Spare battery

Hello Everyone, I'm fairly new to your community and it's great to know that there is a place I can go to get answers when I need them. I bought a Ring 2ND Generation video doorbell a few months ago and then I was told that I could buy an extra battery so I can put that in when the other one is charging. So that's what I did but it doesn't go in as shown on the video? The silver outside cover of the doorbell has 8 little hex screws in the back but I can't imagine they designed it so you would have to take those out? It's Ring battery Model number 5AT3S3. Are there different model numbers for every doorbell? Thank yo0u