[OLPC-AU] XO laptops overheating in power racks

[James Cameron]

G'day Ian,

What are the signs of heat distress that you are seeing?  Are the
laptops suspended?

The cooling system for the CPU is a heat spreader with thermal
monitoring and throttling.  It relies on the back of the laptop not
being covered or insulated.  The heat spreader may be damaged.

You can test the efficiency of the heat spreader inside the unit using
the OpenFirmware command "test /switches", which will also require you
to close the lid, open the lid, and then rotate into ebook mode with the
panel facing up.  A temperature rise is reported, along with an
assessment.

The charging circuit also releases some heat, but not nearly as much as
a left-on laptop.

I would expect a closed-lid laptop to suspend, and then the heat release
is much reduced.

An average time for recharge depends on the usage.  From fully flat, a
few hours.  Once the charging is completed, no significant current is
drawn, unless the laptops are left powered on.

I don't see how an alarm for turning off the power rack would help ...
if it was turned off before the laptops were removed, then there would
be a discharge time, in one of three modes:

1.  laptop fully off, insignificant charge loss,

2.  laptop close-lid suspend, some charge loss,

3.  laptop running, significant charge loss.

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