Does anybody know much about Lithium batteries?

I bought a package of "Energizer" AA Lithium batteries to use in an LED flashlight (actually one of those head lights that you wear on your head) that uses three AA batteries. They were about three times the price of regular Alkaline AAs, but I figured they would be worth it because they claimed to last up to seven times longer. If you read the really fine print, it is seven times longer in "...high-tech devices such as digital still cameras, portable CD players, MP3 players, or wireless headsets."

Apparently my LED flashlight isn't a high-tech device, because I got perhaps half the life from the Lithiums that I get from AA alkaline batteries. Now, I may be casting unjust aspersions on Lithium batteries as a class, because two of the three batteries that I took out of the light still showed reasonable voltages (1.45--1.50 volts), while the third was down to 1.2 volts. Putting them back in the light and checking the voltage of the full 3-cell pack gives me a starting voltage of 3.3 volts, and it drops rapidly as the light shines. After one minute it is down to 2.99 volts and still falling. I'll take another reading when I finish writing this post. The light is already noticeably dimmer than when I started.

So, what's the deal with Lithium batteries and high-tech devices? Is it because they excel only under low current draw conditions? I wouldn't think my LED light would draw that much -- I typically get 50-60 hours out of a set of Alkaline AAs, and I don't think I got even 30 hours out of these Lithium batteries. Did I just get a bad battery, or are Lithium batteries not appropriate for this usage?

tanstaafl.

ps: after five and a half minutes, voltage is down to 2.84 and still falling.

Actually, I think it's the other way around.. they work better in medium current applications. I think one of the issues is that they have a lower internal resistance than other types. I guess this makes a bit of sense since you noticed that one of the batteries has been drained faster than the others.

Non-rechargeable lithium batteries are generally good for one thing: 10-year shelf life (at the store, or in your emergency flash light).

For frequent use, *rechargeable* NiMH batteries are a much better solution, both for you and for this planet.

I do use alkaline AA's in my own LED headlamps, though, as they have a longer "shelf life" than charged NiMH batteries.

Cheers

One other thing too - they work well down to -20C, way below where NiMHs and alkalines have had their internal resistances go through the roof....

Good for using in cameras when skiing, for example.

Hugo