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

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.

__________________
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.

Thanks everyone for feedback. I'm still on the fence. Good to know it CAN be done cheaply if need be!

Some people get a small (150-300 watt) pure sine inverter AND a cheap 600-1000 watt modified sine, using the small pure sine to charge things that are or might be sensitive.

My only concern is the new video camera, I wouldn't want to fry it using a cheap inverter trying to save money and then having a AU$2000 camera fried... thát would be a waste too!

Why would anyone prefer to charge a phone from a mains charger through an inverter rather than a 12volt cigrette lighter socket? Unless thats the only charger you have available of course!

Also, what happens inside a 12volt charger for a phone for example that doesn't happen in an inverter? The "chargee" still must get the same voltage from both, is it just most things like phones require a voltage closer to 12 than 220 so the smaller step means greater efficiency??

In my case, i bought a shiny new pc with lots of disc space for photos etc, thinking i would buy a posh sine wave inverter, encase the pc box in foam to keep the dust out, and have a disc drive, keyboard etc etc on long leads so i would never need to access the pc itself. But having looked at the input wattage of both the pc and the nice efficient lcd screen, and best advice seems to be get an inverter capable of twice what you need, even two sine wave inverters (cheaper than one big one of identical capacity) were more expensive than binning the pc and buying a new laptop that could run happily on 12volts!! Thats before looking at the battery requirements to power a big inverter!

This may be a useful device for some people.

https://powertraveller.com/iwantsome...epower/000193/

Several manufacturers make 12 volt adapters that allow you to run/charge your laptop from a 12 volt adapter, Kensington for example. As we live in a 110/240 volt world, all laptops are sold with a transformer that converts 240 volt to somewhere between 12 and 24 volt. For example, an apple laptop typically runs on 18.5 volt/85 watt. No one makes an adapter allowing you to power an apple laptop from 12 volt, but there is a US company that will adapt you adapter to connect to a kensington adapter and run on 12 volt.

In an ideal world, laptops and battery charges - like mobile phones and ipods - would be charged from 12 volt directly, when travelling on a bike/in a car/having a solar powered house etc.

Otherwise you would be using an inverter two step up 12 volt to 240, then step it back down again to say 18.5 volt, it doesn't take a scientist to understand that that's a very inefficient way of powering your laptop, with a lot of loss of energy, and it drains even a good deep cycle battery rather quickly.

We're travelling with 2 kids, one apple laptop, two netbooks, and more battery chargers for cameras and torches then I care to mention.

To get the apple laptop converted to run on 12 volt + another kensington adapter to run at leaste one of the netbooks sets you back more then even a 1000 watt mod sine inverter that will run anything...

I've decided to go with a 1000 watt mod sine inverter, no kensington adapter for now, one battery charger that will charge AAA and AA batteries from 12 volt (phew), ipods/iphones charge on 12 volt, but everything else will have to run off an inefficient, but cheap, modified sine inverter.

The money I save by not choosing an expensive pure sine inverter and/or kensington adapter to run laptops from 12 volt is invested in a 130amp/hour agm deep cycle battery. This shouls run the fridge for 3-4 days before recharging, and hopefully allow 'some' charging of laptops as well... When they run out of juice we'll just have to go and play outside!