Garmin Forerunner

Fr 55 :
For runners just staring off .
Smartwatch Mode: Up to 2 weeks
GPS mode: Up to 20 hours

Fr 255 :
For triathletes just starting off .
Smartwatch mode: Up to 14 days
GPS-only GNSS mode: Up to 30 hours
All-Systems GNSS mode with music: Up to 6.5 hours

Fr 265 :
For triathletes and runners who want a smart watch with amoled display .
Smartwatch mode: Up to 13 days
GPS-Only GNSS mode: Up to 20 hours
GPS-Only GNSS mode with music: Up to 7 hours

Fr 955 :
For serious triathletes .
Smartwatch mode: Up to 15 days/20 days with solar*
GPS-only mode without music: Up to 42 hours/49 hours with solar**
All-Systems GNSS mode plus Multi-Band with music: Up to 8.5 hours

Fr 965 : 
For serious triathletes who also want amoled display .
Smartwatch mode: Up to 23 days
GPS-only mode without music: Up to 31 hours
GPS-Only GNSS mode with music: Up to 10.5 hours