Laptop external power from batteries (DC/DC)

[Ben Scott]

On Mon, Aug 18, 2008 at 7:07 PM, Bill McGonigle <bill at bfccomputing.com> wrote:
> I've tried doing audio recording with my laptop running off of the car with
> an inverter and the electrical noise ruined the effort.

  FWIW...

  Circa 1992, I spent some time trying to get a personal portable CD
player to play sound through line-in on a car stereo, while also
powering CD player from car 12 VDC (with one of those "universal"
multi-voltage adapters).  Nasty alternator noise in the audio.   Went
away when the CD player was on battery.  Trouble persisted even when I
added a gadget Rat Shack sold to fix such problems (a fat cylinder
wired in series -- prolly some kind of capacitor).  So it appears that
simply sprinkling "magic DC dust" on this class of problem doesn't
solve it.

  I imagine sufficiently good quality components would not have
trouble, but most laptops have cheap parts for both power and audio.
Dunno about that DC/DC regulator you found.  I think that's costing
more than everything I spent on the above project combined (including
the CD player *and* car radio), so maybe it's sufficiently better
hardware.

-- Ben