Replacing the remote key battery

I almost always drive with the key in the ignition to recharge the remote key battery, but I frequently get the low battery warning regardless. I often have to press the button a bunch of times before the car unlocks, and it takes awhile for the door handle to recognize my hand. I suspect this is all due to the battery, although I'm not sure.

The manual says it's a rechargeable battery, but I'm guessing it still might need to be replaced. Does anyone know if that's true? Or should this battery be good to go forever?

My other question is, does anyone know the type of battery I should buy? I tried to open the key based on the instructions on page 38 of the '08 manual, but I'm apparently too stupid to pop open the key in step 2. I felt like I was forcing it too hard and was afraid I'd snap the key.

Same problem any help?

It's not a rechargeable battery. If you’ll look at backside of your key fob, you’ll see a round faint impression of battery in there. If you still have the warranty then BMW will replace it …