Which wire size and fuses do I need for connecting 3 x 60A charge controllers to a lynx distributor?

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vovanenok asked Jun 28, '21

Which wire size and fuses do I need for connecting 3 x 60A charge controllers to a lynx distributor?

I'm upgrading my current solar setup which has 1 array of 4 x 235W panels ( Voc 37v, Isc 8.6a), Outback 150v/60A charge controller, 24v battery bank and Magnum 4000w 24v inverter

Because the parts I ordered will come at different times, I'm planning 2 upgrades:

Upgrade #1

Keep the current 4 x 235W panels ( 2 panels in series parallel another 2 panels in series ) + Outback 150/60A charge controller
Keep the existing 24v battery bank and Magnum 4000w 24v inverter
Add 8 panels: 2 solar arrays (connected in series), each 4 x 330W ( Voc 46.8v, Isc 10a )
Add 2 x Victron SmartSolar MPPT 250/60 charge controllers
Add Victron lynx distributor

Upgrade #1

Upgrade #2 (once my new batteries and Victron inverter arrive)

Keep the current 4 x 235W panels ( 2 panels in series parallel another 2 panels in series ) + Outback 150/60A charge controller
Replace 24v battery bank with the new 48v lithium battery bank
Replace Magnum 4000w 24v inverter with Victron energy Quattro 48/5000/70
Re-wire the current 8 panels (2 arrays x 4 in series) as 1 array (parallel 4 in series + 4 in series)
Add another 8 panels and make the same array: parallel 4 in series + 4 in series

Upgrade #2

As I understand, each Victron SmartSolar MPPT 250/60 charge controller will be receiving 330w x 8 = 2640w, then output will be 2640w / 48v = 55a

My questions are:

Do my diagrams look ok?
Can I use 6 AWG copper stranded wire and 60A MEGA fuse for each positive wire between a charge controller and lynx power distributor? Or should I go with larger wire and fuses?

Many thanks in advance!

Vlad

P.S. This is my first solar system (recently bought an off grid house) and after some researches I feel very confident going with Victron products

wiring diagram

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Vance Mitchell answered · Jun 29, 2021 at 09:12 PM

With all of these cables being reasonably short, bigger is normally better.

1. For your 250/60 smartsolar MPPT units, 16mm (6awg?) would be the minimum size, I would normally go up to 25mm with an 80A fuse.

If you are going with 16mm, check the manufacturer’s current rating and fuse accordingly,(the 16mm I use is rated for 140A but I have seen others rated much lower, an 80A fuse would be a better size for a 60A MPPT)

2. For your inverter and battery bank, 35mm (2awg?) would again be the minimum, I would upgrade to 50mm (1awg) cable and a 200A fuse. (Note that not all fuses are rated for 48v, most ‘automotive’ fuses are only rated to 32v maximum.)

In short lengths the larger size shouldn’t cost much different, and it will reduce any losses.

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vovanenok commented · Jul 06, 2021 at 05:58 PM

Thanks a lot Vance, appreciate

I will check the manufacture rating and consider going with 4AWG and 80A fuse

For the battery it looks like I need 0000 (4/0) AWG, as 3 SCCs x 60A will output up to 180A

Yes I will make sure the fuses are rated for 48V

Thanks again!

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Answer 1 · 2021-06-29T17:14:04Z

vovanenok answered · Jun 29, 2021 at 05:14 PM

adding another diagram showing wires, breakers and fuses (see in violet) that I need to size:

My questions:

Can I use 6AWG wire from charge controllers to the bus bar (Vicron Lynx distributor) and 60A or 75A fuses? The wire length will be under 2ft
What should be the wire size from the inverter to bus bar? Currently I have 24v inverter but it will be replaced with 48v one in Aug
What should be the wire size from the bus bar to the battery bank? Currently I have a 24v battery bank but switch to 48v one in Aug

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