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: Tiedown Hooks (Some models)
CAUTION
Do not use the front and rear tiedown eyelets for towing the vehicle. They
have been designed only for securing the vehicle to a transport vessel during shipping.
Using the eyelets for any other purpose could result in the vehicle being damaged.
Tiedown Hooks
1. Remove the tiedown eye ...
Mazda 6 Owners Manual: C-pillar trim removal/installation
4SD
1. Remove the tire house trim.
2. Turn the seaming welt over.
3. Remove the cap using a fastener remover, and remove the bolt (with curtain
air bag system).
4. Disengage clips A and clip B using a fastener remover.
5. Pull the C-pillar trim forward, then disengage hook C from the body, ...