When using DESS there is electricity imported from the grid while price is high:
I think this is caused because the minimum SOC for the specific time slot has reached too early.
A solution would be a DESS SOC margin. For example, when the minimum SOC is set to 20% and the margin is set to 10% DESS tries to reach 30% minimum SOC but will continue to 20% if the schedule is not matching the actual consumption.
I see this issue with firmwares up to Venus OS v3.60~68.
Hi thanks for the report. We’ will look into this!
I agree that having a configurable margin of some sort would be intersting. I have a fairly large system (4x Quattro 10ks), and the power draw of the inverters themselves is ~400W+ continuous.
I’ve found on low PV days, the system will buy power during a peak period, because the consumption forecast didn’t account for the continuous power draw of the inverters themselves and the system hits the min SOC too early in the day (https://community.victronenergy.com/t/dess-slowly-discharging-battery-when-scheduled-to-keep-target-soc-flat/)
Outside of adjusting the DESS algo to include this continuous power draw, the margin idea may be another work-around.
At this moment I have running the AC, causing a higher consumption.
DESS doesn’t discharge to supply loads although the electricity price is high.
When I disable DESS the grid immediately drops to around 0 watts which is preferred behavior during high electricity price.
During DESS idle periods it would be better to keep grid at 0 watt or less to sell pv surplus instead of holding target soc until the sell period starts and buying expensive electricity or consumption.
I’m using trade mode, in green mode dess starts charging in the morning when the sell price is still positive causing to sell pv electricity during noon for a lower or negative price which is unwanted.
Yesterday and today it happened again. Yesterday because of the air conditioning, today because I was using the oven. Over the year this will cause a lot of kWh bought from grid at high price while the battery could deliver it.
I agree with Jeroen — Dess is behaving strangely. It seems that the battery forecast is being followed, even when actual consumption is higher than predicted. As a result, power is being drawn from the grid at odd times, when it should be coming from the battery instead.
I’ve added two examples:
The first is from last night. The battery did not compensate for the consumption. During the expensive peak hours, power was drawn from the grid to keep the battery at 100%.
The second example is from this morning. Between 3 and 5 AM, grid power was used even though the battery still had a state of charge of 75%.
@mpvader Is there someting wrong with my settings that causes Dess to prioritize maintaining the state of charge over actually responding to the meter (with the goal of zero on the meter)?
Again grid usage because dess wants to keep 100% soc for selling electricity a few hours later while using battery for consumption was cheaper than using grid.
Beside that, the hour after the grid consumption there was even enough solar to recharge the battery to 100% soc.
It would be better if dess keeps the grid at ess grid setpoint (usually 0 watt) until the period of selling starts instead keeping the battery at 100% soc.
I think that the default DESS strategy should always to keep grid at ess grid setpoint and change power only when buying or selling from grid and in the morning to sell surplus pv power directly to grid when it’s profitable.
Any news on this?
This morning dess used grid for consumption because soc was low.
When will a soc margin for dess be available to prevent this?
I am struggling with the same thing. Just last night I had to disable DESS Green a bit after midnight since it decided to sell excess to grid (with a 0.0098€/kWh price!). Battery was at 10% in the morning, and would have been lower if I had not stopped it. There was a risk I would have had to buy energy back with a much higher price.
At this point I find myself having to babysit DESS. Can’t leave it enabled.
I don’t know if this is caused by 3.60~74 but DESS is using the grid instead of battery for most part of the hour while the buying price is much higher than the selling price. I also see this behavior during night. I didn’t see this with earlier versions afaik. Even while the forecast is consumption is about right, it only delivered the first half of the consumption from the battery.
It discharged more to grid in the beginning of the hour than scheduled leaving no soc left for the rest of the hour. I dint know why it did discharge more than planned, it did not give any profit and caused loss.
Beside that I think consumption prediction per hour can often lead to unwanted use of grid power. For example when an stove, oven, dishwasher etc. is turned on. A configurable margin could help.
Although during this hour the consumption prediction was right, but the discharge to grid planning was not respected.
Have you tried using the restrict Grid to battery setting and put your peak rate times in?
It does know the pricing of buying and selling. I can’t restrict battery to grid because DESS decides when it will discharge for maximum profit. The discharge times vary per day.
Grid to battery is almost never used, because the difference between buy and sell price is not profitable.
If you count the cycle cost of your battery (easily 5 to 10 cents per kWh, unless you cheated with the cycle cost in DESS settings), at current prices you would lose money by charging from the grid at low price and selling back at high price - the delta isn’t big enough.
Only excess solar that was put into the battery (for free, because excess solar) is worth selling later, when sell price is at least as high as battery cycle cost.
I’ve seen some strange behavior with DESS recently but don’t have the time to check what’s going on.
Hi all, thanks for the reports. We’re looking into this and this behaviour can probably be further improved, but its not an issue in Venus OS itself.
(Which I’m happy with, since I want to now release Venus OS v3.60 as soon as possible).
have a good weekend.
Thank you for taking a look into this! It is a painful issue. I see you marked the issue resolved. Maybe it was a bit trigger happy decision because no fixes have been confirmed or even developed?
We have been looking into this case in detail now (sorry for the late reply)
We identified a “tiny” bug in the local dess-client, that causes the system to idle the battery here and allow grid-pull. Or say: We identified it as a difference in the interpretion of the selected strategy-set between the scheduler and the local client under very rare circumstances.
A fix is beeing worked on and tested. Will let you know, when it will be available in a new beta.
Quite a relief. I am about to order 3 x Multi RS with accompanying Cerbo, Lynx, Batteries and what more, so I do hope this gets the attention it deserves. DESS is the trigger to turn to Victron for many, so the last reply from staff is very welcome. Please make it work!
Should I sit on my hands or can I rely on resolution?
