Why do Alkaline batteries "recharge" themselves?

Okay, I put some alkaline batteries in a generic flashlight and leave the light on until the alkalines are almost dead. Then I turn off the flashlight and wait 24 hours. Then I turn on the flashlight and it's bright again for a while before it starts to die again. It's like it regained some of it's lost power. It' not like a full charge again but it might gain back 10-20% of it's original life before it dies again. This process can be repeated over and over--each time the batteries gain back a shorter and shorter life until they are finally history.

I've noticed this effect more with alkalines than with rechargeables. The rechargeables only appear to gain a very slight recharge when rested. Alkalines are better at it. I'm too cheap to buy Lithiums so I can't speak for them.

Anyone know how an alkaline battery "recharges" itself (for lack of a better term?)

What you have noticed is a phenomenon mostly of alkaline primary cells. It is called the relaxation effect. It does not happen to any great extent in rechargeable cells.

It is not a recharging, but a small recovery. I was able to dig up a link to a document I read with decent info on this topic. Battery Recovery

Mark

Just a note any "recovery" or comming back to life of a alkaline usually doesnt mean it lasts longer if you pause between
in HIGH current draw situations where a alkie is not outputting any current , and wishes to be rested, a Rechargable of good capacity, will keep going, and going and going , without a rest.
so while the poor alkie is resting, a good rechargable can keep going non-stop.
MEANING , even though the alkie comes back for a final gasp of output (in HIGH consumption devices) a good rechargable would still have Full output, running up to an including 3X as long in high consumption devices.

I have noticed the *recovery* is related to how much of a load it had on it before resting and how much a load it has after it rests. Hit an alkaline with a heavy load till it drops off to nothing then a light load and it may run for awhile..... do the opposite.... run on a light load and hit with a heavy one and you will get a minute or two.