Mailinglist Archive: opensuse (1620 mails)

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Re: [opensuse] UPS : replacing battery with 12 volt Jelly Car Battery
On 11/25/2014 09:54 AM, John Andersen wrote:
On 11/25/2014 9:51 AM, Anton Aylward wrote:
On 11/25/2014 12:48 PM, John Andersen wrote:
Everything inside your computer (beyond the power supply) runs on DC.

With a DC supply, capable of generating 5 and 12 volts, you don't need
anything else.

You can power a 19 volt laptop from 2 car batteries for many days
on end. All you need is a LM7809, which will set you back $1.95 plus shipping.
Which begs the question ... If everything runs on 5V (the electronics)
and 12V (motors, burners), then why is 19V needed?

Actually, virtually everything in a laptop runs on 5 volts or less. Even
the disk drive and fan motors. 12 volts is pretty much absent inside a laptop.

I don't know why they choose to standardize around 19 volts, but I suspect
it has something to do with the voltages needed for the screen.



The laptop will have small DC-to-DC converters and/or regulators to
develop the needed voltages. With 19-VDC from the wall-wart they've
got plenty of "headroom" to run their regulators. Note that there are
other voltages running around in there to power the CPU, which uses
something around 2.2-VDC I think.

Regards,
Lew

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