10% SOC unless there is a grid failure, but the hard limit is when the battery reaches 46v, which is 2.87v per cell, and I charge to 56.25v, which is 3.51563v per cell.

I'm not sure what my useable capacity is, never bothered testing it, but its lots :D
 
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@Ron-ski @Malt_Vinegar

I was intrigued in the classification into ABC cells.

The Bs dont sound super reliable which could be why they have such a discount vs A grade.
Tagging ron as he may have more info.

This was what I base the above on
evreporter.com

Lithium-ion cells - A grade vs B grade • EVreporter

Know the differences between A Grade and B Grade Lithium-ion cells in terms of performance parameters and cost.
evreporter.com evreporter.com
 
I've not heard of that, the main thing is to buy from a reputable supplier, buying cells direct from China can be a lottery, hence why I bought from Fogstar, I also went for grade A as I could afford them and in theory A should be better than B, but it doesn't seem publicity known why they are graded B, so I've no idea what the difference is.

Some sellers will relabel cells, so you do need to be careful.
 
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