On Tue, 06 Oct 2009 11:26:50 +0800, who where wrote:

The brief was "KISS".

KISS is often a euphemism for "cheap".

The end-users were real industrial users, and
quite disinclined to fiddle of even treat the pack and charger as
other than a black box.

True. There are probably some safety issues involved. It would not
do to have the customer twiddle the charging characteristics and
potentially turn the battery pack into a incendiary or explosive
device.

If they weren't getting the specified run time, it would be the result
of improper sizing (vendor fault or user-supplied misinformation), or
faulty pack or charger (vendor responsibility). Easily resolved.

Nope. There's also the possibility of creative testing. The
applications mix used for testing battery life by MobileMark 2007:
http://www.bapco.com/products/mobilemark2007/index.php
has a huge effect on measured battery life. However, there's nothing
standard about the selection of test apps, which could easily be
tweaked by the equipment vendor. I'm starting to see this with
Netbooks, where fairly long battery run times are predicted, but
rarely demonstrated. I had an Acer Aspire One (9" screen) and
currently an Asus 700. Neither has come close to the rated run time
when I use them normally at a local coffee shop.

Recall that the pack size was chosen AFTER the CV limit was
determined.

Good. That covers the vendor in case anyone actually tests for the
claimed capacity or run time.

Just thinking about it, there's enough info here to build a table or
graph of the calculated battery life versus run time terminating at
different EOC's. As you note, the closer to depletion I run the
battery pack, the shorter the battery life (measured in charge
cycles).

... The Kill-a-Watt meter records the watt-seconds
(actually watt-hrs) used. It also compensates for power factor. I
throw in the switcher efficiency of about 85-90%:
http://www.energystar.gov/index.cfm?c=ext_power_supplies.power_supplies_cons umers
and calculate the energy consumption per hour of use. I use that as
the average load for run time calculations.

The problem with those meters is that - being cheap/chinese - they
tend to poorly handle the line current "blips" into a rectifier. And
even if they returned true RMS, that doesn't itself reflect the actual
power drawn in those circuits.

Well, yes. The frequency and transient response of these meters is
rather lousy. My guess(tm) is that it has to be about 10 times lower
than the 50/60Hz it's trying to measure. That would put it at about
5Hz (200msec), which is not all that horrible. Also, the filter caps
in the typical laptop will smooth out most transient current spikes so
that the meter never sees the spikes. I don't have a power line
impairment tester to check this, but can probably trace out the
schematic to see how it works. Here's the patent with block diagram
and description:
http://www.google.com/patents?id=G3MDAAAAEBAJ&dq=6095850

The top photo is the inside of the older 4 button version. The lower
photo is the current 5 button version:
http://802.11junk.com/jeffl/pics/drivel/slides/kill-a-watt.html

Litigatory trivia:
http://greenpatentblog.com/2008/12/24/smartlabs-enjoined-parties-smart-management-focuses-issues-in-energy-meter-litigation/

--
# Jeff Liebermann 150 Felker St #D Santa Cruz CA 95060
# 831-336-2558
# http://802.11junk.com
# http://www.LearnByDestroying.com AE6KS