[OLPC-devel] Battery Charge End Sensing

[Frieder Ferlemann]

Hi,

James Cameron wrote:
> If the software could identify proximity to other mesh members that

Unfortunately this is probably too late: the problem of maximum
allowable current (or to put it positively: friendly load
characteristics) also exists if only *one* OLPC is connected
to a "weak" supply...


Jim Gettys wrote:
> We'll probably end up with considerably more capable battery information
> than most machines, as far as I gather.

Can this information then be used to control the charging current?

Or more low level: is there a means to control the duty cycle
of the switching regulator for the charging circuit (preferably
with little or no load for the main CPU) ?

Note, the ability to charge from "weak" supplies will be quite
a challenge for Delta-V detection (which is not too reliable
anyway as James pointed out before).
A Delta-T detection might also be problematic because of
external temperature gradients and low charge current.


Maybe the term "weak supply" needs a comment - Would it be
reasonable to assume a 2 Watt solar panel (about 10x15cm²
and operating at 40% of its maximum power) to be the "weakest"
supply the OLPC charging circuit should be designed to
"work" with?
Defining the word "work" here as: "reviving an OLPC with
completely discharged batteries within 0.x hours"?

Greetings,
Frieder