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Old 14-04-2011, 21:47   #1
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Running a Laptop Without an Inverter

Given the power losses with converting DC to AC and then the losses with converting it right back to DC again, I have never been a big fan of using an inverter to run a laptop.

My previous laptop would run quite fine from a standard 12V DC cigarette-lighter type outlet using a DC-DC adaper, with adjustable output, so I would just set it to the required voltage (16V, from memory) and off we'd go.

My new laptop, apparently, has some sensor in the power inlet and won't allow me to do this. So at this stage a small (150W) inverter looks like the only solution...

Any alternatives?
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Old 14-04-2011, 21:56   #2
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Re: Running a laptop without an inverter

Quote:
Originally Posted by Weyalan View Post
Given the power losses with converting DC to AC and then the losses with converting it right back to DC again, I have never been a big fan of using an inverter to run a laptop.

My previous laptop would run quite fine from a standard 12V DC cigarette-lighter type outlet using a DC-DC adaper, with adjustable output, so I would just set it to the required voltage (16V, from memory) and off we'd go.

My new laptop, apparently, has some sensor in the power inlet and won't allow me to do this. So at this stage a small (150W) inverter looks like the only solution...

Any alternatives?
Don't worry too much... a DC-DC converter also uses AC as an intermediate step with comparable (but lower) losses. Those losses are for a large part relative to the unit's maximum power output, meaning you're better off with a small inverter as long as the laptop is the only device needing AC power.

ciao!
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Old 15-04-2011, 00:39   #3
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Re: Running a laptop without an inverter

Quote:
Originally Posted by Weyalan View Post

My new laptop, apparently, has some sensor in the power inlet and won't allow me to do this. So at this stage a small (150W) inverter looks like the only solution...

Any alternatives?
What laptop is it? How would it know, I wonder. Dc is dc innit?
In the UK a lot of people use these on boats - 150W Laptop Car Adaptor : InCar Power Adaptors : Maplin
On my toshiba it draws maybe about 60% compared to the invertor.
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Old 15-04-2011, 01:24   #4
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Re: Running a laptop without an inverter

I bought a 19v one of TOSHIBA CAR CHARGER ADAPTER SATELLITE P200 PRO A100 L10 | eBay He has all types and they work.

I dont know the guy I just found him for my problem
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Old 15-04-2011, 01:53   #5
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Re: Running a laptop without an inverter

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Originally Posted by conachair View Post
What laptop is it? How would it know, I wonder. Dc is dc innit?
In the UK a lot of people use these on boats - 150W Laptop Car Adaptor : InCar Power Adaptors : Maplin
On my toshiba it draws maybe about 60% compared to the invertor.
DC is DC yes but your laptop will require a specific voltage usually above the nominal 12 volts available on your boat.

Walmart among others offer DC-DC laptop chargers with variety of power connector heads & adjustable output voltage to suit almost every laptop made. Just check the power output (wattage) is above that required by your machine.
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Old 15-04-2011, 03:25   #6
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Re: Running a laptop without an inverter

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Originally Posted by richardhula View Post
DC is DC yes but your laptop will require a specific voltage usually above the nominal 12 volts available on your boat.
Yep, mine is 19v which works fine with a dc to dc 150w supply for cars from maplins. Fully discharged and running it pulls just over 4a dc/dc instead of over 7a with the ac supply through an invertor.

re the OP I was wondering how a laptop would know that its' power was coming from a dc to dc supply and not an ac to dc supply plugged into the wall. Which is not to say that it doesn't know, some maunufactures may not like the thought of you to be buying cheap power supplies from generic makes instead of their expensive own brand items......

Imagine!

But google often comes up with ways around such control, red rag to a bull for many people.
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Old 15-04-2011, 03:34   #7
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Re: Running a laptop without an inverter

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Originally Posted by conachair View Post
re the OP I was wondering how a laptop would know that its' power was coming from a dc to dc supply and not an ac to dc supply plugged into the wall. Which is not to say that it doesn't know, some maunufactures may not like the thought of you to be buying cheap power supplies from generic makes instead of their expensive own brand items......
I think he was referring to the fact that his latest laptop wouldn't run on straight 12 volts unlike his previous.
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Old 15-04-2011, 03:45   #8
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Re: Running a laptop without an inverter

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Originally Posted by richardhula View Post
I think he was referring to the fact that his latest laptop wouldn't run on straight 12 volts unlike his previous.
Don't think so...

Quote:
My previous laptop would run quite fine from a standard 12V DC cigarette-lighter type outlet using a DC-DC adaper, with adjustable output, so I would just set it to the required voltage (16V, from memory) and off we'd go.
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Old 15-04-2011, 04:50   #9
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Re: Running a laptop without an inverter

You could try an iGo adapter. There are modes that run off DC and have different plug tips for different laptops, so others can use it too. I've had good luck with them over the years. I think they are widely available at Radio Shack in the US.
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Old 15-04-2011, 06:16   #10
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Re: Running a laptop without an inverter

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Originally Posted by conachair View Post
Don't think so...
Mis-read apologies
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Old 15-04-2011, 06:58   #11
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Re: Running a laptop without an inverter

Inverters are not big power wasters. Get a reputable brand. Get one just a little larger than you need, but not much larger, as mentioned above. I use a 300W inverter for my laptop battery charging of 100W. Cheaper inverters may interfere badly with VHF, AIS and SSB. Also cheaper ones tend to be less efficient.

The laptop does it's own conversions inside as the brains run on 1.2V or 3.5V or whatever. All done with DC-DC converters. It's the way the world's electronics work.
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Old 16-04-2011, 17:38   #12
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According to my knowledge from 12 V DC u can feed lesser voltages suc as 9 V etc through electronic circuit. It is available in market, however for greater voltages such as 16 V u need AC therefore inverter i(which convert dc to ac for converting higher voltages) is a must. Both options waste similar energy through heat loss. For inverter option due to electronic conversion of AC the output is not pure sinus wave which i do not like this part, however it works.
Good luck and Regards
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Old 16-04-2011, 18:59   #13
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Re: Running a Laptop Without an Inverter

DC to DC converters can be used to step up the voltage or step down the voltage, so you can go from 12V up to 16V, or down to 9V as examples. Both are based on high frequency switching and a variety of electronic magic. Although there are AC-like intermediate voltages that occur internal the a DC-DC converter, calling it an Inverter would be a misnomer. A good DC-DC converter will be in the 85% to 95% efficiency range.

An Inverter is DC to AC, where the AC output is some approximation of a standard AC wave form (sine wave) at some standard voltage and frequency. Lots of effort goes into the design to make the waveform better match the native AC sine wave form. Inverters run in the 85%-95% effeciency range as well.

Using an inverter to create AC, then plugging in a laptop charger to run your computer is simple and easy, and for intermittent use makes perfect sense. The only real downside is that you are running two converters back to back, so their losses compound. If you are running a laptop all the time, using a DC-DC converter like an iGo or other brand will be more efficient. Whether the difference matters depends on your other loads and whether the laptop is significant, and hence whether the savings makes an overall meaningful difference. On a sail boat, it could really matter. On a power boat, it's probably insignificant.
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Old 16-04-2011, 19:55   #14
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Re: Running a Laptop Without an Inverter

Quote:
Originally Posted by Weyalan View Post
Given the power losses with converting DC to AC and then the losses with converting it right back to DC again, I have never been a big fan of using an inverter to run a laptop.

My previous laptop would run quite fine from a standard 12V DC cigarette-lighter type outlet using a DC-DC adaper, with adjustable output, so I would just set it to the required voltage (16V, from memory) and off we'd go.

My new laptop, apparently, has some sensor in the power inlet and won't allow me to do this. So at this stage a small (150W) inverter looks like the only solution...

Any alternatives?
Weyalan...is it a DELL? I know many of these have a third wire at the dc jack...Perhaps other makes do too,nowadays.They can likely be tricked but....
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Old 16-04-2011, 23:10   #15
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Re: Running a Laptop Without an Inverter

I have several laptops in the house (my systems administrator son supplies me with old stuff from his work when they upgrade).
I have had great luck with this Acer laptop on the boat. I'm writing this post from an Acer 3100. It's decently fast and relatively easy on the DC. It has no problems running on a 12 volt socket and it even charges its own battery at the same time.
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