cable current capacity(ampere)

[Brian Su]

Hello guys,

I have just finished making my set of car jumper cables using 300AMP
35mm square fine strand copper cables. These are orange in color and
preety think. they are Orange Welding cables actually.

I just like to know, how come the cable is only rated at 300amp when
it's so think, 35mm?? That's equiv to 2AWG. I've seen thinner car
jumper cables being sold with 400amp rating.

Ok my guess is that my cables can withstand 300amp sustained current
whereelse those sold off shelves are rated for the peak current which
it wouldn't last after a few seconds of cranking the car's engine?

So how much current can my cables actually carry across to jump a car?
Since they are so think and powerful can they be used to jump start
large diesel engines like a lorry?

Thanks.

 

[Brian Su]

In you case, however, the converse is true. For the very short periods where

a jumper cable actually carries current, heating is not an issue, but
voltage drop IS. The rating in your case is probably the current the cables
can handle without causing the voltage to drop to the point where they are
ineffective. Or, the ratings could just be sales puffery. #2 AWG will carry
a lot of current for a few seconds, which is all it takes to start an
engine. How big is the battery cable in the vehicle? I bet it is no bigger
than your jumper!

I wouldn't worry about burning up your cables. Try them on the lorry. If
they work, good, If they don't due to excessive voltage drop, it won't
matter!

Hello, thanks for your time explaining stuff. Yes the battery cable in
the vehicle may be smaller or of the same size as my jumper leads but
they only run for a feet or 2 to the chasis/starter motor. Wherelse my
jumper cables run for 2.5 meters each. The other thing is that,
battery cables in the car are normally think strand copper cables made
up of about 15 - 20 strands of thick copper wires in them. I believe
thick strand cables can carry more current than thin strand ones?

Yeah I don't think these welding cables can be burned up just by jump
starting a lorry. I'll be suprised if they overheat at all... hehehe.

Thanks.