Wrong battery was fitted and Nissan refuses to take ownership

Hi had my Nissan Qashqai 1.6 diesel AWD techno 2014 model battery replaced under warranty 18 months back as the start stop function stopped working. I thought it strange at the time to be replacing my battery 18 months into a new car but Nissan said they would pay half so I agreed and they went ahead and replaced my battery with a new one.

Now 18 month after that I am being told to replace my battery again with the same fault of my start stop function not working again. I inquired with Midas and they advices me that the battery that I have in my car in now strong enough to support all the electronic functions the car has. I complained to Nissan South Africa about this and they take no responsibility for this mess. Even though they have publicly stated that they have since changed the spec of the battery requirements on my car.

How do you logically take no responsibility for replacing my battery with an inferior product and at the same time say publicly that the spec has been changed to a more powerful battery. I would like Nissans response here for the public to see how duplicitous they are.