He already explained jumping the airplane battery from a car.

That makes absolutely no difference if the master or starter
solenoids are defective, or if cable crimps are corroded. All that
amperage can't reach the starter if there are bad connections
elsewhere. We regularly find bad solenoids in older airplanes, and the
only way to fix it is to either start replacing them, or getting smart
and checking voltage drops across them while cranking. The copper
contacts in them oxidize with age, even in low-time airplanes, and will
be burned in higher-time aircraft. It only takes a fraction of an ohm
to stop things.

Dan