12v direct connecting Laptop - is there such a thing?

[#1]

 

The "in car computing " thread, made me wonder IF there is a 12 v dc laptop available that will run directly from the 12v cig socket.....
(i.e. not using an inverter to make 250v ac, then plug in your laptop power supply to bring it down to 19v !.... )
Just wondering.... 

[#2]

Quick Google found http://www.amazon.co.uk/gp/offer-listing/B002BXXRTK/ref=asc_df_B002BXXRTK964931?ie=UTF8&condition=ne...

[#3]

which is NOT ......

Quote

a 12 v dc laptop available that will run directly from the 12v cig socket..

[#4]

I think it is as close as you will get!

[#5]

you can also get small leads from Maplin that supply the 19 volts  http://www.maplin.co.uk/Module.aspx?ModuleNo=345508#spec  only £10

[#6]

The trouble with this idea is that you are assuming that you will be getting a nice regulated 12V from your lighter socket - which you won't.
The first problem is that most laptops will require a power supply that is within 10% of the nominal voltage, across the full current loading.
Having spent some time diagnosing electrical problems on my own car, just connecting a simple volt meter across the battery shows that -
1)  the voltage can drop to below 6V (or less) when starting the engine.
2)  when running with no load, the charging voltage is approaching 15V.
3)  when things like the headlights are on, the voltage can be all over the place, depending on engine revs.
4)  cars electrical systems have all sorts of voltage spikes caused by switching and from inductive loads.
You might get away with running a 12V laptop is that car is not running, but if you were to switch anything on/off you risk injecting a nasty voltage spike up the laptop.

If you look at how people make DIY computers for their cars, most will use very low power requirement motherboards (such as mini-ITX and pico-ITX) and they use wide input voltage (6V to 30V) switching regulated power supplies, that convert the car's DC to the voltages needed for an ATX connector (which plug directly into the ITX motherboard.  Recently ITX manufacturers have started integrating the switching PSU into the motherboards, and are now making motherboards that can take regulated 12V directly from power supplies like this http://www.short-circuit.com/product/DC-DC-USB.html

[#7]

Thanks for the technical info Purleigh.... that is the sort of response I was looking for.... 

[#8]

in the case of a lap top, it is usual to run it from its battery, which is kept topped up by the power lead, so the differences above will not have much effect  and the Maplin one can handle a large input variation
Specifications:
Input Voltage: DC 12~24V
Output Voltage Range: DC 7.5, 9.5, 12, 15, 16, 18.5 and 19V
Output Current: 2A max.
Efficiency: >88% (typically)
Low Voltage Protection: Yes, will cease working if input voltage
Short Circuit Protection: Yes
Line Regulation: ±5%
Load Regulation: ±5%
It replaces the lead you usually use

[#9]

You might find this UK site of interest -
  "Car PC components" - http://linitx.com/viewcategory.php?catid=52&pp=52
  and
  "In Car Power" supplies - http://linitx.com/viewcategory.php?catid=54
maybe you will be inspired to build your own from scratch !

[#10]

other than  what I said in the companion thread to this  
a couple of points

Quote

1)  the voltage can drop to below 6V (or less) when starting the engine.

a  good battery under starting  conditions should be able to maintain 9 volts minimum at its terminals
anything much lower than this denotes a high  internal battery resistance
and a new battery is needed

2)  when running with no load, the charging voltage is approaching 15V.
3)  when things like the headlights are on, the voltage can be all over the place, depending on engine revs.
4)  cars electrical systems have all sorts of voltage spikes caused by switching and from inductive loads.
preventing this  is the purpose of the electronic regulator situated inside the cars alternator(AC generator)
so does a good earth system

the fact that one would even think of wiring   a pc  into a motor vehicle is highly  irresponsible

[#11]

Oh dear I've suddenly lost interest in this thread, and I really don't care about how the light output of a bulb is measured either 

[#12]

So you'll need to change the thread again

[#13]

speaking from a position in relation to the department of transport

[#14]

Now I understand your Psuedonym...... you just keep going round and round and round and round and round and round and round and round.... ad infinitum.
thread closed,.... nuff said.

[#15]

Quote from: purleigh

3)  when things like the headlights are on, the voltage can be all over the place, depending on engine revs.

By the way you feel a car hesitate when you switch it on, I'd say air con was probably the thing that has the biggest affect.
Edit: I tried Googling car air conditioning power consumption - and wished I hadn't!