My wife and I own two Casio Exilim cameras that use the NP-20 battery. Within a month, the first battery was bad. Attempting to charge it results in a flashing red light, which is an error condition indicating the battery will not charge. A few weeks later, the second battery was dead too. Casio did send us two replacements for free, and acknowledged having trouble with these particular batteries. After 6 months, one of the replacements died. Another call to Casio, and thankfully they provided another replacement.So we've had 5 of these batteries, and 3 were defective. We don't use the cameras often. We checked all the batteries using both of our charging docks, and confirmed in each case that yes, the battery was the problem and not the charger.Casio has treated us well and acknowledged the problem, though. My recommendation is to call for replacements on they day you buy a camera that uses this battery -- you're going to need them.