[amsat-bb] Re: Mobile Computer / Radio Installations

Tim Tapio tim at timtapio.com
Thu Apr 30 08:21:22 PDT 2009


You will find many military power supplies that do the inverse, convert DC
to AC back to DC...my 50 KVA UPS units at work convert AC to DC to AC....

If your engine is already running and already producing DC, I think the lack
of efficiency is of very little consequence....especially if you're looking
at the 90 watts or less that is required to run a fairly powerful laptop.

Many people drive with their lights on during the day, I'd say that is less
efficient than charging/running your laptop from an AC inverter.

73 de Tim, K4SHF

-----Original Message-----
From: amsat-bb-bounces at amsat.org [mailto:amsat-bb-bounces at amsat.org] On
Behalf Of Ben Jackson
Sent: Thursday, April 30, 2009 10:28 AM
To: Clint Bradford
Cc: amsat-bb at amsat.org
Subject: [amsat-bb] Re: Mobile Computer / Radio Installations

I did some research into this many moons ago and compiled a good amount of

Clint Bradford wrote:

> Personally, I would never run my laptop off a vehicle's charging 
> system while the vehicle is running. You won't find many reputable 
> laptop manufacturers recommending this.

I know for a fact that Dell, HP, and Acer all make car chargers. I consider
them fairly reputable. :)

What kills laptops are adapters that don't "insulate" (for lack of a better
word) the initial spike when you start your car. That can be fairly crazy on
voltages and if the adapter passes that through, it can be fatal to computer

> Tripp Lite PVINT375
> (although this model comes with a cigarette lighter plug, that 
> connection has to be one of the electrically most UNreliable for what 
> we are doing - so the plug gets whacked off and the unit is wired
> directly) ... or
> Astron Pi-250W
> 12VDC-to-120VAC inverter made for such circumstances. Wire it in to 
> your vehicle's 12VDC system, and simply use your existing AC power 
> supply. Immediate benefit is the ability to power/ charge other 
> electronic items you may have using regular AC chargers.

While, yes, these will work, this is the most inefficient way of charging
your laptop. Essentially you're getting AC from the alternator, converting
it to DC for the car, converting it back to AC via the inverter, only to
convert it back to DC to charge your laptop. Not good..

Ben Jackson - N1WBV - New Bedford, MA
bbj <at> innismir.net - http://www.innismir.net/
Sent via AMSAT-BB at amsat.org. Opinions expressed are those of the author.
Not an AMSAT-NA member? Join now to support the amateur satellite program!
Subscription settings: http://amsat.org/mailman/listinfo/amsat-bb

More information about the AMSAT-BB mailing list