(I realise there's actually a lot of work going on with DESS. So this is something for the list, and not a 'something is broken' report.)
DESS in green mode does have a tendency to empty the battery. Not every night. But often.
At first, this gave me a good feeling — I may as well profit from the stored energy, right?
But thinking mathematically, there's an efficiency loss in going via the battery. The battery discharge is recouped only a bit later on in the day, when the sun comes up, as the battery starts to charge. Less what is lost to heat. Plus extra strain on the battery. (Point is: don't discharge, just wait, and feed in the PV direct, avoiding the battery.)
The battery discharge, even in green mode, feature does make sense to me. But only when charge-from-grid prices are favourable. At least for me, that seems logically to be when sell price >> buy price * efficiency factor. And generally, I'd not want to do that if the difference is marginal (what's the point in stressing the equipment and making all the noise and heat in return for making £0.01?), but when prices go low, and especially when they go negative, then it's a no brainer — discharge ahead (so long as we can re-charge quickly enough to recoup, and don't breach the low batt threshold due to concurrent consumption), and then turn on the charging taps to the max!
Was going to pop this on the issue list in GitHub. But it occurred to me there may be different views so I thought I'd start a discussion.
