On 10/3/2015 11:35 AM, Vic Smith wrote:
On Sat, 03 Oct 2015 10:50:46 -0700, Don Y
wrote:

Someone once claimed that AA and D cells were essentially the same
"internals", just different shells. I'd find that hard to believe
(unless it's akin to the "11 oz Coors" scam). One *hopes* the
big, heavy, bulky D cells are actually *giving* you something
for the extra size/weight!

They measure capacity in MaH. This is useful:
https://en.wikipedia.org/wiki/List_of_battery_sizes

Yes, but *actual* capacity is all over the map! Like buying
a "bottle" of milk and discovering it really only holds a
quart -- even though it *looked* like it was gallon sized!

With LED bulbs I'm satisfied with AA life-span.

I think it depends on the device, the peak power drain and
the operating ("per use") lifetime.

E.g., our portable vacuum cleaner is good for a couple of
minutes of operation (batteries are old and don't hold a
strong charge). This is OK for us as we only use it when
we have "a few crumbs" to clean up -- and don't want to deal with
dragging out the REAL vacuum cleaner for such a small task.

A cordless soldering iron that I have is similar: uses lots of juice
but for just a few seconds at a time. Then, set it back in its
stand (which, amazingly!, is a CHARGER! : ).

OTOH, if I'm stringing network cables on the underside of my work
benches, I will typically use something like:

http://www.harborfreight.com/media/catalog/product/cache/1/image/9df78eab33525d08d6e5fb8d27136e95/i/m/image_14142.jpg

sitting flat on the floor, pointing upwards to illuminate the
underside of the tables. After a while, the batteries (esp
if they are the original HF batteries) go dark. So, swap
them out (if rechargeable) with the spare set in the charger
for *next* time.

[crap! I've been meaning Harbor Freight and think I've been
saying "HD" -- instead of HF! : Apologies to Home Despot!]

It's amusing how 9v "transistor" batteries have fallen from
favor since the days of youth (in "transistor" radios). Aside
from the smoke/CO detectors, I can' think of anything that
uses them (so, why keep them on hand IN ANTICIPATION of a
failure?)

I don't know why they still equip smoke detectors with 9v.
But when I buy some more I'll look for AA equipped.
I see they sell them.

I think originally it was because the semiconductor "process"
wasn't as effective at lower voltages and power levels.
When making safety related things, change always draws attention
to you:

Atty: And why, sir, did you authorize the change from the
long standing, well proven, reliable design to this
NEW design? The design that was present in the home
of my client's LATE parents??