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Old 04-08-2010, 16:11   #1
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Powering My Netbook / Laptop

Last year I used a 150W inverter to keep my laptop recharged. This cigarette lighter plug in inverter drew about 4 amps DC while charging.

But last week I got a netbook and wanted something a bit more compact and maybe more efficient to keep it charged while on the boat. So I ordered a $10 (including shipping) car charger from a Hong Kong based outfit. I found them on ebay at TOSHIBA NOTEBOOK LAPTOP CAR ADAPTER UNIVERSAL CHARGER - eBay (item 270611680890 end time Aug-21-10 22:56:57 PDT)

If that address is too intimidating, go to ebay and search on eleknuts laptop car charger.

The charger arrived today and it is a nice piece of stuff. CE rated, it has a sliding switch to select output voltage from 15 to 24 V. It comes with 6-8 adapters, one of which fit my Toshiba netbook. Unfortunately none of them fit my Dell laptop, but that isn't what I bought it for.

The netbook says it uses 1.6 amps at 19 V. I measured the converter draw at about 2 amps at 12 V, so that makes its efficiency better than 100% so the Toshiba spec is obvously conservative.

While powered by the converter the netbook's power indicator said it was charging and after 5 minutes, the battery capacity had increased about 5%, what I would expect from the wall adapter.

So, I am very happy with this new device and you can't beat the price. I'll get a chance to try it out next week on a two week cruise on a friend's boat.

FWIW all sorts of electronics are available dirt cheap from Hong Kong. You have to search ebay to find them, but I have yet to be dissapointed.

David
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Old 04-08-2010, 16:28   #2
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G'day, David, just an FYI. Most of these lower cost voltage transforming devices put a fair amount of electronical noises in radio circuits. You might want to test your radio coms with someone while this device is operating. Cheers.
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Old 04-08-2010, 16:56   #3
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We use a couple of these for our computers and they work well. The amp draw ratings on computers are for highest loads. They usually stay below this unless the battery is discharged and you are really running disk and CPU intensive applications while watching a movie.

They create a lot of RF noise on our SSB. I cut this down by 80% with ferrites, but really just turn them off when using the SSB. No problem on the VHF.

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Old 04-08-2010, 17:16   #4
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I just tried the converter in the car with the radio on. No interference on FM or AM bands.

David
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Old 04-08-2010, 18:08   #5
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Most laptop chargers are ac->dc converters. There's a lot less going on in a dc-dc adapter, and you'll use less power since you're not generating as much heat through the typical ac->dc transformer.
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Old 04-08-2010, 19:16   #6
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Great tip... thank you. I've got mine on order (feedback already generated) ... life's good.
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Old 04-08-2010, 19:59   #7
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I've always wondered -- which would, in the long range, draw more amps from the boat's house battery? Keeping the laptop's battery charged and operating the laptop from its battery or just operating the laptop directly from an adapter from the boat's house battery? Or...is the way a laptop works is that even when it's plugged into the wall, it's just charging the battery and the computer is drawing current from the battery?
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Old 05-08-2010, 06:35   #8
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There is always an energy loss in charging. If the computer's batteries are full, you will use less energy running off the house over charging/running down/charging/etc. How the computer draws its power is probably computer dependent. Ours will run without the batteries installed when plugged in.

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Old 05-08-2010, 06:58   #9
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If I could just get one of these with a mag safe adaptor at the end so I could charge the Mac - life would be good.

I am familiar with the one at mac wizards but its over $100
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Old 05-08-2010, 12:03   #10
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If I could just get one of these with a mag safe adaptor at the end so I could charge the Mac - life would be good.

I am familiar with the one at mac wizards but its over $100
I went to the Apple store, asked one of the "geniuses" if they had any bad or unwanted power supplies in the back, was given one, cut the adapter off of it and wired it to the DC/DC converter. Works great.

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Old 19-08-2010, 07:55   #11
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I have been wondering why with a bit of resoldering it would not be possible to run a laptop directly off 12v.

Desktops do not need more than 12v for any of the components and laptops are in theory lower powered and hence lower voltages....?

Let me know if you have any experiences, otherwise I am going to see what hapens to an old laptop that I have.
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Old 19-08-2010, 08:26   #12
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We've been using the dc-dc adapters on our two HP's for better than two years. Work great, no problems.
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Old 19-08-2010, 08:31   #13
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Some laptops, (most electronics) have an internal regulator that takes whatever incoming power and converts to a dc voltage. Some cheaper models may depend on the external power supply to regulate it before it comes in. Safest is to have some sort of regulator with surge protection especially on a 12, (10-13.8) volt circuit that may be powered by an alternator and get massive surges from starting currents. I did notice that an external monitor I had wired in to get a second(bigger) screen for my chartplotter used 12v internally, and wired it directly to the house battery,(thru a fuse), but I unplug it when starting the engines. Better is Radio Shack sells a 12v to 12volt regulator for about $20.00 that has internal protection. CPU's are generally very sensitive to noise and shifts in incoming power.
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Old 19-08-2010, 08:44   #14
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I have been wondering why with a bit of resoldering it would not be possible to run a laptop directly off 12v.

.
I have been told you can run the laptop fine at 12 volts but it wont charge the battery. Thats fine normally on a boats nav station laptop
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Old 19-08-2010, 10:29   #15
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.....snip...... Safest is to have some sort of regulator with surge protection especially on a 12, (10-13.8) volt circuit.............snip

Thanks Capn_Bill, sounds like good advice the 12v - 12v regulator
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