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Old 09-01-2007, 07:09 AM   #21
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Thanks, Curt,

The AC power supply states INPUT: 100V-240V 1.3A-O.6A 50-60Hz
So is it as easy as that being 130 watts-144 watts since there's a range given?

OUTPUT: 19.5V 4.7A

I would hope that just charging up the battery or trying to locate a campground won't overload the circuitry.
I have a Dell Notebook PC and its AC Power Supply that says INPUT: 100V - 240V 1.5A 50-60 Hz

I have a 300 Watt DC to AC converter that I use to power a portable TV. It will only power the Dell for about 10 minutes, then the converter trips its thermal overload protector. I would suggest that you get something greater than 500 watts. Or better yet purchase a DC to DC converter. The one I purchased from Dell is only a 75 Watt converter and it runs the Dell PC all day when plugged into the Escalade.
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Old 09-01-2007, 11:02 AM   #22
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The AC power supply states INPUT: 100V-240V 1.3A-O.6A 50-60Hz
So is it as easy as that being 130 watts-144 watts since there's a range given?
Yes, that's how I would interpret these ratings.

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OUTPUT: 19.5V 4.7A
That's 19.5 x 4.7 or about 91 watts, typical of modern laptops (but not enough for the largest screens and biggest processors). A perfectly efficient power adapter would then need only 91 watts of input power (less than 8 amps), but as the AC input spec shows, they do waste a significant amount of the input power as heat (the extra 40 to 50 W)... if you get the AC power from an inverter, it's wasting power too. A DC-to-DC supply as Curtis uses might be more efficient, which would mean less current drawn from the battery, but we're still talking about less than 10 amps in the worst case.
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Old 09-01-2007, 11:59 AM   #23
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Okay, sounds like the VAIO is a powerhog like the Dell and that getting a DC-to-DC will reduce the amount of power wasted that would occur with a DC-to-AC conversion. With DC-to-AC I might have to go as high as 500 watts to avoid tripping the overload and those power inverters are quite expensive and bulky, so a DC-to-DC auto adapter will actually be less expensive and waste less energy.

Thanks for the input, everyone!
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Old 09-02-2007, 06:12 PM   #24
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Don't forget that an equipment-specific adapter of any kind becomes instantly worthless when the equipment is replaced by a newer whatever, whereas an inverter continues to be useful.

My laptop's brick has a output power spec (3.16A@19VDC) which is 60Watts (19x3.16), but the input spec of 1.5A is unclear as to which voltage is used (100-240VAC), so I dunno if it is 360W or 190W (Probably the latter). The brick gets pretty warm in use, so input energy is being wasted creating heat. In fact, there's a lot of wasted energy because the CPU gets hot also.

Also, because the laptops may require higher voltages than a home unit (to recharge the battery, I would guess), we don't really know how inefficient the DC-DC adapters may be. They can't just drop the voltage because it needs to be higher than 12VDC.
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Old 09-03-2007, 10:28 AM   #25
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Don't forget that an equipment-specific adapter of any kind becomes instantly worthless when the equipment is replaced by a newer whatever...
...which is a good reason to use a universal adapter, which just needs a different output tip to fit the next computer. The tips not only physically fit the equipment, but also signal the adapter to put out the right voltage.

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The brick gets pretty warm in use, so input energy is being wasted creating heat. In fact, there's a lot of wasted energy because the CPU gets hot also.
Other than the bit of light coming out of the screen, essentially all of the energy going into a computer comes out as heat - they don't really do physical work. I'd rather not waste too much before it even gets to the computing electronics!

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Also, because the laptops may require higher voltages than a home unit (to recharge the battery, I would guess), we don't really know how inefficient the DC-DC adapters may be. They can't just drop the voltage because it needs to be higher than 12VDC.
True; the nominal voltage of laptop batteries is routinely more than 12V... my Compaq and HP machines have used 19V inputs. A DC-to-DC converter putting out more than 12V is doing some of the same things as a 12VDC-to-120VAC inverter, but not inverting. On the other hand, it's still more efficient to do fewer conversions, and a good converter (stepping up or down in voltage) is much more efficient than a simple "throttle" which passes current while throwing away excess voltage, like an old 12V to lower voltage car power adapter.

I'm not currently using a DC-to-DC converter for the computer, and have used the 12VDC to 120VAC to computer-required DC path. It works, it's just not the ultimate in efficiency or simplicity.
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