The last few days with lots of sunshine, I was very happy with DESS in Green Mode. But today, the first day with lots of cloud cover and rain for a long time, unfortunately not at all:
Due to the low solar forecast, the target SOC was significantly reduced. According to DESS, the battery will not reach a charge level higher than 26% today and will draw energy from the grid for several hours later in the day:
I can confirm the DESS soc is stuck at 25%, supplying loads and feeding back to the grid. After a few bad weather days, I’ve got an MPPT full of solar and it’s not charging the batteries
99.9% sure that the flow isn’t going from the battery into the grid, but going from the battery to the loads and from the PV installation to the grid. And I know that all the numbers don’t add up correctly. That is because they are always best effort estimates of how the energy flows in the system.
The problem is, that energy is sold to grid instead of charging the battery!
In Green Mode PV surplus should be used to charge battery instead of be sold to grid. Only after battery is full, energy should be sold. That’s also written here:
Target-SOC stayed very low for the whole day yesterday, nevertheless DESS sold PV surplus to grid instead of charging the battery. That doesn’t make any sense?
I am seeing the same behaviour on a couple of occassions but maybe for a different reason. I’m running the UK Octopus tariff on DSS and I’ve just seen a situation where the price fluctuates which would be the ideal opportunity to charge the batteries from the grid in a burst.
Currently I’m sat with min ESS soc and DESS target soc at 15%. My solar yield is very low due to bad weather so that’s just covering a little of the loads.
ESS 1 Soc low has kicked in but is just holding the battery SOC ahead of what appears to be scheduled on the hour for a grid charge under DESS at a negative and positive price point. Sadly the hour of negative / neutral is 30 minutes past the hour respectively.
Looking at the graph further, my understanding is that whilst tariffs are running at 30 minute intervals, the schedule is based on an hourly interval ? Which would make this expected behaviour but inefficient for the tariff and a possible anomaly for some expectations of DESS.
I think, thats a different story. You are discussing charging battery from grid at low buy prices.
The problem i want to discuss here is that PV surplus is sold to grid instead of charging the battery although SOC is at a very low level. That’s a behavior which shouldn’t be at Green Mode
I have had the exact same issue where solar has been exported rather than charge the battery.
My last message was a little distracting and I wasn’t meaning to waddle off topic there. Apologies for that. That said, my observation outlined had me thinking with regard to the solar export (prompting the message) and I do wonder based on tariff if it is owing to the schedules being in hourly blocks where as the tariffs in some cases have more granularity with 30 minute blocks. Yes, the priorities for Green are clearly outlined but there does appear to be a cost monitoring process that may override that?
I’ve got my install set to 1min / realtime however when I get a mathematical benefit to a tarrif that crosses 30 minutes past the hour e.g 10:30 - 11:30, the relevant action is not evaluated or re-evaluated hence my query around schedules. That said, I haven’t been able to find any half hourly breakdowns of the schedules as yet which may provide more insight on the actions.
I think that issues are actually being mixed up here. The topic I mentioned here “PV surplus goes to the grid in green mode instead of to the battery” has nothing to do with 30min tariffs. I have a 60-minute purchase price and a constant sales price.
Concerning 30min tariffs please move to another thread - thanks
Today Green Mode looks good: PV surplus is used for charging the battery instead of selling it to the grid, although target SOC higher than actual SOC:
