I just set up a new ess installation in my new house using 3 (3phase) multiplus-II 6k5’s with a total of 32 kwh of capacity in batteries.
Solar is not in the game yet, it will be soon.
I had an installation in my previous home as well which was single phase and a bit smaller. So this is not the first rodeo.
What am i working with:
Dynamic energy tarrif that changes every 15 minutes (tibber)
Lower sell price then buy price (changed beginning this year at tibber in NL)
Trade mode
DVCC is in use
Batteries talk over CAN
All house loads are on AC Output, nothing is on the incoming grid.
Currently i am facing the following puzzle that i have not seen with my previous installation:
Whenever Dess has reached its target charge, in this example of today 33% i notice that it goes in a sort of idle state where it keeps discharging ~ 160 watts of the battery with the inverters on. 160 watts / 3 = ~ 53 watts per inverter, which puts it well outside of the “normal power” range of the 6k5’s and its not really generating any meaningfull power, just wasting energy all day by not staying idle + burning this energy as well. (I have an external meter before and after the multiplus to do my efficiency calculations in realtime, in this state i actually end up having a higher total power usage then when the inverters would simply go to idle.)
The weird thing is, i never noticed this on my previous installation, it would just go to idle / passthrough and i have been searching what it could be for 2 days now. The only sollution i have found is setting ess mode in vrm portal to “external control” effectively disabling it, the inverters go to idle in that case and just pass through and battery power is going to 0 watts in that case as well.
Any help would be greatly appreciated, if there is any more info i need to provide please let me know. Under here i add a few screenshots of what i feel is relevant:
This has nothing to do with DESS. This is simply the “self-discharge” of your overall system. 3 Inverters, Zero-Load Power 28W each, Self-Consumption of the BMS (each module) sums up as well.
Combined with low precision of measurements around “0 Power”, that is to be considered “normal”.
@dognose thanks for the feedback. I am aware of that. This does however not explain my main concern
The inverters stay “active” and discharge the battery, instead of going to idle like they do when i switch to external control, i assume then they get powered from the grid as the screens on my bms do not show any amps flowing when idle.
idle seems a lot more efficient when i look at the difference of battery discharge watts in non idle state vs grid load when in idle.
Basicly the only moment when i see the inverters switch to idle is when the minimum soc has been reached. (or when i manually set external control in vrm portal) As soon as there is more then that in the batteries the inverters will stay in a discharging mode.
My advice would be to switch to a Smart Shunt or Lynx Shunt. It looks like you are using a JK or Seplos BMS and those BMS-es don’t register low currents very good.
In my test setup I have a 16kwh battery with JK V19 BMS and also a 300A Victron Smartshunt. During idle (like in your situation) the JK BMS reports a current drawn from the battery of about 1,7A, which would make ik about 89 watt. However my Smartshunt is only reporting 0,3A being drawn from the battery, which is only about 16 watts.
I have confirmed this with a clamp meter, the smartshunt is correct.
Btw I am using a Multiplus II GX 48-3000 in my test setup.
My main system (3x Multi RS 6000 and 152kWh battery) only draws about 100 watts from the batteries in total. Which would be around 30 watts per Multi RS and a few extra for the Cerbo & touch screen. This is measured from a Lynx Shunt. Since I am using 10 batteries in total, all with JK BMS, not a single BMS is reporting any current drawn from the battery, since it would be too low to be measured by the BMS (0,19A per battery).
I use 6x 8kVA Multiplus with a total of 38.4kW power and 214kWh battery storage and the idle load is approximately 170Watts, I also use a SmartShunt1000A.
Ok i definetly will get a smart shunt to get a more accurate reading
After i have it i will report back on my findings.
At the moment i made a node red flow that checks the dynamic ess schedule and if the soc matches the soc of the schedule i switch to external control. (also catches discharging under the planned schedule etc).
