Quote Originally Posted by Phil DeFrame
Last year I bought a Brand X Li-ion battery for a fraction of the price of the Canon product. It worked great until a few weeks ago, when it suddenly went dead. The specific problem is a very high internal series resistance. It cannot deliver anywhere near enough current to run a camera (or anything else), even though the charger considers it "fully charged". In any case, the battery is now useless.

My question is: has anyone else had a similar experience? Is this typical of cheap batteries, or did I just get a lemon? Are there any non-Canon batteries that are as reliable as the official, very pricey item?
Cheap batteries require luck. Some work fine, some burst into flame! I have a no-name battery that works as well as the Canon brand. A friend had the same problem as you have now. With Canon, you get better battery-to-battery consistency, with cheapies you get better prices. Pick your choose.