Getting messages that smart key not detected ,changed the battery ❓❓❓

Make sure the replacement battery is a well known brand and that it has a long shelf life.
Cheaper battery's and those near the end of their shelf life are often not detected by the vehicle.

Had a message saying Smart key battery low on the key that I've been using for nearly 3 years. OK then . I'll start to use spare which hasn't been used since new. Ok for a day and then I get a message that this battery is low, even though it's never been used. Do these keys have timers on them! New batteries in both now so hopefully that's it. By the way I've had the one I usually use in a silicone cover since new and when I took it out, there's was loads of sticky glue all over it and the plastic cover to the buttons was loose around the edges so this glue must have 'melted'. Or oils have come out of the silicone. Still works though, but this is now the spare. Not using the silicone cover on the one I'm using now.
Just for info

cheers