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: Reporting Safety Defects (U.S.A.)
If you believe that your vehicle has a defect which could cause a crash or could
cause injury or death, you should immediately inform the National Highway Traffic
Safety Administration (NHTSA) in addition to notifying Mazda Motor Corporation (Your
Mazda Importer/Distributor).
If NHTSA receive ...
Mazda 6 Owners Manual: Recording of Vehicle Data
This vehicle is equipped with a computer which records the following main vehicle
data related to vehicle controls, operation, and other driving conditions.
Recorded data
Vehicle conditions such as engine speed and vehicle speed
Driving operation conditions such as accelerator and brake ped ...