Investigating Lithium battery generators

[Nealh]

Most won't have the opportunity of a night tariff, like me one is stuck with a std rate tarrif night or day. Even if one had a battery set up and opportunity to use cheaper night time tarrif to charge one still is conned by the daily std charge rate for not using power.

 

[WheezyRider]

It depends on what you want it for. E.g. as part of an every day off grid system without mains or a back up system for the mains as you cannot afford to be without power...in these cases, cost is less of an issue.

It is also important to bear in mind the cycle life of the battery. This can be 6000 cycles or more for LFP cells. In the example I gave above, (£1k for 3.88 kWh) it works out at about £260 for each kWh capacity. So even if you have cheap energy at 10p/ kWh and cycling 6000 times, you could process 6000 kWh, or £600 of electricity per kWh capacity, so more than twice the cost of the battery. You might even think it worthwhile to have a power wall that stores over night at 10p /kWh and then releases during the day when it is 44p/kWh. Not discharging as deep will also increase the number of cycles that are possible.

If you are not able to take advantage of variable rates, looking at renewables and maybe going at least partially off grid is looking increasingly attractive.

 

[Woosh]

in my particular case, I am thinking of installing 20KW solar panels on our roofs, so a powerwall will be needed. Our economic case is compelling at the moment but in view that the uk wholesale gas price is falling fast, in a year time, the present plan may not stack up.

 

[Nealh]

After a quick scoot around some forums I'm getting a surprising answer. There is a repeated theme of newer fridge freezers working 80-90% of the time, whilst older ones run 50%. How they get to A rated energy if that's the case, I don't know.
Anyway, this would put things in the 7-8kwh/24hr area.

I was in the mind set that compressors work 30 mins on, then 30 off and so on.
But as flecc say's, use a power meter for an exact figure.
Your maths is almost correct except for the decimal point, the power user per 24hrs should be in the realms of 70 - 80 wh. 0.300w x 24h.

 

[Nealh]

Can get 3.8kWh leisure battery with smart functions for a grand:

Lithium Batteries

The Fogstar Drift range of leisure batteries contain the very best EVE Grade A Prismatic Lithium Iron Phosphate (LiFePO4) cells, integrated JBD Battery Management System (BMS), built-in Heating, Bluetooth and Fogstar Drift App for external battery management.

www.fogstar-drift.co.uk

Yes Fogstar sell both the modules and 12v Drifts with the smart functions but with BMS one will have issues if wanting a series 24v battery. All will depend on the pv voltage rating.
The 12v Drifts have a 10 year warranty.

 

[WheezyRider]

in my particular case, I am thinking of installing 20KW solar panels on our roofs, so a powerwall will be needed. Our economic case is compelling at the moment but in view that the uk wholesale gas price is falling fast, in a year time, the present plan may not stack up.

Although gas prices are dropping, I think prices are going to be volatile for some time and it's good to be isolated from that if you can. If there's a sudden cold snap, expect prices to shoot up again.

Plus, you are doing your bit for reducing reliance on fossil fuels etc.

World facing 'first truly global energy crisis', report says

Russia's invasion of Ukraine will have long-lasting effects on energy supply, a new report says.

www.bbc.com

 

[Woosh]

my worries are that I will be dead and gone long before the 6000 cycles (20 years) of the batteries or the Chinese LFP batteries set fire to the building. None of them say which cells they use. If they are CATL then I may click the go button.

 

[WheezyRider]

my worries are that I will be dead and gone long before the 6000 cycles (20 years) of the batteries or the Chinese LFP batteries set fire to the building. None of them say which cells they use. If they are CATL then I may click the go button.

Lithium Iron Phosphate batteries don't pose the same fire risk as Li-ion:

https://en.wikipedia.org/wiki/Lithium_iron_phosphate_battery#Safety

 

[Nealh]

Related to battery storage is the efficacy of collecting those rays whatever the weather but more so when the sun is shining. The below calc allows you to input all the facts to see the best angle or direction to orientate panels.
PVWatts Calculator (nrel.gov)

On top of the page (at the my location /top left) one can set their postcode to pin point the location. For most panel settings on a roof the angle can't be changed as their roof dictates the pitch but on a flat roof you are on to a winner, an angle for us in the UK is best suited for 0 - 10 degrees and collects more wh's then a std roof of 30 - 40 degree pitch. One reason why solar farms use the flatter angles.
In my case my house is oriented 80/260 degrees and by splitting panels to get both a.m & p.m sun the efficacy is only approx. 4.4% worse then a 180 degree azimuth.
For my location the westerly produces slightly more wh's then the easterly, but for best of both worlds split azimuth laying of the panels at 5 degrees offers the best angle apart from horizontal. 5 degrees gains 8% more wh's then a 30 degree angle.

If the calc is correct then just 4 x 400w panels can supply 50% of my electric use for the house, which would cover the power used by the white goods in the garage of 2 x freezers , w/m & t/d and the pump for my pond which is low power and on 24/7/365. I can use also the set up to charge my bike batteries and other small gadgets

The factor is pricing and whether one thinks it is worth the outlay and recouperation of the outlay. A modest 1600w panel set up with batteries, etc etc is likely to be 4.5 -5k. At current electric prices one may expect break even to be about 8 years.

 

[Nealh]

The fogstar's whether drift or modules use EVE LFP modules.

 

[WheezyRider]

I think a 1600W off grid system could be cheaper than £4.5 k without much effort.

Panels are around £0.65 or less per peak watt, so about £1k for panels

5kWh storage even with 105Ah cells would be around £1k, would be cheaper with 280Ah cells

BMS around £100

Charge controller around £100

Cables, mounts sundries £300

Inverter pure sin wave 3kW around £250

All in for less than £3k.

Have I left anything off?

A note about flat roofs, I think max protrusion is 200mm without planning permission, which can limit your panel angle.

 

[Woosh]

Lithium Iron Phosphate batteries don't pose the same fire risk as Li-ion:

https://en.wikipedia.org/wiki/Lithium_iron_phosphate_battery#Safety

true, I once put a nail through one of those LiFePO4 cells to see what happened. Still, Tesla 3 cars use them and some still go up in flames after battery damage.

 

[Woosh]

The fogstar's whether drift or modules use EVE LFP modules.

do they say the cells are A grade?

 

[Woosh]

Have I left anything off?

for commercial buildings, it has to be done by competent fitters for insurance purpose. That rules out a lot of possibilities.

 

[WheezyRider]

do they say the cells are A grade?

Yes, those are A grade cells. They also sell some B grade, but make it clear what is what, so you wouldn't buy B grade by mistake.

 

[WheezyRider]

true, I once put a nail through one of those LiFePO4 cells to see what happened. Still, Tesla 3 cars use them and some still go up in flames after battery damage.

Have you got a reference to an LFP based Tesla 3 catching fire after a crash? I've seen pics on the web of severely crashed LFP Teslas that didn't catch fire.

 

[Woosh]

Google tesla 3 battery fire

 

[WheezyRider]

Google tesla 3 battery fire

But there are older model 3s still around with Li-ion packs. How can you be sure which pack they have from a you tube clip?

 

[Nealh]

I think a 1600W off grid system could be cheaper than £4.5 k without much effort.

Panels are around £0.65 or less per peak watt, so about £1k for panels

5kWh storage even with 105Ah cells would be around £1k, would be cheaper with 280Ah cells

BMS around £100

Charge controller around £100

Cables, mounts sundries £300

Inverter pure sin wave 3kW around £250

All in for less than £3k.

Have I left anything off?

A note about flat roofs, I think max protrusion is 200mm without planning permission, which can limit your panel angle.

A flat roof depends where it is, ultimately for planning the flat roof is the main house roof but like me if you have a garage flat roof area this is some 3m below the main roof ridge line.

Cost is all down the spec of the system esp battery storage, there will be days/weeks where some of the heavier demand like t/d & w/m aren't used so making the most of the captured power would ease the October to March usage , the four poor months of production are Nov - Feb.
Off grid for my garage is very doable.

 

[Nealh]

For battery storage it is assumed that ultimately one isn't going to use some 40% of the cycle to ensure good cycle life so what ever ah/kwh capacity one is looking for one needs to factor in a battery some 40% greater then the proposed.
If one wanted a 5kwh usage then one needs to cater for a 7kwh storage solution.