Yes. One product that makes this possible is the Automobile Power Adapter
from Lind Electronic Design. As we understand it, with the Adaptor, you
can operate a Macintosh Portable while charging its battery from the
12-volt DC battery in an automobile, van, or boat. The adapter unit
contains a voltage regulator and current-limit circuits that ensure safe
computer operation and battery charging from a mobile power source. Lind
includes cords for an automobile cigarette lighter and for the computer's
power adapter jack with the adapter.
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