On-grid domestic battery storage 5 December 2016 at 4:57PM edited 30 November -1 at 1:00AM in Green & Ethical MoneySaving 1.8K replies 199.3K views

Solarchaser

Thats been my problem also, its what pushed me to batteries, exporting all day for no benefit,  to then buy it back an hour later.

This thread may be helpful,  I did it a few months ago to outline what I had seen with a year of batteries. 

https://forums.moneysavingexpert.com/discussion/6111409/a-year-with-home-batteries-and-more-solar-and-an-ev

And in comparison to that thread, since ive been 3 months with 2 lux systems and 17kwh of batteries,  instead of buying 650kwh in last 3 months, (last years) I've bought 265kWh so around 90kwh a month, which will be mostly the electric showers, as the two inverters can't cover that, but these are the sunny months, so that won't last all year.

Exiled_Tyke

Pulpdiction said:

Hi, I hope you don't mind me asking some real noob questions but interested in getting some battery storage.  I have a 3.6kw solar system which has been in for 5 years, I don;t have any software of anything clever that tells me what I am consuming (I don;t have a smart meter so can't assess real time usage) but am using approx 8400kw/h of electricity as well, that is what my electricity bill is telling me, so how do I go about assessing my requirements and doing a cost benefit analysis for buying some batteries?  Once I have determined that it makes sense, it probably won't pay for itself but I like the idea anyway which systems are recommended and are there any national installers (I'm in the Midlands) who are recommended?

Thanks

With your consumption profile I'm guessing that the economic case for a battery is going to be very poor indeed for your household.  I know mine won't come near paying for itself even though it's converted a lot of exported electricity into self-consumption.  I'd focus on matching your peak usage with peak production if you aren't already.  A key issue here it that on a good day at this time of year (if we ever get one of those again) the production will just about match consumption but once you get away from the peak months the system barely produces, you'll import almost all your electricity and the battery will be redundant. 

Solarchaser

Exiled_Tyke said:

Pulpdiction said:

Hi, I hope you don't mind me asking some real noob questions but interested in getting some battery storage.  I have a 3.6kw solar system which has been in for 5 years, I don;t have any software of anything clever that tells me what I am consuming (I don;t have a smart meter so can't assess real time usage) but am using approx 8400kw/h of electricity as well, that is what my electricity bill is telling me, so how do I go about assessing my requirements and doing a cost benefit analysis for buying some batteries?  Once I have determined that it makes sense, it probably won't pay for itself but I like the idea anyway which systems are recommended and are there any national installers (I'm in the Midlands) who are recommended?

Thanks

With your consumption profile I'm guessing that the economic case for a battery is going to be very poor indeed for your household.  I know mine won't come near paying for itself even though it's converted a lot of exported electricity into self-consumption.  I'd focus on matching your peak usage with peak production if you aren't already.  A key issue here it that on a good day at this time of year (if we ever get one of those again) the production will just about match consumption but once you get away from the peak months the system barely produces, you'll import almost all your electricity and the battery will be redundant. 

I'm intrigued as to why you would say that?

With high consumption of electricity, especially in the evening, as pulpdiction has said theirs is, the case for batteries is stronger not weaker imo, as the batteries will be cycled almost every day, making the offsetting of electricity cost at its maximum. 
Add in a time of use tarrif for the winter months, like octopus agile, and you can lower the winter bill by say 50 - 60%

For me, the case for batteries (and more batteries) is much stronger for high usage as you can maximise their usage, and weaker for low consumption as you would struggle to cycle the batteries every day, making the roi much longer.

chamelion

Solarchaser said:

Exiled_Tyke said:

Pulpdiction said:

Hi, I hope you don't mind me asking some real noob questions but interested in getting some battery storage.  I have a 3.6kw solar system which has been in for 5 years, I don;t have any software of anything clever that tells me what I am consuming (I don;t have a smart meter so can't assess real time usage) but am using approx 8400kw/h of electricity as well, that is what my electricity bill is telling me, so how do I go about assessing my requirements and doing a cost benefit analysis for buying some batteries?  Once I have determined that it makes sense, it probably won't pay for itself but I like the idea anyway which systems are recommended and are there any national installers (I'm in the Midlands) who are recommended?

Thanks

With your consumption profile I'm guessing that the economic case for a battery is going to be very poor indeed for your household.  I know mine won't come near paying for itself even though it's converted a lot of exported electricity into self-consumption.  I'd focus on matching your peak usage with peak production if you aren't already.  A key issue here it that on a good day at this time of year (if we ever get one of those again) the production will just about match consumption but once you get away from the peak months the system barely produces, you'll import almost all your electricity and the battery will be redundant. 

I'm intrigued as to why you would say that?

With high consumption of electricity, especially in the evening, as pulpdiction has said theirs is, the case for batteries is stronger not weaker imo, as the batteries will be cycled almost every day, making the offsetting of electricity cost at its maximum. 
Add in a time of use tarrif for the winter months, like octopus agile, and you can lower the winter bill by say 50 - 60%

For me, the case for batteries (and more batteries) is much stronger for high usage as you can maximise their usage, and weaker for low consumption as you would struggle to cycle the batteries every day, making the roi much longer.

ditto this. 
I'm a heavy user. I currently consume the vast majority of what I generate, with the little spare on top going into batteries. However I am soaking up loads of battery charge when it's cheap / free / paid for overnight, and my battery kicks in during the day to supply power if electricity prices are high - all of this controlled by octolux. On Octopus, I basically import 0 energy between the 4-7pm window when it's most expensive, and the battery trickles into the house if prices go higher than 7p/kwh. 

orrery

Why not do a simple calculation to see what the limit is to the payback - i.e. that point which can never be reached? Assume that you can store and use all your export (a smart meter will measure that), and if you have economy 7 then assume you can displace all your peak usage with cheap rate. Even with these two unattainable figures, I couldn't see a payback.

If you are doing it for personal satisfaction, or for environmental reasons then get on with it and work to maximise the payback later.

Solarchaser

Thought I'd do a wee update to show the difference of my switching to lux from sofar, and going from 3 batts to 8.
For the last 3 months I've spent a total of ~£45 on electricity which works out at around 55kwh/month at 14.7p/kwh  and then the standing charge.
The vast majority of this will be using electric showers which use more electricity than the lux inverters can cover, and some will be days of poor generation. 

At the moment my standing charge makes up 40-50% of the monthly bill depending on the month.

So for April, May and June I paid for ~165kwh (326kwh last year according to sofar, I can't tie up the bills from last year due to edf/bulb smart meter disputes)

Using the lux data (ct clamps)
Gen 3460 (last year was 3005 according to sofar)
Export 1406 (last year was 1160 according to sofar) 
Unfortunately I was not recording the smart meter export every month, so cannot say how true the figure is/was. Smart meter says 1550 this year vs the 1406 on lux ct clamps. (10% out)

And so consumption of around 1946kwh for this 3 months. (Please note I am not using the consumption figure from the ct clamp data as its garbage due to the parallel/not parallel operations of the lux) plus 165kwh bought.

If I had no solar i would have paid ~£285 not inc standing charge
My fit 4Kw system generated 1450kwh in this period, and so it could be argued that fitting the second system last year has saved me 500kwh that I would have had to buy, so £73 (assuming I used all the fit system gen and batteries caught all export... unlikely,  so in reality the second system will have saved quite a bit more im sure)

According to the lux the battery output has been 980kwh, so a little over half of my 1946kwh consumption,  and so from the batteries directly, a saving of £144.
Now there's no denying there is a fudge factor here, as some of that battery output is lost in the inverter, but it varies from 30w to 400w depending on output, and so i guess maybe a 10% fudge would be reasonable,  so £130 saving purely from the batteries. 

I'm more than a little annoyed with myself that the data i recorded was not as consistent or as complete as I thought.


So what does it all mean?
Not really that clear. The fact i exported more than last year would suggest the additional batteries are doing not very much at all, though there is clearly additional generation also.

I think it says that I am not using the full amount of the batteries each day or the battery figure would be 91 days x 17kwh = 1547kwh, though the figure is roughly 2/3rds of that suggesting around 10-12kwh is likely about right... and thats what I've always thought (got 4 batts cheap on ebay, so "had" to buy them 🙄)
However it does show that the 6kwh batts I was using last year were not enough as 91 x 6 = 546 so roughly 55% of the last 3 months discharge.

Its fair to say covid is messing things up also as there will be more daily consumption due to tvs being on, lunch cooking instead of school meals.

So to sum up it seems the additional batteries and inverters have made a marginal difference... however what it doesn't show is the undoing of the "solar optimisation" that those of us with solar panels tend to do.
No more putting the washing machine on at midday etc (which was always a fight with the white goods lover) the house runs exactly as it would if we had no solar. 
If the tumble dryer, dishwasher and washing machine are to go on at the same time, all good, crack on, and that has made a difference in terms of friction between geeky solarchaser and white goods lover wife, and reducing friction in married life during a lockdown is no bad thing, let me tell you!!

cdunne

Thanks for this. Last month I purchased a SOFAR 'ME 3000SP' unit (from a supplier on eBay he was quick at responding pre-sales but hasn't responded to me after sales, my first point was the battery spacers shown on his eBay pictures weren't included. I've  realised the units are are quite 'clunky!' I've failed to get my phone to configure it to use my WiFi network (I get a page not found) when I try to login!
Anyway until today it did seem to be working OK but today I isolated it (both from AC and DC to install the feed for my 'maintained' supply contactor from it's non grid output. I've failed to get it to re-energise since. I've proven that there is electricity on the 'grid connection' but the screen doesn't come no, nor do you hear the relays in it clunk closed when it works out it needs to charge / discharge. I'm also switching to the Agile Tariff (smart meter install Weds) and do NOT want the batteries to feed into a load I end up creating (I've a 40Amp feed to a second consumer unit in an office in the garden earmarked for this!) I don't think there is anyway to control the SOFAR via software so I was thinking of a simple hardware mod that switches the SOFAF CTs inputs to a dummy one suggesting that solar is generating and there is little load demand hence it will try to charge the batteries until they fill! Does the Lux have a similar setup of a solar and grid CT, is it easier to control via software? Can someone recommend a good model / hardware supplier of it. I would like to have the option to buy more batteries if they drop in price. Does it also cope with 8 packs like my existing one?
Hopefully I can use the leverage of eBay to get a refund on the SOFAR!
Thanks

Chris

Solarchaser

Hi Chris, from what you have said it sounds like the sofar either isn't seeing the batteries or isn't seeing the grid.
From memory I think batteries need to be on (and running) and then you give it mains.
Sofar won't really work with agile, however several of the forum members are using the lux running a script (not gonna lie i don't fully understand it) to integrate with octopus tarrifs, so it really sounds like thats more what you are looking for.

Plus the lux switches on with either battery or mains (vs sofar requiring both).

There was a good YouTube video on how to configure the WiFi using your phone by think renewables/ gigabiz/ homeswitch/infinity/pv pro, might still be there, was like 10 mins.

I couldn't find it, but this one should help

The solar man app can grab data from the sofar, but really the lux is better as you can actually set charge and discharge limits/cycles etc with the lux app, whereas the sofar can only show you information. 

The lux can take 8 batteries yes, though Michael from think renewables etc did tell me they can now take unlimited batteries... ive not seen that confirmed anywhere. 

htsoft

EVandPV said:

I cobbled together a serial cab!e to use with the Pylons and the Batteryview app and I'm finding it quite useful not just for checking battery temperature (the Lux doesn't yet display this) but also for checking what's going on with all battery modules in the stack.
It provides info such as voltage, charge current and capacity of each module plus the voltage of each cell which will be useful for checking for faulty cells.
This is the cable I used ..... 

Which I spliced to a modem cable with the wiring in this thread .....  

Did you simply match the wire colours to make the RJ11 (using the green, red & orange of the USB converter in pins 2 3 4)? 

Thanks
t

EVandPV

htsoft said:

EVandPV said:

I cobbled together a serial cab!e to use with the Pylons and the Batteryview app and I'm finding it quite useful not just for checking battery temperature (the Lux doesn't yet display this) but also for checking what's going on with all battery modules in the stack.
It provides info such as voltage, charge current and capacity of each module plus the voltage of each cell which will be useful for checking for faulty cells.
This is the cable I used ..... 

Which I spliced to a modem cable with the wiring in this thread .....  

Did you simply match the wire colours to make the RJ11 (using the green, red & orange of the USB converter in pins 2 3 4)? 

Thanks
t

Yes, pretty much. It's a while ago since I did it but I followed this diagram ......