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: Opening and Closing the Trunk Lid
Opening the trunk lid
Using the remote release button
Push the remote release button.
Using the electric trunk lid opener
(With the advanced keyless function)
A locked trunk lid can also be opened while the key is being carried.
Press the electric trunk lid opener on the trunk lid, then rais ...
Mazda 6 Owners Manual: Diagnostic trouble code number inspection
1. Remove the glove compartment.
2. Short the A/C check connector to the GND terminal using a jumper wire.
3. Shine a 60 W incandescent light from a height of approximately
100 mm {3.9 in} onto the solar radiation sensor.
Note
When incandescent light does not shine on the solar radiatio ...