Re: Re[2]: AC vs DC lamps

[Huw Powell <human@nh.ultranet.com>]

-- [ From: Huw Powell * EMC.Ver #3.1a ] --

> difference depends on the impedance of the alternator-battery  connection.
 An alternator generating 100A peak currents into a 0.05  ohm circuit could
generate 5 volts of peak ripple on top of the  battery voltage.  Its not the
ac component of the ripple but the 13.6V  for a charging battery plus 5
volts of interconnecting wire drop that  gets you!

I think your assumptions are a little shaky there... let's come back into
real world numbers, if I assume my 90 amp alternator running full peg, I
just measured an eight foot bit of 10 GA wire, with two 16" 16 GA leads, on
my GenRad bridge and got .025 ohms.   Hmmm I'll run and get some 4 GA which
is what the two 8 GA wires on my car are equivalent to .... ok the closest I
could find lying around was an 8' piece of 6 GA.  Which without the 16"
leads measures .0055 ohms.  So that wire would yield a voltage drop of about
half a volt.  So 14 V at the alternator would yield 13.5 V at the battery. 
And I suppose, of course, the return line would also cut the voltage even
more at the lights.  I dunno.  If I start popping bulbs like popcorn I'll
worry about it.


Huw Powell
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