DESS does not respect the price settings and loses money.
I noticed that DESS (in trade mode) sells from the battery in the evening and buys at a higher price in the morning. Since the price differences are small, I wanted to be sure and tried to change the formula for the purchase price +1EUR. This increased the purchase price tenfold and the price differences are clear. But the DESS algorithm behaves the same. It loses money.
Example in prntscr:
11.9.2025, 9h … I increased the purchase price +1EUR
11.9.2025 19-21h … DESS sells from battery to grid (for 0.14-0.18EUR)
Same problem appears when I using fixed prices. DESS also did not respect the purchase price.
I solved the problem with the Czech importer. He acknowledged the defect and wrote that he does not know why this is happening. He refused to solve it further.
Please advise how to fix it, or repair DESS. This can happen to many customers who are not paying attention.
Petr
What Is the DESS forecast for the morning hours like? Ist it “expecting” to buy from grid, or is it expecting to have enough battery left for these hours?
It is a known issue currently, that DESS sometimes underestimates the nightly consumption, and therefore sells “to much” in the evening, which causes grid-pull in the morning.
But from your screenshot, there are about 27% SoC left, so there should be enough to drive loads I assume?
In that hour, you had 330 Wh Consumption and lost ~1% Soc. Not knowing your battery size, but that seems like battery is used, despite the energy graph does not show that?
Do you eventually have ESS set into “Battery Health” Mode? This will raise the minsoc daily by 5%, when It couldn’t reach 100% during the day. That may continuously “lock down” the 5% DESS calculated to work with during the morning hours?
The weather forecast for the next day is not important, because the sun does not shine between 0-6a.m.
I remember that DESS had in its forecasts on 11.9.2025 that it would buy between 0-6a.m. I left it to him to see if he really did it, because we consulted with the supplier at that time.
My night consumption between 0-6a.m. is still about the same. The prediction is not complicated.
My min SOC is set to 20%
My battery is 14kWh. So 7% of the battery is about 1kWh. That is not enough for 0-6a.m.
On the contrary, it can be seen that DESS sold about 2kWh on the evening of 11.9., which it then bought from the network 12.9.2025 between 0-6a.m. And it had planned it in advance.
The same thing happened on the night of 10-11.9.2025. I am attaching a prntscr from 10.9.2025, when in the evening DESS sold 4kWh and between 23-24p.m. bought 0,6kWh + on 11.9.2025 between 0-8a.m. bought 2kWh.
This has happened several times and that is why I increased the purchase price by 1EUR (11-9-2025 at 9a.m.) and tested if it will do it again. DESS doesn’t care - it doesn’t take that formula into account. You already know more from the first message of this ticket.
I know about Active SOC, but I hope that DESS also knows it and works accordingly. If not, please fix it. (I currently have Active SOC turned off = Optimized without battery life, but I used it before)
Also, theoretically, there could be a problem in the currency of our state. We do not use the EUR currency, but CZK, but the prices in the graph look calculated correctly.
BUT please take into account that I increased the formula for the purchase price to more than 1EUR, so DESS should prevent buying from the Grid. But DESS doesn’t care - it doesn’t take that formula into account. I think it’s clear that it’s calculating the SPOT price and not the price entered in the formula by the user. In that case, buying and selling could make sense.
I didn’t mean the weather forecast, but the forecasted energy flows on your system:
What does this graph show for tomorrow moning hours? 330Wh Grid2Consumption or 330Wh Battery2Consumption?
The difference here would be: If it “expects” Grid2Consumption, then it is indeed a false planing in that area.
If it expects “battery2consumption”, then the plan is to keep enough energy in the battery - but it fails for other reasons. That could happen if you have higher consumption in the evening (after selling) than the forecast expected.
Can you also double check, you have configured the right battery size in VRM? Providing a “Optimistic large capacity” will make DESS to overestimate how much energy could be stored “in 7%” causing it to run out of energy, when scheduling “too close” to minsoc.
OK, about energy flows forcast … As I wrote in last chat: “And it had planned it in advance.”.
Please, don’t forget that I’ve been watching this for a few days and paying attention to it. At 9 am I changed the purchase price by EUR. I was paying attention to what DESS was planning and doing. But OK, I can be wrong.
The plan is good, only the consumption has changed - I completely understand you and that’s exactly how I thought. I remember that DESS calculated the purchase in advance and the only explanation that came to my mind is that the SPOT purchase price at night was low and DESS does not take into account the price formula entered by the user. May be there is some formal error in formula ?
Yes, theoretically I could confuse Battery2Consumption and Grid2Consumption but the difference between them is big. Red and blue colors, you can’t mix them up. But I understand you - I can be confused. It’s no problem to simulate it again. Unfortunately, we have bad weather here now and therefore an insufficiently charged battery and therefore I’m not selling now. Maybe in a week.
It’s a shame that the Czech representative of Victron, the company Neosolar, wasted a month when it had administrator access to my power plant. I asked them to pass it on to the manufacturer’s programmers, but they refused.
I’m attaching a prntscr where I have the battery defined.
Please also look at the formulas defining the prices to see if there is any formal error in them, etc.
You are running in Trade-Mode. Trade-Mode does not care about self-consumption - it will only buy when it’s cheap and sell when it’s high. Your prices also don’t indicate any trading-possibility - what you see in terms of selling is just “deferred selling of solar” collected during the day.
So, you probably better switch to Green-Mode. Green-Mode will actually do what you expect: Try to maintain enough Battery-SoC to cover nightly consumption.
According to the last chat it seems that you are not finding a solution to the problem and therefore you are recommending me to stop using DESS. I’m afraid that in your last chat you are:
oversimplifying the DESS task
missing the problem
ad 1) Trade mode is not supposed to sell all the energy regardless of its own consumption. It is not described in the description of the mode. It is supposed to sell excess energy and it is supposed to do it at the most appropriate time (higher selling prices).
You yourself have described DESS this way in previous chats and all users logically assume it is like this.
(In addition, I would like to remind you that I have already written that I have also tried the fixed price mode and it contains the same defect and I think Green has it too)
Trade mode is the best choice for users on SPOT and therefore for me. Trade mode sells in the morning at a time of higher prices, when high production is forecast. So that at noon, when prices are lower, it has enough space in the battery and does not sell. It waits for the evening to sell. It does its job well.
But it has a defect and it needs to be fixed.
I believe you will succeed.
ad 2) The problem is not that I wrote it here, but that DESS lose money. I described the case and provided real graphs where DESS repeatedly fails. This is not an isolated case or a random defect. This is a systemic defect. I will provide other cases with a forecast like you wantm, when we have sunny days, but Victron certainly has a simulation environment, so it can simulate the situation and see the behavior of its algorithm.
The fact that DESS fails is a defect and many users are paying the price for it. You will not solve this by advising me not to use DESS. The problem persists and there is no choice but to solve it, otherwise Victron will lose real money to users. (Increases electricity bills)
Please do not forget that I am a Victron fan and I am trying to help. I am not your enemy
Petr
The topic of this ticket is “DESS does not respect the price setting and loses money.”
This is not about which DESS mode I should use.
After all your verification questions, we have not come up with a reasonable reason why DESS behaves in such a way that it loses money.
Even if it were better for me to use Green mode (which it is not and I wrote the reasons why), I think that the interest of all Victron employees should be that Victron works meaningfully. That it respects the data entered by the customer and that it does not lose money.
Is your position on the matter the official position of Victron, or will you please forward this ticket to the responsible person at Victron?
You are a Victron staff according to your business card and yet you can neither solve the problem nor pass it on to a competent colleague?
So Victron has no way of receiving feedback from customers?
No way to tell the customer that you thank them for documenting the problem and when can the customer expect the problem to be fixed?
We can communicate privately by email.
DESS is still losing money.
A month has passed and DESS is still making the same mistakes.
ScreenShots:
6.11.2025 at 16-18h. DESS sells from the battery
and from 6.11.2025 23h to 7.11.2025 8h DESS buys energy more expensively.
