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: Input/turbine speed sensor inspection
Caution
Water or foreign objects entering the connector can cause a poor
connection or corrosion. Be sure not to drop water or foreign objects on the
connector when disconnecting it.
1. Disconnect the negative battery cable.
2. Remove the battery and battery tray.
3. Remove the air cl ...
Mazda 6 Owners Manual: Scheduled Maintenance (Mexico)
Follow Schedule 1 if the vehicle is operated mainly where none of the following
conditions apply.
Repeated short-distance driving
Driving in dusty conditions
Driving with extended use of brakes
Driving in areas where salt or other corrosive materials are used
Driving on rough or muddy ...