A few helpful comments (Pseudo battery expert...FWIW)

In the recent postings I have noticed that the AA cells are underated, For
Alkaline
in recent and past tests this cell to 0.9V/ cell using 4 of them for 3.6 volts
min and
6.2 volts max 1.55 V cell start.   These consistently provide 1.7 Amphours. at
12 mA drain rate, the low dropout 3.3v regulator really helps.  If they are
"older"
shelfed for 6 months this is 1.6AHr.

Industrial NiMH AA cells provide 1.4 and 1.5 AHrs (buttoned) and solder
tabbed,
I have these and they really pour out the storage and the Ultra High
Watts/Litre.

Most folks do not know that the "A" fat cell (18mm dia and 57mm long) made by
Sanyo (NiMH) has a whopping calculated 390 Watts/Litre... There is the little
brother the 17 mm diameter that has a 3.8 AHr rating that is commonly used
in Laptops in last 3-4 years.   L ion is lighter has less cycles and not that
much
advantage in volume, only by weight.

I do have 12 of these 17mm dia cells with solder tabs that have never been
used (5 months old).   If any piclister is interested they are 4$/per and the
/schematic and charge circuit is at MAXIM using the MAX2003 or MAX713
in NiMH setting for voltage.   They have 900 typical full cycles and really
pour
out the power for those that use PIC to control "physical things".

The Industrial AA NiCad provide 850-1000mAHr rating.

The Alkaline 9V Battery provides 300-200 mAHr of power.   This is scaled from
AAAA is 1/2 of AAA is 1/2 of AA.

I like Alkaline D cells and F cells best bang for buck in primary cells.

Eriuc Borcherding