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: Schedule 2
Chart symbols:
I
: Inspect: Inspect and clean, repair, adjust, fill up, or replace if necessary.
R
: Replace
L
: Lubricate
C
: Clean
T
: Tighten
Remarks:
*1 Use of FL-22 is recommended when replacing engine coolant. Using engine coolant other than FL ...
Mazda 6 Owners Manual: Fuse Panel Description
Fuse block (Engine compartment)
*Some models.
Fuse block (Left side)
*Some models. ...