Dear Victron team,
it looks like the EVCS Auto mode has a design "imperfection" when used when batteries are fully charged (especially in off-grid systems).
The problem occurs:
- IF the batteries are full (i.e., chargers are in Absorption or Float mode), AND there is not enough AC "consumption" (including no energy "export" back to the grid, e.g. in off-grid system)
- => THEN the MPPT chargers are throttled down, thus producing only a little power, and thus EVCS in Auto Mode is utilizing only a little power
This is because of the inherent positive feedback loop (a "poisoned feedback"):
- EVCS in AUTO sets the consumption (the charging power) according to the current production
- MPPTs are producing just enough to cover current consumption (because batteries are full and there is little consumption)
So, a little EVCS consumption leads to little MPPT production -> which leads to little EVCS consumption -> which leads to little MPPT production, etc....
The observation of this problem has been reported numerous times (e.g., last report here: https://community.victronenergy.com/questions/309902/ev-charge-station-min-charge.html), so it really looks like a design flaw.
At the same time, I believe it has a very easy fix:
- allow EVCS charger in Auto to discharge batteries from 100% down to, e.g., 95% (or anywhere back to the Bulk region)
This will break the "poisoned" feedback.
When the batteries are back in the Bulk region, then all Solar assets (DC coupled & AC coupled) will produce their maximum power => EVCS will have a better estimate of the available Solar power and, thus will be able to appropriately set the charging current.
Could you, please, consider this enhancement for the next firmware version of EVCS?
