It sounds like the waveform that it is outputting is not suitable for the laptop charger, either that or it cannot supply enough power based on the fact that it is the inverter shutting down. I just had a look at my acer laptop power brick and it takes 100-240v ~ 1.5A. So, you are at the limits of the power that the inverter is able to supply.
Why not just get a UPS device to ensure compatibility? Or, you could get a DC/DC converter and get much more battery life. (something like this:
http://accessories.dell.com/sna/productdetail.aspx?c=us&l=en&s=dhs&cs=19&sku=310-8814#Overview)
Some interesting reading:
"This is a 300 volt-amp (VA) 12-to-240 volt inverter of slightly elderly design, with a not-so-great surge power rating - the amount of power it can deliver for a brief moment.
Watts may equal volts times amps, but only for DC circuits, or AC circuits running purely resistive loads, like heaters or incandescent lights. Computers and monitors aren't resistive loads. Technically speaking, they have a pretty nasty "power factor". A 300VA inverter can be expected to run only about 210 watts worth of PC gear; maybe even less. For more on this as it applies to computer UPSes, check out APC's PDF format white paper on the subject, here.
Just because a computer has a 300 watt PSU, though, doesn't mean it needs a 430VA inverter. It'll only need that if it fully loads every one of its PSU's output rails, which it almost definitely doesn't.
These days, you can get a 300VA inverter with a 900VA surge rating and better than 90% efficiency for about $AU160 - Jaycar have one, MI-5062, at that price. For less than twice the money, you can get a 600VA continuous, 1500VA surge inverter, which is enough to run pretty much any PC, and its monitor.
Surge rating matters, because many devices draw a lot more current on startup than they do when they're running. Laser printers and refrigerators, for instance, have such huge startup current demands that you need an apparently massively over-rated inverter if you want to run them. Computers aren't that bad, but CRT monitors can still be a problem.
The computer I powered from this rig is a humble Celeron box with a 15 inch monitor. The PC without monitor draws a peak current of about 8.5 amps from the battery, through the inverter, on startup. Then it settles to less than six amps.
The monitor's degauss circuit, though, draws more than the peak power capacity of the inverter.
Since practically all CRTs automatically degauss when they're powered up, that's a problem. Another 15 incher I tried just pegged the needle on my ammeter for a moment when turned on, and then sat there in standby mode.
Fortunately, the old Mitac monitor in the picture can still start up when it tries to degauss itself and fails. It just draws a nice steady eight amps, with no scary surge. So the PC with monitor has a peak draw of a bit less than the inverter's constant output capacity, and then settles down to about 70% of capacity.
Note: If you don't know how thick a wire to use to carry, say, 20 amps (to give a decent safety margin), that's a good sign that you're not quite ready for this project.
The solution to the monitor surge problem, of course, is either to use a more modern inverter with a big surge rating, or to use a lower power monitor, like an LCD screen. 15 inch LCDs (which have more screen area than a "15 inch" CRT) draw less than 40 watts and have no startup surge to speak of. So they're excellent candidates for "alternative power" applications.
Inverter waveforms
The "waveform" of an inverter is how the inverter's output voltage changes as it goes through its positive/negative alternating-current cycles. The rate of oscillation for all Australian 220/240 volt inverters should be the same 50 Hertz (cycles per second) as ordinary mains power in this country, but the voltage-versus-time graph of an inverter's output can be quite different from that of mains power.
If, for instance, the voltage rises practically instantly to full positive, holds there for half a cycle, then drops practically instantly to full negative for the other half-cycle, then you're looking at a "square wave".
Normal mains power alternates in a smooth sine wave - well, it does when it's not being polluted by spikes and sags and surges, anyway. This sinusoidal waveform, shown in green in this picture, is only accurately imitated by more expensive "sine wave" inverters. You can buy UPSes that have sine wave inverters - you're looking at maybe $AU900 for a 750VA line interactive one. You can buy sine wave inverters as separate items, too.
PCs don't need them, though. They'll work fine on modified square wave power - that's the red waveform in the picture. Inverters that output this waveform are cheaper than sine wave units.
Most AC motors - power tools, for instance - will run OK from modified square wave power as well, but they're likely to draw about 20% more power than you'd expect, and may buzz annoyingly. Things with circuitry that relies on clean sine wave power - electric clocks, bread makers, some battery chargers, the "shaded pole" motors used by ceiling fans - are likely to misbehave.
The blue waveform in the picture, by the way, is a plain square wave. It's pretty hard to find plain square wave inverters any more. Which is good, because you probably don't want one. They can run some, but not all, motors, and they're fine with incandescent lights. But even computer power supplies aren't guaranteed to work properly on this exceedingly "dirty" power."
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http://www.dansdata.com/diyups.htm
http://www.ttlg.com/forums/showthread.php?t=132080 - Notice one of the posters mentions problems running a laptop without a pure sine-wave inverter.
"Depending on the psu in your computer, it might or might not like the modified sine wave.
My laptop transformer is happy with a modified wave but my mates isn't and he had to get a new psu.
So you're really looking to get a pure sine wave inverter if you want guaranteed reliability."
More info on output waveform - look at the last reply.
http://askville.amazon.com/plug-HP-...swerViewer.do?requestId=6486704&tag=tec06d-20
