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amt 9th July 2007 07:28 PM

aux. ps for laptop using SLA
..well kinda Power Supply Design..

Id like to run my Vaio laptop for longer than an hour off-grid and thought an SLA battery would work. Im going to get a car adapter and am not sure what voltage battery to use. The stock AC adapter supplies 19VDC(smps so regulated correct?) yet the car will only supply 13.6 to the car adapter. So will a 12V SLA battery work or should I add a 6V in series for 18V? I dont know if the DC-DC adapter acts as an inverter so that if the cars voltage drops below 12V, it will still supply power.


megajocke 9th July 2007 08:03 PM

If the adapter is for use in a car you will have to supply it with the same voltage as the car does. Not more.

amt 9th July 2007 09:59 PM

I believe the laptop needs 12VDC to operate but no vehicle Ive ever owned actually puts out 12VDC at the lighter or aux. power outlets. My Subaru puts out 14.4VDC. Vanagon 13.8.

I would think that the adapter has voltage regulators in it and they usually need an extra few volts to operate - hence my 18VDC question. Maybe not for smps. Dont know.

So will a straight 11-12VDC from a battery operate the adapter?


luka 10th July 2007 06:24 AM


Or you can make something like this . It is from gev, also N-channel made one that is very good if you ask me... His is in post #18.

KISS 10th July 2007 12:18 PM

You can buy this:



which Radio Shack sells versions of, uses a TIP to set the power connector, voltage and polarity of the adapter. It works well.

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