Infiniti shares its engineering with Nissan, and that is good news for battery work. Most models take a standard sealed battery and accept a new one without registration on a diagnostic tool. The catch is access. On the Q50, Q60 and the older FX and QX70, the battery sits at the back of the engine bay under a plastic cover near the windscreen, so it is not the first thing you see when you lift the bonnet.
The QX80 is a different job. The 5.6 litre V8 in most of them and the long list of electrical equipment call for a large battery with a high cranking rating, and a weak one shows up first as slow cranking after the car has stood for a weekend. Newer Infiniti models with idle stop-start need a battery made for that duty. We use a memory saver during the change, then check that the one-touch windows and saved settings are as they were.