On 7/14/10 11:41 AM, Doug McNutt wrote:
At 14:08 -0400 7/14/10, Dan wrote:
Best to try things in advance...
Yep. And it would be pretty hard to find a power converter that
would damage any of today's computer power converters. If it doesn't
work don't leave it hooked up too long and pay attention to hot spots
that shouldn't be.
Switching power supplies rarely have problems. Linear supplies (the
denser wall warts) can have problems but are usually okay.
Cheap converters for automotive cigarette lighters almost always
convert to a square wave form of AC power. The voltage changes
quickly from +115 volts to -115 volts about 60 times per second.
That's quite different from utility power that changes as a smooth
sine wave that averages out (in delivered power) to 115 volts.
They actually switch from +160V (or so) to zero to -160 to zero and back
to +160. It's what is called a modified sine wave (modified square wave
would be more accurate).
More expensive converters as found in mobile homes do a better job
matching the voltage waveform.
Even many of the high power inverters are modified sine wave.
The internal power converters in computers these days make an effort
to avoid drawing current that is not sinusoidal. It's called harmonic
suppression and is required in many countries but not in the US of A.
When the harmonic suppression circuitry encounters a square wave
voltage, which has terrible harmonics to start with, it can get
confused and not work properly because it tries to accept current
only while the voltage is changing. For a square wave the voltage is
only changing for very short periods of time.
I haven't encountered any problems like that but I could see it happening.
I have several battery packs that I charge from solar panels for field
use. The loads are either 12V (LED lighting), off an inverter or car
adapters for the laptops. I prefer using the car adapter instead of the
inverter / AC power supply as it's more efficient. I don't worry about
leaving them plugged in and running down the battery. The OP listed an
inverter that draws .4 A with no load. While that's not a lot of power
it can run down the battery if your not careful. The laptop, once it's
fully charged draws much less power when using an auto adapter.
Most digital equipment will work okay with an inverter output. TVs
(older analog sets) and radios may have significant noise because of the
inverter.
--
Clark Martin
Redwood City, CA, USA
Macintosh / Internet Consulting
"I'm a designated driver on the Information Super Highway"
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