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: Door Locks
WARNING
Always take all children and pets with you or leave a responsible person
with them: Leaving a child or a pet unattended in a parked vehicle is dangerous.
In hot weather, temperatures inside a vehicle can become high enough to cause brain
damage or even death.
Do not leave the key in ...
Mazda 6 Owners Manual: Excessive Speed Warning
If the vehicle speed exceeds the speed limit sign displayed on the active driving
display, the warning sound is activated and the area around the speed limit sign
displayed on the active driving display flashes 3 times in amber, and if the vehicle
speed continues to exceed the displayed speed ...