I have an existing off-grid set-up for a cabin constisting of:
One Multiplus II 48/3000 GX
One BlueSolar MPPT 100/20
Two 495 Wp panels facing south-east
One 48V 100Ah Haicen LiFePo battery
I am now looking to expand the system with one more 495Wp panel facing south-west, and one more panel facing north-west. The panels don’t deliver sufficient voltage to charge the battery on their own, so I believe two traditional MPPTs are out of the question. Is this a correct assesment? I am therefore considering adding microinverters to the panels and connecting these to the AC-IN of the Multiplus.
Enphase microinverters seem to play well with Victron from what I have read, but I don’t like that an expensive gateway is required for installation. Is there another microinverter that can be recommended?
I also frequently turn the Multiplus (and battery, via a built-in fuse) off for longer periods when I am not at the cabin. I assume a microinverter would then also shut down, as no grid is available anymore? Is this safe?
That’s how I solved it with the existing two panels, but as these additional ones are supposed to be pfacing different directions it seems to make little sense to me to put them on the same mppt.
I am also considering leaving our the north-east facing one and only installing one additional panel, which would mean that a traditional mppt definitely wouldn’t work.
how different directions?
It is always possible to put 2 different (direction) strings on one MPPT. Whilst this may not give all of the potentially available power, it does work.
I still test a similar setting at a caravan with a solar camping table which is connected to an envertec microinverter.
This microinverter is pluged in an power outlett of the camper connected to AC-OUT of a 12V MultiPlus-II.
(At home I use the solar table at the balkony.)
All PV microinverters I know needs right voltage and frequency at the 230V side.
Otherway they shut off within 200ms. (Maybe rules are different in your country.)
When you disconnect a Plug or switch off a circuit breaker you don’t want to have power on the disconnected side.
Its the same with the MultiPlus-II inverter.
When you plug in shore power or a generator to AC-IN the Multi checks voltage and frequency, then it starts to shift its internal phase slowly to the same phase of the soure. When this is done, the two relays in the MultiPlus-II switch the AC-In power on.
In the moment you disconnect shore power the two relays switch off imediatly. You don’t have 230V at your shore power plug.
You wrote you are offgrid. So AC-IN will not work.
The AC-IN of a MultiPlus-II is for shore/ grid or generator power.
You have to connect the PV microinverter(s) to AC-Out.
And you have to do some configuration/ settings at cerbo and MultiPlus-II
As long as your MultiPlus-II is inverting, the PV microinverter will suply solar Power to your internal grid and chrage the Battery via MultiPlus-II.
When you switch off the MultiPlus-II the AC PV microinverter(s) stop too.
Then only the DC PV MPPT charger will charge your Battery.
When you use a microinverter with two PV input ports it can get the optimum out of every PV modul. You don’t have the problem that one shadowed modul pull down your string voltage/ current.
And maybe you have lower losses on the 230V AC line.
Thank you, that makes sense.
Besides some brands offering better integration for monitoring via the Victron VRM, the choice of microinverter shouldn’t really matter as long as it’s compatible with the modules, right? Frequency shifting seems to be standard with VDE 4105 as well from what I can tell.
You can use a Shelly PM for monitoring,
for example I use a Shelly Outdoor Plug S Gen3.
It has a PM - Power Meter too.
Connect it to your “iot” WiFi or direct to the Cerbo AP.
With MQTT and a NodeRed rule you can read the figures, virtual energy Meter PV-inverter.
On Cerbo / VRM you will see two Icons PV MPPT charger connected to battery
and PV inverter connected to AC out/ loads.
Check the frequency shifting settings on MultiPlus-II AC-OUT settings for your AC coupled inverter. (47.5 - 51.5 Hz - you quote the right VDE 4105)
Further more you can use NodeRed for automatic rules like …
- If MPPT OFF switch MultiPlus-II OFF
(or if Battery <= 70% SOC, …)
- IF Battery reaches absorption voltage (and >= 95% SOC…) switch MultiPlus-II ON/ Inverting.
- Use a virtual slider/ switch on CerboGX for NodeRed to switch this Automatic on and off.
So you can automaticly boost the battery charging by using the microinverter as well.
It is possible to switch it remotly via VRM portal eg. the day before you reach the cabin.
Then hopefully battery will have 100% SOC when you arrive.