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Yeah, they are. It can be changed though with the right tools. I’ve never done it, but there’s people that have and said it wasn’t terrible to do.

Does Apple Genius Bar replace iPad or repair battery? Do you know that?
 
I've actually noticed that my iPad Pro battery drains a lot faster in 11.2.X than it did in 11.1.X My iPad also feels a little bit sluggish too. Hopefully Apple will push out a new optimization patch soon.
 
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