# Inverters again...



## bognormike (May 10, 2005)

Have read up on here & should have done it at Newbury, but I'm thinking of getting a cheap little 150w inverter to run my laptop on the go, and when not hooked up. If I get one of the plug in the ciggy lighter socket type units, presumably I can plug it in the the one in the dash when driving, and then when parked up, move it over to one of the ones wired from my leisure battery to preserve the vehicle battery? 
Another point, do I have to go this route to run the laptop? I would be taking 12v output up to 240 (ish) and then plugging in my laptop mains adaptor to take it down to 19.5v. Not very efficient? Are there units out there that do the job from 12v to 19.5v (or thereabouts) on which to run the laptop? Thinking this through, the mains adaptor would go out of the line; does this leave the laptop open to fluctuations in voltage etc from the source?
Basic techy stuff only pease - I'm only a simple accountant  . 
Also are there any deals out there at the moment?
Thanks all.....


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## klubnomad (Mar 6, 2006)

Hi

Maplins do an inverter that does 15v - 20v for about £15. It plugs into the cigar socket and is called a laptop power supply. I use one to run my 15V LCD TV

HTH


Dave

656


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## Boff (May 10, 2005)

Hi,

being a physiciste I also originally thought that generating 19.5-ish volts out of 12 via a detour over 230 volts would be not very efficient. 

However, meanwhile I have learned that those dedicated 12-volts laptop power supplies usually have a lousy efficiency, in most cases below 80%! So if you use a good (not necessarily cheap) inverter in connection with your laptop's standard mains power supply you achieve at least the same, if not a better efficiency.

And with the inverter you have the advantage that you can also run other devices from it, e.g. mobile phone chargers. 

A rule of thumb says that an inverter runs most efficient at approx. 50% of it's rated power output, so a 150 watts inverter would be just an ideal fit for a laptop.

Best Regards,
Gerhard


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## spykal (May 9, 2005)

Hi Boff and Mike

I too thought that taking 12v up to 240v via an inverter and then back down to 16v for my laptop was not going to be efficient but persuaded by evidence found on MHF that is how I did it at first. Then one day when in Maplins browsing, I came across a Kerio Laptop adaptor that was really tiny, and on offer, so I bought one ..it is very much easier to store away in the glove pocket behind the laptop.

now the interesting bit ...results from some tests.

Using a Nikkai N65AV 300 watt invertor
on standby, switched on but no load .38 amps
powering an IBM laptop via its normal 240 v mains adaptor (16volts output)
the amperage varied from
2.55 amps - 4.25 amps max

the lower figure is while there was no processor or disk duty, the higher figure when the disk drive was accessed and the processor showed high activity.

Using a Kerio Energy Energy Knight laptop adaptor P70 W (claimed to be over 90% efficient and It is the smallest and lightest car / air adaptor, weighing only 139g. 95L x 42W x 21H)
standby switched on but no load .04 amps
Powering the IBM laptop directly, the amperage varied from
1.6 amps - 3.25 amp max

So there you have it......and I am not arguing a point, just reporting my findings ...*my Kerio adaptor *is way more efficient than *my invertor*.....maybe a 150 watt invertor would be better but I am not sure and in any case the Kerio adaptor is tiny, silent and easily stowed compared with the invertor.

IMHO there are some good efficient DC-DC adaptors and obviously some bad ones...hence the varying results that I have seen reported.

mike


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## 88927 (May 10, 2005)

Nice post Mike, very helpful as usual mate....
A good piece of research there that would convince me to try to kerio adapter in preference.
Thanks

Keith


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## DABurleigh (May 9, 2005)

Yes, it is difficult to be generic, I'm afraid, beyond:

1) Caveat emptor
2) Inverters are most efficient when operating at 50% rated continuous output, but can be very inefficient at small fractions of rated output.
3) Turn off an inverter when not in use.
4) Inverters have "gearing" in terms of multiple uses, specific adapters don't.

Dave


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## spykal (May 9, 2005)

DABurleigh said:


> 4) Inverters have "gearing" in terms of multiple uses, specific adapters don't.
> Dave


Hi Dave

Yes that is true and I would not be without my invertor for all the other jobs that it can do. It comes in handy powering my inkjet printer when I want to print off a local walking/cycling map or print a photograph of a neighbour & their van (always impresses that does :lol: ). It is handy too for the charging all the rechargeables in the van ( torch, camera etc) and on top of all that, this year I am hoping it will get used very often to power the 240 volt silent electric fan I have got to keep us cool in the van :roll: (not much need of it at the mo its tipping down here)

So it is still a highly valued bit of kit ..

mike


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## DABurleigh (May 9, 2005)

I thought I had a silent big diameter deskfan to keep cool when it got hot in France before I had aircon, but the particular fan I had hummed like crazy on a 300W Maplin modified sine-wave inverter. Inductive loads such as electric motors can have problems with modified sine-wave inverters; just luck of the draw.

Dave


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## 96950 (Dec 14, 2005)

bognormike said:


> Another point, do I have to go this route to run the laptop? I would be taking 12v output up to 240 (ish) and then plugging in my laptop mains adaptor to take it down to 19.5v. Not very efficient? Are there units out there that do the job from 12v to 19.5v (or thereabouts) on which to run the laptop? Thanks all.....


If i was powering my laptop using a DC-DC power supply, would be the only avenue i would venture, just purely because it's more battery friendly

C McQ :wink:


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## Malc (May 9, 2005)

How many more crafty adverts are you going to put on here Craig?
If you want to contact Nuke there is a provision for advertising albeit at a small charge.
Malc


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## 96950 (Dec 14, 2005)

Sounds like the way forward, can you pass me on his contact details please

Best Regards

Craig


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## Malc (May 9, 2005)

Left hand column, 3rd entry down Advertising.
Regards Malc


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## spykal (May 9, 2005)

ampcraig said:


> Sounds like the way forward, can you pass me on his contact details please
> 
> Best Regards
> 
> Craig


Hi Craig

Malc is spot on with the advice, you can find the section on advertising

*HERE*

Dave (Nukeadmin) will be pleased to help you with advertising the Amperor products on here.

You may also like to discuss with him the possibility of some discounts for members of MHF.

Mike

P.S. Thanks Malc :wink:


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## solentviews (May 9, 2005)

spykal, Will you let me know the make of the silent electric fan and where you got it please. I must admit I haven't looked for one but if wifes mood in this hot weather is anything to go by maybe I should.
Thankyou
Ian


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## spykal (May 9, 2005)

solentviews said:


> spykal, Will you let me know the make of the silent electric fan and where you got it please.


Hi Ian

The fan that we have is a 9" Taurus desk fan made by Expelair....it was a second hand purchase and it runs almost silently on speed 1. It consumes about 20 watts when running from the invertor. The reason that I had commented that it was silent was that we had bought one of those 12volt clip on "trucker type" fans but it was no good for using when just sitting in the van..far too noisy ....I guess most folk use them when motoring along and the noise would not be so unacceptable.

I noticed that DAB said earlier in the thread that the fan he tried on an invertor made a humming noise...so I guess I was just lucky to find one that runs just fine.

Mike


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