12V LAPTOPS

alisdair4

alisdair4

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18 Jan 2004
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Isle of Bute
midnightdrifter.net
I always seem to ask the daft electrical questions! I see lots of adverts in the yachting (and motoring) press for invertors which convert 12v DC to 240v AC, in order for the yachtsman/ Road warrior to plug in his laptop AC/DC adapter (average voltage output IRO 13.5v).

Would it not be simpler for laptops to run on 12v dc, so that they could be hooked up to a cigarette lighter in a car or yacht.

From my (non-technical) standpoint to invert 12v to 240 and than back to 13.5 through an adapter is nuts! If no-one makes a 12v laptop, does anyone make an invertor which converts 12v to 14v? DC.

(Stands back to await the onslaught from the technically adept!) /forums/images/graemlins/blush.gif
 
There are loads of "laptop adaptors" on the market. As an example, there's this one from Maplin. They plug into a 12V lighter socket. It's worth getting a 120W version.
 
If your adapter block is chucking out 13.5v to power your laptop then you can probably run it direct from the 12v supply - because it isn't actually at 12v...

Our old Tosh (now retired) took 15v - but this was partly to charge the battery (knackered anyway) so ran direct off 12v without a hitch.

Unfortunately the replacement (HP) takes 19v - and 12v is just not quite enough to power the laptop even with the internal battery fully charged.

There are two main options
1) As you suggested - Invertor (although some of the quasi-sinewave ones don't give a smooth enough supply) to power the laptops own brick.
2) A DC -> DC convertor - Maplin do these to convert 12v to 12v-20v - and will give stabalised power to the laptop - this is (believed to be) the more efficient method of converting - but less convenient if you need other 240v appliances to run.

My current method is a 300w inverter permanently installed and connected to the battery (with a fuse and T switch in the way) which then feeds into the boats 240v system via the shore power intake (can't have shorepower and inverter on at the same time see!) although I do have to remember to turn of the immersion heater first ...
It is quite interesting that I can run a 240v energy saver bulb that is brighter than the cabin lighting but uses less energy - even with the inherent losses in the inverter.... /forums/images/graemlins/laugh.gif (I was bored - so took some time and measured the drain with various combinations...)

If I was to start again I'd probably go for the DC-DC converter though...
 
Inverters and Computer Power Supplies are fairly efficient bits of kit - you don't lose much power through them. Hence why the dc-inverter-dc AND the dc-dc convertors are BOTH popular.
 
I agree - not having a DC 2 DC converter I can't test it, but my inverter does draw a little current when there is no load on it - runs the fan for one ...
The laptop powerblock also gets hot - so that must take some power ... probably not enough for me to worry about though ...
 
I ran my laptop on board throughout this season using a DC - DC device from Maplins. It appears to work very efficiently, as it never even gets warm. Laptop remains fully charged and I cannot say that I have noticed a reduction in charge level on the boat's batteries.
 
This comes up quite regularly on one forum or another.

I bought an old Panasonic Toughbook for the boat from a computer firm advertising on ebay. They also offered a 12 volt charger - plugs into a lighter socket. I run the laptop off this for my nav software without trouble.

The kit is on the boat so can not check charger manufacturer but think it was other than Panasonic. Presumably they are available for other makes / models.

Have fun.
 
Most will run direct of 12V ........ just take out battery or tape over contacts and put back to balance machine ........... or get a DC - DC converter from Maplins ..... To have best performance ... again isolate battery so that converter is not wasting amps charging battery.

Of course you could go for an ITX jobbie that is a desktop mini job that runs of 12V ....
 
Most laptops run on 19 volts so either an inverter up to 240 V ac or a 12 to 19 volt dc adaptor will be required. I run my boat PC off a 500 watt inverter but it's probably less efficient than the dc to dc route. Also the inverter interferes with my ICOM SSB receiver that I use for weather text. Interesting to see good reports on the converter from Maplin. Thinks I'll get one!
 
The only reason normally for the "extra" voltage is to charge the battery.

Think on this .... even desktop mainboards are running at 5V or even at 3.3V ....
 
Check your connection to the laptop. I have to use an invertor because the laptop connection is a Dell which will not be a plug which Maplins offer.
 
Thats interesting ...I was just wondering if my laptop would run without its battery installed..I had rather assumed that the battery might operate as bit of a balance tank to smooth out fluctuations in the voltage in the system...Mine is typically 12v to 13.5 volts depending on whats charging or running.

Nick
 
My Tosh Tecra 8200 has a 10v battery pack - runs fine when plugged into 12v, & charges battery when engine pushes out 13.5V. Gets a bit hot, but been like that for 2 years now.
 
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