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: Outside Temperature Display (Without Multi-information Display)
When the ignition is switched ON, the outside temperature is displayed.
NOTE
Under the following conditions, the outside temperature display may differ
from the actual outside temperature depending on the surroundings and vehicle conditions:
Significantly cold or hot temperatures.
Sudden ...
Mazda 6 Owners Manual: Rear bumper removal/installation
1. Disconnect the negative battery cable.
2. Remove the rear combination light.
3. Remove in the order indicated in the table.
4. Install in the reverse order of removal.
Rear Bumper Removal Note
Pull the rear bumper ends (wheel arch) outward to disengage with the bumper
slider.
Cautio ...