My fellow writers and neighbors who have added these lines following the proper codes report the minimum cost to be near $ 1,000, and one of my colleagues whose home did not have
enough amperage and whose panel was already maxed out paid $ 4,000.
It's usually a factor of not having enough jumper cable (too thin of cable will not pass
enough amperage), not
enough amperage output from the donor car.
Low battery voltage under load (cranking) will produce
enough amperage to energise the starter solenoid and pull in the pinion to mesh with the flywheel (or flexplate ring gear).
Not exact matches
Sometimes it appears there is a good connection there (especially when using side post terminals), yet there is only
enough of a connection to allow the low
amperage stuff to work.
As said in comments, make sure you have large
enough cables to send the
amperage over, but you should be able to attach both cars to your battery at the same time if you hook them up carefully.
Either the drive belt to the alternator is slipping at low rpm's or the alternator is not producing
enough voltage and
amperage at low rpm's.