question

Hi, check your email please.

I have a similar observation about this issue:

- IF the batteries are full, AND there is not enough AC consumption (including AC Load and/or potential feed-in back to the grid), THEN the MPPT chargers are throttled down (in "absorption" or "float" mode), thus producing only a little power, and thus EVCS in Auto Mode is "Waiting for Sun".

From my experimentation, the Auto Mode starts charging when there is at least ~650 W of solar production (with setting 'Allow Battery/Grid power for auto mode' turned ON).

Even though the EVCS starts charging (by accidentally "sensing" higher production thanks to the increased consumption), typically it is not utilizing the full solar potential because of the "poisioned feedback control loop":

• EVCS in AUTO sets the consumption (the charging power) according to curent production
• MPPT are producing according to current consumption (because batteries are full)

So little EVCS consumption leads to little MPPT production -> which leads to little EVCS consumption -> which leads to little MPPT production, etc.

This typically happens in off-grid systems (like I was testing on my site, and like you are observing in your system with disabled feed-in too.

I guess this can be easily fixed once it is identified as an issue in the firmware. One of the possible solution would be to add new options (option group), called something like this:

• Allow fast battery discharge to 90% SoC[default: true]
  • Fast battery discharge SoC: [default: 90%]
  • Fast battery discharge power: [some value, e.g., 4000 W]

This may work as follows:

• EVCS is in Auto mode, it detects car, and wants to start charging
• IF Battery SoC > "Fast battery discharge SoC", THENstart charging at minimum power (6A)
  • IF Battery Power > (minus) "Fast battery discharge power", THEN increase charging current +1 A
• IF Battery SoC <= "Fast battery discharge Soc", THEN revert back to standard Auto charging algorithm (i.e., adjusting the power to match production, or using Battery/Grid power for a set timeout
• IF Battery SoC raises above "Fast battery discharge SoC", THEN switch to 'Fast battery discharge' mode (to drain battery safely back into the 'Bulk' region)

So, imagine the situation:

• it is a nice shiny noon, batteries are already full, MPPTs are throttled back (off-grid system)
• you connect your EV to the charger
• According to "Fast battery discharge" procedure, the charger will start immediatelly to drain power (no matter if there is any immediate prodution or not), either from PV or from batteries. This will make nice and fast initial charging of the vehicle, and will pull batteries (and MPPTs) from Float/Absorption region back to Bulk region
• Once the batteries are below its max (e.g., 90%), MPPT chargers are safely in the Bulk mode, trying very hard to harvest every Watt from PV panels -- and these Watts can be immediatelly consumed to charge the EV => and this is what we want :-)

I believe this simple procedure can be done, e.g., in the Node-Red flow (and I will probably try to implement it in the near future), but it would be very nice to have this feature implemented in a supported EVCS firmware, because as mkr correctly pointed out, the "deadlock" with full batteries and throttled-back MPPTs seems to be a bug.

Thanks in advance to the Victron team for considering this improvement.