DIY storage battery

DrPhil

Distinguished Member
Hi folks

Thought I'd share the latest step on my solar journey.

1 year ago I finally got around to having solar panels installed. It's been on the "to do" list since we bought the house but after a few years of saving and a few years of shopping around I finally got it done.

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6.2kwp split array, 2.8 south and 3.4 west. Came with 2 x 2.4kWh PylonTech batteries, a Zappi 2 car charger and an Eddi hot water diverter cost me just north of €8k (I'm in Ireland) after grants.

On reflection, I shouldn't have bothered with the additional PylonTech. The grant here covered about 60% of the cost of the first one, but the second one was a luxury purchase. That said the installer added it at cost so it wasn't too bad, around €900 installed.

However, after exporting over 150kWh in the first month alone, I was already considering a change. In Ireland we have no feed in tariff so anything exported is a waste. We'll it's green energy going to someone else so not a waste as such, but I don't benefit financially.

First thought was recycled car batteries. A friend of mine has a large storage battery made from the battery of a written off Nissan Leaf. But there's a fair bit of work involved with that, plus the chemistry of those cells is more prone to heat and (if things go wrong) chemical leakage and fire. Given that the batteries are in my attic, that's not comforting.

So I went the LiFePo4 route using lithium ion phosphate.

Cells purchased from China.
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BMS purchased from Australia.
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Layout courtesy of Microsoft Paint...
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Shelving unit, multimeter, cables, crimp terminals all other items from Amazon.
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So I now have a 20kWh storage battery. The overall cost of the project was a little over €3k, and I've sold my PylonTech batteries for €1,400. I still have some old cabling and the PylonTech storage cabinet to sell which will bring it up to about €1,500 recouped which is essentially what I paid for them a year ago due them being grant discounted.

No more export, plus through the winter I can charge the batteries on night rate for about 6c a unit, and run off them for 2 days rather than spending the day rate of 17c.
 

eob

Well-known Member
Great thread. Subscibed.
This is a big one on my todo list, but I can't justify the £6 - 8k that it will cost for storage.
I'll watch the price come down as I'm sure it will but I'm not sure yet what the sweet spot will be to pull the trigger.
It kills me to watch all the energy being exported, although I do have 15 years left of the previous owners FIT at around 15p/kw. Got my cheque for the summer last week. Nearly £500. :cool:

Getting my first EV in November, but now I'm working from home it won't be used as much as it would. I have (or used to have) a 300 weekly commute.

Funnily enough, I just watched this video this morning:
 

DrPhil

Distinguished Member
This is a big one on my todo list, but I can't justify the £6 - 8k that it will cost for storage.
£6-8k?

I just spend €3k (euro) which is about £2.6k.

How big are you planning to go?

Feed in tariff is my main driver. We don't have one in Ireland yet. Its planned for this year but will undoubtedly be rubbish since its rumoured to be only 5c for export, and coupled with a high peak rate.

Currently I pay 16c daytime and 6c overnight. No way will I switch to a feed in that bumps my peak time evening rate to 25c.
 
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eob

Well-known Member
£6-8k?

I just spend €3k (euro) which is about £2.6k.

How big are you planning to go?

Feed in tariff is my main driver. We don't have one in Ireland yet. Its planned for this year but will undoubtedly be rubbish since its rumoured to be only 5c for export, and coupled with a high peak rate.

Currently I pay 16c daytime and 6c overnight. No way will I switch to a feed in that bumps my peak time evening rate to 25c.
I'll admit that was probably the higher end of the market. (I wanted a tesla powerwall).

I havn't really done the sums yet as to what size I need. I only installed the monitoring software (Emonpi) in Feburary, sp I dont know the impact of a long, dark Scottish winter yet but from what I can tell, the panels have generated 2332kWh and we have used 3433.4kWh meaning we get 70% of our power from the grid.

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With the new car and the Zappi charger then it will divert most of that export into the car but I wont really be using the car so it probably wont be taking much charge.
 

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