I have one installation where DESS is in testing (FW v.3.50 in Cerbo GX). Export limit to grid is set to 9 kW and charging/discharging power to/from battery is set to 5 kW. But today during high energy price battery was discharged to grid (which is completely OK), but with higher power than 5 kW. It seems that limit was somewhere around 130 A, which corresponded to approx 6,4 kW, but limit for charging power seems to be followed correctly.
What could be the reason for this behaviour?
Are mentioned options only for set system capabilities (for DESS calculation) and battery limitation is determined by BMS? Because it would be more logical if lower actual limit (DESS setting or BMS) will be followedâŚ
Yes the DESS settings are only used for planning, but donât limit anything. Limits are only defined by BMS resp. DVCC
But then the reality is different compared to the settings and leads to intentional error in calculationsâŚ
Exactly. And therefore the numbers in DESS battery settings need to be set correctly to the true capabilities of the system.
If you want to limit charge / discharge power, this can only be done in GX/ESS settings - as grua already pointed out - and then the numbers in DESS battery settings need to be adapted accordingly.
Yes, I see. But this setting is âhardâ setting and actual charging/discharging battery power can be different for example due to battery temperature (by BMS).
If I understood correctly DESS make calculation every hour, so it could be possible to adjust actual available battery power for every hour - Cerbo GX have all necessary information to do itâŚ
The DESS settings for max power are only being used for planning so that DESS knows how long it should take to e.g. charge the battery to desired target SoC in the schedule and when it makes sense to start charging.
The actual charging power will be determined by GX based on current SoC and target SoC. So it may even charge with lower power than max if that is enough to reach the target.
Schedule for the target SoC and whether the battery is allowed to charge or discharge is being stored inside of GX for the next upcoming hours and this schedule is also being adjusted based on reality.
