Low battery warning always on

Most battery meters measure by small fluctuations in voltage. Your battery may be faulty, old, or perfectly fine. If the camera is turning off because of the low battery, its very possible it has lost capacity. Fully depleating and fully recharging batteries during their life everytime, or just once and a while helps ensure their health. Not doing this at some point in time will cause a battery's life to shorten. You may want to look into a new battery soon, but you should see if you can find one you can test with it first (or find a multimeter and see what kind of voltage you're getting from it). Hope this helps.