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: Indication/Indicator Lights
These lights turn on or flash to notify the user of the system operation status
or a system malfunction.
*Some models.
*1 The light turns on when the ignition is switched on for an operation check,
and turns off a few seconds later or when the engine is started. If the light does
not t ...
Mazda 6 Owners Manual: Front buckle removal/installation
1. Perform the following procedure for vehicles with seat belt warning.
(1) Disconnect the negative battery cable.
(2) Remove the front seat.
(3) Disconnect the buckle switch connector.
2. Perform the following procedure for vehicles without seat belt warning.
(1) Remove the console.
...