To ensure the maximum battery life out of a new Makita cordless power tool, there are several best practices which you must be followed as general maintenance for Milwaukee M18 Cordless Power Tool Battery.
The Milwaukee M18 drill battery will perform best if it is charged at room temperature. Do not charge in temperatures below 400F or above 1050F. Under these conditions, the cordless drill battery will not take a full charge, and may be permanently damaged.
If the Milwaukee M18 tool battery is hot, let the it sit out of the charger for a least 2 hours until the battery is at room temperature. Otherwise, immediately place the Milwaukee M18 power tool battery pack in the battery charger.
Place the Makita 1420 Drill Battery in the charger overnight to allow for a full charge on each individual cell (A minimum of 8 hours at room temperature).
Do not try to discharge the battery beyond the point where the tool no longer performs with the power and torque needed for the job, because it may cause permanent damage which will prevent the battery from taking a full charge.