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: Starting procedure for on-board diagnostic test mode
Note
All DTCs displayed in the on-board diagnostic test mode should be
entered in the Audio Repair Order Form.
1. Turn the ignition switch to the ACC or ON position.
2. First press the POWER button, then simultaneously press the AM button and
TAPE/MD button for 2 seconds or more.
N ...
Mazda 6 Owners Manual: Automatic Brake Operation Display (Type A Instrument Cluster)
“Smart City Brake Support activated” is indicated in the active driving display,
and “Smart City Brake Support Activated” is indicated in the multi-information display
after the SCBS brakes or the brake assist (SCBS brake assist) is operated.
NOTE
The collision warning beep sounds ...