Idiot's guide to a self build battery

[Joeboy]

My experience with LiFePO4 battery packs has been that there is almost nothing to be gained by discharging them below 3V per cell and the same for charging them to anything over about 3.6V per cell. The shape of the capacity curve is such that almost all of the capacity is available between 3V and 3.6V and testing seems to show that battery life is enhanced by stopping them going outside those limits.

Interesting that raw cell prices are so reasonable when compared to buying packs. Looking at the price of Pylontech packs at the moment makes me glad I decided to bite the bullet and by six US3000Cs last year. At the time I was convinced I'd gone way OTT, and would never need 21kWh of capacity, but I'm now really glad I made that decision. The only issue with having lots of capacity is being able to get enough charge.

I really need to look at adding some more panels to catch the early morning sun, as our 6kW system doesn't really start to get going until late in the morning, as it faces more or less SW. Ideally I want a mounting system that fits to a wall and forms a cantilevered covered walkway from our back door to the place where we stow the bins. That way the panels can do two jobs and deliver some morning generation and provide shelter when we need to go out to the bins when it's raining. I haven't been able to find an off-the-shelf panel mounting system that can do this. Probably need to get something fabricated to do the job. I could get about six 330W panels along that wall, but would also need a couple of panel-sized sheets of glass for the bit that runs past a window.

Thanks for that reassurance OGB, much appreciated. As with PV.count, none of us say 'damn, too much storage'!

Can you simulate at ground level for the proposed PV before going to.trick mounting system? By cantilevered I am assuming for walkway cover aesthetic rather than angle adjustment to chase sun?

[Joeboy]

£1,687- 15 of LF280K (A) batteries incl del, bus bars n bolts
£60.72 - 1 of 15s 5A balance board.

£1,748 total

Well, that's my Christmas sorted!

[Caesium]

That's a really nice price. I assume there will be VAT to add though. Will be interested to hear where you sourced them once they turn up. I'm looking at fogstar who want around £2700 for the cells alone.

[Joeboy]

£1,687- 15 of LF280K (A) batteries incl del, bus bars n bolts
£60.72 - 1 of 15s 5A balance board.

£1,748 total

Well, that's my Christmas sorted!

Also making up my Amazon list with some 18 awg twin core for the balancing board, a heat shrink kit and a new solder kit too. I am looking forward to sourcing the aluminum framework on return home. A quick tape measure needed but likely three banks of 5. The heavy DC cables I'll source nearer the time. Its becoming a real thing in the mind. Anyone have a link to decent DC isolators? Thinking I will make the three banks independently pullable off the wall so would like to be able to safely isolate a troublesome bank.

[Oldgreybeard]

Can you simulate at ground level for the proposed PV before going to.trick mounting system? By cantilevered I am assuming for walkway cover aesthetic rather than angle adjustment to chase sun?

I'm really stuck for space to the east of the house, which is where I think some additional panels would be useful. There's a hedge around 1.5m away from the house along that side, but I have about 7m of wall, with the backdoor and the kitchen window in, that I could hang maybe 1.5kW to 2kW worth of panels. I've been sketching idea out today and with the panels angled at about 45 deg they would fit above the door and window and not get any shading. Just need to find some brackets that will do the job. Might need to get something fabricated, like a gallows bracket, but with the vertical bit extending upwards to take the top rail and some way to attach the bottom rail at the tip of the horizontal part. I think this should work OK with standard panel mounting rails etc if I can find someone that can fabricate half a dozen wall brackets. I'm surprised they aren't available off-the-shelf, TBH, but either they aren't or my search fu is weak. I've run a 2kW array through PVGIS and the output looks useful, around 1,900kWh/year, so around 30% more than we generate at the moment, but with a decent boost in the mornings, when we could really do with it.

[Joeboy]

Can you simulate at ground level for the proposed PV before going to.trick mounting system? By cantilevered I am assuming for walkway cover aesthetic rather than angle adjustment to chase sun?

I'm really stuck for space to the east of the house, which is where I think some additional panels would be useful. There's a hedge around 1.5m away from the house along that side, but I have about 7m of wall, with the backdoor and the kitchen window in, that I could hang maybe 1.5kW to 2kW worth of panels. I've been sketching idea out today and with the panels angled at about 45 deg they would fit above the door and window and not get any shading. Just need to find some brackets that will do the job. Might need to get something fabricated, like a gallows bracket, but with the vertical bit extending upwards to take the top rail and some way to attach the bottom rail at the tip of the horizontal part. I think this should work OK with standard panel mounting rails etc if I can find someone that can fabricate half a dozen wall brackets. I'm surprised they aren't available off-the-shelf, TBH, but either they aren't or my search fu is weak. I've run a 2kW array through PVGIS and the output looks useful, around 1,900kWh/year, so around 30% more than we generate at the moment, but with a decent boost in the mornings, when we could really do with it.

I have been a big fan of aluminium 90 deg 50mm stock in 4.2mtr lengths for years. Used it offshore for decades to support hundreds of kilos of kit on ROV's. Get Some countersunk allun screws and nyloc nuts in stainless steel at about M8 size and you can literally build anything and it will look good forever with zero maintenance. Easy to work with too. The right angle size down to even 30mm is load bearing.

[Countrypaul]

Can you simulate at ground level for the proposed PV before going to.trick mounting system? By cantilevered I am assuming for walkway cover aesthetic rather than angle adjustment to chase sun?

I'm really stuck for space to the east of the house, which is where I think some additional panels would be useful. There's a hedge around 1.5m away from the house along that side, but I have about 7m of wall, with the backdoor and the kitchen window in, that I could hang maybe 1.5kW to 2kW worth of panels. I've been sketching idea out today and with the panels angled at about 45 deg they would fit above the door and window and not get any shading. Just need to find some brackets that will do the job. Might need to get something fabricated, like a gallows bracket, but with the vertical bit extending upwards to take the top rail and some way to attach the bottom rail at the tip of the horizontal part. I think this should work OK with standard panel mounting rails etc if I can find someone that can fabricate half a dozen wall brackets. I'm surprised they aren't available off-the-shelf, TBH, but either they aren't or my search fu is weak. I've run a 2kW array through PVGIS and the output looks useful, around 1,900kWh/year, so around 30% more than we generate at the moment, but with a decent boost in the mornings, when we could really do with it.

Ia this the sort of thing you were thinking of: https://www.ebay.co.uk/itm/232104085859

[Oldgreybeard]

Ia this the sort of thing you were thinking of: https://www.ebay.co.uk/itm/232104085859

Sort of, but I was hoping for something a bit neater. Ideally I think the brackets need to be a bit like this canopy frame in concept, but made of metal so they are a lot slimmer and not so obtrusive.

Canopy.jpg (132.58 KiB) Viewed 6516 times

[nowty]

My recent purchase was Basen Green Cells, but I bought them off Ebay from a guy in Wales so they were already in country so got them within days. He said everything from China is taking months at the moment.

Just been looking at the Basen Green website, looks like your getting yours for similar price.
https://www.basengreen.com/product/catl ... on-lifepo4

Just one more waffa thin battery eh ?

There's always space for one more.

[Joeboy]

My recent purchase was Basen Green Cells, but I bought them off Ebay from a guy in Wales so they were already in country so got them within days. He said everything from China is taking months at the moment.

Just been looking at the Basen Green website, looks like your getting yours for similar price.
https://www.basengreen.com/product/catl ... on-lifepo4

Just one more waffa thin battery eh ?

There's always space for one more.

It will be interesting to see how this all plays out, I am expecting about £2.5k all in leaving me with the new stack looking good and a couple of new handtools/stock going forward. I worked in Shenzhen back in the day so its nice to be buying direct again. TBH I'm also OK paying the vat, its an RE project but 'we' have never hung about waiting for govt to catch up to us so best just to craick on. Is your tweaked stack all good Nowty?
Mr Creosote eh? There goes Howard...