Battery shouldn't have anything to do with it. Manual is manual. If it is not unlocking manually then you probably have a bad actuator. Order a new one and replace, it is not that hard. Take it all apart and look at it to see if you can tell what is wrong. First thing I would do is take out the door lock. Search youtube a guy put up a good video about it. If you unscrew the allen bolt and push out the lock assembly about a half inch, it should be out of the actuator. Check to see if the key will turn fully. If so, you most likely have a bad actuator. They go bad, I have had to replace to of them.