john1

Hi,

I want to run my laptop in my car, i was hoping that it would run
directly off the battery, but it wont.
It wont 'see' any externally connected supply until it goes over 15
volts, so i have to make an adapter of some sort to 'bump' up the 12
volt battery supply, to 15 or so volts. The AC adapter that came with
the laptop gives 20 volts (no load) so i spose i could use anything
that would bump up the feed from my battery to between 15 and nineteen
volts.

It would have to provide about 1.75 A normal running, but with peripherals added on it could demand a little over three Amps.

John

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tom3000

DC to AC inverter -> laptops dc power supply -> laptop

Leftyretro

Yea, no real cheap easy way to do it. Did you try with the engine running as the charging voltage of a typical auto is very very close to 15 volts when running.

Lefty

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picbits

Maplin every few months have an offer on a Car Laptop adapter - it boosts the 12v up to 12-24 volts (and a lot of voltages inbetween) at up to 3.5 amps.

Prices range from £20 to £30 in the sale and ..........

http://www.maplin.co.uk/Module.aspx?...APTOP&doy=25m9

There you go - 20 volts at 3.5 amps for a tenner - you can buy me a beer later

john1

Tom,
Looked at that, didn't like it.

Lefty,
Yes, checked that out, laptop flicks between internal and external
at 13.5v and the screen backlight changes brightness, that may be
intentional to save a bit of battery. Screws itself up after a bit and
jams in external, while still changing backlight brightness.
Laptop didn't like it.

Picbits,
Thanks thats just what i need.
I will be in touch with Maplins to obtain one.

John

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tom3000

what's not to like it ?

it's the most simple, logical and effective solution !

$40 bux and it's done !

picbits

DC-AC inverter - lossy
AC inverter back to DC power supply - even more lossy
Size = Inverter + Power supply = quite large
Efficiency - poor

12V to 20V switching regulator - better

Cost $20
Size - about the size of a packet of cigarettes

1Steveo

here is one
http://www.mcrent.com/workbench/dcdc1216/


steve

tom3000

i dont know where you get your parts or stuff, maybe in england they're the size of a refridgerator

and buliding that thing is a waste of time - Like I said !
because plain and simple .... you got the inverter and you have the entire 110V (or 220V whatever it is where one is) AC at your disposal to do whatever, instead of just 1 single output voltage

i powered my 20 inch screen with it once.

john1

Hi Tom, Hi Lefty, Hi Picbits, Hi Steveo,

I did consider making a device like 'Steveo' or possibly something
similar like an oscillator feeding a transformer outputting three or
four volts on a separate winding, to feed a diode bridge and cap,
which could be added to 12v to give me 15 or 16v for my laptop.
I reckoned that 3v at 2.5 Amps would need about 10 watts, maybe a
single transistor running a small transformer at about 18Kc might
do it. Didn't fancy a "buck inductor" circuit, looked a bit too
complicated to me ....

And yes, if i wanted a mains-voltage supply for additional reasons
then yes, i would take my inverter unit with me and use that, as
using an inverter to feed the laptops DC unit is perfectly acceptable
but i want something small just for this job.

Ive been in touch with the nearest Maplins, and they have these units
in stock for £9:99 GBP so i will be going over there tomorrow to get
one.
It will be unlikely to have the 'Dell Latitude' proprietory fitting
in its choice of fittings, so i will have to steal the one from the
latitude mains adapter.

Unless anyone knows where i can get one like it ... ?

And ive just remembered, i dont have a cigarette lighter point in my
car, so thats another job. Its fun like this that keeps me going ...

Cheers, John

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Leftyretro

"And ive just remembered, i dont have a cigarette lighter point in my
car, so thats another job. Its fun like this that keeps me going ..."

LOL, ever get the feeling that nature just hates progress?

Lefty

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Nigel Goodwin

Are you sure? - what sort of car is it? - I don't recall ever seeing a car without one? (not counting antique cars).

They are often hidden behind a flap, or pullout ashtray.

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john1

Hi Tom, Hi Lefty, Hi Picbits, Hi Steveo, Hi Nigel,

Nigel you are quite correct.
Its inside a pull-out flap which contains the front ashtray.
I dont smpke, and i only looked in there once when i got the car,
i never used it, and i clean forgot about the cigarette lighter in there.

I went to uxbridge and got one of those Maplin car-laptop units.

And i cut the lead from the DELL mains unit to the laptop fancy plug,
and put a more normal plug and socket to join it back together,
the same type that is used on the Maplin car-laptop unit.

So now the fancy DELL plug for the Latitude now has a short lead,
with a more normal plug socket on it, which can plug into the mains
supply unit from DELL, or the car-laptop unit from Maplin.
The fancy DELL plug has three connectors, only two seem to be used.

Its been in regular use for a while now with no problems.

John

Attached Images

Latitude_plugs.jpg (582.5 KB, 11 views)

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