My newest rechargable D cells have less total energy storage than my newest AA batteries. It's counter intuitive. But the industry seems motivated by volume to work on AAs, and so D cells haven't moved forward as fast.

I wish my electric socks used a pair of AAs instead of a single D. That would give me more than twice the endurance. They'd last all night (i do astronomy). And, they wouldn't stick out from my legs so much.

The battery inside the Nokia is 1500 maH. One might think that a single AA, at 2400 maH is better. And it might be. But energy is watts * time, and watts = amps * volts, and i have no idea what voltage the internal battery generates. Why does it have 4 pins? If it were just a battery, why not have two? Anyway, at the moment, all i know for sure is that i don't know the answers. Usually, you don't know what you don't know.

This rating in maH drives me nuts, since i think i'm interested in total energy. For example, AA disposable batteries say that they're 1.5 volts. If you measure a new one you often get 1.6 or more, and an older one might be 1.1 volts. Rechargable NiMH say they're 1.3 volts, but a new fully charged one might be 1.7 volts. And, under high load, NiMH holds voltage better than disposables, which makes a difference in cameras. But is it 1500 maH at 1.3 volts or 1500 ma at whatever the voltage happens to be? I generally punt the math and just see how long it lasts in a real device. That was the real question anyway.

I probably do know what the voltage is. It came up in another thread.