Dear Victron team, I’ve been working on the DESS project for two years now. I’ve been following its development with great interest and read many posts here in the forum. Some of the criticism is justified, but some users also go a bit overboard. Many problems have been solved, and great things have been achieved. Since I also have some contacts with operators of competitor systems, I think I can assess it fairly realistically. The problems mentioned there in connection with forecast-based charging and similar systems remind me strongly of the initial problems with DESS. Now, however, to my actual thoughts. There’s one problem that repeats itself very often here in the forum and runs like a common thread through it. Too much electricity is often sold or too little is added to the storage system when the forecasts aren’t 100 percent accurate. This then leads to unnecessary references and often to criticism. The special “DESS min SOC” has also been frequently discussed and tested in this context. My idea now would be to introduce a third mode. This mode should aim to always load as much PV power as possible into the storage system and, if possible, only sell what exceeds the storage system’s capacity. As a practical example: The system expects 100 kWh of PV yield, 40 kWh of consumption, and 20 kWh of storage capacity remaining in the system in the coming time interval. The system would then ONLY sell the surplus of 40 kWh at the most expensive time. Maximum utilization of the inexpensive PV power would be ensured. However, the previous strategy would have to apply to the additional power purchased, and only the absolutely necessary demand (Soc) would be purchased. Perhaps you could discuss this approach internally.
I would suggest a mode when the DESS off / Green mode / Trade mode switches itself on or off depending on dynamic day ahead prices.
My common practice at the moment.
When difference between 0 an 6 cent/kwh DESS OFF / std ess mode solar goes to battery, house supplied from battery.
When difference between 6 and 12 cent/kwh DESS green mode ( minor losses due to heavy load to the system )
When difference higher than 12 cent/kwh DESS Trade mode. Most benefit, even with high roundtrip losses.
Just to clarify, the issue doesn’t affect me personally at all, because I don’t sell any electricity. I think even if Victron develops a suitable mode for each individual unit, it would be a bit too comprehensive. But this issue of having to buy back from the grid due to excessive sales is a recurring theme in many, many comments.