Inverter: pure or modified sine?

Although this might be a bit of a retorical question, I'd love to have some second opinions in this one:

My auto electrician - who's not the one paying for this - recommends I get a good pure sine wave inverter. I've seen a 600 watt one for AU$450, while a 'good' one can easily be double that.

Or I go for a good quality 1000 watt modified sine wave. I've done my research, I 'think' I understand the difference, the former being same as 'house 220v and the latter pretending to be that but with the current following a more or less 'square' wave, and the more you pay for the mod sine inverter the 'less square' the wave hence the better it is for both the equipment you're running/charging as well as - to a limited degree - the battery it's getting it's 12v current from in the first place.

Now there are plenty of people that report using the mod sines with no problems, but there are also stories of people that have stuffed there digi video camera when charging it from mod sines.

Am I being a cheapskates? Should I just bite the bullet and get a pure sine?

Travelling by car with wife and 2 kids, so there's a laptop, 2 netbooks, video camera and battery chargers for still cameras all dependent on the inverter. No, I don't want to stuff the video camera, and getting Kensington 12 volt supplies for each laptop is expensive too...

Any advice appreciated!

I'd go with the best you can afford. The Square wave inverters are very 'dirty' and cause various problems on some sensitive kit. Things like your camcorder will be fine if charging when switched off, but some laptops really don't like the crap the cheap inverters put out.

Also consider getting one with a built in shut off if it detects the vehical voltage has dropped below a set level, as they will prevent you from getting stranded with a flat battery! Or at least having to kick the family out for a push start...

Buy the decent one (pure sine). Two reasons.

1. Square wave or "modified sine" ones generally have a high power due to the shape of the output wave form. This is not the kind of power that is useful as it only appears as heat in copper components... Most older psu's can cope they have a transformer that ineffect smoothes this out to "more" of a true sine. Most newer psu's are switched mode. The chinese are very good at producing cheap (few component) switched mode psu's. These also do not like dirty mains. Better designs generally cope much better.

2. Cheap inverters have cost savings built in. best place to save cost is in copper. This means under specified output components, and can result in fire.

But having said that, I have a S**ty 150 watt inverter by ring. My netbook psu stops working every now and again. One day I will buy a proper one.

Hope that helps a little.

Dan

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Cheers Dan
gettinglostagain.com

Another idiosyncrasy with mod sine invertors:

I bought one, intending to use it to power a 220v fluorescent strip light from a car battery so I could have light in my lock up. It fired the tube up but it didn't like it at all..! Got very hot, very quickly, beeped alarmingly then, (thankfully) switched itself off. I've since been told fluoro tubes require a different, presumably pure, wave.

One to bear in mind, maybe.

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Beware the dark, mechanical bird.

But then I've had no probs charging a laptop, charging phone, camera, MP3 etc using a modded 600W inverter. Surely the answer is to try one out at home and if it works for you fine. If not.... They are so much cheaper than pure sine wave inverters that I'd take a chance on wasting your money.
Q

I'd agree with Quintin. I've used a 75w Ring modded sine wave inverter to charge phone and cameras with no issues. Cost all of 20 quid. The only equipment I've ever heard of having issues with a modded sine wave are flourescent tubes as already mentioned and TV's. Also be aware that inverters are very inefficient and use a fair bit of power when just sitting powered up and idle so buy as small a unit as you can get away with and watch you don't flatten your car battery if you don't have a secondary battery fitted.