On Wednesday, April 10, 2019 at 9:16:02 AM UTC-4, wrote:
right, the answer is "it depends"
as is the answer to so many interesting questions..

if the battery is good but just needs to be charged,

He specifically said jumping a car to get it started. To me, that
doesn't imply charging it, it's when you've left the lights on
in a parking lot or have a battery that is going bad and use someone
else's car to jump start it right away.



a thin wire carrying a handful of Amps for a few minutes will recharge it enough to start the car.

The problem there is that if you are really "jump starting" it,
to me that means connecting it to another car's battery/alternator
or similar capacity source. If you do that with a dead battery
or mostly discharged battery like you can expect to find and a thin
wire, it's going to melt the wire, because there is nothing to limit
the current to just a few amps.





The actual starting current comes from the recharged battery, not via the cables.

but if the battery or connections are actually defective, and the current to actually start the car needs to come directly via the cables, heavy wire will be needed.

m