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Elimac avatar image
Elimac asked

Multiplus parallel wiring advice (to balance power)

I'm in the process of adding a 2nd Multiplus 3000/24 in parallel to the existing one. This is mainly to assure inverting power. I would like to ask the community, specially who has done this before, about the practical wiring details of this setup.


1. I have done already a DC bus bar with copper, 150 mm2 cross section, and connected the battery to the centre, with 70mm2 (OPzS 730 Ah C100)

2. Both Multis will connect to bus bar trough 60cm cables with 50mm2 cross section.

3. I will place only one ANL fuse (200 ~300A), on main 70mm2 cable, not on individual connections of each Multiplus. Hesitating on this one, but would like to keep DC resistance minimal...

4. AC input comes from dedicated AC board, 2 MCBs of 10A, 150 cm cable. Will use 2.5mm2 but could use only 1.5mm2


5. - Main question -

AC out: >> I'm planning on using cables with 150cm long and 2.5mm2 cross section from each multiplus to the AC board, and a 16A double pole MCB in series. The output of these MCBs (Schneider iCH) are shunt and then one 4mm2 cable connects to the main AC distribution board.


This AC out cable, with 150cm / 2.5mm2 corresponds theorically to exactly 10mOhm resistance. And then, we have to add also the 2-pole MBC resistance. Will this be ok to provide correct power balance to the Parallel Setup of 2x Multiplus 3000/24/ 70-16 ?

MultiPlus Quattro Inverter Chargerbattery chargingwiring
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3 Answers
wkirby avatar image
wkirby answered ·

That seems well thought out to me.
The AC-Out cables are the most vital part. Your design is good and I can't think of any problems there.

Of course, unsymmetrical resistances out of the MultiPlus' will cause problems, but you can also have too low of a resistance on the output cabling which can result in balancing issues.
1.5 metres of 2.5mm cable plus switch gear, I don't foresee any problems with that.

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Paul B avatar image
Paul B answered ·

the only area I think you need to look at is below.

You may find this to be two small re item 3 - as each inverter at max overload can take 250 amps so maybe consider a larger fuse say around 500 to 600 amps

your cable size is large enough to cover it.

the fuses are not cheap so you dont want to keep blowing them


3. I will place only one ANL fuse (200 ~300A), on main 70mm2 cable, not on individual connections of each Multiplus. Hesitating on this one, but would like to keep DC resistance minimal..

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Elimac avatar image Elimac commented ·

Right! I do have a 300A ANL fuse that I can use, and I will also limit current on that section, see below my followup. And I might get some 400A fuse later too. Thanks!

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Elimac avatar image
Elimac answered ·

Thanks a lot for your contributions!

Since I have a Venus GX, I will make use of the available settings wich enable to impose certain limits. For example, DC current from battery, AC loads, and so forth. I will also use 2 time schedules, day and night, to try make use of direct Solar power from MPPTs instead of battery. I will try to limit current in battery to a safe limit for its size - 730Ah C100// 540Ah C10, I would say 70 ~80A is safe, both in charge and discharge, do you agree?

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