> I've been kicking around the idea of doing some battery
> life testing for awhile now, since I can never seem to
> find the information I REALLY want.

I can see a cooperative effort aborning.
I too have an intetest in battery life testing for several reasons.
- Camera battery capacities
- El Cheapo battery performances wrt brand name
- Battery impedance under peak loads throughout discharge life.

> What I'd like to do is set up a test rig which allows me
> to constant-current load a battery at, say, 100 uA,
> 1 mA, 10 mA, 100 mA, and just maybe, 1 A, and then
> log the voltage on the battery for later analysis.

I was most interested in time to end point under various discharges, 
but curve shape is also of interest.

As well as constant current I'd also be interested in constant energy 
or, even worse, constant energy out of a converter. This better models 
modern equipment such as (surprise) cameras where the device wants a 
certain voltage and current and the converter produces this regardless 
of battery voltage. The load need not be an actual converter but needs 
to be able to model this. eg it may increases power aat a certain rate 
as battery voltage falls to model a converters falling efficiency with 
voltage. eg it may draw 100 mA at 6v in and 250 mA at 3v in (rather 
than the expected 200 mA).

> In the end, I'd like to have a moderate sample size (say,
> four to eight cells of AAA through D cell, of each of the
> top few manufacturers, plus the same quantity of 9V
> batteries, at each discharge rate).

I'm interested in both primary cells and rechargeables.

Tests I did a while ago showed that certain clone rechargeables are 
well down in capacity on claimed values.

> Making the test rig, etc, is easy enough, but I'd like
> to then make this info available online, but I don't know
> if that'd open me up to legal action on the part of a
> battery manufacturer who's displeased with my
> findings.

Could happen. I've seen a number of comparative battery tests 
punblished over the years. Being careful to publish only accurate data 
and a few disclaimers may be wise. "Just becaise Ev-O-Vac batteries 
performed superbly when I tested them doesn't mean ... "

> Or, if anyone knows of a site with hard data
> (NOT nebulous graphs made under poorly defined
> circumstances, which is what I always seem to find),

I've found Eveready data and graphs better than most. Also, Rayovac 
did some good stuff on their rechargeable Alkalines which may be 
reflected in their other data.

I had in mind controlled constant current source loads with voltages 
monitored. I was thinking of using a (treason) ATmega48/88 as that's 
what I'm using most at present. Discharge recharge capability would be 
nice in my case but not essential.



        Russell McMahon



-- 
http://www.piclist.com PIC/SX FAQ & list archive
View/change your membership options at
http://mailman.mit.edu/mailman/listinfo/piclist