alternate power (was Re: Elusive Serial Cable/Plug)

Brian Smithson (
Mon, 25 Jan 1993 11:14:02 -0800

On Jan 25, 9:00am, Todd Inch wrote:

> Now, has anybody actually built a cigarette-lighter adapter cable for power?
> I wouldn't necessarily need to charge the molicel unless perhaps the long
> skinny battery is discharged when the requested adapter is connected? It
> looked like, from the pinouts previously mailed on this list, that there
> was about 12V, charging current, and 5V for the expansion bus. Can anyone
> confirm/deny this? This would also allow me/us to use a standard 12VDC
> supply instead of the normal AC adapter/charger, which would meet my need
> for having one at home and one at work. Anybody experimented further?
>-- End of excerpt from Todd Inch

A while back, I described a procedure for tapping into the internal battery
wiring and adding a switched jack for external power. When something
is plugged into the jack, it disconnects the battery. I used it with a
standard 12VDC switching supply at work so that I didn't need to drag around
my charger (and it's pathetically short brick-to-ultralite cable). It should
work OK for a cigarette lighter adaptor, except that I'd worry a little about
spikes, noise, overvoltage, and stuff like that if I were connecting it to an
automotive power system -- some kind of protection circuitry might be a good

As was pointed out later, a more sophisticated technique would be to use the
existing external power connector in some fashion. I didn't look into that
any further, though. Has anyone else done something like that?

-Brian Smithson