A rubber glove or one of those vinyl pads used to open jars works fine. The function of the little "screw" cover is not defective (it would be a pain if they opened too easily) ... just that the dimple to grip is shallow and any amount of oil (like you would get from your hair!) makes them a bit slippery. This IS NOT an issue ...
I have to admit ... that I am completely perplexed by this issue. We are on our fourth set of these. We gave one set to hearing impaired friends, we wore out one set and we are now using two sets on one transmitter so hubby and I don't have the volume war on the TV. There was one time where we could not easily get the battery compartment open - put on a rubber glove and it was a piece of cake. These headphones have performed very well for us and others we have recommended them to. The green light will not come on until a few seconds after it is being fed a signal by your TV or component and the red light only comes on when you have the headphones on the charger. If you have it plugged in to your DVD player audio output and you are using the TV but not the DVD player ... the base unit isn't receiving a signal and green light won't go on. JMO
I wrote the company and asked them what to do to open these things. Of course by this time the cover is full of scuffs. Then I read this post/s about rubber gloves and it worked! If I told anyone that I need rubber gloves to install batteries they would think I was nuts!
Rubber gloves did not work. What did end of working well was a tiny bit of machine oil around the compartment. That made it move a teeny bit. Then I very gently slid a box cutter razor into the grove. That got it open.