Get yourself a digital meter for testing the batteries. These meters come with an instruction booklet. The bars shown in some cameras are a guide line but basically tell you nothing. Once a battery gets down to 1 to 1.2 volt, its time to replace or recharge if using rechargeable batteries. One good rechargeable battery is 1.5 volt out of the package (Pure Energy) found at most WalMarts. The cheaper rechargeable batteries are 1.2 to 1.5 volt. Any good battery set will all gradually drop in voltage as a set. If one drops more than the others, this has a fault. Low voltage will cause the camera to receive poor or false signals resulting in 1) shorter than normal night videos, 2) color distortion etc. Cold weather will also effect the out put of any battery.