On-grid domestic battery storage

Visualman

I have been quoted £3900.00 for an 8.2 giv energy battery solution fitted to my 3.9kw solar system
does this sound like a good price I could find it any cheaper then this

Starfrog

seems ok since I was quoted £2800 for just two 2.4kwh aoboet batteries to add to my existing 4.8kwh batteries 

QrizB

For anyone feeling brave (and with more cash on hand than me) I see you can buy 13.4kWh of LiFePO4 cells from AliExpress for just over US$2k delivered:

Add another $100 or so for a 100A 16S battery management system, a few quid for crimps and cables and you'll have a 280Ah, 48V battery on your hands, ready to connect to your favoured brand of AC- or DC-coupled inverter.

(If you do this, I'd love to know how you get on and please be careful not to burn down your house.)

QrizB

I've taken the plunge. I've bought a refurb Sofar ME3000SP from an eBay seller and have 16 LiFEPO4 cells and a BMS on a slow boat from China.

I didn't choose the 280Ah ones pictured above, I decided I'd experiment with some much smaller ones for now; 25Ah for a total nominal capacity of (25 x 3.2 x 16=) 1.28kWh, or 1kWh at 80% DOD. If these work out well I can add more capacity at a later date.

I will let you know how it goes but it's going to be at least six weeks, and possibly more, until the batteries arrive!

QrizB

QrizB said:

I will let you know how it goes but it's going to be at least six weeks, and possibly more, until the batteries arrive!

Well I've got everything I need (Sofar, cables, 16S LiFePO4 BMS) *except* the batteries, which weren't actually shipped until the middle of this week (grumble) and so are still six weeks away ...

Some time ago - October 2016! - @Martyn1981 was looking forward to batteries at £150-£200 per kWh. Assuming it actually arrives, I've ordered a tiny 1.28 kWh battery (16 x 3.2v, 25Ah cells) for £240 which is right at the top of his target range (I will probably have to pay 20% VAT and 2% duty, too). If that works out OK I'll order a set of bigger cells; 100Ah (so a further 5.12 kWh) would be around £500 (plus VAT and duty), well below Martyn's lower target. [200Ah is around £1000, a similar price per kWh but the numbers for my PV system struggle to make the case for a battery that big. If I had 5kWp, then maybe.]

Edit to add: the 25Ah cells could be retained alongside the 100Ah ones (so a total capacity of 6.4kWh) or I might reconfigure them as a 4P4S 100Ah 12.8 volt system and donate them to my retired parents' campervan.

QrizB

I'm still waiting for my LiFePO4 cells to arrive from China ...

However this guy is in the US, and has been living off-grid in his self-built campervan for 1000 days now. (It seems quite an idyllic way to spend your retirement, if you're single with no commitments.) His electrical power is almost entirely solar PV and is serviced by a pair of 6v, 225Ah wet lead-acid batteries like these that he cycles to a max of 50% DoD (so 1.3kWh capacity). He reckons that if they died tomorrow they would have cost him $1.88/kAh (15.7c/kWh, or 11.1p/kWh at current FOREX rates). He does mention repeatedly on his blog that he keeps a close eye on his charge/discharge parameters and tops up the cell electrolyte levels regularly.

Seems like there's still a case to be made for lead-acid if you take good care of them.

frugalfran

anyone having any battery problems in this heat - due to continue for another 5 days?

QrizB

frugalfran said:

anyone having any battery problems in this heat - due to continue for another 5 days?

My cells arrived safely from China but unfortunately my BMS is duff so my battery isn't connected yet.

Lithium batteries should be OK to +40C at least, which I'm not expecting to see in my house. Are yours somewhere particularly hot?

EVandPV

Just checked ours, they're sitting at 27°C so no problems there.
Operating as normal.

chamelion

frugalfran said:

anyone having any battery problems in this heat - due to continue for another 5 days?

No issues here! Mine discharge at night after my agile go faster rate jumps at 130am so sit pretty idle except for picking up some surplus during the day. My base load is high so there's not much of that. Next activity 830pm when it charges up on go faster and when it's cooler.