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: Clutch switch inspection
Note
Perform the following inspection only when directed.
Continuity Inspection
1. Verify that the clutch switch is installed properly.
2. Disconnect the negative battery cable.
3. Remove the clutch switch.
4. Inspect for continuity between the clutch switch terminals using an
ohmmeter. ...
Mazda 6 Owners Manual: Outside the United States/Canada
Government regulations in the United States/Canada require that automobiles meet
specific emission regulations and safety standards. Therefore, vehicles built for
use in the United States/Canada may differ from those sold in other countries.
The differences may make it difficult or even impossi ...