The word you're looking for is internal resistance. Here's an on topic application report from (one of many) manufacturer of single cell upconverter chips. ht

The word you're looking for is internal resistance. Here's an on topic application report from (one of many) manufacturer of single cell upconverter chips. http://www.ti.com/lit/an/slva194/slva194.pdf http://www.ti.com/lit/an/slva194/slva194.pdf Internal resistance rises ridiculously fast with depth of discharge but even in the range of "ohms" you can still squeeze out a good fraction of an amp, a decent fraction of a watt. Its surprising how much you can do with a tenth of a watt or whatever, this will work quite well with a remote control or wireless game controller or a kitchen timer, maybe not so well with RC cars or laptop power supplies or the stereotypical "charge your cellphone with a AA battery" product or 1000 lumen flashlights. In the long run nobody's ever going to use cells in series so as to avoid depolarization / cell reversal type stuff. Its feasible now for low current stuff, what I'm getting at is "someday" people will be running portable drills off single cells. Its a long term trend in power conditioning.