Mailinglist Archive: opensuse (1620 mails)

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Re: [opensuse] UPS : replacing battery with 12 volt Jelly Car Battery
On 11/25/2014 02:30 PM, James Knott wrote:
On 11/25/2014 02:22 PM, Anton Aylward wrote:
The question was "why 19VDC?"

You'll have to ask the whoever designed the computer. I have seen other
voltages, so there's nothing sacred about 19V. However, you'll
generally find higher voltages with higher power devices. One advantage
to using a higher voltage is lower resistance losses. If the target
voltage were provided by the power supply, you'd have to worry about how
much the voltage would drop in the wires. A lower voltage means higher
current for the same amount of power, but the higher current increases
the resistance losses. On the other hand, an on board regulator
eliminates most of that issue and if the voltage sensor is right at the
load, eliminates it.


Yes, there's nothing sacred, but I suspect it is something that the
laptops 'inherited' from a previous generation -- the "lug-ables".

The reason I think this is because we have a new generation, the phones
and tablets, whose wall-warts are 5V 1A or 5V 2A. I have one mega-wart
with five outlets that light up as you plug the USB charger cords in :-)
I'm sure there's one that lights up in different colours for the 1A vs
the 2A.


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