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: Air bag module and pre-tensioner seat belt deployment procedures
Warning
A live (undeployed) air bag module and pre-tensioner seat belt may
accidentally deploy when it is disposed of and cause serious injury. Do not
dispose of a live (undeployed) air bag module and pre-tensioner seat belt.
If the SSTs (Deployment tool and Adapter harness) are not ava ...
Mazda 6 Owners Manual: Maintenance Monitor
The following maintenance period notifications can be displayed by turning the
Maintenance Monitor on.
Scheduled Maintenance
Tire Rotation
Oil Change
For the setting method and indications for the maintenance monitor, refer to
the Maintenance Monitor.
The maintenance monitor displays ...