Which Battery Cable size

[veedub565]

I want to operate my vintage military HF rig from a leisure battery. It is 250W max output, with a rated max power consumption of 640W (CW, key down. )

So I reckon 640W at 12V is around 50A.

Question is which wire guage is appropriate. I did a bit of research and came up with AWG 4. Just looking for an extra opinion on whether that sounds about right.

I'm not actually going to be using it at full power. Indeed I'm only an M7 so 10W max. And even then I use SSB not CW. I thought it prudent though to set things up for what the rig is potentially capable of. Rather than what I use it for now, and then have to upgrade it later.

[TimFox]

How long a cable do you need?  Probably the voltage drop is a more important consideration than wire current rating.

[geggi1]

If the cable is very short (1m) 10mm2 would be sufficiant.
In case the cable lis longer go for 16mm2 but keep it as short as possible.

[veedub565]

Thanks, its probably only going to be a couple of meters tops.

[Dehv]

#4 sounds right, with a fuse compensating for increased amps due to voltage sag as the battery gets down to 10.5v.

[veedub565]

#4 sounds right, with a fuse compensating for increased amps due to voltage sag as the battery gets down to 10.5v.

Yes that's a good point, as the battery voltage drops it's gonna suck more current to compensate. I hadn't thought of that. I haven't actually gotten around to doing this yet, various other things taking up my time.