DIY Powerwall / Battery

[johnb80]

This is an excellent thread, John. Food for thought. Plus Sideways excellent thread, I'm seriously thinking about doing something similar. I have the Emporia energy monitor and have access to a wealth of data over the year(s) which should give me a good idea as to what size 'battery' /system is needed.

One thing I don't understand is right up there at the start, your first system, you said your available power dropped to 3KW. I don't understand that bit....why the drop ?

When I was getting quotes for a system I avoided the ones that came back with a 3.6kW inverter because that isnt enough, nowhere near. Switch on the kettle and toaster you'd be importing power from the grid. The quote I chose told me it had a Growatt SPH6000 6kW inverter which it does What I had not seen and it seems standard on all of the Growatt SPH series of inverters is the maximum output when fed from batteries is 3kW. I was most annoyed when I found out about this, it was clearly in the specs of the equipment on the quote, I just hadnt spotted it. Due to this, a shortage of inverter power at crucial times and the need for more storage I embarked on this AC coupled battery setup I've done. If I were to have time over again, I wouldnt bother with Solar PV just inverter and batteries on a good EV tariff.

 

[woodieallen]

....If I were to have time over again, I wouldnt bother with Solar PV just inverter and batteries on a good EV tariff.

You are speaking to the converted !

Still seriously impressed by the quality of your workmanship. And analysis and approach. Proper job, mate

 

[Sachakins]

MCS is a necessity IMHO. Unlike you, many don't have the technical capacity or knowledge. OK, if its their own life in their hands, but not others and certainly not the next occupier.
To me it's akin to the gas safe registe. I can envisage many insurance companies ducking out of claims for none MCS Installations. Just my observation.

 

[Ollie78]

MCS is a necessity IMHO. Unlike you, many don't have the technical capacity or knowledge. OK, if its their own life in their hands, but not others and certainly not the next occupier.
To me it's akin to the gas safe registe. I can envisage many insurance companies ducking out of claims for none MCS Installations. Just my observation.

Octopus no longer require MCS certification for their tarrifs. You can still get niciec cetificates for the electrical safety of everything.
As long as it is inspected and certified by an appropriately qualified electrician then I can`t see a problem.

 

[Sideways]

MCS is a necessity IMHO. Unlike you, many don't have the technical capacity or knowledge. OK, if its their own life in their hands, but not others and certainly not the next occupier.
To me it's akin to the gas safe registe. I can envisage many insurance companies ducking out of claims for none MCS Installations. Just my observation.

But if you do have the knowledge, there should be a way.
MCS is just an approval scheme to try and set a minimum standard. Some of us want work done to a higher standard and if you aren't knowledgeable yourself, MCS has no means to guarantee that.
I dislike trade monopolies on principle.

 

[Sachakins]

MCS is a necessity IMHO. Unlike you, many don't have the technical capacity or knowledge. OK, if its their own life in their hands, but not others and certainly not the next occupier.
To me it's akin to the gas safe registe. I can envisage many insurance companies ducking out of claims for none MCS Installations. Just my observation.

Octopus no longer require MCS certification for their tarrifs. You can still get niciec cetificates for the electrical safety of everything.
As long as it is inspected and certified by an appropriately qualified electrician then I can`t see a problem.

True and Yes, it still a valid certification, its the uncertified by appropriate body I have a concern with. Apologies I did not make it clearer.

 

[Ollie78]

But if you do have the knowledge, there should be a way.
MCS is just an approval scheme to try and set a minimum standard. Some of us want work done to a higher standard and if you aren't knowledgeable yourself, MCS has no means to guarantee that.
I dislike trade monopolies on principle.

I agree, MCS reminds me a little of Fensa. Just because a company is MCS registered does not mean the installers are. There is a huge amount of sub contracting in this industry.
I think if you file a g98 or g99, notify building control of the solar panel install (structural on roof etc.) and get an niceic certified electrician to wire the battery and inverters which he will notify through nic, then you should be covered.

 

[Sideways]

My installer who should have been a good one, messed up the roof survey.
The morning they arrived they raced straight up onto the roof and started laying out the brackets for the support bars.
I asked "what about the survey to confirm the load is OK"
"Oh, xxx from the office is organising that to be done today"
Come the end of the week, I asked "when did you do the roof survey ?"
The apprentice was hurriedly tasked and filled in a photocopied proforma with some beam dimensions. Unfortunately our roof isn't a standard design and what he noted was utter gibberish.
I drew the actual roof structure and walked him through it making him measure all the dimensions correctly.
I was disappointed by this but they had done the rest of the job so far quite well and simply figured that if they bust my roof, well I'd sue their @sses !
6 months later, I hadn't had the calcs or approval back and chased the installer. This got them to express the info to an agency who do a ton of this for solar companies and the calcs came back next day, based simply on a calculation of the weight of my roof (timber + tiles), per sq metre, and the weight of panels etc per sq metre.
As long as the added load is less than 10% that's almost all they need to consider and no need to notify building control.

I recall another installer - at the quoting stage, did wind load calcs, pullout calcs on the fixing screws and verified that they were using enough bracketry and long enough screws to fix them. They had weaknesses in other areas but their roof survey was done far better than the guys I used.
So don't trust your installer to do a good job, do ask the questions, and don't pay them until you have all the correct paperwork in hand. I had to chase the G99, the warranty registrations, the MCS doc pack... their admin was totally out of control.

 

[johnb80]

MCS is a necessity IMHO.

Each to their own, I'm only making people aware that it's no longer essential for some energy suppliers.

Unlike you, many don't have the technical capacity or knowledge.

There are many people like me that do though. I'm an apprentice trained, ex steelworks electrician now retired. I have the technical know how but obviously Im not a member of any of the schemes such as MCS. To be honest, some of the installation work done my home by MCS contractors didnt meet my standard and I did some of it again when they'd gone.

OK, if its their own life in their hands, but not others and certainly not the next occupier.

MCS does not guarantee safety in any way. When I'm dead and gone the DIY battery system is easily removed, 3 wires from the mains connections, unplug the batteries and remove, job done, nobody in danger.

To me it's akin to the gas safe registe.

It really is not

I can envisage many insurance companies ducking out of claims for none MCS Installations. Just my observation.

Insurance companies are signed up to some certification body and under the Ombudsman yet you still fear they would refuse a claim due to non MCS, how could they justify that? Just because a contractor is signed up and pays the fee to MCS does not mean the quality of their work is guaranteed.

Remember, the Titanic was designed and built by experts, the Ark was built by a rank amateur in his garden

 

[Jameshow]

Can you of you come up with a system that will provide for a men's shed which uses approx 6kwh per week.

At we are being asked to pay £100 p/m by a neighbouring charity which h I think is extortionate.

We have a 30 x 16' flat roof.

 

[johnb80]

Can you of you come up with a system that will provide for a men's shed which uses approx 6kwh per week.

At we are being asked to pay £100 p/m by a neighbouring charity which h I think is extortionate.

We have a 30 x 16' flat roof.

We would really need to know more about the requirements and the shed. For example does it require continuous power or only when occupied? Could a portable battery system be used where you take the battery away to charge it up? If you want to go the solar route, does it need more power in winter time (heating?), what sort of maximum power demand do you have, kettle 3kW, coffee maker 3kW, fan heater 3kW etc?

 

[Jameshow]

We would really need to know more about the requirements and the shed. For example does it require continuous power or only when occupied? Could a portable battery system be used where you take the battery away to charge it up? If you want to go the solar route, does it need more power in winter time (heating?), what sort of maximum power demand do you have, kettle 3kW, coffee maker 3kW, fan heater 3kW etc?

Yea only 2 hours at a time 3 times a week.

Max individual power is 3kw kettle, although we could possibly get a solid wood stove if the insurance would allow.
What's the maximum distance of lithium80%?

 

[johnb80]

Yea only 2 hours at a time 3 times a week.

Max individual power is 3kw kettle, although we could possibly get a solid wood stove if the insurance would allow.
What's the maximum distance of lithium80%?

It depends really on how much you want to spend.

A 3.6 kW Hybrid Inverter will cost you circa £500, you may find some at about 2/3 of that price used or end of line. A battery such as Fogstar that would give you 2.7 kWh storage would cost around the £600 mark. The battery can be taken away and charged, returning to the man shed when needed. You really go as far as you like from this sort of baseline, the inverter would reside in the manshed, connected to the consumer unit, battery plugged in and power is on.
Other considerations, small gas stove for the kettle, 12v LED lighting and a leisure battery that can be taken away to charge etc. We could really do with more of a picture of what the use is and how far do you want to go to being offgrid.

 

[SeanT999]

I'm going to have to re-read this a few times. But one of my first takeaways from this is you could serve the Vanlife community well in information, if not those module containers

Speaking of which, do you have any more detail on how to accomplish such excellent work?

Thanks
Sean

 

[johnb80]

I'm going to have to re-read this a few times. But one of my first takeaways from this is you could serve the Vanlife community well in information, if not those module containers

I did use one battery module on my Bailey Senator Wyoming caravan, it gave me a true 280 a/h capacity with the same weight as the leisure battery it replaced. They are easy to put together and in my caravan version I built the BMS system into the module.

Speaking of which, do you have any more detail on how to accomplish such excellent work?

Thank you for your kind words. Try as I do, I havent managed to master Solidworks CAD program which would allow true 3D drawings and make ups of the modules. I use Autocad only in 2D mode which is what I need for my laser cutting, the 3D vision is in my head LOL

Here are some of the drawings from within Autocad and I'll try and comment about them if it helps.

This is a typical 3 view (front, side and top) of my batter shed. The 4 battery modules can be seen in the bottom half and the inverter and other items in the top half.

These are the component parts of the battery module. Starting at the top left the small parts make up a mounting for the Anderson Connector. The next part along is the base of the module which rests on threaded rods underneath and keys into the endplates. The next 2 items are the endplates and they are doubled up for added strength. The 7 round holes are where the threaded rods are used to apply compression to battery modules. There are differences between left and right hand sides, the left has a series of rectangular slots, this is for one end of the clear acrylic cover to go into, the right hand one has a notch along the top and two smaller notches at the bottom of that slot, the two small notches contain magnets to hold the cover in place. The next item along is the front of the module, it has the small holes where the Anderson Connector mount is assembled onto and the cable exit above, to the right of the cable exit is the round connector for the balance socket. The tabs at either end and the bottom locate into the endplates and the bottom. The final part on the bottom left is the clear acrylic cover, the two holes at the right hand side I put some steel grub screws which stick to magnets holding the cover in place, I also added a finger hole to lift the cover up, the magnets were stronger than expected LOL. Once the parts are loosely assembled, the threaded rod is place 3 on base, two at front and two at the back. The threaded rod is sleeved in Silicone tube to provide a little bit of cushioning and some insulation although this aspect isn't really needed. At the ends of the threaded rod I used sleeve nut to provide a flat fastening. Once assembled loosely the cells can be placed into it, each one the opposite way round to its neighbour so the supplied busbars can link +ve of cell 1 to -ve of cell 2, +ve cell 2 to -ve of cell 3 and so on. Once all of the cells are in place the sleeve nuts are tightened to apply compression via the endplates to the cells, they just need a little compression, they swell slightly in operation so that finds the compression required, just tighten all nuts evenly. Add the cables to the Anderson connector if used or wire directly to your load. The balance socket is connected to -ve of cell 1 and every +ve of cells 1, 2, 3 & 4.

If you need any more detail just give me a shout, I can cut the mdf for you if youre wanting to give it a go, I can also provide you with a shopping list for the parts - Anderson connector, screwed rod, sleeve nuts etc.

J

Thanks
Sean

 

[johnb80]

Further to the above, attached here are PDF's of the battery housing, anyone is free to use them for personal use, I have also put the dxf file (battery module.zip) in there for import to CNC machines laser or router. The PDF's are all full size so they can be printed, pasted onto wood / plastic / metal and cut accordingly. The module was designed for EVE 280A/h cells which are 72mm x 200mm x 172.5mm. Adjustments to cater for other cell sizes or numbers can easily be done, just message me.

 

[Sideways]

What impresses me from this is the improvement in LFP cells.
Prompted by this thread I've been looking at the prismatic cells that @johnb80 has used and comparing to the commercial battery pack that I bought only a couple of years ago which uses the same chemistry.
My battery is assembled from 6 modules wired in series. Each module has an output around 50V DC so it's made of 16 cells in series, and a capacity of 2.76kWh
Dividing the two numbers, this means the cells are rated about 54Amp hours.
Label pretty much agrees

John's EVE cells are rated at 280 Amp hours. That is a massive increase in capacity and it sounds like a 300Ah cell is on the way.
With EVE grade A cells costing under £100 apiece in the UK now and around 70 Euros on promotion in Germany, the economics of battery storage is really changing.

 

[johnb80]

What impresses me from this is the improvement in LFP cells.
Prompted by this thread I've been looking at the prismatic cells that @johnb80 has used and comparing to the commercial battery pack that I bought only a couple of years ago which uses the same chemistry.

I purchased my cells in May 2022.

My battery is assembled from 6 modules wired in series. Each module has an output around 50V DC so it's made of 16 cells in series, and a capacity of 2.76kWh
Dividing the two numbers, this means the cells are rated about 54Amp hours.

The numbers seem a little odd there, 6 modules wired in series at 50v each would give 300v into your inverter?
A module to have a terminal voltage nominally of 50v would need 16 LifeP04 cells per module, have you got 6 x 16 = 96 cells in your system? If the cell count is wrong and fact it's 16 cells in total, how do split that across 6 modules? I'm confused (easily done LOL).

John's EVE cells are rated at 280 Amp hours. That is a massive increase in capacity and it sounds like a 300Ah cell is on the way.

314 Ah cells have been on sale for over a year at Fogstar at £104.99, it would make a nice 16.6 kWh battery for only £80 more, bargain in my book.

With EVE grade A cells costing under £100 apiece in the UK now and around 70 Euros on promotion in Germany, the economics of battery storage is really changing.

A trick that used to work on Fogstar was to make an account, login, place 16 cells in your baskey and then just leave the site, dont logout. Leave it for a couple of days you used to an email reminding you there were items in your basket and it gave you more discount to complete the order. Like this:-

Worth a try to see if theyve closed the loophole. I did it three times in total I built two more batteries for a couple of friends.

 

[Sideways]

Yes.
It was a commercial supply and fit so I've never been inside the battery boxes, but they are indeed 16 cells per module, 6 modules wired in series so a 300V DC input into the hybrid inverter.
The 16.6kWh stack can degrade to 80% capacity and still deliver 6.5kW at 0.5C. One of my requirements basically to allow us to cook a family dinner without leaning on the grid.

This BYD HVM system can have upto 8 modules / 400VDC / 22kWh in a stack controlled by a BMS in the top box. Up to 3 stacks of the same voltage and each with their own controller, in parallel.

COVID supply chain disruption etc meant it took 9 months for this to be delivered after I bought it as part of the solar installation and I didn't become aware of Fogstar until another UKW member mentioned them, a year or so after I posted my own solar story here.
https://www.ukworkshop.co.uk/threads/one-familys-solar-story.138482/

I think this is one of the great benefits of people like us sharing our stories. You need to find transparent and detailed sources of information to make informed decisions.

It would have been great to have your thread to refer to back in Feb 2022 when I was choosing components and an installer

 

[johnb80]

Yes.
It was a commercial supply and fit so I've never been inside the battery boxes, but they are indeed 16 cells per module, 6 modules wired in series so a 300V DC input into the hybrid inverter.
The 16.6kWh stack can degrade to 80% capacity and still deliver 6.5kW at 0.5C. One of my requirements basically to allow us to cook a family dinner without leaning on the grid.

I commissioned my DIY battery on 24th December, 2022 so that I could hopefully cook Christmas dinner off grid. I did achieve that much to my surprise, there no hiccups along the way it all ran smoothly. We ran out of battery power at about 21:20 on Christmas day having had all of the family round, dinner for 12 etc I was very pleased.

This BYD HVM system can have upto 8 modules / 400VDC / 22kWh in a stack controlled by a BMS in the top box. Up to 3 stacks of the same voltage and each with their own controller, in parallel.

View attachment 186318

I've seen a few inverters appear that now have high voltage DC input, protection is key to any such installation I'm sure youre aware of just how well DC can sustain an arc and how difficult it can be to break it (air blast circuit breakers in the steelworks LOL). Having 300v+ with a few thousand amps behind needs absolute care and respect.

COVID supply chain disruption etc meant it took 9 months for this to be delivered after I bought it as part of the solar installation and I didn't become aware of Fogstar until another UKW member mentioned them, a year or so after I posted my own solar story here.
https://www.ukworkshop.co.uk/threads/one-familys-solar-story.138482/

I think this is one of the great benefits of people like us sharing our stories. You need to find transparent and detailed sources of information to make informed decisions.

It would have been great to have your thread to refer to back in Feb 2022 when I was choosing components and an installer

Feb 2022 I was still plucking up courage to buy the parts LOL, it was nothing more than a thought in my head and sick feeling in my stomach, I did just flip one day on impulse and bought all of the parts then had the 'OMG, What have I done' moment just after.