48v Wiring advice

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richie-gorrod asked May 26, '23

48v Wiring advice

Hello.

Looking for some advice regarding the DC wiring of this setup

upgrading to 48v system from 24v.

Multiplus II 15KVa.(running ESS)

4 x 280Ah Seplos DIY Packs with EVE 280aH Batteries. (might add more)

40 x 250watt Solar panels. + 2.6kw Ac coupled system on roof (Inherited when bought house)with ET112 energy meter.

4 x 250/85 MPPT.

Couple of Questions.

1. Do I need to fuse between Busbars and Multi.

2. can I use Blue Sea 6006 switches - Only rated at 48v.

Many thanks

Cheers

Rich

Solar Overview.pdf

wiring

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Modifications Space

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Answer 1 · 2023-05-26T20:37:54Z

richie-gorrod answered · May 26, 2023 at 08:37 PM

Not sure if the PDF uploaded.

1685133402370.png (86.2 KiB)

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Answer 2 · 2023-05-26T20:55:08Z

pyrorider answered · May 26, 2023 at 08:55 PM

Please consider that even Victrons Mega-Fuses only have I think 2kA short circuit current rating, with a 16S 280Ah battery bank you would get much higher short circuit currents (Pylontech already requieres 2500A rating per 5kWh battery), with eves 280Ah cells you would at 55V and 0.25mOhm per cell get a short circuit of at least 13.000A. (varies a bit die to busbars, contact resistance, the place where the short happens...)

So please use some proper high dc current rated fuses. I am using NH-Fuses

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Answer 3 · 2023-05-27T10:19:00Z

richie-gorrod answered · May 27, 2023 at 10:19 AM

Many thanks Pyrorider,

I have NH fuses in my system currently.

I presume I need to keep the cable length the same from each battery to the fuses. Does both the negative and positive be the same length?

I have a 3 pole disconnect and thinking of doing a negative bus bar and positive into the 3pole disconnect. (Buy another 3 pole for the 4th and future proof for another 2 batteries.)

Or do I need to fuse each battery Just put a disconnect switch between it and the bus bar and then fuse the busbar with NH2 fuses.

or would a lynx distributor be better?

Sorry for all the questions - just would like to do it right.

Many thanks.

Rich

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seb71 commented · May 27, 2023 at 02:28 PM

Battery positive wires can be different length than battery negative wires.

Use a fuse between each battery positive and the positive busbar, like in your drawing. But if you use two busbars, also protect the wire between those busbars with a (larger) fuse. Same for inverter positive wire.

There are NH holders which can double as battery disconnect switches.

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pyrorider commented · May 27, 2023 at 07:24 PM

if you have a 60mm busbar system (basic busbar system for NH-load breakers) you can put 3 pole NH load breakers on it and use one for plus, one for minus and keep the middle one empty. Use NH2 with up to 500A for the inverter (15kVA would be >300A at 48V) and NH1 for the batterys (up to 355A).

Every of the 4 batterys need one fuse (NH1) on the positive to the busbar and then one fuse (NH2) from the busbar to the inverter

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pyrorider pyrorider commented · May 27, 2023 at 07:26 PM

Also connect the inverter with fuse directly to the battery busbar to reduce the amount of contacts and then connect the mppt-busbars to the battery busbar

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