Definition
A rating that specifies the number of amperes a fully charged battery can deliver for 30 seconds at 0°F (-18°C) while maintaining a terminal voltage of at least 1.2 volts per cell. It measures a battery's ability to start an engine in cold conditions, when the oil is thick and chemical activity within the battery is reduced.
Plain English
A number that tells you how much electrical current a battery can push out in cold weather to crank an engine over. The higher the number, the better the battery starts a cold engine.
Context Anchor
Seen in aircraft battery specifications, maintenance records, and cold-weather starting discussions.
Derivation
Three plain words doing exactly what they say: 'cold' (the test temperature), 'cranking' (turning the engine over to start it), and 'amps' (the unit of electric current). The phrase is the test condition packaged into the rating itself.
Why Pilots Care
Confirms the battery can reliably start the engine in cold conditions, avoiding start failures that affect safety and schedules.
Grounding Statement
Cold makes a battery less able to deliver power, so this rating tells you how strong the battery is under a hard starting condition.
Intuition Check
Cold-cranking amps is not the number of amps the aircraft always uses during start. It is a test rating for how much current the battery can deliver in very cold conditions.
Example Sentence 1
Before winter operations, the mechanic checked the battery's cold-cranking amps to make sure it could still start the engine on cold mornings.
Example Sentence 2
Maintenance replaced the battery when its cold-cranking amps fell below the minimum required for reliable engine starts.