i have gone over old posts, but still not clear.

1) Are the non-essential loads supplied by a blend of solar and grid and the rest of solar pv ( if available ) goes to charge the battery

2) when grid is not available, are the essential loads supplied by pv AND battery or JUST battery

              or am i completely wrong

Also recently converted to a Multiplus II so did a bit of digging, not sure if this post helps at all?

https://community.victronenergy.com/questions/16699/multiplus-ii-ac-out-2.html?childToView=16705#answer-16705

 

Any hints as to how essential loads are powered from VenusOS? I would imagine that it would work similar to other inverters where the battery makes up for anything that solar can't produce.

When you run a Multiplus in hybrid mode (aka with the ESS assistant), then it runs grid parallel. Now for reference, if I had two batteries in parallel and some 12V loads on it... which battery powers the load?

Well, both of them of course!

The same is true when you have the Multi in parallel with the grid. The loads (on both input and output) are powered by both the grid and the inverter, but by carefully controlling how the inverter feeds power into the grid you can proportion the power so that most of it comes from the inverter and only a small portion comes from the grid.

The upside to this setup is that if the Multi cannot handle the full load, the difference seamlessly comes from the other source (the grid), exactly as it would in my battery analogy.

Now for a bit more detail. The PV is DC-coupled, that is, the solar power connects directly to the battery, and the Multi itself does not distinguish between the two. The Multi simply draws as much power as it has to (up to its own capacity, or the maximum configured limit if any) from the DC side to minimise the power drawn from the grid. If you have enough PV for this, then no battery power is used, if you don't have enough PV the rest comes from the battery. Again, the PV and the battery is in parallel, so they naturally share the load and whichever one has the lower impedance will supply the bulk of it... which basically means PV powers the loads first, and then charges the battery.

When the battery SOC goes too low, the inverter switches off (it goes into a kind of bypass mode) and all PV is used to charge the battery, until the SOC has been raised 3%, then it goes back into self-consumption mode.

An ESS system's default state is "self consumption". It will always use as much PV and/or battery to eliminate using grid power... until the battery goes too low.

58 minutes ago, iops said:

Any hints as to how essential loads are powered from VenusOS?

VenusOS is software... it does not power anything in the conventional sense 🙂

When the Multi runs grid-parallel it closes the backfeed relay (the relay that serves as a changeover switch as well). When it does this, the grid, the inverter, and the loads are all running in parallel. When the grid fails, this leaves the inverter as the sole source of power... but because the grid has a very low impedance it will cause a momentary voltage dip (because the inverter, which is connected to the grid, obviously cannot power all of it). This is an example of an islanding event, something that tells the inverter it has lost the grid. It will then open the backfeed relay. This leaves the "essential loads" powered (since they are wired to the inverter side of the backfeed relay).

Without the ESS assistant, the backfeed relay operates in the usual UPS manner: interlocked. Either the inverter powers the loads, or the grid powers them. ESS is an extension (an app that runs on the inverter, a firmware extension) that allows it to run both at the same time instead of interlocked.

 

Another question, when grid is available, what source or sources  is/are powering the non essential loads,

Edited June 18, 20206 yr by Tariq
Wrong word

1 hour ago, Tariq said:

 

Another question, when grid is available, what source or sources  is/are powering the non essential loads,

Both sources are powering the non-essential loads, but the idea is to balance it such that very little comes from the grid. That is why you install the grid meter right where your supply comes in. The inverter pushes power back until that meter is close to zero, so that the inverter powers all the loads. But the grid remains connected at all time and any extra power you inject goes into the grid, any shortfall comes from the grid.

When the backfeed relay is closed there is essentially no difference between essential and non-essential loads. Everything is in parallel, and the Multi is simply adjusted to feed enough power to get that grid meter to zero (ie, power all the loads). Where the distinction between essential and non-essential comes in as when the grid fails. Then the backfeed relay opens, and the non-essential loads are left for dead on the grid side... 🙂

 

If no grid meter is used, then in what manner does the system perform

13 minutes ago, Tariq said:

If no grid meter is used, then in what manner does the system perform

Then no power is fed to the loads on the input side (because it has no way to know about them), the input of the Multi itself is then kept at zero. So only loads on the output are then powered by the Multi (and if there isn't enough, the rest just flows seamlessly from the grid, since the backfeed relay is still closed).