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Can I power a laptop with a car's USB socket?


blackrose

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Hi, I'm going for a job interview tomorrow and I've got to do a presentation.

 

I wouldn't mind practicing it once more just before the interview and the hire car I've got has a USB socket.

 

Can I directly power my laptop from the car's USB socket (using just a USB cable), or would it need some sort of regulation?

Edited by blackrose
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Do you have a laptop power adapter that accepts USB as a source of power? And is its power supply 500mA or under?

 

No.

 

best to use a 300watt inverter and the computers mains lead. thats what i do if needed. also charge power tool batteries with mine.

 

I don't have one to hand.

 

Perhaps the laptop battery will be sufficient. It usually only lasts about 15 minutes.

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Hi, I'm going for a job interview tomorrow and I've got to do a presentation.

 

I wouldn't mind practicing it once more just before the interview and the hire car I've got has a USB socket.

 

Can I directly power my laptop from the car's USB socket (using just a USB cable), or would it need some sort of regulation?

 

All the laptops I've had in the past have had an input voltage of greater than 12v so I've not been able to just plug it in to the 12v cigarette socket.

 

I did try a device that took the 12v up to the required voltage but with different devices requiring different connectors and voltages it was easier to use a small inverter with the supplied mains adaptor.

 

It does seem a shame to take it up to 240v ac just to bring it back down to about 20v dc but it works.

 

Good luck with the interview.

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We use a 12v to 19v gizmo from Maplins on the boat that we can also plug into the fag lighter in the car. I suspect you don't have time to get one in time though. Hopefully you'll have enough battery to have a run through.

 

Best of luck.

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Hi, I'm going for a job interview tomorrow and I've got to do a presentation.

 

I wouldn't mind practicing it once more just before the interview and the hire car I've got has a USB socket.

 

Can I directly power my laptop from the car's USB socket (using just a USB cable), or would it need some sort of regulation?

 

Absolutely not possible. In any case the USB socket(s) on your laptop offer only 5 volts and limited current to power external devices, not the other way around.

 

The best/only way to power a laptop directly is with a car adapter, basically a DC to DC converter run from the cigar lighter socket if it has one. Google for one or try Maplins.

 

A less efficient way would be to use a small, say 100 watt AC inverter powered from cigar lighter socket, to run normal AC adapter.

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The USB port on our FIAT 500 is AFAIK only capable of charging/powering an iPod (Having said that the charge indicator does not show when it's connected) but predominantly it's for the playing of ipod content through the car's sound system - I too would doubt it has enough 'oomph' to power or charge a laptop, that is why there is an adjacent 12V socket I guess.

 

Good luck with the interview.

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A bit late for the interview but for future reference here's a bit more detail about what can be used.

 

Like Ange we have a Maplins adapter that runs from a cigar lighter socket. They sell various of these offering differing power and voltage outputs. Ours can be set to voltages between 15 & 20V and will work off inputs of 12 to 16V.

 

As already said, a USB socket won't do the job.

Edited by trackman
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As this has now run its course, there is just one thing bothering me (in the words of Columbo.) Why does a laptop need 20V or so, when a pc tower can (IIRC) run off 12V and 5V power supply? Or put it another way, which component requires 20V within a laptop, and why? Just a curious mind :)

 

Hope the interview went well :cheers:

Edited by Guest
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As this has now run its course, there is just one thing bothering me (in the words of Columbo.) Why does a laptop need 20V or so, when a pc tower can (IIRC) run off 12V and 5V power supply? Or put it another way, which component requires 20V within a laptop, and why? Just a curious mind :)

 

Hope the interview went well :cheers:

 

Screen??? - just a guess though.

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I don't know either, but as lots of LCD screen TVs run happily at 12 volts, the screen thing doesn't have to be an issue, I'm guessing.

 

I think it is more a case that most serious sized laptops have always typically revolved around battery packs and power/supply chargers that use a higher voltage, because there is no need to be restricted to lower ones.

 

Many people will never want to run them in cars or boats, and with adaptors that easily allow you to do so, (for most brands!) cheaply available, it is kind of a non issue.

 

I still can't quite believe the Maplin 120 watt ones at £3. I now have two as reserves, albeit that they will not drive my Dell.

 

Anyone know for definitive why the default voltage for full-size laptops has remained well above car battery voltage, then ?

Edited by alan_fincher
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As this has now run its course, there is just one thing bothering me (in the words of Columbo.) Why does a laptop need 20V or so, when a pc tower can (IIRC) run off 12V and 5V power supply? Or put it another way, which component requires 20V within a laptop, and why? Just a curious mind :)

4 cell Li-ion batts need up to 16.8v when charging, plus a bit for the buck regulator.

 

cheers, Pete.

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4 cell Li-ion batts need up to 16.8v when charging, plus a bit for the buck regulator.

 

cheers, Pete.

I see, thanks. So basically the machine is built around the available battery/charger voltage, which explains a lot.

:cheers:

 

I once had a very old lap top which ran quite happily from the 12 volt socket on the boat.

 

Dave

You have got me thinking here. I have an old Toshiba laptop which is a cracking machine and even runs 7 well. The battery is completely shot, but I might try it to see if it will run off 12V. You never know your luck in a raffle :)

Edited by Guest
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We use a 12v to 19v gizmo from Maplins on the boat that we can also plug into the fag lighter in the car. I suspect you don't have time to get one in time though. Hopefully you'll have enough battery to have a run through.

 

Best of luck.

 

I got one of those too. Amazing the difference it made compared to running the laptop via the inverter - takes a lot less out of the batteries.

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Thanks for the wishes - I didn't take the laptop in the end (sorry :blush:). I just ran through the presentation a couple more times before leaving home and it went fine.

 

I think I'm more likely to get another job I went for up in Leighton Buzzard, and if so I'll have to make some decisions on whether to commute from Old Windsor every day; try to find a mooring up there, or just CC (not something I really want to do while working long hours). The other option would be to rent a cheap room in LB during the week and come back to the boat on weekends. That's not ideal either but it might work out cheaper than all that petrol and much less time-consuming than commuting.

 

I'd rather not leave the Thames, but as Norman once said "On yer bike!"

 

Mike

Edited by blackrose
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Thanks for the wishes - I didn't take the laptop in the end (sorry :blush:). I just ran through the presentation a couple more times before leaving home and it went fine.

 

I think I'm more likely to get another job I went for up in Leighton Buzzard, and if so I'll have to make some decisions on whether to commute from Old Windsor every day; try to find a mooring up there, or just CC (not something I really want to do while working long hours). The other option would be to rent a cheap room in LB during the week and come back to the boat on weekends. That's not ideal either but it might work out cheaper than all that petrol and much less time-consuming than commuting.

 

I'd rather not leave the Thames, but as Norman once said "On yer bike!"

 

Mike

 

Whichever job you get, Mike, I sincerely hope it goes well for you

 

Job chasing is an extremely stressful, and frustrating, process - and although the end result is normally worth it - the discomfort of the intervening period can be bad.

 

Chin-up, and may you achieve your goal with the minimum of discomfort.

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Thanks. Indeed it's been a couple of years of low paid and often filthy work in the boatyard to keep myself going while finishing my PhD and looking for proper jobs.

 

The good news is that I had a phone call earlier today telling me I've been offered the job in Gloucestershire! Would I be insane to eventually envisage finding a liveaboard mooring on the Avon? There must be some safe moorings?

Edited by blackrose
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