Solar panels and battery - any real world reccomendations?

Mercenary Keyboard Warrior said:
Your array size and inverter size do not need to be that closely linked when you have batteries as well
You, well your installer, should be speccing a hybrid to match both
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Do you know how much less efficient solar panel wise would a 5kw be than a 3.6, not done any gaming today, thought I was ready to bite the bullet but now im lost again on what to get lol

Givenergy don't do a 5kw AC coupled so would have to be standard dc hybrid setup, solax do a 5kw ac one though.
 
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alphaomega16 said:
Do you know how much less efficient solar panel wise would a 5kw be than a 3.6, not done any gaming today, thought I was ready to bite the bullet but now im lost again on what to get lol
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You would need to check the manufacturers specs

You need to check startup voltage isnt a lot higher on 5kw, or that it can take all 9 panels on one string, else 4 and 5 could be an issue

The efficiency of a 5 vs a 3.68 should be basically the same.
Arguably a 5 might have more longevity since it will not work as closely to max so should be able to handle the heat better
 
Mercenary Keyboard Warrior said:
You would need to check the manufacturers specs

You need to check startup voltage isnt a lot higher on 5kw, or that it can take all 9 panels on one string, else 4 and 5 could be an issue

The efficiency of a 5 vs a 3.68 should be basically the same.
Arguably a 5 might have more longevity since it will not work as closely to max so should be able to handle the heat better
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Roger, will have a sneak peek
 
Startup voltage is same on both, 150 but on the 3.6 and 5 inverters the battery charging stays the same, only difference is output current.

Edit
Ok this is really confusing, in the hybrid inverter page it says AC output for the 3.6kw and for the 5kw inverter the ac output is 5kw but for battery info on BOTH it says "Max. Charge / Discharge Power 3300W / 3600W" this is from the official datasheet but the battery itself only lists 80A as charge/discharge.

Im getting a headache again, got like 30 chrome tabs open, I am getting the suspicion that 3/3.6kw is the kind of breaking point of charging speed.

Edit 2
Decided to lob GE an E-Mail.
 
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alphaomega16 said:
Startup voltage is same on both, 150 but on the 3.6 and 5 inverters the battery charging stays the same, only difference is output current.

Edit
Ok this is really confusing, in the hybrid inverter page it says AC output for the 3.6kw and for the 5kw inverter the ac output is 5kw but for battery info on BOTH it says "Max. Charge / Discharge Power 3300W / 3600W" this is from the official datasheet but the battery itself only lists 80A as charge/discharge.

Im getting a headache again, got like 30 chrome tabs open, I am getting the suspicion that 3/3.6kw is the kind of breaking point of charging speed.
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Start up voltage seems high to me….my 3.6kw inverter has a start up of 100v on both mppt’s
 
Welshman said:
Start up voltage seems high to me….my 3.6kw inverter has a start up of 100v on both mppt’s
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This is their official datasheet, seems like a broad copy paste job for everything lol.

image.png


What is odd is that for all those the charge discharge is 3300/3600 respectfully at 65/81A but the AC coupled at 3kw is 3000 charge discharge at 60A, something with all these datasheets just seems really off.
 
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Welshman said:
Just be aware that if you do try and build something in the garden to house extra panels, that 4 may not be enough for 150v start up for the 2nd string
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I would be thinking about building something if I was looking at it face on 10ft left to right and 20ft down to be storage and woodworking shed space for dad

Going to give up googling for tonight, been at it nearly 4 hours now, wait to hear back from GE and installer.
 
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Ron-ski said:
I thought we'd already established the chimney wasn't going to cause significant issues.
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oh we did but I was just answering a question, I just liked the idea of individual panel monitoring to know if one is playing up and if one goes poof the rest will work and it will be nice to know which one has gone wrong or is playing up.

I like seeing individual data rather than the whole and they are supposed to do better in lower light conditions.
 
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Its a nice to have, and I have it on my SolarEdge system, I originally thought the same as you, but its extremely rare that I look at the data. Its also extremely rare for panels to go poof, as being better in low light, no real idea, but if the light is low then there isn't much power there anyway. Your also adding another point of failure, and optimisers / micro inverters are far more likely to fail than panels are.

I didn't bother with optimisers on my second array.
 
I would agree with Ronski, when I looked into it, inverters (of all sizes) were the highest point of failure especially around the 10 year mark.
Panels are outlasting original thoughts considerably.

Once you get to know your system you will know what it can produce anyway and hence will be able to see a trend change over time if a panel is down.

I would only get micros myself if I could get them loft mounted (I have seen some installers do this) so they could be changed without a full set of scaff etc
 
Looks like the 3.6kw hybrid should charge the batteries up at 3.6kw so can get 14.4kw charged during the go period, apparently only used 5kw last night of electric like before the hot tub was switched on, must be hot enough out to not have needed to warm the water up at all. Need to look into getting some insulation to wrap around the thing for winter.


MCW I looked into the solax and you can have max 3 batteries in series on single phase ( 15.5kw usable from 17.3kw total) but it reports them at only having a 4kw charge rate max for 5 minutes for the triple x batteries and the 3.0 only up to 12kw storage on a single inverter.

I think the GE 3.6 is going to be best bet for now unless I swap out 2 9.5 batteries and see if I can squeeze in 2 all in 1 units.

Edit
Definitely won't squeeze 2 of the all in ones into budget, ~14kw on cheap tariff will more than make up for any usage on grid during the day if I cannot float on solar.
 
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Only just noticed today when I spotted my battery wasn't charging that my discharge at 4pm was still enabled, although in Eco mode it just sits static. Stupid Givenergy.
 
Think I might go for the AIO unit, 1 for now til they get parallel system working then pick up another later in the year. Mum has turned hot tub off now so daily usage is back to sub 15kw and hopefully by winter they will have it working and ill pick another up for when she wants the hot tub back on so should clear the daily kwh usage easily still.

Apparently can't use any other battery system or hybrid inverter if I go with the AIO unit so its a kinda if you do this you stuck with this type deal but you can get 10 year warranty on it so should be absolutely fine.
 
I don't think you'll need more battery than the AIO unit most of the time anyway.

Even in winter sun still does something for load.

Excess battery is nice to have but not critical, and the 1st battery will give the most value/return.

Don't forget in Go the cheap energy can also power the home for 4 hours, so you only need enough to cover the other 20.
 
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I agree with the Hippo here.

When I was playing around with models of usage and cost , I found the sweet spot to be around 50-70% of daily usage as battery storage when you have a half decent array.
In the proper depths of winter, just accept you are not going to generate much and most days will be short when taking solar + battery compared to usage.

But for at least 9 months of the year, many days will generate enough solar that your grid usage of peak units (I am assuming with batteries your on a cheap unit deal for some point off peak) will be low and hence grid cost will be fairly minimal.
And for probably 6 months thats going to be practically zero. Bar the odd day.
Attempting no peak units from the grid ever, just like generating enough solar to never draw from the grid are simply uneconomic in the UK.

When I was simming my potential system I seriously considered adding an extra 5kwh. When I simmed it the ROI came out at 10 years, because the additional benefit was very time limited. (Due to above). 10 year ROI with 10 year warranty? Nah.
Every person and every situation will be different so there is no right or wrong here in general, you need to understand your likely position.
There is a "rule", called the 80/20 rule. And it applies to solar as well, 20% of the spend will see 80% of the benefit. And ever increasing spend will see lower and lower marginal gains.
The 80/20 part is not specifically true (its probably more like 40/60), its just getting across the marginal spend and marginal benefit are not fixed, you need to assess each potential "step" in order to see how that will perform.

The biggest challenge with solar and system paybacks is that they rely on a load of inputs that will without fail be in constant change
The normal price of electric, the relative price of cheap vs expensive tariffs (ie off peak subsidised), your usage, special tariffs being available at all etc.
So many factors mean you need to make a sensible assumption and go with that.

I would say that if your primary motivation is saving money then its a harder call and better to be cautious and not spend too big. If your primary motivation is doing the right thing for the environment and not specifically for saving money long term then its easier to go for something larger with the higher risk of a longer (or possibly never) ROI.
 
So battery update time.

This morning I triggered a formal complaint to my installer.
Solax came back yesterday with the same nonsense where they take a limited sub set of data and say its working fine. I am not sure if its that they are deliberately attempting to mislead or if they are just not up to the logic and maths required to support the query.*

So the fortnight starts ticking today for my installer before I can escalate to MCS.
I have offered that the fortnight can be extended, I am after all only looking to fix the lacking storage position, but with the proviso that I believe what they are offering is likely to fix the issue.
Otherwise its 14 days then escalation.

In order to prove, yet again, the problem I fully discharged the batteries last night. The charge again followed exactly the same as historical, pulling around 5450w for 1.75 hours which gives a total input of around 9.5kwh.
This moved the SOC from 10% to 100%, which should in reality require somewhere around 11.5kwh, allowing 0.5kwh for Ac to DC conversion loss.

* the way they approach this is to take a partly charged position, and work out the charge added to move from say 50% to 100%. As I have explained before this works if a fully charged battery has partly discharged. It doesn't however work for a fully discharged battery.
A fully discharged battery will show the correct charge until around 80% when it will jump very quickly to 100%.
I am almost certain the issue is as @Ron-ski has said that 1 or more cells are out of balance, and as such once those cells reach the correct voltage the whole system assumes that all cells are full.
The system does not seem to be able to correct itself, so even if it is monitoring and balancing individual cell voltages, after 6 months it has not corrected itself.
If it was possible to correct itself you would have expected by now that it would show a different gap between actual input and required input. The gap remains constant (within reasonable calculation with 5 minute data intervals)
 
HungryHippos said:
I don't think you'll need more battery than the AIO unit most of the time anyway.

Even in winter sun still does something for load.

Excess battery is nice to have but not critical, and the 1st battery will give the most value/return.

Don't forget in Go the cheap energy can also power the home for 4 hours, so you only need enough to cover the other 20.
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That is what I was thinking about with the 2x 9.5kw battery option but my install hopes went from 5kw+ to sub 4 panel install on roof hehehe.

Was going to initially set a 10% reserve so the battery didnt drain completely and -4 hours that batteries wont power house during the 4h period.

Wish I was more well off, would be a lot easier to make decisions.
 
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