On-grid domestic battery storage

joefizz

zeupater wrote: »

Hi

I believe the point made was related to the rate of VAT that applies to a supply & install of qualifying energy-saving products.

Following the rules & installing a solution that includes both new generating capacity & storage moves the whole to the 5% reduced rate of VAT, with the difference between that and the standard rate likely equating to the additional equipment (if everything is well planned!), effectively making the additional generation capacity 'free' ....

HTH
Z

Correct. However...

Ive actually done it and was charged 20% on everything that was additional. Both separate suppliers stated the 5% only when installed by MCE qualified people. Self install is always 20% (which of course may offset the installation fee).


Hence my comments about if Id installed the system I have now instead of just the initial install it would have had 5% (plus installation costs of course) instead of 20% on the additions.
Saying that though I couldnt have had the sofar/pylontech here as the battery installers are exclusively tied to specific products...
...plus if someone upgrades an approved gb fit scheme they may lose the fit depending on the contract and when they signed it, over here theres a max export cap instead of tying your contract to what you installed initially. Thats worth checking.

mre15

1961Nick wrote: »

Device>Inverter>Battery>Cumulative Discharge.

If your plant setting is set to Storage then it will show on the details page.

zeupater

joefizz wrote: »

Correct. However...

Ive actually done it and was charged 20% on everything that was additional. Both separate suppliers stated the 5% only when installed by MCE qualified people. Self install is always 20% (which of course may offset the installation fee).


Hence my comments about if Id installed the system I have now instead of just the initial install it would have had 5% (plus installation costs of course) instead of 20% on the additions.
Saying that though I couldnt have had the sofar/pylontech here as the battery installers are exclusively tied to specific products...
...plus if someone upgrades an approved gb fit scheme they may lose the fit depending on the contract and when they signed it, over here theres a max export cap instead of tying your contract to what you installed initially. Thats worth checking.

Hi

It's nothing to do with accreditation, it's a standard efficiency related VAT accounting requirement from HMRC ....

Suggested reading ... https://www.gov.uk/guidance/vat-on-energy-saving-materials-and-heating-equipment-notice-7086

HTH
Z

joefizz

zeupater wrote: »

Hi

Probably find that ET's point covers things other than the batteries, for example the MTBF of electronics, including inverters etc ...


Years ago there was much debate on the lifespan of PV inverters and how this would have an effect on 'payback' with a general consensus that allowance for inverter replacement every 10years would be wise ...

... a number of members of this very board have experienced failures well before 10 years has been reached, but that's just averages (as in 'Mean-Time') ...

For clarification, the cycle duty as used by manufacturers is simply on charge capacity deterioration to a standard preset point, so 6000 cycles would generally be accepted to be to 70% of 'as new' ... ie, a 3.7V 2850mAh (~10Wh) battery cell would be expected to hold 7Wh after 6000 cycles, with the normal caveats of usage as set by the solution manufacturer ... unless there's a form of warranty on the battery solution as a whole which includes any failure, including individual cells, then the cycle performance guaranty alone doesn't necessarily apply ...

HTH
Z

Plus all of the above in reality is just bench tested with specific equipment and applied so YMMV.
Ive just fixed a 32 inch monitor which cost me 800 quid a few years ago with a new PSU board costing 14 quid just bought off ebay. You wouldnt expect an 800 quid monitor to have cheap chinese electrolytic capacitors in the power board but they did. As time and failures progress so too will the cost of fixing things.

We probably arent anywhere near the law of diminishing returns on home inverter design but its probably not far off. As soon as you see selling of bells and whistles and new interfaces and so on then you know its past peak design for what actually matters.



As Z says the stuff will decay and will decay with both time and usage. It depends on your usage though and its good to go through complete cycles at times, particularly with these type of batteries.

All the stats will be on bench tested straight cycles or 70/80% cycles etc and extrapolated out to a number of years. They will take a few off and thats the warranty.

A lot of battery failures will be just dead cells, I go through a lot of AA high power batteries and some go for years, some cant hold charge in a year, others are good enough to use in non-high power applications. Ive a battery charger that can refresh the AAs and give me an indication of the Ah rating at any point in time. I dont see the bigger batteries being any different.

Those of you with pylontech might see a benefit after winter of doing a couple of refreshes/resyncs when it starts doing full cycle charging again. Michael from think renewables has put a few videos up on youtube and the install new batteries bit is the refresh/resync.
I do this regularly with my AAs just to mix and match sets of similar power, at some point I might split my batteries from one run of 4 to two runs of two if they start decaying at different rates...

As mentioned MTBF is just that a mean, I mentioned a couple of pages ago we worked out 97% of fails occured in a particular piece of kit in the first 48 hours so every piece of kit was run for 48 hours before boxing up!
Also a lot of the kit will have a lot of stuff buried down in the spec sheet and that will all be optimum and very little of it will be related to real world experience. You might prolong the life of the kit by keeping it at a constant temperature with additional or variable airflow and cooling or you might install all that and get the one thats DOA or dies within the warranty period.
I have my tumble drier outside in an insulated metal building - not bloody having one of those things in the house, far too dangerous. It broke after 13 months but it was just the drive belt snapped, even though theres a 10 degree temperature variant between ambient and inside, that doesnt really help when its -18C. The constant and wide varied temperature changes were outside the design scope and weakened the cheap belt enough for it to go bang even though I hardly use the thing. I fitted an uprated belt and its still going.



Where you mount the stuff is important. My inverter was put in the loft and it gets bloody hot up there in summer, just when its producing the most heat... I do expect that will shorten its lifetime somewhat but I have to balance that out with putting it somewhere I have to look at it or box it in.



I do see the whole system as modular and prone to single point failures and accept that if I live another 20 years then parts of the system will be replaced. The solar panels will lose efficiency (replace or add more), the inverter will certainly go or lose efficiency (replace or get a smaller one and run two strings) and the batteries will drop off a lot (room for replacement/expansion) etc.



One of my main concerns with the battery is ventilation and possibility of a thermal runaway fire, so mounting point is the farthest corner of the house in the spare room with the bit of most ease of access for the fire service! Yes I do have a notice about lithium batteries and their placement outside...

Its also a good mounting point because some of the losses it produces is heat so I have been able to turn the thermostatic valve down in that room just on the losses produced by the sofar and batteries. I do monitor temperature occasionally with my hand, not just the apps ;-)



Kev, if you are reading the web browser interface for solarman (http://home.solarman.cn) gives a lot more detail, or at least its a lot clearer, well when it doesnt revert to mandarin it does..

joefizz

zeupater wrote: »

Hi

It's nothing to do with accreditation, it's a standard efficiency related VAT accounting requirement from HMRC ....

Suggested reading ... https://www.gov.uk/guidance/vat-on-energy-saving-materials-and-heating-equipment-notice-7086

HTH
Z

Thanks for that section 2.1 states 'If you supply energy-saving materials without installing them, your supply is standard-rated.'
So if you install its 5%, if you supply its 20%.

zeupater

joefizz wrote: »

... Its also a good mounting point because some of the losses it produces is heat so I have been able to turn the thermostatic valve down in that room just on the losses produced by the sofar and batteries. ...

Hi

Surely if you wanted the room to be have a minimum temperature before installing the batteries and achieved this with a TRV, then adding the battery would just mean that the room would generally be warmer & the TRV would cut-off the flow more often ...

... as an overall energy saving measure, wouldn't turning the TRV down apply equally with & without batteries?

HTH
Z

joefizz

zeupater wrote: »

... as an overall energy saving measure, wouldn't turning the TRV down apply equally with & without batteries?

HTH
Z

Best energy saving measure would be to turn the heating off completely and sit in the dark save for a candle made of my own ear wax and trying to ward off scurvy...

Solarchaser

1961Nick wrote: »

Device>Inverter>Battery>Cumulative Discharge.

Wow!
I had no idea there was so much data lol, feeling pretty daft

However now Ive found those fields, theres nothing there.
It says 0 under cumulative discharge
Only fields that have numbers are battery voltage, current, soc and generated current.
If I go to history, all the figures in all the fields are the same as total generation.

I'll maybe email the solarman team.

zeupater

joefizz wrote: »

Thanks for that section 2.1 states 'If you supply energy-saving materials without installing them, your supply is standard-rated.'
So if you install its 5%, if you supply its 20%.

Hi

Correct observation, but all it does is confirm the original point made that it relates "to the rate of VAT that applies to a supply & install of qualifying energy-saving products" - however, it likely applies to the majority as they wouldn't be looking to go down the DIY route for the reasons discussed previously ...

... also, you could use the document to correct the error made by two separate installers that 'stated the 5% only when installed by MCE qualified people' ... as HMRC clearly don't say this!

... 15%, what's that on an installation package around £4k-£7k? ... just over £500 to around £900? ... so not insignificant if, for example, the battery system can take a direct DC feed from additional PV panels and the installation was on the grid side of the existing TGM, thus not impacting on MCS certification & simply becoming a DNO compliance issue ...

Only mentioning it because it's not just a theory exercise ... it actually happens, as some members of these boards could corroborate.

HTH
Z

zeupater

joefizz wrote: »

Best energy saving measure would be to turn the heating off completely and sit in the dark save for a candle made of my own ear wax and trying to ward off scurvy...

Hi

But that's just a silly & unnecessary response to a valid logical observation ... placing a heat source into a room with TRV controlled heating simply results in the TRV cutting out with less heat input, whilst turning the TRV temperature down simply reduces the minimum temperature in the room ... as such, I would have thought the majority would surely recognise the validity of the point made!

HTH
Z