Inverters

[RayF]

I need to educate myself about inverters We are shortly leaving on a 4 month trip and need a small inverter to be used for running a laptop and charging phone and camera batteries and suchlike.Pretty well everything in the van bar microwave and aircon is 12 volt. We have a generator but I don't want to run that for battery charging. My idea is to have a small sine wave inverter with a dedicated 240 outlet in the van. I need info in regards to size,reliability of different brands etc. Our 12 volt supply is 360 amp hour of batteries with 40 amp charger and 2 X 85 watt panels. Thanks

[Motherhen]

Hi Ray

Best thing that happened last year when the sine wave inverter died was the advice from another forum. I then purchased a Jaycar 'power supply' for $79.95 or thereabouts. It goes from 12 v to what ever you need to select for you laptop (16 v, 19 v). So much easier to use than plugging into inverter, and more efficient than going from 12 v to 240 v and back to 16 or what ever. You could then get a small cheaper modified square wave one for the batteries and fit it to a power outlet like you planned.

Computers can be fussy, and my Toshiba Satellite would not run from the 500 w sine wave inverter although if turned off the battery would charge. My daughter's similar vintage Toshiba Satellite ran from both our inverters (on the square wave one only until we got the power supply).

[Bitpacker]

Just watch the laptops ..... some brands will not charge the battery from the so called 12vdc in to 16v dc out etc type supplies... they have "smarts" in their own brand power supplies.... eg Dell. It will run off the converter but tells me quite plainly that there is not a DELL supply hooked up, so, will run, but WILL NOT charge the Li-battery.

Regards, Ned.

[droversdog]

Hi Ray
I bought a 150w full sine wave Inverter last year for the same reason as you. I wanted a 300w unit but the Jacar store I went to only had this 150w one left so I got it cheap. It charges the laptop and phones ok however it wont run my 21" TV so I will have to get a bigger one or check the powersupply that Motherhen mentioned. The TV instructions reckon it needs 60w but the inverter just starts it then sets off an alarm and turns off. I don't know why as 60w is a long way short of 150w, maybe someone on this forum can tell me why but if you do get one get at least 300w.
Cheers, Ray

[Colin@1943]

Hi Ray,

If the inverter is beeping, it often means low voltage. Check your 12V wiring and make sure it is OK and also check how you connect it.

If you can, measure the 12v line right at the inverter when it is beeping. That will tell you what is going on. It may work OK until you start to load it up with the TV and the voltage starts to drop.

[Peter_n_Margaret]

(Approximate) VOTLAGE DROP =
[cable length (in metres) X current (in amps) X 0.017] divided by cable cross-section in mm.sq.
(courtesy of Collyn Rivers)

You must add the lengths of the +ve and -ve cables together.
I suggest a maximum voltage drop of 0.5V at maximum inverter load. Less is better.

Cheers,
Peter

[RayF]

Interesting about the Dell laptops. Mines a Dell XPS and checking the power supply it runs on 19.5 volt. So looks like I need an inverter and not a power supply. So what size and what brands have people had good or bad experiances with?

[Budget Barry]

Interesting about the Dell laptops. Mines a Dell XPS and checking the power supply it runs on 19.5 volt. So looks like I need an inverter and not a power supply. So what size and what brands have people had good or bad experiances with?

Hi Ray
I have been running laptops on MSW inverters for about twelve years. Twenty bucks will get you one from DX at 180 watts if that is all you need.
It is often much more convenient to use a small inverter and plug in the mains power packs for the small stuff.
Better to have a dedicated small inverter without the need to have a fan included, when running small draw appliances. Keep the big inverters for the big stuff as they will be inefficient running the small.
To answer your question about brands, I have never had a bad inverter and I always buy the cheap ones.
I keep giving them to friends and family so then buy more. I have that problem with a lot of stuff from DX.
Here is the last inverter I got from DX and then gave to my brother. It runs Dell laptops just fine, and is silent without need of a fan in this size.
http://www.dealextreme.com/details.dx/sku.21323

Now I am bound to start an argument about the need for pure sine wave.
You need that for only specific applications. The power bricks which plug in to mains would not know the difference between MSW and PSW and in fact are sometimes more efficient on MSW.
Converting dc to dc is likely to have similar losses to converting dc to ac, with an inverter, and back again with the power bricks. The dc to dc converters have to go through an ac stage to change voltage anyway. They just don't need to use 240 volts as the ac stage.
The power bricks match your appliances and are designed for them. Best to use those, rather than mucking about.

I like to mount inverters near the batteries, and have the long run in ac, to avoid voltage drop issues. I also like to get rid of those cigarette plugs and wire directly, but you can get away with them with a small inverter if that is more convenient and having the plug disconnect itself, with its spring loaded centre pin, will not cause issues.

[Peter_n_Margaret]

Barry and I disagree on this....

MSW OK for some things, some things not......
Small inverter OK for some things, bigger one for other things..........

It depends on your needs, but we bit the bullet and installed a decent size high efficiency PSW inverter and had it hard wired with powerpoints scattered through the van. Leave it running 24/7 unless we are very low on power. End of storey. Total convenience.

NOTE that we have no 'shore power' connection capability, so can not (and don't need to) connect to outside power, ever, nor do we carry a generator.

Cheers,
Peter

[Budget Barry]

We probably do not disagree on much, Peter.
I have a 350 watt MSW permanently wired in and on 24/7. Paid about fifty bucks for that one five years ago. I have one that large because it also runs my house battery charger along with the Dell laptop and Gateway modem. It also has a fan, but only resorts to that when the load is high enough to generate enough heat to need cooling. Some of the cheap inverters are also nasty, in that they run the fan all of the time. Avoid those.
I do agree that the same solution is not best for everyone, especially around electrics and self sufficiency in energy.
I have such good ventilation that I have no need to run an ac fan. If I did I would probably need pure sine wave. It is a short list of things which require pure sine wave, and I have none of them. Those who do, different story.

[richardandmia]

Ray, is your 21"TV a tube type or LCD? It sounds like tube to me if it draws 60 watts of power. If this is the case, a tube tv needs a lot more juice to start it.ie the instant you turn it on (like a motor or aircon) You might need more watts and pure signwave. Telly will run better too.
Cheers, Richard

[Motherhen]

When i purchased the Power Supply from the Leading Edge Store (Jaycar agent) in Roma, they insisted i bring the laptop into the store so they could ensure they sold me the right product for my laptop. The voltage range can be selected from a large range, and there are numerous adaptor sockets to fit into each brand of laptop. It was not the only power supply in the store - just the one that was best suited to my needs, and the one used by the ExplorOz members who gave me the tip.

[Colin@1943]

Richard,

My two day old Kogan 19" LCD TV is rated at 12 V 5 A - that's 60 W. The fact that it only draws 2 A is a mystery - maybe that is when the DVD is running too. My Sharp Aquos 19" is rated at 43 W but it is AC - no idea of actual power.

[Bob]

If you look closely at the plug that goes into the laptop battery port, they usually have a slight step very close to the end and my understanding is that this step is what tells the laptop that the correct power supply is plugged in.

The standard DC plugs like you get at Tricky Dickies have a straight shaft. I have a second 240V power supply that I got for my laptop (it is a Targus brand) and it came with about 6 - 8 different female plugs to put on the end of the lead - just select the same as your original supply.

From what I have seen the 12V supplies also seem to come with a selection of plugs for the end of the lead.

Sorry if OT but I try and buy stuff that will run on 12V so have not yet needed to use an inverter.

[Collyn Rivers]

I fear that I too disagree with Barry re this.

Whilst it is true that many devices will run from dc chopped into blocks with the corners more or less rounded off - , without an osciiloscope there is no way of telling how well or otherwise the above has been done.

It is simply a fact that some devices are wrecked by some such units, many other devices draw more current whilst doing so, most such inverters are not electrically isolated, some do not generate 240 volts (they put out 12-0-120 volts).

I ask generally - why on earth take the risk simply to save a few dollars?
Collyn

[Budget Barry]

I ask generally - why on earth take the risk simply to save a few dollars?
Collyn

Geez, Collyn.
If I said that was not my primary aim, you would roll over laughing.
However, I will take you to task on a few points.

MSW or PSW is not an indication of quality or electrical isolation.
MSW was all that was available for many years without taking out a second mortgage, and worked just fine. It is quite unlikely that the more recent availability at affordable prices is an indication of quality improvement. In fact, anecdotal reports of early failure of some of the PSW inverters might indicate that the MSW ones are at a mature stage of development.
You did not acknowledge the case when a MSW inverter feeding a switch-mode device, may inherently be more efficient.

No argument that some devices should be run on PSW. These devices would not have been run from inverters when PSW was not available.

I have asked myself this question before.
If PSW inverters were priced the same as MSW, would I switch.
I doubt it. I am very happy with MSW.

Now, if PSW became substantially cheaper than MSW, I might have to rethink.

Folks, Collyn is very knowledgeable on these issues, and you would be well advised to take note of what he says, and buy his books.
Me, I am just fond of an argument, but will tell it as I see it.
Collyn might even persuade me to switch to pure sine wave one day.

[metoo1956]

sorry budget barry, at the moment i must agree with Collyn
they do not look like they are designed for australia and i doubt their electrical isolation
if you are going to use one anyway; i would strongly suggest 1 appliance only and have the metal inverter case on an insulating surface
& keep away from the case when you are using whatever you have plugged in

wrapping a couple of metal bands arround it & screwing it to a wall/floor is not keeping it insulated

[daryl]

Some pictures for interest showing huge spikes on top of wave form on a Red Arc 150W inverter, the spikes are so high i have shown the next 2 pics top & bottom of wave forms, the scale is 50V/cm. Cheers Daryl

[Budget Barry]

Hi metoo
You lot are ganging up on me today.
No doubt I deserve it.
Buying in the shops or buying online may or may not make a difference to quality.
With Free Trade, you are going to get good stuff and junk both ways.

I just bought a new battery from Hong Kong, for my Dell laptop.
$45 from HK delivered and $120 from an Australian source on eBay delivered. I did a bit of research and the one costing more than double was older stock with a smaller Wh capacity. Many would believe that if they paid more they get better. I suppose such thinking has to get lucky sometimes.

[Peter_n_Margaret]

You lot are ganging up on me today.
No doubt I deserve it..

And.....while we are on a roll......

15 years ago, I bought a 500W MSW inverter.
5 years ago, I gave it away and bought a PSW inverter.
A total tally of 2.

What's your totall tally B3?

Cheers,
Peter