[lanier ledford]

If I know the cold cranking amp of my battery, how do know how long a item will run before it will kill the battery without any recharging while its operating. thanks

[beertracker]

Batteries are rated in amp hours. So if your battery is rated at 850 cold crank amp hours it will sustain a load of 850 amps for 1 hour. If the load is 425 amps the battery will sustain this for 2 hours.

bt

[DanielC]

"cold crank amps" is a battery manufacturer term that has nothing to do with the actual amp hour output of a battery, other than they generally go up more or less together.

Keep in mind that the more you discharge a battery, the fewer charge, discharge cycles you have. It is a bad idea to run a battery down. Deep cycle batteries are a little better in this regard, but they will still have longer life if you do not discharge them close to their capacity.

[lanier ledford]

So I get he cold cranking amps, and divide by the amps drawn and thats tell me how long it'll run. thanks

[DanielC]

"So I get he cold cranking amps, and divide by the amps drawn and thats tell me how long it'll run."
NO!

"Cold cranking amps" is just a salesman term! It does not have really relate to anything, other than how much current the battery will put out at a certain temperature, for a brief period of time.

The amp-hour rating of a battery is the rating that tells you directly the capacity of a battery.
For example, a 60 amp hour battery will put out 60 amps for an hour, 10 amps for 6 hours, 1 amp for 60 hours, you get the idea.

A 60 amp hour lead acid battery is capable of putting out a lot more than 60 amps for a shorter period of time. This just a WAG number, but I would not be surprised if a 60 amp hour battery could have a CCA rating of 300 to 400 amps.

So when they are trying to sell you a battery, it sounds more impressive to try to sell you a battery with 600 to 800 CCA, even though another battery may actually have a higher amp hour rating.

[sparkchaser]

Cold cranking amps is the max the battery will deliver at 0 degrees F for 30 seconds. Most battery manufacturers no longer list amp hours on the battery and instead list reserve capacity, which is the time in minutes the battery will supply 25 amps and still have a voltage above approximately 10.5 volts.