Dear community,
I have a recent installation with 9kWc of PV panels, a 10kW Multiplus II inverter, two MPPT 250/70, and two 16 kWh batteries (NKON). I don’t sell excess power to grid yet, and even later it will be 4cts/kwH so not worth it. The goal is to optimize self consumption.
The system is operational since feb the 5th, and DESS configured since feb the 21st.
I have been very pleased to discover the DESS option able to manage the TEMPO option available in France, as I thought it would require some coding or manual adjustments.
I checked some posts about this option, and understood that it is based on some “learning curve” of consumption habits over 8 to 15 days. So I let it run and “discover” without any manual adjutments, in order to see what would happen.
Since then, we only had 2 “white days” an no “red days”.
During blue days, the behavior was a little “strange” trying to charge the batteries during “off peak hours” and discharge during “peak hours”. This is a nonsense, the price difference is very small, and given the charge/discharge efficiency of batteries + power losses in cables and converters it does not make any sense. I increased artificially the battery cost to 0.03 cts/kWh in order to compensate, and it seems better now.
But, I notice that the system tries to overcharge the battery, and on the opposite, for me it should start the day with minimal charge in order to be able to use the excess solar power, and at worst case use the grid at night if solar power was not sufficient as the price difference between night/day is not significant. The ebst economy is to use solar power, not to use off peak hours rather than peak hours, for bue days.
Solar power is never garantied, so it is a risk management.
On “white” days, the peak hours are more expensive, so the grid should not be used during peak hours unless it is necessary. but again some tolerance is accepted as the price is not so high.
On the 1st white day (march 3rd for my installation), it worked quite well. Almost no consumption from grid during peak hours :
However, today march the 9th, 2nd white day, the system tried to overcharge the battery to 100%, which was not possible due to bad weather, but it has used the grid power although the price was high and the battery already charged enough. May be it tried to balance the battery cells, but this should never be a prority during peak hours ! I configured a balancing every 14 days, and it should be intelligent enough to postpone this balancing during white or red days.
I have seen othe posts saying that during “red days”, some systems still use the grid during peak hours when the price is dissuasive. I hope to see some red days in order to check the actual behaviour in my case. Of course, as a DESS user, I can accept some “errors” as the algorithm cannot be 100% adapted to my home, but some basic rules are expected for any TEMPO user : I have read all the DESS posts, and all of them tend to come back to their node-red codes, as the DESS errors seem unacceptable. One even says that it worked fine until october 2025, and then had wrong behaviour after a software update. We can accept some bugs and progressive improvements, but it seems that this is a black box, without any communication from the development team, bug fixes and version history, etc… This is not what is expected in 2026.
We really need some communication, essential to build some trust, as well a good reactivity when odd behaviours are reported.
Anyway I think that this DESS option is a good thing, I hope that it will be refined and improved rapidly, especially for red days !
Cordially,
Jerome
