Makita · DUR190/DUR191 Trimmers
If you can see the red indicator on the upper side of the battery button, the battery cartridge is not completely locked into the tool.
Click steps to track your progress.
Remove the battery cartridge by sliding the button on the front of the cartridge.
Align the tongue on the battery cartridge with the groove in the housing.
Slip the battery into place and push it all the way until it locks in with a click. Ensure the red indicator is no longer visible.