Eneloop AA Batteries
I've had a Canon A540 digital camera for several years, in fact most of the photos on this site were taken with it. I chose this model because it takes 2 AA batteries, and in those days Lithium batteries were not as common, and I thought I could always pack a spare set of cheap AA's, which I use as well with my hand-held radios.
At first the camera worked great. With two 2000 mAh NiMh batteries, I could shoot all day without the batteries running down. As time passed I could even get 2800 mAh batteries which should last even longer.
Then I began to notice something -- I would charge up the batteries, put them in the camera, turn the camera on, and it would indicate "battery low"! I bought new batteries, and the same thing happened. I even contacted Canon support the see if they had some useful suggestion, but they told me to take it in to a service depot. I wasn't interested in doing that, as it would probably cost as much as buying a new camera.
Sometimes the camera would take a few shots before indicating "battery low", and I did not feel as if there was anything actually wrong with it. Around this time I stumbled across the Eneloop battery, from Sanyo, which claimed to deliver a higher cell voltage and hold a charge much longer. I found a local vendor and bought 4 of them. They were marked "2000 mAh typical, 1900 mAh minimum".