What is the type of the members of gBatteries? Number? Dimmer? Number:Dimensionless? What type it is will dictate what is appropriate for the filter.
Secondly, you are passing an Item name to the transform but your MAP only has numbers in it. Furthermore, the MAP will only work if what you pass to it is exactly those values. You will get an error if the battery happens to be 91 or 90.000001. So unless you have Items named 100, 90, 80, etc. this is almost certainly not what you want. You should have the name of the item on the left and a “human readable” version of the name on the right. See Design Pattern: Human Readable Names in Messages