At 07:00 PM 8/5/2009, mark drillock wrote:
>The important lesson for people to understand is the voltage can seem
>fine when little charging is needed but after the battery gets run way
>down you find out the wiring can't fill it back up fast enough because
>the current flow is low.

To amplify this a little bit -- the main problem is that VW chose to
use an alternator/regulator with internal voltage sensing on a
vehicle with long cabling runs.  Since the internal sensing is based
on the proposition that cable losses can be ignored (because the
cable is only a couple feet long) this was an unfortunate decision on
VW's part.  The correct method is to use a separate wire from the
battery positive terminal or nearby directly to the regulator so that
it knows what voltage the battery is actually seeing.  It will then
regulate the alternator to produce the correct results at the
battery, automatically compensating for cable losses because the
cable is now *inside* the control loop.

Done that way, an inadequate charging cable will waste a certain
amount of power, and a really inadequate one will overheat; but
unless it fails catastrophically the battery will receive the actual
charging voltage that the regulator is built to deliver.

  --
David Beierl - Providence RI USA -- http://pws.prserv.net/synergy/Vanagon/
'89 Po' White Star "Scamp"