Well, I think I'm going off a bit on a tangent, but there is a difference in ideal conductor configuration between direct and AC current.
The NEC is biased towards AC, and there are differences in recommended wire gauge between AC and DC.
Solid wire in AC can carry more current as there is more material to resist heat, but electron travel is different in DC.
DC needs to carry electrons throughout its length and also tends to be lower in voltage, so higher amps for the given power delivery (watts) means you need more surface area on the conductor than for AC, or it will heat up.
A lot.
In the low amperage levels under the hood, not so important, but in large scale solar systems (I've designed and installed several of them), the appropriate wire selection is critical.
In this actual example, a 30 volt 100 amp dc circuit for a multi-panel array will overheat a ~ 20 strand of 4 AWG, where a braided 4 AWG with ~ 200 strands will remain cool in the same application.