question

lepatrick avatar image
lepatrick asked

Victron Multiplus-II + SmartSolar MPPT vs some Grid-Tie inverter

Hey Volks,

I am new on solar systems. I plan to setup solar system. It's planned to put about 45 panels (400Wp) at the roof. I know Vicron from my VAN and it's never failed. So I prefer to use Victron in my house too. Let's discuss some ideas questions.

Idea:

  • 45x 400 Wp Solar
  • 3-4x 450/100 Victron Solar MPPT
    • connected to 48V batteries (10-15kwh)
      • connected to 3x Multiples II

Questions:

  1. when AC loads turned on during day, use Multiplus II solar energy direct from MPPT or does it discharge battery while MTTP charge it?
  2. what happens if battery is full? can send Multiplus II energy to grid?
  3. better to use some grid-tie inverters?


Thanks!


Multiplus-IIMPPT Controllers
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3 Answers
wkirby avatar image
wkirby answered ·

1. When load is less than available MPPT power then load is covered and remainder goes to the battery. When load is more than available MPPT power then all MPPT power goes to the load and the remainder comes from the battery.

2. When battery is full then loads are covered and the MultiPlus can be configured to export the remaining power up to its maximum capacity.

3. Grid tie inverters can be used. 18kW PV is a lot, so it depends upon your network operator. PV inverters can be connected at AC-IN side of MultiPlus then export directly to network unless there is a network outage. Grid meter can be used to take some PV power to charge the battery up to the capacity of the MultiPlus.
PV interters connected at AC-OUT side of MultiPlus can charge the battery up to the capacity of the MultiPlus but total PV power can not exceed the capacity of the MultiPlus. PV Interter keeps working if the network goes out.
https://www.victronenergy.com/live/ac_coupling:start

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lepatrick avatar image
lepatrick answered ·

Thanks wkirby to make it more clear for me. In this case there is no need to use Hybrid or Grid-Tie-Inverters, when I am right.

When using PV inverters like in 3.- it means: Solar DC --> AC via PV inverter --> DC to charge battery!?

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wkirby avatar image wkirby ♦♦ commented ·
You do not need to use PV Grid Tie Inverters at all if you don't want to.

DC coupled energy from MPPT chargers can be used to feed in excess energy via the MultiPlus. Of course the amount of feed-in power is limited by the capacity of the MultiPlus subtract AC loads on AC-OUT. 18kW of PV would need a large bank of MultiPlus' or a large Quattro if you want to feed in large amounts of excess MPPT power.

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lepatrick avatar image lepatrick wkirby ♦♦ commented ·

My idea now, because of your help:

  • 2x MPPT 250/100 (6 panels in series, 3 parallel), think it's better then 150/100 (3s6p)
  • 3x Multiplus II 8000 VA

When using the rest of the panels (9) with Grid-tie inverters, I must use 3 phase Grid-tie inverter or not? Is it fine for synced Multiplus when only one of three has connected inverter in ACI-IN or must I use 3 phase inverter, which is connected to all three Multiplus

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lepatrick avatar image lepatrick wkirby ♦♦ commented ·
Or better MPPT 450/200 + MPPT 250/100 if possible to combine
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kevgermany avatar image kevgermany ♦♦ lepatrick commented ·

Can be combined on output side. Separate groups of panels for each MPPT.

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lepatrick avatar image
lepatrick answered ·

So guys, I am on the way. :)

3x MPPT 250/100 va 1x MPPT 250/100 and 1x 450/200 costs nearly the same. There is a difference in max Amps I can get out, with 450/200 I can get +20A more, so it's 220A va 240A. Batterie should not get more than 200A. The three Multiplus accept 3x 100A. Which combination should I choose. ;-)

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