All computers run on DC sooner or later.
It's stupid to supply 12V DC to an inverter to operate a laptop's 117V AC
supply to provide some DC back to the laptop. The laptop has internal
regulators that translate the unregulated battery voltage to whatever
regulated +5V etc. is needed by the computer itself. Unfortunately, some
older computers used high voltage batteries that are nearly discharged at 12
V. A dc-dc step-up converter is needed.
My Dell Latitude runs from a 17V 2.3A DC supply. 17V is required to charge
the internal batteries to 100%. I cut the DC power cord between the computer
and the supply (only because my laptop's DC connector is uncommon) and fed
the laptop directly with 12V. It worked fine down to 11V. The battery meter
indicated about 25% charge at 12.0V. If the batteries were fully charged,
they would discharge to the 25% point where the 12V external supply would
take over. If the power was interrupted, there was enough juice left in the
internal batteries to hold on for about 20 minutes.
I made a splice in the Dell power cord with a 30A PowerPole connector.
Whenever I want to run it from the car I put in the 12V cord (cigarette plug
with internal 3A fuse) and everything is peachy. A truly low noise, low cost
solution.
Dick Frey k4xu
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