I’m thinking of building an off-grid system, with a Multiplus II 5kw inverter, 5kwh battery, and 5kw PV. I’m also connecting the AC-In to the grid.
My goal is to use most of the solar and battery power first.
Question 1: For example, at night, after using all the battery, it starts pulling power from the grid.
Is this possible?
Question 2: If I try to pull more than 5kw from the AC-Out of the inverter, for example 7kw, is it possible to “merge” the 5kw from the battery/inverter and 2kw from the grid?
The Energy Storage System (ESS) assistant can be installed in the multiplus to provide these features and more. You will need a Cerbo GX or other GX device to control the system.
It is somewhat complicated, but here is the starting point:
And what would be the maximum amp output (240v) that it can achieve?
For example, I have a 32A breaker for the AC-In. So it can draw 7.6kw from the grid and 5kw from the inverter combined? It will output 12.6kw on the AC-out?
Note that a 5 kVA inverter will only do 4 kW continuous power.
Assuming you want the 230V version of the Multiplus-II, see:
The Muliplus-II has max feed through current of 50A. The inverter can add to that on the output lines. You must size the conductors on the output to handle the maximum current.
With ESS, it will max out the inverter power to a limit that you can set. The rest will be drawn from the grid. You can also set grid import limits to prevent the 32A breaker from tripping.
Another feature called PowerAssist does the opposite. It uses as much of the grid as possible and supplements with inverter power. These are mutually exclusive, and I assume you want the ESS design.
Be sure to check your country and power provider requirements for connecting a grid-interactive device (ESS). Victron supports a variety of grid-codes for many countries.
Hum, how do I check that? I’m in Portugal. I thought this system would not have any implication, since it’s an off-grid system that, sometimes, pulls power from the grid. The system never injects power into the grid. Maybe I’m seeing this wrongly.
When you merge the power from the battery and grid (as you mentioned in question 2), the system becomes hybrid because you are running in parallel to the grid.
You can largely prevent backfeed to the grid with the ESS settings, but there is always a small pushback to the grid when large loads shut off.
If being off-grid is mandatory for you, then you cannot use ESS legally. Technically, it will work fine of course.
Hope the power outage did not affect you too badly.
For my system I’m going to use 4 ECO-WORTHY 12V 100Ah Lifepo4 in series (48V).
Is it necessary to have the Victron Shunt on my system? Or it will work fine only with the Multiplus II, MPPT and Cerbo GX?
If these are the Ecoworthy batteries, they do explicitly allow series connection to 48V.
Not all vendors do that.
It isn’t a great idea, however, because eventually those 4 batteries will get out of balance with each other, which will require you to either add an active balancer device, or occasionally take them apart and recharge each of them to 100% with a 12V charger. It depends how often they are cycled.
I always recommend a Victron shunt because there is no other way to get accurate State of Charge measurements. The new 300A one is not very expensive.
If the battery vendor explicitly says that they communicate in closed loop with Victron via CANbus, then its BMS state of charge will be used, and you will not need a shunt.
I personally do not trust any BMS to accurately count coulombs, and have a SmartShunt as well. And the SoCs do tend to diverge over time due to drift.
