[Power] [UKids] 12V wiring for XO-1s, XSCE and networking infra om Haiti

[James Cameron]

These are all good questions for an electrician, because they depend
on regulations, and availability of cable.

However, knowing that this is a fly-in fly-out venture, I guess
listing the load currents and picking compatible cable should be
enough for a start;

- your XSCE server at 16 watts peak should be no more than 1.3A at
  12V, but if it has external hard drives don't forget to include
  them,

- your networking equipment shouldn't be more than about 0.5A each,

- the XO-1 laptops shouldn't draw more than about 2A each.

You would need to decide between losing power over the cable, with a
consequent loss of voltage at the far end, versus the cost of copper.

You would have to determine the minimum battery voltage you wish to
operate at, and the minimum voltage your XSCE server will run from.

Here's what I would do:

- use two core cable designed for at least 8A current, with at least
  110V insulation rating, in a star configuration,

- or use three core cable with an extra sheath, same minimum
  specifications, as it will last longer; e.g. buy and take extension
  cords (no lead) and cut them up on arrival, disable and dispose
  safely of the unused plugs and sockets,

- use one cable for the XSCE server, one cable for the AP and 3G
  router, and one cable for every two XO-1 laptops,

- get a distribution panel with many DC circuit breakers, something
  like 6A or less (must be less than the current rating of the cable),
  and make sure each cable is controlled by one breaker,

- make sure you have a suitable DC circuit breaker for the entire
  panel, to protect the thick wire to the battery, which for dozens of
  XO-1 would be somewhere between 36A and 72A rated.

-- 
James Cameron
http://quozl.linux.org.au/