Inverter query

Thanks JohnnyC. I was starting to think I should get two inverters - one for high load appliances (eg. laptops), the other for low load (eg. shavers, toothbrushes).



What are your thoughts on charging laptops ... only use a pure sine wave, or is modified square wave OK?

Hi Russler,
Lots of people say use a pure sine wave inverter, but perhaps I've been lucky, but I've had no problems with 3 different laptops running off a 380w modified square wave inverter. Try it first, could save you money.
Gerry

Gday,
I have a small inverter about the size of a coke can which only cost about $50, plugs into the lighter socket and I use it for running laptops, charging handheld radios and phones etc, its just a modified sinewave type and causes no problems.
Don't forget that the 240 v power in your home is not too clean or sinusoidal either, with noise and spikes, most consumer electronics use universal type switch mode power supplies that are happy with anything from 90V to above 250 V and are almost immune to dirty power, they have to be.
I also have a 650 watt inverter which needs to be connected direct to the battery but found that I never use it.
cheers.

I have a coke inverter with cig plug would plug overheat using small laptop.

Out of interest I set up my coke can inverter today to measure the input current whilst it was powering a laptop, its a 15" HP so not a small one.
It was fluctuating between 5 and 6 amps, or 60 to 75 watts, well within the capability of the inverter which is rated at 150W continuous.
With the laptop off the inverter standby current is about 0.3 amp.
So the inverter/laptop setup draws about the same as a Waeco or Engel car fridge, the cig socket should handle that OK.

Thanks JohnnyC.
I may have been referencing the wrong sticker when trying to determine how much power my laptop requires (it's a Toshiba 15.5"). The charger input in 240V AC at 1.5 Amps, whereas the laptop itself says 15V DC at 5 Amps. If I understand this correctly, the laptop requires 75W (ie. 15x5), not 360W (240x1.5).

But if I want to charge the laptop battery, not just run the laptop, do I need to supply 75W or 360W?

Hi Russler,
The anomaly with calculated power at 240v and that at 15v is all to do with AC power factor of the power supply and inrush current when starting up. If the power supply says 240v at 1.5A, then you may need an inverter capable of about 375 watts to start the power supply. Then the current will settle back, using less power.

I should have added earlier, and I know this has been said many times before, that if you're running a laptop from your car, you are better off getting a DC/DC converter to run the laptop. This saves converting the power twice, thus efficiency is improved. You can get some quite reasonable converters for laptops now for around $40, complete with a range of adaptors to suit your lappie, and with selectable voltages, usually from about 15v right thru to 24v. Jaycar, Dick Smiths and Altronics keep them. I currently have a dual-voltage power supply which runs off both 110-240vac and 12vdc. Picked it up from Software City about 6 months ago on special for about $30. (not there now!).
cheers,
Gerry

Hi joc45,
Yeah, have heard of the DC/DC converters, but haven't looked into them. Was toying with the inverter option though because it gives more options for running AC appliances. Good idea though, which I shouldn't so readily discard.

Try this for a cheapie, ex HK:
Deal Extreme
With the $A at parity, this is great value. Free postage, good company to deal with.
No connection, just a happy customer.
Gerry