estimating the life left in a battery.

[sonhouse]

You can tell how much life is left in a battery, like a regular alkaline AA
or some such with a DVM, like about 1.6 volts for a new one and
maybe 1.2 volts for one getting on in years:) But is it possible to
measure the life left by an extremely accurate scale?
Like accurate to picograms or better? I don't think regular batteries
are totally hermetically sealed, so it seems like if there were gaseous
products they would exit the battery and so make it lighter.
Anyone know about this?

[Astronuc]

I don't know that it is easy to measure or 'know' the residual life of a battery.  Batteries are designed with a certain amount of stored chemical energy - which corresponds to so many Watt-hrs (in units of Power * time = Energy).

As you mentioned, the voltage also decreases slightly with age.

One could perhaps with knowledge of the designed life (energy capacity), subtract the energy used, and estimate the remining stored energy.

One way to measure battery life is to take a population of batteries and simply run them down - http://www.energyquest.ca.gov/projects/battery.html

Here is an interesting website on batteries - http://www.batteryuniversity.com/index.htm

Well that's a good start.  I dig around to see what else is out there, and meanwhile I'll think about the other questions.