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MS laptop powered in car


steve_d
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Have an old laptop to run Megasquirt stuff in car.

Battery is shot so choices are buy it a new battery to get 3.3 hours run time in car or find some way to supply it some power.

It will run off 18VDC or 240AC.

A step-up 12 to 18 would seem the most sensible but the only commercial ones I have found are silly money.

A cheapy mains inverter would work but just seems a long way round.

Any ideas or anyone know where/how I can arrive at the most cost effective solution?

Thanks

Steve

PS. I have not tried it on just 12v I just assumed it would not.

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A lot of laptops are 19V but will run fine at 13.8V. The difficulty is that some will discharge the battery if it is present, and of course they won't survive the voltage drop during cranking if you remove it.

You can get around this by removing/refitting the battery as required, but it's fiddly.

The last 3 or 4 laptops I've used were fine at 12V if you ignored all the warning lights etc., including my current toughbook (dunno the model but its a P-266).

Cheap mains inverters are undesirable for all sort of reasons, but many people use them without issue. Just watch for the whistling caused by cheapo imitation mains - it can cause the laptop psu to overheat or fail.

Some laptops (e.g. some toshiba) will happily hold on to the external supply down to 12V but won't switch over to the external power until it gets to a higher voltage - there are some cunning tricks to fool the laptop in this situation.

Last laptop I had used an odd psu connector, so I smashed open the battery pack, removed the cells and wired 12V directly in. Drastic, but effective, and kept it out of landfill a bit longer. (It's part of the scenery at Brickiln Farm now except for the bits scavenged by Fridgefreezer!)

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What current draw does your laptop PSU have?

300W at 240v is only 1.25 A, and that's assuming you're actually getting the full 300w (is it input or output? - % efficiency?)

My dell PSU draws something like 4A, granted it's a few years old now, but it's something to check.

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Thanks very much everyone.

Found the Maplin one but it is now £29.99. http://www.maplin.co.uk/Search.aspx?criteria=L40BB

Had a Google and found/ordered it at P3online for £25.

My Compaq N610c needs 3.5A and this supply gives 6A so should be fine.

I'm sorted but feel free to continue discussing other peoples needs or problems...is that a whistling I hear?

Cheer

Steve

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Thanks very much everyone.

Found the Maplin one but it is now £29.99. http://www.maplin.co.uk/Search.aspx?criteria=L40BB

Had a Google and found/ordered it at P3online for £25.

My Compaq N610c needs 3.5A and this supply gives 6A so should be fine.

I'm sorted but feel free to continue discussing other peoples needs or problems...is that a whistling I hear?

Cheer

Steve

The cheapest way is to get a car adapter. I paid about a fiver for a 20V car adapter for my dell on ebay..

It's also a lot neater than having a power supply plugged into a power supply.

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Can someone explain why my 300w Ring branded inverter won't power my laptop (Dell Latitude D410)? I just get the whistling noise as TSD mentions. :(

Cheers

Michael

Tried running mine through my 300w invertor. Now i know my alernator is abit on the noisy side as i cant run a 12v dc lcd tv from the cig lighter either. it comes on then goes off then wont come back on again.

As for the invertor, on mine it does power it, however its so noisy that it turns it off and on every second or so..... think its time to get a new battery for the lappy b4 i install dual batteries into the landy.

or maybe i should fix the noisy 12v cig lighter socket problem.... Lamps, phone chargers, ipod thingy all work fine in it though

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