I believe that I neither have enough panels nor storage at the moment. But now have up to twice the storage I did 48 hours ago (up to maybe 4 or 5 days' worth), and I have ordered a 100W panel which should nearly double daily energy capture: heavy overkill in summer but then I may be able to divert some of that 'extra' energy sensibly as well as taking down a few of the panels...
Am I answering your question?
PS. To be clear: I don't much care about battery chemistry (though anything other than just LA makes life more complicated), only about 'usable capacity' which I take to be about 50% of nominal for LA and nearly 100% for Li.
Here's where I was going with this. There seems to be a fine line of balance on needed versus available to use and replace, with respect to most RE systems.
My Solar system is no where near as large as yours, but I get great SUN during the winter months due to trees losing their leaves. Even now after having moved my panels up a full 11/2 stories higher than they were, I still have shade problems in the latter part of the day.
In the winter time with my small (90watt) system I can fill my NiCd battery packs (currently 64Ah at 14.4Vdc) if drained completely in about two days of winter sun, as of last years testing, and they bounce right back. If I were to try that what the backup pack of SLAs which are 12Vdc at 72Ah, they would not last much more than a season or two.
Since you have long term data of your system, I was trying to see if there's a more defined correlation.
I of course am not taking into account losses either since we use the packs every morning (coffee pot being the heavy hitter at 600watts).
Plus, if you were up for the challenge, I would offer some of the NiCd packs for you to try and re-purpose into packs similar to what Norm has done
These and a Ghurd controller would be all you would need for all the extra power you have in the summer.
CO has a BD person in London now and can ship to him, then to you.
I know and understand the environmental impact of Cadmium but my stance is to completely use them up before recycling.