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Old 08-08-2006, 03:52   #1
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Running a laptop from 12 volt supply

I'm certain that there is a simple explanation to this but sometimes my brain hurts!!!

Other than using an inverter is there a way of running a laptop using some sort of voltage converter to bring it up to the 16 volts or so that is needed?

If the inverter is the only way how much power is attenuated within the inverter itself?

I'm sure that there is a good reason but it seems strange to me that laptops are not run using 12 volts instead of slightly more.
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Old 08-08-2006, 05:50   #2
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Yes you can buy car adaptors. one source is here

http://store.yahoo.com/shopbattery/index.html
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Old 08-08-2006, 05:53   #3
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Depending on the laptop brand there are bricks for 12 volt. My Dell hasa a brick that converts 12, 24, 120 and 240 volts to make 19 volts out. On long trips I just plug straight into the cigarette lighter of the car and code away. How it works I can't say. You know the old joke: How many programmers does it take to change a light bulb...
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Old 08-08-2006, 06:02   #4
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Thanks for your great info. The Shop Battery site has just what I'm looking for.

Fair winds both
David
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Old 08-08-2006, 06:18   #5
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Just found a snag. Battery Shop will not ship outside the US/Canada and I live in UK. I have emailed them for suggestions but would welcome anyone who has the name of another company who will send an adaptor to the UK
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Old 08-08-2006, 06:32   #6
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How about a place that sells such power supplies for desktops? Ones that can plug into your 12 volt system?
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Old 08-08-2006, 06:36   #7
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http://www.newegg.com/Product/Produc...ubCategory=538

Plenty there to choose from. I don't work for them, just buy a lot of stuff for the office from them.
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Old 08-08-2006, 07:10   #8
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Dunkers,

Aside from the shipping to UK question, you need to be aware of a couple of things when using a "car adapter" with a laptop.

1. Laptops use a fair amount of power. Many draw as much as 65 or 70 watts (say, 5 or 6 amps @ 12VDC). They can draw down your house batteries at about the same rate as electric refrigeration.

2. Most car adapters are made to function in a vehicle, and one which is running. Voltage in a vehicle is usually 13.8 or higher. Many adapters will not charge your laptop batteries when connected to the typical 12V battery bank on a sailboat, unless the engine is running.

Typically, they will run your laptop OK as the voltage drops below 13.5 or so, but they won't charge your batteries. Indeed, the batteries will be drained.

I've tested a number of these, including ones from IBM. Finally found a source of extremely well made adapters which, if you so specify, can work well down to about 10.5 or 11 volts input. These are from Lind Electronics
http://www.lindelectronics.com/

I bought two of them and they have worked extremely well, even with low voltage.

I don't know if they ship overseas or not, but I'd bet they do. It might be worthwhile to send them an email enquiry and ask about shipping outside the U.S. They will need the specifics on your laptop: brand, model #, etc. You also need to specify that this is for use on a small sailboat where voltages often are in the low 12s or even less, so you want an adapter which will charge the batteries even with that low voltage.

Good luck,

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Old 08-08-2006, 08:16   #9
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For UK consumers, the best I have found (and now use) is the 120w version by maplins. http://www.maplin.co.uk/Module.aspx?...20120w&doy=8m8

This includes most of the plugs used by the manufacturers except Dell.
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Old 08-08-2006, 15:42   #10
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I bought an adapter on Ebay. It plugged into a 12V "cigarette lighter" type plug and could be set to anything from 10V to 18V. It also had a selection of about 8 different outlet plugs, to suit various different types of laptop power inlet.

It worked fine for me, and cost about $10. Unfortunately, I cannot find the link to the seller.
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Old 09-08-2006, 07:43   #11
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Thanks for all the replies, I'll start looking around on some of the suggested sites

Cheers
David
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Old 09-08-2006, 08:07   #12
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What you need is 'true sine wave' inverter/adapter to charge laptop, etc. batteries. The 'typical' cheapy inverters/adapters will only allow you to 'run' the laptop but wont be able to 'charge' the batteries. True sine wave inverters/adapters are 'pricey'.
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Old 09-08-2006, 11:19   #13
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Why would you need a true sine wave inverter for a laptop, and why would you want to waste so much energy converting your DC to AC and back to DC. a DC to DC converter is the most efficient system.
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