Cable sizes for SmartSolar 100/50 with 24V 230Ah LiFePo

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scseba asked Nov 22, '22

Cable sizes for SmartSolar 100/50 with 24V 230Ah LiFePo

Hello,

I have 4 x 380W solar panels, 2 of them in series and these two then connected in parallel. These go into my Victron SmartSolar MPPT Solar Charge Controller 100/50 with a 6mm² cable.

From there I still need cables from the SmartSolar MPPT to my 24V LiFePo 230Ah battery. The cable length is approx. 50cm - 100cm.

What size cable do I need for the connection? (And up to what maximum cable size does the SmartSolar 100/50 support?)

Would you put another fuse between the SmartSolar MPPT and the battery and if so, which one?

The idea is that I can charge the battery in the workshop and then bring it into the house to feed it in later if necessary. I have a feed-in socket in the house. A 3000W inverter is used here (max. 6000W at peak). Here, too, I have the question of which cable size I need (length 50cm) and which fuse.

Many thanks in advance.

MPPT Controllers MPPT SmartSolar setup

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Answer 1 · 2022-11-22T10:34:03Z

Alexandra answered · Nov 22, 2022 at 10:34 AM

@scseba

In the tech specs it says 16mm²

Fusing here.

Fusing is for cable size, are you feeding DC or AC across?

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scseba commented · Nov 22, 2022 at 09:36 PM

Thank you for answer. Feeding into the house grid is done with DC.

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Alexandra ♦ scseba commented · Nov 23, 2022 at 06:04 AM

I realised i was too vague in my second question.

If you are using the multi 2 the biggest you can fit there is 16mm² and max feedback is 32A AC.

But the 16mm² may be a little unnecessary for your setup.

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scseba Alexandra ♦ commented · Nov 23, 2022 at 09:07 AM

I dont use the multi2. I'm using the SmartSolar 100/50 and for feeding into house: "FCHAO Continuous Power 3000 Watt Pure Sine Wave Inverter", which supports 3000 Watt continuous power and 6000W in peak.

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Answer 2 · 2022-11-22T18:34:02Z

ahtrimble answered · Nov 22, 2022 at 06:34 PM

Checking the manual (4.2. Battery) for the 100/50 is states the min fuse rating should be 55a and the max fuse rating should be 70a.
Based on that, the wire/cable should be 2AWG - 6AWG depending on the length of the run of the wire/cable.
That being said, on my 150/70, I use 2AWG wire/cable with a fuse for 4AWG wire/cable. That ensures that I am protecting my wire/cable. I currently use an 80a ANL fuse. I am upgrading my system and will switch over to an 80a MEGA fuse inside my PowerIn.
Why do I use an oversized wire/cable for the MPPT-to-Battery? I have seen various conditions where the wire/cable might try to handle more current than expected...and I don't want the wire/cable to fail before the fuse...ever.
Remember, the fuse is there to protect wire/cable failure.

2AWG = 33.6mm²

4AWG = 21.1mm²

6AWG = 13.3mm²

Better safe than sorry...and I like to sleep really well at night.

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