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: How to use USB mode
This unit does not support a USB 3.0 device. In addition, other devices may not
be supported depending on the model or OS version.
USB devices formatted to FAT32 are supported (USB devices formatted to other
formats such as NTFS are not supported).
Playback
1. Select the icon on the home
...
Mazda 6 Owners Manual: Average Fuel Economy
The average fuel economy is calculated every minute from the total traveled distance
on the trip meter and the total fuel consumption, and the average fuel economy for
either TRIP A or TRIP B is displayed.
The average fuel economy and trip meters can be reset by pressing the INFO switch
for ...