I tested the battery in motoring abroad (thus not possible to recharge every day). During the first charging, the battery showed signs of slowing from the 2nd day. I then thought it was less efficient than the original. After a second full charge, it took five days, more than 400 photos; So my final advice is: at least as good as the original, or even almost better. FYI, I went from FZ28, I kept 2 years FZ38. After 2 years, the battery "used" the FZ28 still had more autonomy than that (new) of the FZ38, while they are a priori identical. I may have fallen on a bad run ...
