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: Adaptive Front Lighting System (AFS) (Some models)
The adaptive front lighting system (AFS) automatically adjusts the headlight
beams to the left or right in conjunction with the operation of the steering wheel
after the headlights have been turned on and the vehicle speed is about 2 km/h (2
mph) or higher.
A system malfunction or operation c ...
Mazda 6 Owners Manual: Side air bag sensor removal/installation
Warning
Handling the side air bag sensor improperly can accidentally
deploy the side air bag module, which may seriously injure you. Read AIR BAG
SYSTEM SERVICE WARNINGS before handling the side air bag sensor. (See
SERVICE WARNINGS.)
1. Turn the ignition switch to LOCK position.
2. ...