Some competition car audio set-ups are using tens of thousands of watts, usually at 14.4 or 18 volts, so the amperage can get into the thousands. The wiring use

Some competition car audio set-ups are using tens of thousands of watts, usually at 14.4 or 18 volts, so the amperage can get into the thousands. The wiring used for that is usually multiple runs of 0-gauge or better. 4/0 is a bit less than half an inch and is rated for 300-400 amps.