I hope this is the right category for my post. I haven’t realized the system yet, but I’d like to share my project (still on paper) to get your opinions and clarify some doubts.
To start, I already have two on-grid systems (5 kW on the east side and 3 kW on the north side) on my house, but the electrical energy is never enough.
I have the opportunity to cover my carport/garage with approximately 15 kW of panels. However, since the grid in southern Italy, where I live, isn’t capable of accepting such additional energy, I’m considering installing an off-grid system for my EV car and other loads.
Specifically, it would be a “partial” off-grid system, as I plan to use the grid only when the panels and battery can’t meet the energy demand.
The system would consist of:
1 MultiPlus-II 48/15000
4 SmartSolar 150/100 - this is because I would not exceed the 150 V DC for safety reasons.
1 Cerbo GX + GX Touch 50
1 SmartShunt 1000A
1 or 2 Lynx Distributor
2 or more batteries LiFePo4 15kWh / 51.2 V / 290 Ah each.
I’ll keep you updated on the progress of this project, but I’d appreciate your feedback on this system.
I also have a question for you. I understand that to keep all cells of the LiFePo4 battery well-balanced, it’s good to charge the battery to 100% at a certain frequency (e.g., once a day, once a week). However, how can I achieve this if, for example, during winter, the PV panels can’t fully charge the battery?
Is the MultiPlus-II 48/15000 capable of charging the battery at a set frequency, or do I need an external device for this?
Another doubt is whether or not to use blocking diodes for the photovoltaic panel strings.
Since the strings are composed of three 500 V panels with approximately 45 VOC, I would need 10 strings and therefore 10 blocking diodes, and the additional cost is not negligible. I wonder if the use of diodes is necessary, given that the panels are subject to shading, especially in winter.
With 3x MP5 you do not get real redundancy. If one gains, all shut down. The remaining not to be reconfigured via VeConfigur.
3x MP2 are much more work to do the wiring.
If you have managed batteries with an BMS and no other DC sources or consumers, you do not need the shunt.
If you want the touch screen, consider the Ekrano. In DE it’s cheaper compared to Cerbo + touch.
You could build an off grid system and use a server power supply to recharge batteries from grid when needed. Look for Eltek FlatPack 2.
Than you could save the energy meter.
Ekrano and Cerbo use the software Venus OS.
HA-Integration is based on features provided by Venus OS.
You could even run a Raspberry Pi with CAN-bus hat.
About the battery charger.
The ve-bus system does not support an island or off-grid system with side charging the batteries from grid by a 4th MultiPlus assuming 3 MP2 for a 3-phase system. There is no advantage to use Victron gear for this,
A used server PSU with voltage and current control is cheaper than a MP2.
The Cerbo/Ekrano could switch on/off the PSU to recharge battieres from the grid in case you solar is not sufficient, likek generator control for an offgrid system.
Pls do not connect the MP2 and the batteries to the side ports of the Lynx, but to the fused ones.
One normal Lynx has 4 sets of ports to connect 4 devices, each positive and negative.
You might need a third Lynx as the MP2 might be connected with two sets of cables.
I recommend connecting at least two battery stacks directly to distribute the current. Expect 400-600A with your MPPTs and MP2.
Distribute the batteries amount the Lynxes to distribute the load.
Use Adler EF3 fuses and not Mega-Fuses for the batteries.
Consider DC switches between MPPT and Lynx for maintenance.
Consider DC switches between battery stacks and Lynx for maintenance. The batteries seem not to have a breaker or switch.
Yes, if you can control a Relais like a Shelly from NotRed you could switch on/off the PSU based on values from Venus OS.
You could also use a relais assistant in MP2. But Node Red is more flexible. I am. It sure if you could control the relais in MP2 and/or GX device via Node Red. With that Relais control the external power Relais for the PSU. This would be my preferred method.
could you elaborated on the doesn’t support ? (why? what if MPII is powered by batteries only in island mode ?)
also interested in battery charger max voltage output. is the Eltek 53.5v not to high ?
If I am asking it’s because the MPII does NOT have the CEI 021 certification for Italy and can NOT be connected to the grid at all. Looking for turn around…
In off-grid mode it “could” be possible, the 230v grid could not be connected to the MPII out or in, but from a “next door” feed solution just power the batteries charger. it’s just a load after all.
I would like to hear advice and objection about this set up.
My 2cts on Home assistant to integrated Victron → look for MQTT bridge between VenusOS and Mosquito seem less prone to packet loss than the other Victron integration.
All MP2 of a Ve.bus system
Act as one cluster. You cannot have 3 MP2 as 3-phase off grid system and a fourth as grid connected 1-phase to charge same battery.
The whole system
Is either grid connected or disconnected not mixed.
Though if you want to side load you battery, you can do this with any DC source which is not controlled via DVCC. Consequently you do not have advantage by using an Victron product like a MP2 for this.
If MP2 are not certified Italian grid, you might be allowed to build an off grid system. Than connect a normal appliance (charger) to recharge you batteries from grid. I cannot judge the legal aspect. For Germany there are very long discussion about without final result.
If the charger is set to a voltage equal or lower float you should be save.
