12V BCI Group GC12 AGM Powercell Battery. 
Can be used as a reserve and/or starting battery.

Specs:
Voltage : 12V
Wattage: 5000W / 7500W
MAX Amps: 6000
CA: 2050A
Ah: 172
RC: 374min
 
Dimensions:
Weight Lbs.: 99.65 lbs
Weight Kgs.: 45.2 kgs
Length: 13.35 in
Height: 10.91 in
Width: 6.81 in
 
M6 Terminal Hardware Included.