There is a little tab on the Makita LXT tools that prevents the LCT batteries from fitting.
Step 1: Locate the Tab on Your LXT Tool Where the Battery Slides In.
In this photo, it is the blue tab on the left side of the tool.
Step 2: With a Sharp Knife, Carefully Cut Out the Tab
Use a sharp blade and carefully cut out the blue tab.
Step 3: Viola, the Tab Is Cleared Out!
Yup, done. tab cleared.
Step 4: Attach the Battery to Your LXT Tool.
With the blue tab cleared away, you can attach the 1.5Ah LCT battery to any of your Makita cordless LXT tools. You probably void the warranty by doing this but....