Ordinary AA or other standard size rechargeable cells are Ni-Cd or Ni-MH and want to be 100% discharged before they are charged.

Charge Often!
Modern Li-ion batteries love to be charged often. They don't like being fully discharged. This is completely opposite from older style batteries.

Alternate Between Two Batteries
After every use, put the battery on the charger and take the second battery from your case and put it in your camera.

Don't bother if you've used it for only a few shots or used less than 10% of the charge.

I don't know the exact numbers, but you'll get about four times as many charge cycles out of them if you only use 50% of the charge each time, and twenty times as many cycles if you only use 25% of the charge each time.

Summary:
Charging Li-ion batteries is like lunch: do it early and often.

http://www.kenrockwell.com/tech/battery-life.htm

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