The battery is unbelievable, I have an 11 mo. old son and take loads of pictures. I haven't even come close to worrying about battery life. Literally hundreds of pictures and it is hardly affected. I actually thought the battery readout was not reading correctly at first because it rarely needs chargrd
From what I found on-line the battery is good for up to 540 pictures. From my experiance, I took over 900 pictures and only had to charge it once after the initial set up charging period. Two charges for that many pictures seems to match up to the claims. (I probably could have gotten more before the second charge, but I was doing some cold nighttime star shots!) As for the battery - I have yet to get a second battery. I heard you can use a knock off battery, but the camera won't recognize it and record the individual photo's information. As for the camera - I love it!
It lasts much more than 540 shots. But, I bought spare battery pack anyway. "Wasabi Power Battery and Charger Kit for Panasonic DMW-BLC12..." This pack has 2 batteries, one universal (110-220V) worldwide charger, one European plug converter and one car power supply. Adapter and batteries work great. Batteries are compatible with FZ200 and charger can also be used to charge original FZ200 batteries.
The battery has been very robust so far... I have used the camera off and on for 3 weeks, taken about 400 photos (most without flash) and 10 mins of video all on one charge! I do recommend extra batteries though I purchased the two pack with charger from Wasabi power for $20-25 and they work great as a backup. Do yourself a favor and get a screwing glass filter as well to protect the lens