Post by Richard Malcolm-Smith Post by E. Scrooge
Probably needs a good heavy duty battery. I wonder how hard these things
are on car battery if the car isn't running at the time?
I was gettnig about an hour out of it before the low battery cutout kicked in,
Still plenty left in the battery to start the car. That was with 1 laptop
Thats on a car battery smaller then any I have seen before. I think one laptop
is about 60-70 watts.
Cheap inverters put out square wave voltage/current. As there is a
significant DC component in the waveform, gear that expects a varying
voltage will not work so well with it. Thus you may not be able to draw
the full rated load if your equipment contains, say, a simple power
supply with a 50 Hz mains transformer, since the DC will not pass through
the transformer, only the very small part of the waveform where it goes
instantaneously from +230 to 0 (or is that +115 to -115) will be passed.
Thus the power that can be drawn off will be less than the usual
V*I*power factor bit that would be expected.
Can't remember what the other limitation of a square wave output are - I
think it has something to do with the peak being at 230 V instead of 325V
as is the case with a sine wave - or the RMS voltage or something.
I was at a place where a guy ran an audio amplifier off an inverter, the
amp would have had an ordinary 230V 50Hz mains transformer, rectifier and
caps in the power supply. The thing actually hummed quite a lot - only to
be expected as the power supply caps would have insufficient capacity to
smooth out a much rougher DC waveform that the transformer would supply.
That said, most computers these days use a switchmode supply that
converts the incoming AC to DC then back to high frequency AC, passing HF
transformer and out to the various voltages. I wouldn't expect these to
be affected to the same extent by this problem.