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: Height Adjustment
Adjust the head restraint so that the center is even with the top of the passenger's
ears.
To raise a head restraint, pull it up to the desired position.
To lower the head restraint, press the stopcatch release, then push the head
restraint down.
Front outboard seat
Rear outboard seat
...
Mazda 6 Owners Manual: Automatic transaxle removal/installation
1. Disconnect the negative battery cable.
2. Remove the battery and battery tray.
3. Remove the aircleaner component. (See INTAKE-AIR SYSTEM
REMOVAL/INSTALLATION.)
4. Remove the front tires and splash shield.
5. Remove the under cover.
6. Remove the steering gear and power steering pipe. (See ...