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agentxs Top Student
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12v Power supply for an EliteBook

EliteBook 8570p
Microsoft Windows 7 (64-bit)

I'd like to run my EliteBook 8570p from a 12v AGM battery while traveling, but without having to introduce the inefficiency of an inverter, so I'm looking for a power supply that'll convert the 12v nominal (11-14.6v) source to regulated 18.5v as output by the existing AC supply. I've been unable to locate a 12v HP supply and so wondered if anyone had already done this using other sources or equipment. 

 

Currently I'm looking at using a "uxcell Power Converter Regulator DC12V(10V~16V) Step-Up to DC19V 8A 152W " found online. The 19v output should be close enough with plenty of available power to keep the load near 50% of its capacity (giving me 96% efficiency). I'll use a 15A fuse on the +12v and have a DC switch inline. I can't find it in the laptop spec., but it looks like the EliteBook needs a 7.4mm x 5.0mm power connector, anyone know for sure? Finally I'll connect any ground (such as that to the laptop) to the -ve supplied by the battery, as this is also connected to the chassis of the vehicle. 

 

Can anyone see any problem with the above, or describe their own solution?

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Provost Provost
Provost
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12v Power supply for an EliteBook

I really cannot recommend this arrangement but if you can rig it up to get 19v and enough amps into the right plug I guess it will "work" but slightly nonstandard current can wreak havoc with laptop circuitry. I can only recommend you use a laptop power supply with the correct specifications through an inverter. 

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agentxs Top Student
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12v Power supply for an EliteBook

Hi Provost I unfortunately don't have much space, and the battery used to power the laptop would require frequent recharging (i.e. engine running) during the work day if I used a pure sine wave inverter and the existing AC brick, so a DC to DC converter is the solution I need to make work. I did find an alternative to using the buck–boost converter I originally floated - while I think my selection of parts would have worked, it would not have had an insulated case and why reinvent the wheel if there's an inexpensive off the shelf solution? Finding the right product came down to figuring out the correct search terms; I used something like "Car 12v laptop power supply" on a well known online store and this produced several acceptable results. I ultimately ordered a tiny 90 watt DC Universal Adapter made by V-markable which I'll use as my main supply on the road. I also ordered a 120v AC/12v DC 90 watt supply made by Westronix Inc. which will be a backup and for mains power when I have it. The HP brick I have I'll leave home as it is twice the size of the Westronix and 10 times that of the V-markable. Both supplies came with multiple tips for different notebook brands, both plug into a standard 12v DC car outlet, and both produced around 19.5v - and work great in the two days I've had them. Bonus, they also have 5v USB outlets for charging phones on them. I don't know what the DC power conversion efficiency of these two products is, however they must be better than I'd get with an 80% efficient pure sine wave inverter followed by probably 70-80% on a standard AC supply, which gives something like 50-60% compared to what I hope is nearer 95%.
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Provost Provost
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12v Power supply for an EliteBook

You seem to have it all figured out and I am glad you are happy with the setup. Good luck. 

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