I tried giving DESS a new chance after some weeks. It was running for a week now, and behaved quite well for most of the time.
Still minimizing grid useage and feeding all solar to the battery is the most economic approach for me.
Today AWATTAR is selling the kWh for enormous 55c/kWh at 19:00 and still DESS thinks it’s clever to sell solar production to the grid instead of charging the battery. IMHO this is just wrong behaviour.
I’d really like to see an approach were charging the battery has ALWAYS TOP priority and nothing is sold back to the grid. I get paid 4c/kWh. And I’d like the system to charge from the grid at lowest possible price if there is no sun expected.
Full agreement, the same thing happens to me almost every day. At the moment with enough sun, this has little effect, but if we wait for the winter, then it becomes a problem.
Are you refering to that 0.12 kWh that got send from solar to grid? Small mismatches will always happen. The plan was to charge from the grid at the low point of the day, as you wished.
Also it looks like you are consuming about the same as your solar yields. Which is good in a way, but doesn’t leave much room for charging the battery for night consumption.
In green mode, the system will use the solar yield to cover the predicted consumption till next sunrise first and only if it has more energy above that, it will feed back into the grid at the highest price.
Do realize that the system has been developed to make the optimal schedule, based on predicted solar, consumption and prices. And, which is the main time and thus money saving part, save you from having to do that manually.
Nah. No exactly what happened. It was pushing back 500W+ to the grid (which resulted in 0.12kWh back to the grid, but only because I was switching DESS off, otherwise it would have continued with it). And after that I was switching DESS OFF. And from that on the system was leveling out grid to 0W, until I switched to “keep batteries charged” at 11:00.
You’re correct that the solar power is quite low for my load and the relation solar power to battery capacity is bad (5kWp solar : 13.5kWh battery). The system will not be able to handle pool pump and pool heat pump, the whole house hold AND charge the battery. It will though when pool season is over (in a week or two). Then, noone will be home during the day, and all solar will go into the battery. It would be bad then if DESS decided to charge at a later time and redirect solar directly to grid. This is ALWAYS a bad thing in my setup. Battery was super cheap, buying from the grid is expensive, and selling to the grid is useless.
So the best setup for ME: Put everything surplus into the battery, and charge at low rate in case there is too little sun, to cover high grid buy rates in the evening time (always between 18:00-21:00).
See, this is what I don’t understand: Why discharge to the grid for a 4c/kWh profit, and then buy from the grid at a later time for like 25c/kWh, when this energy could be stored for later anway.
I’m not sure it was a glitch, as this happened a few times the last days, and it lasted for some time. But little do I know about the internals, maybe I was too impatient.
If you access those settings via beta VRM, you can even set that restriction for certain hours of the day. That might already solve some of the issues.
Meanwhile I will search a bit further on what happened on the system between 9:00 and 9:12 this morning.
The system was NOT discharging from battery to grid (something that is completely turned off, as noted in your post from the very beginning). The problem was, that there was no charge to battery, but solar to grid - and I was expecting this surplus going to the battery instead of grid.
We did look deeper into the data and for now can only conclude that the system did what it was instructed to. If that instruction was correct, based on the info the system had at the moment, is the next thing to check (but that will probably be tomorrow).
Note that the scheduling is always done based on assumptions and forecast . There is always a chance that the system makes the wrong decision. In this case the forecast said that there will be lower solar forecast (~0.4 kWh) than reality (1.1 kWh). And consumption estimate was 0.8 kWh. That hour was not treated as excess solar, causing the system to opt for blaming offsets in the forecast on the grid. In this case selling resulting in selling the difference to the grid.
Do also realize that this decision has nothing to do with the high grid price of this evening, as you seem to suggest in the subject.
First of all: You know like 100% better what the system does than I do. Unfortunately I’m really bad in writing code like that. That’s totally over my head.
And I’m pretty sure there is a reason why the system does what it does. It just doesn’t match my personal goal 24/7. Especially unexpected and unplanable high power demands like phev charging and such makes planing impossible.
That’s why my approach would be different: Charge the battery with SOLAR excess as much as possible. NEVER let any solar energy go to the grid, and find the most cost effective charging pattern that makes the system go “off grid” over night, or at least cover high cost peaks during the evening/coming home/dinner preperation period.
Summed up, I know way to little about the system. I can just post my suggestions and hope that it’s helpful for other ppl and you guys.
And still: IF there is solar excess the system always should have the chance to adopt on that and charge the battery a little earlier and reduce the forecast for that amount maybe?!
Thanks a lot for your support and explanations! Much appreciated.
