[Server-devel] 12 Volt power system for School Servers.

Jerry Vonau jvonau at shaw.ca
Wed May 29 17:38:06 EDT 2013

On Wed, 2013-05-29 at 15:03 -0500, David Farning wrote:
> Tony could you share more information about your work on 12 Volt power
> supplies for School Servers?
> Whenever I see a School Server setup containing a 12V Battery, an
> inverter, a power strip, and a couple of 120V to 12V power supplies to
> provide power for the server and the AP... my eyes start to tear up:(

Is the inverter really needed for a XO? The step-down transformer used
on the XO puts out 13.5v but the XOs only need 11 volts to charge[1].
Therefore I believe you could run and/or charge the XOs directly from a
12v source like a storage battery, perhaps though a regulator. I just
don't want to cut the cord off of a working power supply to find out. 

> The situation I am looking at has power part of the day so we can
> recharge the battery. To keep things simple we would like to use a
> Trimslice or XO-4 and off the shelf AP.

Most of the networking devices use a transformer also but with perhaps a
different voltage rating, with a regulator that takes 12 DC in we can
output the voltage needed for the lower (<12v) voltage DC devices. If
they run on usb power or < 12v dc this should be do-able.

> Ideally we would like to have 'kit' that contained everything except
> that battery that can be set up and tested before arriving at the
> deployment.
> Thanks

Recharging the storage battery is limited by the means that are
available to recharge the storage battery perhaps via solar or wind, and
is the related to the issue of how many XOs are in use that need


1. http://wiki.laptop.org/index.php?title=Battery_and_power

> -- 
> David Farning
> Activity Central: http://www.activitycentral.com
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