Dear all, appreciate some help with large fluctuations in power readings in my grid meter when loading my Pylontech batteries.
My current system setup:
3 phase grid tied with 3 Multiplus 5000/48 inverters (one each phase)
Energy Meter VM-3P75CT between grid and three Multiplusses.
All loads on the AC-Out
SolarEdge 10kW inverter on the AC-Out, integrated through modbus (working)
6 Pylontech US5000 batteries (27.6 kWh in total)
All batteries connected individually to 3 Lynx Distributors (3 x 2) and each Lynx distributor connected to one Multiplus 5000/48 (Parallel operations with two batteries per Lynx per inverter)
Cerbo GX to control the system.
Settings inside the GX
ESS with no battery life chosen
In case of negative grid prices, the SolarEdge is limited
Gridsetpoint at -280 Watt (or -480 in case of night).
No alarms on the batteries, health status 99% system up for ¾ of a year in 3 phase mode.
Behaviour noted.
In case of battery full or low discharge power, the power reading on the Energy meter are smooth and do not fluctuate that much ( a few 10’s of watts maximum).
I discharge the battery for about 10 kWh every evening (19:30-22:30) with at grid setpoint of ~-3000 Watt for 3 hours. Then the settings is returned to -480 Watt Gridsetpoint.
Depending on the SoC at 19:30 the SoC at 08:00 in the morning is ~40 % and normally charging commences.
If i charge rapidly (charge current not limited) with solar energy (if available) there are fluctuations visible on the grid power setpoint but within limits, they are larger than the ones when fully charged.
If i charge slowly (allowing some solar energy to flow back to the grid and charge current around 3000 Watt) and charge later on rapidly i start to see large fluctuations on the grid power from -1000 to +1000.
What i notice is that the higher the charge current the larger the fluctuations and the longer i charge the larger and longer the fluctuations
When the battery is full the fluctuations reduce and after a while they go the minor ones noted at the beginning.
What i have tried to do so far with no result:
-
If i do not discharge the 10kWh in the evening the batteries are at 70% in the morning and the fluctuations are within limits when chargng the batteries.
-
Make sure the batteries are charged for 100% for a 4 hours they day before
-
Check the Voltage of my batteries, they are between 3.371 and 3.376 (5 mV)
-
Use a different Grid Setpoint (+100 Watt)
-
Limit the max current to the batteries (5000 Watt)
Any suggestions on what i can do next or pointers to where the system needs a check ?
what sort of loads do you have running that might be causing this change … 
…. Better safe then sorry …