Hi,
I have a 3-phase MultiPlus 2 (5000) system with DESS activated.
When charging, it seems to go through 15 minute cycles, here’s an example from today.
Anyone got a clue as to why this happens? I’m pretty sure it’s not an overheating issue (charging at about 2800W max per phase ), room temperature is fine.
Most of EU just now switched to a 15 minute interval for dynamic pricing. In some regions, the cheap intervals are NOT consecutive.
See example: https://nordpool.didnt.work/ where today, the last 15 minutes of many hours are more expensive.
So you may need to check what is happening to your pricing. Maybe that solves the mystery. May no.
DESS target soc is per 15mins. DESS reactive strategy will try and ensure smooth transition between the windows. As long as your DESS configuration is set to charge a little bit less than what it is technically capable of, the system will have time to smooth transition.
If you want more, simply “up” the charge kWh a bit in DESS settings to closer resemble the system capabilities. Once you reach that, it will charge continuously as it may never reach the DESS target soc. Find the number that works for you so the stops at the end of the windows are shorter and DESS will still make schedule.
Dat klopt. DESS werkt met 15 min. blokken. Het gedrag wat je ziet wordt veroorzaakt doordat de Target SOC (Remote Console → Settings → System Setup → ESS → DESS) eerder wordt bereikt dan berekend. Dat komt waarschijnlijk door verkeerde instellingen. Als je bijvoorbeeld de SmartShunt zegt dat de batterij groter is dan in werkelijkheid dan bereikt hij eerder de Target SOC. Hetzelfde gebeurd als je de DESS instellingen verkeerd zet. Als je bijvoorbeeld de Maximum charge power lager zet dan hij kan, let op, kan dan zal hij harder laden dan verwacht met hetzelfde resultaat. De setting Maximum charge power is geen begrenzing als een soort peak shaving maar geeft aan wat het systeem maximaal kan. Maar ook in de DESS settings kun je een grotere batterij aangeven dan hij werkelijk is met weer hetzelfde resultaat.
Even proberen en puzzelen dus.
That’s correct. DESS works with 15-minute blocks. The behavior you’re seeing is caused by the fact that the Target SOC (Remote Console → Settings → System Setup → ESS → DESS) is reached earlier than calculated. This is most likely due to incorrect settings.
For example, if you tell the SmartShunt that the battery is larger than it actually is, it will reach the Target SOC sooner. The same thing happens if the DESS settings are incorrect. If, for instance, you set the Maximum charge power lower than it actually is then it will charge harder than expected, with the same result.
The Maximum charge power setting is not a limit in the sense of peak shaving, but rather indicates what the system is capable of at maximum. But in the DESS settings as well, you can specify a larger battery capacity than the real one, again with the same outcome.
So it’s a matter of experimenting and fine-tuning.
what is the size of your battery and how much power can you charge/discharge? If the energy per 15 minutes gets near to 1% of your battery capacity, the DESS power setpoint controller lacks resolution (stepsize 1%) to do a good job. Could it be that you are experiencing a control artifact related to that?
That’s not it, as this has been going on for weeks and these 15 minute intervals are not specific to a certain part of the hour either. My DESS pricing setting is per hour still.
The same thing happens if the DESS settings are incorrect. If, for instance, you set the Maximum charge power lower than it actually is then it will charge harder than expected, with the same result.
( I’ll reply in English so more people can read it )
Is this the setting for Dynamic ESS in the VRM under Battery? I have that set to 4kW for both charging and discharging. This setting is somewhat puzzling too, as when discharging for DESS, it discharges with 4kW, but for charging is charges with about 6500W in total, despite that setting, which includes both grid and AC OUT coupled PV.
I’ve read elsewhere that the VRM DESS setting is only used for calculations, but why does it discharge with the 4kW as per setting then?
I’ve also read that you can use the settings under Peak Shaving in the ESS menu. But those are per phase input limits, which is incorrect, as there’s also PV incoming at AC OUT and I don’t really care about a setting “per phase”, I want to limit the power going into the battery, not limit the power coming in from the grid.
The only option I can find would be “limit charge power” under ESS, currently no limit is set, and to be honest, I have no idea why it’s charging with the current it’s currently charging with from the grid, that’s probably the DESS algorithm then.
All in all, I would welcome a setting that limits power going into the battery, regardless of coming from the grid (either phase) or AC OUT coupled PV.
It’s a 48V 280Ah system (LiFePO4, so 51,2V nominal), no connection between Cerbo and battery. It’s currently not limited as per settings in the Cerbo, VRM DESS max charge/discharge both set to 4kW.
Ok, thats about 14.3 kWh corresponding to 0.143 kWh per 1.0% SoC. With 4.0kW power limits or 1.0kWh per 15 minutes, your system will at max charge/discharge 7.0% SoC per 15 minutes. In that case you would not be affected much by the 1% SoC (per 15 minutes) resolution of the ‘target SoC% for current time slot’ control system.
In contrast, we run 88kWh, 0.88kWh per 1% SoC. with same 1kWh per 15 minutes that is 1.1% SoC per 15 minutes, which is severely affected by that 1% control system resolution.
Can you tell a little bit more about your setup? Inverter type, 1 fase or 3, SmartShunt settings, DESS settings, etc.
40A single phase mains, MP II 5000 plus an additional 8kW boost charger (on the MP II’s AC-out) to max out that 40A mains during low price windows (neatly limited by the MP II’s ability to limit AC-in amps). 88kWh batt, BMV 712 batt mon (for accuracy), DESS Trade only (no solar). Tibber NL dynamic 15m pricing. And all house loads running off a separate 3kW inverter, freeing the MP II to act as a dedicated trade system.
Jan my question was meant for @MartijnT
not sure what shunt settings you want.
With 4kW per MP2, 12kW total, the system can do 3kWh per 15 minutes corresponding to 20.9% SoC per 15 minutes, which should work fine with a 1% resolution for the target SoC% control system. Any issues experienced are likely originating elsewhere.
With 4kW per MP2
But it’s not charging at 4kW per MP2 (12kW total), it charges at about 6500W total (around 110A into the battery).
There must be something like this.
And a screenshot from your DESS settings would be helpful as well.
What comes to mind first is the battery capacity is underrated for your system. As a rule of thumb I use 1:3 DESS trade mode meaning when you have 15 kVA inverter power you need 45 kWh battery capacity.
I’m afraid a SmartShunt (not the Lynx) doesn’t have this screen on the Cerbo, but … Victron Connect to the rescue.
Here’s the VRM DESS settings…
It’s just like with boats: we all need a bigger battery.
isn’t that battery charge/discharge power per system? then you should up that to 12kW (pending max current of your BMS as limiting factor)
