Originally Posted by: Dr_simonWhat is the best way of estimating how much life is left in a 9V battery ?

I used to just touch the electrodes with my tongue and see if it sizzled however, as i get older I am thinking that their has to be a more elegant way and even quantitative way !

Duracell and I think Energizer sells 9V battery packs with little testers in them. At least they used to, maybe they've been phased out now that they have the built-in testers.

Anyways, what I'm trying to say is that, at one point, I bought a pack of 9V batteries which contained a little tester strip that you held against the terminals and a little bar would turn yellow and indicate how much juice was still left.