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: Interior Lights
NOTE
Do not leave the lights on for long periods while the engine is turned off.
Otherwise the battery power could be depleted.
Overhead Lights
NOTE
The rear map lights also turn on and off when the overhead light switch is
operated.
Front Map Lights
When the overhead light switch is i ...
Mazda 6 Owners Manual: Power brake unit inspection
Warning
The following inspection methods are the simple inspection methods
to judge the function of power brake.
If there is malfunction in power brake unit, replace the power
brake unit as a component.
Power Brake Unit Function Check (Simple Method)
Step 1
1. With the engine stoppe ...