Using Ford Fiesta to jump start my Peugeot Partner MVP. Before attempting starting Peugeot run engine of Fiesta so that battery didn't get drained.

Connected both batteries correctly and slow turn over with Postive lead getting hot.
Changed the position of the Negative jump lead from the Peugeot flat battery to a good earth on the engine still slow almost nil turn over, again hot Postive lead:

The question is Why did the postive jump lead get hot.?

bob, December 2012

thanks Peccavi will check

bob, December 2012

Starter motors take lots of current - up to and in excess of 100 Amps - smaller cars a bit less.

The junction at the Positive lead very probably has a high resistance. Just a few ohms and a high current will generate lots of heat.

Inspect the crocodile connector for a poor connection - peel back any sleeve and have a good look - crimp in a vice or solder if you have a big soldering iron.

Heat = Watts
Watts = Amps squared x Resistance

Just half an ohm at 60Amps will make 1800 Watts

This is why...

Peccavi, December 2012