As per the header, how are cold cranking amps calculated? Im trying to understand what a rating of 20AH means if I want to use it as a starter source.

  • As the answers show ; AH and cold crank capacity are 2 different ways to define a battery. Dec 4 '17 at 20:32

Cold Cranking Amp is a measure the ability of a fully charged new battery, in a cold environment (0°F/-18°C), to discharge a load (in amperes) for 30 seconds, while still maintaining a voltage equal to or higher than 1.20 volts per cell.

It sounds like you are describing a deep cycle battery. Don't confuse a deep cycle battery with a starting battery. They are quite different. A deep cycle battery, rated in AH, usually cannot deliver the burst of energy needed for starting an engine.

Deep Cycle vs. Starting Battery


That 20AH will not tell you about the cranking capacity - you need to find the cranking capacity for the battery you are looking at - this is given by the manufacturer usually at a specific temperature.

The 20AH means the amount of current the battery can deliver : basically 20A for 1 hour (=20AH), 2A for 10 hours, or 1A for 20 hours. However, this is more a guide and not exact.

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