Current carrying capacity for DC cabling

[Isetech]

A quick question with regards to battery cables (lets work on 52 VDC) and considering the battery cables are normally less than 5 m long.

Speaking to a supplier the other day, they indicated their 50 mmsq cable can carry 225 amps.

Then you look at the spec sheet, ok but that is if you use it for the purpose it was designed, welding, so the rating might be 225 amps but only for 5 minutes.

The current rating for 50 mm sq "welding" cables @230 VAC is 151 amps @230 VAC, which means at 52 VDC a 160 amp fuse holder with 160 amp fuses is perfect?

So what would be the nominal current carrying capacity for a 52 VDC system charging and discharging ... around 125 amps (100% duty cycle 24/7) ?

A sunsynk battery can only fit 25 mmsq cables into the battery plug in terminal, which is perfect because the battery we use is a C0.5 rated battery and we set the charge discaharge for 2 batteries @ 100 amps or 150 amps for 3 batteries connected in cascade parallel.

Connecting it like this means you have 2 x 25 mm sq red and 2 x 25 mm sq black cables connected to the 160 amps DC fuse disconnector, with 160 amps fuses.

The cable between the fuse holder and inverter is never more than 2m, so a 50 mm cable would be well within spec?

Manufacturers spec over rule SANS specs, right?

https://www.alverncables.co.za/download/catalogue/alvern-cables-appendix-2.pdf

https://www.alverncables.co.za/download/catalogue/equipment-cables.pdf

[Isetech]

The batteries are 5.1 kwh, 52 VDC with built in BMS.

[Aumy]

Stick with the 25 mm sq cables for your battery connections since they match your battery's rating. For the fuse holder to inverter connection, a 50 mm sq cable should be fine for the short distance you mentioned.

[Isetech]

The way I wire up the batteries, from the fuse holder to the battery there is 2 x 25mm cables, one feeds the top of the rack and the other the bottom of the rack, then I just link the middle batteries together.

I have been using 50 mm to link the fuse holder to the inverter, depending on the the fuse rating which would normally be a 160 amp fuse, because we normally only have 2 batteries.

However now that we are reviewing the plant data, we can now see where we can improve the money saving part of the system, rather than just a load shedding solutions.