I'm having a little problem. I let the battery charge using the normal charger and instead of the light turning green (from red) at some point the light just goes off completely. At that point the battery claims to be half charged. And it acts like it's half charged too, not giving me a lot of time to shoot. Any idea what's going on? Is the battery bad? The charger? Both? I'm not sure if this is a common problem. Thanks!