MPPT

[Paul Fox]

wad wrote:
 > 
 > The context is that we are trying to ensure that an Maximum
 > Power Point Tracking algorithm can be implemented on the DC
 > power input of the XO-1.5.
 > 
 > On Aug 5, 2009, at 10:56 PM, Richard A. Smith wrote:
 > 
 > > John Watlington wrote:
 > >
 > >> The problem comes from the need for the algorithm to start
 > >> from a position of low current drain.  The MPPT algorithm
 > >> should probably be disabled when the laptop is running and
 > >> the battery is below some threshold (say 10 -15% ?)
 > >
 > > Yep.  I don't think it will matter though.  The core of the
 > > problem is that our peak CPU power draw is > 10W where on
 > > gen 1 is was <=10W and we aren't going to fix that.
 > 
 > We should play with having the power daemon clock down the CPU in  
 > some cases.

how much would that save?  how fast would the reaction time need
to be?  (i.e., how responsive does the MPPT algorithm need to be?

 > 
 > Perhaps modifying adding a "solar power provided or removed" subtype  
 > to the Battery Status Change SCI interrupt from the EC ?

how would this be detected automatically?  by voltage level?

 > This could be used to limit the peak processor clock when the battery  
 > is very low.
 > 
 > Limiting the peak processor clock when the battery is very low
 > and we don't have any DC input might extend the battery life
 > slightly as well.

how much remaining runtime are we talking about, when we talk about
"very low"?  and again, how much can we affect the end result?

paul
=---------------------
 paul fox, pgf at laptop.org