I have been suggested that this rating is only true at 230v and that if I was to drop the voltage the current capacity of the cable may increase. My understanding is this is not related, and even at 12v the cable would still only be rated to 6amps?

You often see "12V automotive" cables with an apparently much higher rating than the same c.s.a. building installation cables. But that's down to a number of factors - slightly different formulation of plastic than can withstand higher temperatures is one, higher allowable termination temperature is another, but probably the biggest is that plastic insulation degrades with heat and time - and vehicle wiring is only expected to last for the commercial lifespan of the vehicle (7-15 years say) whereas building wiring is expected to last generations (70 years is often quoted) so all else being equal it has to be treated a lot more gently heat-wise. The actual system voltage isn't really a direct factor as such.

  - Andy.

I have been suggested that this rating is only true at 230v and that if I was to drop the voltage the current capacity of the cable may increase. My understanding is this is not related, and even at 12v the cable would still only be rated to 6amps?

You often see "12V automotive" cables with an apparently much higher rating than the same c.s.a. building installation cables. But that's down to a number of factors - slightly different formulation of plastic than can withstand higher temperatures is one, higher allowable termination temperature is another, but probably the biggest is that plastic insulation degrades with heat and time - and vehicle wiring is only expected to last for the commercial lifespan of the vehicle (7-15 years say) whereas building wiring is expected to last generations (70 years is often quoted) so all else being equal it has to be treated a lot more gently heat-wise. The actual system voltage isn't really a direct factor as such.

  - Andy.