The battery can be at any percent between 49 to 50. It often shuts down between 49 or 50 and once it shuts down it cannot be turned on. I have to charge it from zero percent again. I have changed batteries but it remains the same.
One more thing, the percentage won't decrease for a long time. It stays put on say 41, then after using for a bit it suddenly starts draining rapidly and shuts down before it hits zero percent.