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Old 10-09-2009, 20:10   #1
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Laptop Power - Direct 12vdc?

Hi Folks

I am useing 2 power supplies for the Laptop:

A cigaret lighter DC to DC voltage changer that puts out 19V that my laptop asks for input. The converter is adjustable: 15, 16, 18, 19, 20, 22, 24 V
But it has just stopped working.

And a

Cigarettle lighter Inverter 240V 150 watt output. But it uses BUCKETS of power!

Someone told me, and I don't remember if it was on this forum, they they just bunged a 12 volt DC cable straight into their laptops plug and it works fine.

Is this so?

Will I be a goose if I try it?

Will Sea Life blow up?

Should I buy an other converter?

Any advice?


Thanks


Mark
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Old 10-09-2009, 20:16   #2
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2 parts.

First, if your computer requires 19v, it won't work directly wired in.

Second, even if it required 12v, it would quite possibly die after a while wired directly in. The voltage is not steady in a car, and often worse on a boat.

Conclusion: Just get another 12v charger with a 19v output for your computer. You can find 'em cheap, just make sure they are rated for the amps you need.

-dan
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Old 10-09-2009, 20:57   #3
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Mark You are in the right place to get new bits!! Does the inverter work? High current aside.(the higher current will test your socket & wiring) What voltage is required to run the computer? You could select the next voltage down just to try. ie if you are using 16V try 15V. Otherwise enjoy the shopping. Check for a fuse in the tip of that laptop power supply. It might be blown.

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ps now what do I want out of that part of the world?
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Old 10-09-2009, 22:01   #4
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Mark,
Computers work on three internal voltages, 12 volts, 5 volts and 3.3 volts. There is an internal power supply unit (PSU) in all computers which creates a very precise and steady voltage. Computers cannot function if their three internal voltages are all over the place, even by a few tenths of a volt. The three different voltages and the need for very steady voltage are why they are necessary.

These internal PSU's are designed to accept voltages that varies in its range. The computers specs will say what is the minimum and maximum acceptable voltages. The allowable voltage range varies from one PSU to another.

Check your computers specs to see if the voltage you plan on sending to the internal PSU is within its design range. If for example the minimum voltage is 10 volts and the maximum is 18, then you will be okay with a 12 volt system, which typically fluctuate from the high 11's to the low 14's
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Old 10-09-2009, 22:12   #5
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Quote:
Originally Posted by MarkJ View Post
.....
Will I be a goose if I try it?
Yep, considering, as others have already mentioned, you are now in the electronic gadgets capital of the world. It would be reasonable to try it if you back was against the wall .
Quote:
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Will Sea Life blow up?
Hmm... make sure Nicole is off the boat before you try it
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Old 10-09-2009, 23:25   #6
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Old 11-09-2009, 02:36   #7
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So that this doesn't happen again you may want to throw a fuse in line with your cigarette lighter socket so that when something blows up it will be that and not your power supply that breaks.
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Old 11-09-2009, 04:35   #8
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Quote:
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Hi Folks



Someone told me, and I don't remember if it was on this forum, they they just bunged a 12 volt DC cable straight into their laptops plug and it works fine.

Is this so?
Mark I do remember the thread you refer to. The post claimed success at powering several laptops direct from 12V.
My laptop requires 21V so I have never given it a try. Laptops have to tolerate a fairly variable input voltage and still run, so it is feasible that nominally 19v laptops will run happily on 12V, but the higher current required at the lower voltage has some potential to cause some long term harm and I would try it myself if laptop was old and due for replacement.
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Old 11-09-2009, 04:56   #9
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Only on a laptop with close to 12 Volt reqirements. Note your battery will float above and below 12 (10.5 - 14.8 or so) which makes the whole solution neither stable nor good for laptop's internals. Go get a nice 12 V > 12 V stabilised source (if you already have a 12 Volt laptop, but I have not seen many around). Or get a 12 Volt to X Volt cigarete laptop adapter. Get it to work above your laptop nominal just in case you want to bundle some other equipment later on.

b.
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Old 11-09-2009, 05:05   #10
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adapters for laptops powered from a car supply are readily available.

This provides the stabilised power source at the voltage required. I normally run mine at 1 volt below the required voltage as I have less problems with the laptop battery
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Old 11-09-2009, 08:42   #11
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I bought a DC-DC converter from Lind Electronics for our laptop. It wasn't necessarily cheap at around US$70, but it's efficient, designed specifically for the power requirements of each laptop, and in the end cheaper than ruining the laptop from unfiltered power at the wrong voltage.
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Old 11-09-2009, 09:25   #12
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The bottom line is that the range of DC voltages that the internal PSU can accept must be greater than and lower than the range of voltages that the boats 12VDC system goes through. If these requirements cannot be met then an external regulated power supply will be required that does come within the minimum and maximum allowable voltages for the internal PSU.
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Old 11-09-2009, 10:19   #13
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Mark,

Here's another vote for Lind Electronics products. One problem with using devices designed for automobiles is that they may not work well with the typically lower voltages found on cruising sailboats. Automobiles while running have voltages in the 13-14.4VDC range. Cruising sailboats often have house battery voltages as low as 12.2V or even lower.

EXAMPLE. I have several IBM laptops which require external voltages around 18VDC. I have tried several IBM "car adapters" with them, and find that they work fine when the engine is running, but when voltage drops below about 12.7 or so the car adapters don't put out enough voltage/current to charge the laptop batteries. Sure, the laptop will run, but its internal battery is discharging, not charging.

SOLUTION: I asked Lind Electronics to make an adapter for me which will take input voltages as low as 9.5VDC and will still put out the needed 18VDC. They did just that, it cost around $70 a few years back, and it continues to work perfectly. It is a very well made product, not the typical $30 piece of junk.

Bill
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Old 15-09-2009, 07:32   #14
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thanks bill,

i will have a look at those lind power adapters as i have the same problem and by times the voltage is as low as 10 volts. this gives an enormous amount of current needed to charge the laptop and finally it just stops charging.

nice to know that there is an solution
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Old 15-11-2009, 19:44   #15
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Thanks all - I was about to ask the exact same question!
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