Matt wrote:

Of course if you've done it loads of times you connect both wires to
the good battery, walk to the flat one and connect the +ve one a
second or two before you do the -ve one and all is well .......until
the day you get distracted, put the clips on the floor, then there is
a spark and the leads start smoking and glowing, the good vehicle revs
drop and the alternator blows, the battery explodes and showers
everyone with acid.



Lead acid batteries do have a rather low internal resistance! Great for
fireworks and rapid heating of jump leads