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: Dsc hu/cm removal/installation
Caution
When replacing the DSC HU/CM, configuration procedure must be done
before removing the DSC HU/CM. If configuration is not completed before
removing the DSC HU/CM, DTC B2477 will be detected.
Do not drop the DSC HU/CM. Replace it if it is subjected to an
impact.
1. Configura ...
Mazda 6 Owners Manual: No.8 brake system warning light stays on more than 4 seconds with ignition
switch on
Diagnostic procedure
When performing an asterisked (*) troubleshooting inspection, shake the
wiring harness and connectors while doing the inspection to discover whether
poor contact points are the cause of any intermittent malfunction. If there
is a problem, check to make sure co ...