PV Array and Victron

Hi,

I am about to hit the buy button on 16 panels like this :
https://www.solartraders.com/upload...d44acSrEJf-sQs21prdS6xQWE3eEFDPf-Te95gOJ3aeLA 310wmodel.

I have a house where i will be placing 8 panels on one side and 8 on the other (the house has about 45% inclination and it's not facing south, one part of roof pointing NW and one SE).
I am in process of making a diy LiFePo4 power wall made of 26650 cells and hope it comes up to 15kw). We have about 20-25kw usage in a day (2kids and 2adults).

I was looking at Victron Multiplus II 5000 and one or two solar chargers from Victron. I am not sure i gain much from getting two MPPT chargers. What's you opinion ? Is it worth it ?

I was thinking and mounting 2 strings of 4 panels in parallel on each side meaning 4x40v = 160v then parallel with the other string will give roughly 20A of current on one side of the roof then parallel with the other side so in total 160V and 40A. As far as i can see i need to get either one SmartSolar 250/100 or buy two SmartSolar 250/60. What's your take on this ?

Also what happens in following scenarios :

- I have a consumer needing 1kwh but the solar only produces 500wh but there is battery left. Will it still give 1kwh to the consumer, 500wh from solar and 500wh from battery?
- I have a consumer needing 1kwh but the solar produces 1,5kwh and the battery is not fully charged ? Will it give the consumer what it needs and the rest will be put into the battery ?
- I have a total consumption need of 6kwh, battery is full and solar produces 5kw, will the inverter give 5kwh and 1kwh from the grid ?
- I have a total consumption need of 6kwh, i have no battery left and no solar, can the inverter bypass and pull from the grid or will it shut down because it's not specified for 5kwh ?
- ..................... i have probably more scenarios but let's start with these

/donnib

In an instance where your generating more power than you are consuming the batteries are charged and any excess fed back to grid.

I.e generation - load - battery charging -> remainder fed to grid

In the opposite situation, where your consuming more than you are generating, the multiplus will use batteries to make up the difference, and if necessary draw from the grid to cover the load.

Ie load is covered by generation + battery + grid

You need 2 mppt trackers since you have 2 directions. Going with One only would be foolish and the Lost solar energy is very quickly gained using 2 trackers even though it cost more.

I have 3 directions = 3 trackers.

IF im not mistaken above inverter is just an inverter. It can not feed back to grid? But My knowledge in victron is none

Its kw not kwh. Kwh is energy ver time.

You need a hybrid system for feed back to grid. IF you go with Na offgrid any excess is just not used. But yes depending on how you set it Up it takes energy from primary and or secondary sources.

daromer said:

You need 2 mppt trackers since you have 2 directions. Going with One only would be foolish and the Lost solar energy is very quickly gained using 2 trackers even though it cost more.

I have 3 directions = 3 trackers.

IF im not mistaken above inverter is just an inverter. It can not feed back to grid? But My knowledge in victron is none

Its kw not kwh. Kwh is energy ver time.

You need a hybrid system for feed back to grid. IF you go with Na offgrid any excess is just not used. But yes depending on how you set it Up it takes energy from primary and or secondary sources.

Click to expand...

I thought you were running using Victron, so you still use MPP ?
Anyway, ok point taken 2 trackers. Now if somebody could tell me if i am wrong with the choice and yes if it's just an inverter then the problem with feeding back is non existent. I don't want feed back since i would have to register it so that fits me well.

I am still in doubt whether it can mix sources e.g between solar, grid and battery.

Donnib: The victron Multiplus II is not a solar inverter - Its a Battery inverter/charger - So panels don't plug directly into it.

The OP has suggested two MPPT inverters - one for each of the strings. These are efficient as there is only DC/DC conversion going on, but if I were the OP I would look at the option of using AC inverters for the strings (like regular solar inverters) - these will be available cheaper and possibly second hand compared to the the victron units and the Multiplus can handle them on either INPUT A or B. It will deal with and transfer any energy either into the load, battery or if excess is available - the grid (if exporting is Ok)

Either way, using two Victron MPPT units or two AC solar inverters - the OP will have no problem

@slimf:
Doing it DC will be more efficient & the Multiplus is designed to be used with a battery but I don't think dynamically like it seems you're suggesting with full AC bi-directional current at the inputs? Yes is can load share with an AC source but it's battery charge side is limited.

Use 2x Victron MPPT (DC) controllers like daromer suggests
Q's:
- I have a consumer needing 1kwh but the solar only produces 500wh but there is battery left. Will it still give 1kwh to the consumer, 500wh from solar and 500wh from battery?
Yes, that's correct
- I have a consumer needing 1kwh but the solar produces 1,5kwh and the battery is not fully charged ? Will it give the consumer what it needs and the rest will be put into the battery ?
Yes, that's correct too, battery gets whatever the load doesn't use
- I have a total consumption need of 6kwh, battery is full and solar. produces 5kw, will the inverter give 5kwh and 1kwh from the grid ?
No I think it will give you 6kW for a few seconds then shut off with overload.
- I have a total consumption need of 6kwh, i have no battery left and no solar, can the inverter bypass and pull from the grid or will it shut down because it's not specified for 5kwh ?
The spec sheet is here:
https://www.victronenergy.com/upload/documents/Datasheet-MultiPlus-II-inverter-charger-EN.pdf
Rating (230V system) for max AC current in is 50A (12kW) & same for the large change-over contactor inside but rules have to be set in s/w & those conditions (eg flat battery) have to stay present.
Best to ask the supplier on this one.

Ignore Redpacket - The inverter will NOT shut down.

Multiplus II is designed to have main loads on input A - in other words on the GRID side of the inverter. Therefore you can run a 30A air con if you want.. The Mulitplus will try to give it as much as it can given its power rating (say 5kw) - the rest comes from Grid.

Only critical loads should be connected to input B on the inverter.

Happy to be wrong. I have a multiplus I unit with grid mains backup & when overloaded, it switched off vs switching back to grid. Maybe I have it misconfigured!

I read up more on the multiplus II units capabilities & yes, it seems they are more grid interactive friendly than mine.
The config of this looks like it is not simple & the victron manuals seem vague.

It seems donnib would have to have a full "ESS" setup?

If power is required in grid failure situations, then at least some loads need to be connected to the output side of the inverter not just parallel connected to the main input or the anti-islanding protection will switch the inverter off & nothing has mains....

Decision trees for different top level configurations can be found here:
https://www.victronenergy.com/blog/...system-configs-rev-01_16647716-1_16653685.pdf
Per that link, it seems donnib wants self consumption, no feed-in & DC coupled. And probably one of the "optimised" self consumption options eg to protect the batteries some.

The advantage of the new Victron is that it actually CAN combine Grid + battery. Not many Inverters can do this

As an Example the PIP can do it BUT it does it by using its built in charger and this is a big loose situation

Grid -> AC -> DC -> Battery
Battery -> DC/AC -> Load
Solar -> DC/DC Battery


So you basically convert it twice.

Though im not sure how the Victron does it.


The Hybrid version does it like this instead

Grid <-> AC/ Bidi HVDC BUS
Solar -> DC/DC HVDC BUS
Battery <-> DC/DC Bidi HVDC Bus
HVDC Bus -> Load

So with that setup you do not transfer everything back down to 48V but keeps it rather high and that makes it more efficient.

Thank you all for the replay, going back i can see now that if i want to use Victron i am looking at 3700 (Multiplus II, Venus GX and 2 SmartSolar chargers) which i could defend if it weren't for the risk of being asked to pull the whole installation down since the inverter is not on the approved list in Denmark. Now i am trying to figure out what other options i have where the price for the inverter/MPPT charger is not that high.

What other options do i have ? I looked at Fronius and Kostal but the problem is i can't use my own power wall so i guess the last option is MPP, is there an option in MPP that can support the array described bellow ? @daromer you have a lot of experience with MPP, are there a solution with this ? If so is there a way to lower the standby usage in the months when there is no sun ?

btw. i now have 20 panels so that is 10 on one MPPT charger (2 strings of 5 panels then the 2 in parallel). Total 6,2kW PV array.