[Power] [support-gang] 3 portable solar choices for XO-1? (and other XO laptops, if poss!)

[James Cameron]

On Tue, Jan 14, 2014 at 09:28:14AM -0500, Adam Gordon wrote:
> Would one of these http://www.256.co.uk/?page_id=355 be more
> efficient than the 18v limiter?

Yes, if the efficiency is good (it is unspecified), and if you couple
it with a 12 volt lead-acid battery, or check that the device is also
supported for loads that are not a battery.

The microcontrollers in a charge controller for lead-acid batteries
use the voltage of the battery to guess at the state of charge of the
battery, and may make certain decisions.

The decisions might go against the goals of charging an XO laptop, if
the laptop is the only load connected.  This is because the voltage
sensed by the controller may bear no relationship to a lead-acid
battery.

Going back to efficiency for a moment; a solar panel with a limiter
should be more efficient than a PWM controller.  An MPPT controller
may be more efficient.  The device you refer to does not appear to be
an MPPT controller.

The XO-1.5, XO-1.75 and XO-4 contain an MPPT controller.

To test this device standalone, use two XO-1 and our solar power
logging program, which is olpc-panelpwr-log in the olpc-pwrlogs
repository:

http://dev.laptop.org/git/users/rsmith/olpc-pwrlogs/

As control in the experiment, use an XO-1 directly connected to the
panel.

To test this device with a lead-acid battery, use:

- power metering between the panel and the device,

- power metering between the device and the battery,

- power metering between the battery and the XO-1, and;

- our olpc-pwr-log from the same repository.

CC: power@ (mysteriously dropped, blame support-gang@ list
configuration)

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