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:
set battery minimum SOC to 100% so it never gets used, but don’t want to store the battery at 100% long term.
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.
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.
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.
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!
Well, setting DVCC → limit charge current to 0A kind of worked but not really.
It seemed to work for a while, then next time I checked it AC from the grid, not even PV coupled AC, was charging the battery.
I tried a few things including changing the grid set point, turning DESS off, DESS green vs trade mode, DESS buy/sell price changes, setting grid current limit, changing minimum battery SOC, optimized with BatteryLife vs optimized without BatteryLife, and a couple other things. Many had some level of positive impact for a time, but none really helped long term. There is so much going into the algorithm that eventually something tried to fix something else and AC started charging the batteries eventually. I’m sure in many cases this is ideal, but I’m curious if we could get a Net metering config added.
Victron could this be added as a new feature?
A net metering setting for net metering grid tied operation where the price to buy and sell is the same and in this mode priority is using AC coupled PV for AC loads first, then export to grid rather than to battery to minimize loss due to inverting. Unless specifically told to use grid energy to charge batteries (before a storm for example). DC coupled PV can be stored or used as necessary while adhering to BatteryLife settings, etc…
Thoughts? @mpvader or is there someone else to tag/ask?
For me this DVCC setting of current limit set to 0A is working fine.
But in addition you should enable DC coupled excess feed in. Then the MPPT DC chargers will still charge the battery, the Multiplus will idle. When the battery is full, the exess from the MPPT will be feed in into the grid.
I’m using this config during summer to avoid the Multiplus charging the battery knowing the MPPTs will anyway fully charge the battery through the day.
I wonder if battery capacity to PV production ratio plays in here. I don’t have enough DC coupled PV to get to full charge each day so maybe it knows and feels it needs to pull from AC coupled PV to charge daily? It would need to in order to get a full charge each day, I just don’t care if it doesn’t get to a full charge each day.
In my system the MP2 does not charge the battery if I set DVCC to 0A. “Luckily” I had a day with low solar income to check this behaviour. And yes, it works even when the battery does not get full with DC only.
One point that just came to my mind, - what is you ESS setting regarding the mode? Is it with, or without BatteryLife? This might also have an effect on the charge behaviour.
I think the MultiPlus II doesn’t charge the battery much if DVCC max charge current is set to 0A, but does some. Never more than 1A though. If multi is on, DC coupled PV charges battery but a little more does come from multi. 48v system so usually 30W or so - not more than 1A.
I assume it rounds to less than 1 so the system thinks it’s okay.
BatteryLife on or off doesn’t fully answer it. It does seem to impact. If the battery has been recently fully charged, it will use it to keep grid setpoint at set value if it can. If the battery hasn’t been fully charged recently and BatteryLife is on the battery won’t get used, I assume because it wants to get a full charge in so it only charges and will even use grid power to try doing this sometimes.