I did find this link. It says when it is placed on COLD concrete ground. It was 70 and sunny when I took the pics so the battery is fine.
* Batteries on cold concrete floors develop a thermal gradient with the plate near the floor slightly colder than the top. This creates a slightly different potential which can mess with the balance of that cell. The idea that backs up this claim is the notion that submarine batteries bubble air through their battery’s electrolyte liquid thereby maintaining flow of the liquid which stabilizes the liquid’s temperature via mixing.
* Battery housings use to be made of materials that conduct heat more thus making them more susceptible to the previous issue.