A battery has two ratings:

Reserve Capacity

The reserve capacity rating is an estimate of the maximum length of time possible to travel at night with a minimal electrical load and no generator output. Expressed in minutes, the rating is the approximate time the fully charged battery can support a 25 A load without the battery terminal voltage dropping below 10.5 V at 27°C (80°F).

Cold Cranking Amperage (CCA)

The CCA rating, expressed in amperes, is the minimum amperage which must be maintained by the battery for 30 seconds at -18°C (0°F), while meeting a minimum voltage requirement of 7.2 V.