Thread: Batteries, CCA and Amps

Originally Posted by jx2mad

I know there are threads on here covering this topic but I cannot find an answer to my question. I have a small lead-acid battery rated at 240cca. There is no indication of the amp/hr rating so I cannot work out how long this battery will sustain a load drawing 12A. Any suggestions?

When fully charged and healthy, your battery is capable of supplying a load drawing 240A. How long for? More information is needed.
What is the make and model no. of your battery?

Unless the battery is rated for deep cycle use it is unlikely you will find any specifications mentioning amp-hours. Try googling the battery manufacturer. Or buy an ex UPS battery from ebay, there are heaps about.

There is a rule of thumb for normal starter batteries but I cannot remember it - something like divide the CCA by 10 or 12.

Hi Garry and sorry mate but there is no connection between the CCA and Ah of any battery.

The only way you will know the Ah of a battery is if the manufacturer lists it.

For example, and Optima 55 amp deep cycle battery has a CCA of 750 and if you divide the CCA by the Ah, you get a ration of 13.64.

Where as a similar sized Exide cranking battery has an Ah of 50 but only a CCA rating of 400, thats a ration of 8.

As you can see, no comparison and note, even the same cranking size Exide batteries have different Ah.

Hi jx2mad, as posted, you will need to get the exact Ah info from the manufacturer, if they have it available.

As Drivesafe has said there is no relation between the CCA and AH.


Have a look for a reserve capacity number.

Reserve capacity is the number of minutes a battery can maintain a useful voltage under a 25 ampere discharge. The higher the minute rating, the greater the battery's ability to run lights, pumps, inverters, and electronics for a longer period before recharging is necessary. The 25 Amp. Reserve Capacity Rating is more realistic than Amp-Hour or CCA as a measurement of capacity for deep cycle service. Batteries promoted on their high Cold Cranking Ratings are easy and inexpensive to build. The market is flooded with them, however their Reserve Capacity, Cycle Life (the number of discharges and charges the battery can deliver) and Service life are poor. Reserve Capacity is difficult and costly to engineer into a battery and requires higher quality cell materials.

I know there are threads on here covering this topic but I cannot find an answer to my question. I have a small lead-acid battery rated at 240cca. There is no indication of the amp/hr rating so I cannot work out how long this battery will sustain a load drawing 12A. Any suggestions?

Just to try to be helpful I will say that based on a say 440 CCA battery being unlikley to have more than say 40AH, I would guess that a 240CCA battery would be unlikely to run your 12Amp load for more than 2 hours and probably a bit/lot less.
Regards Philip A

Originally Posted by drivesafe

Hi Garry and sorry mate but there is no connection between the CCA and Ah of any battery.

pftttttt - party pooper - I read it somewhere so it must be true - is only a rule of thumb so has some inaccuracies.

Originally Posted by jx2mad

I know there are threads on here covering this topic but I cannot find an answer to my question. I have a small lead-acid battery rated at 240cca. There is no indication of the amp/hr rating so I cannot work out how long this battery will sustain a load drawing 12A. Any suggestions?

Hi jx2mad, I forgot to mention that your battery is probably way too small to maintain a 12 amp load for anything but a few minute without doing some serious harm to your battery.

Maximum CONTINUOS load for any battery should not exceed 10% of the battery’s total Ah ( which you need to determine )or you risk shortening the battery’s life span.