Preventing AC coupled PV from charging batteries?

DIY
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1

I have MultiPlus II configured with ESS with both AC coupled PV and DC coupled PV.

I am on a stable grid and can net meter, so I can export power to grid and get it back at no markup or charge which makes ensuring batteries stay charged not critical.

On a normal day the PV from both DC and AC sides charges the battery. My only concern here is the efficiency loss.

If I don’t put it in battery, the excess energy flows to grid and I can get it back with virtually no loss.

When I put DC coupled PV in battery, my loss is minimal - probably less 2%.

When I put AC coupled PV in battery, I have somewhere between 10-18% loss due to AC to DC conversion, battery storage, and DC to AC conversation. For all that, it seems just sending to grid would be better.

Is there a way to tell the multi to not use AC coupled PV to charge batteries regularly?

I’m coming up with some hacks I don’t like. For example:

  1. set battery minimum SOC to 100% so it never gets used, but don’t want to store the battery at 100% long term.
  2. set grid setpoint to -5000 (more than I produce) so it’s always exporting and rarely charging. Could work but I don’t like the idea necessarily.
  3. turn the inverter off during the day but I don’t have any third party platforms integrated I could schedule with, don’t necessarily want to do that, and don’t want to be manually changing it daily.

Any setting I’m missing that just tells the multi to not use AC coupled PV for battery charging?

AC coupled PV is enphase and doesn’t communicate with victron to my knowledge.

2

This is a common problem. My installer was aware of this and kept the PV grid-tied and installed a 450/100 MPPT. This gives us plenty of solar for power loss, which is infrequent, maybe after a cyclone. You can use DVCC to adjust the MultiPlus charger. If you set it to 0 the MPPT is not throttled just the AC to DC charger.

I dont know if it’s the same with AC-coupled PV. Maybe if you set DVCC to 0 then the MPPT will only charge and the PV will pass through.

This is what it looks like on a dashboard. It’s a little cloudy ATM, but DVCC is set to 0, the MPPT power goes into the battery. If I increase DVCC it will start to use excess power from the grid. The total amps comes from the sum MPPT + CHARGER. So the MPPT is good for 100A, and the internal charger is good for 70A, which will give you a max charge of 170A. I have my slider set to 120A max.

The clouds have broken up a bit this might make more sense. The AC in power is taken from the grid-tied PV, and the internal charger adds extra charge to the MPPT charge power.

3

We’ll see what happens during next production hours but I caught the end of it and set DVCC max charge current to 0 and it seemed to lay off the charging batteries with AC coupled PV. It did charge with AC power (I don’t remember if it was PV or grid) for a few minutes when active SOC minimum kicked in and it was trying to add a half a percent back to the battery but otherwise it seemed to work in the limited time I had PV production to watch so that might be helpful. I had ignored DVCC assuming it was more advanced and not needed since it warned to read the manual first. I have yet some more reading to do. Thanks!