lead acid battery EN standard
If a typical car battery is 55Ah with 750 CCA then that sounds right. I also read that 12V 180 Ah = 1100 A comes from Varta.

I'll let someone else dig up the EN standard.... assuming it exists.

I forget exact details on CCA temperature 0'C? vs CA for 25'C

But I recall CA is defined at room temp as the max current sustained for 30 seconds at 7.5V from a fully charged 12.5 V battery.

.. Battery U cites " SAE J537 specifies that a battery with a CCA reading of 500A can deliver 500A at –18'C (0'F) for 30 seconds without dropping below 7.2 volts."

So I conclude ESR= (12.5-7.5)/CCA at cold temp.  or replace 7.5 with 7.2 ??

ESR lowers as Ah capacity rises but is not necessarily in a perfectly inverse relationship because Capacity is mainly condition of dielectric and its specific gravity while ESR includes Anode and Cathode materials and condition. 

Therefore ESR is a great indicator of electrodes but a poor indicator of dielectric or the Ah Capacity

Electrode degradation from sulphation or deep discharge of the dielectric causes ESR to rise so it  not a great predictor for normal operation of Ah capacity but generally must be lowered at some material cost for increased high density batteries with rapid charge rates. (&lt;1h)