A low level of electrolyte fluid will cause the battery to discharge quickly.

Inspect the electrolyte level at least once a week. If it is low, remove the caps and add enough distilled water to bring the level between the upper and lower level (illustration).
Do not overfill.
Examine the specific gravity of the electrolyte with a hydrometer, especially during cold weather. If it is low, recharge the battery.
Battery Maintenance
Battery RechargingMazda 6 Owners Manual: Electric Parking Brake
The electric parking brake equipment applies the parking brake using an electric
motor. When the electric parking brake is applied, the electric parking brake switch
indicator light turns on.
WARNING
Do not drive the vehicle with the electric parking brake applied:
If the vehicle is driven ...
Mazda 6 Owners Manual: Warning Light and Brake Pad Wear Indicator
Warning Light
The warning light turns on when the system has a malfunction.
Refer to Warning Indication/Warning Lights
Brake Pad Wear Indicator
When the disc brake pads become worn, the built-in wear indicators contact the
disc plates. This causes a screeching noise to warn that the pads shoul ...