At a developer roundtable with some creators of the Nintendo Switch 2 the press asked some questions that has gained us some more knowledge about the hardware inside Nintendo's latest console.

Producer Kouichi Kawamoto, technical director Tetsuya Sasaki, and director Takuhiro Dohta answered a few questions from the press about the new console, with one of those questions being in regard to the Switch 2's battery life. According to Nintendo's official specification sheet for the console, the battery for the Switch 2 is a 5220 mAh battery that's expected to last anywhere between 2 and 6.5 hours on a single full charge.
As pointed out by the press, that is quite a discrepancy, and according to the Nintendo officials, that is a "rough estimate" as many variables can severely impact battery life.
According to Sasaki, the battery life of the console is heavily dependent on the type of game being played, along with the conditions the system is in. Presumably, this translates to whether the console is running in a 60FPS mode or its maximum 120FPS mode. As for the type of game. Running the graphically intense Hogwarts Legacy will be more demanding than running a "lighter" GameCube title that has very little graphical fidelity. These factors dramatically impact battery life off a single charge.
However, Dohta adds that the Nintendo Switch 2 has many more baseline features in general than the original Switch, such as GameChat, and because of that, the variability of the battery life is much "wider" than the original Nintendo Switch.
I think it's reasonable to assume the minimum 2 hours of battery life for the Switch 2 occurs in a situation where the console is pushed to its limits in terms of performance. So, this would mean a graphically intense game running at a high frame rate. In most cases, the average game won't cause this problem, but for big AAA titles - many of which are coming to the Switch 2 - the battery life will be on the lower side of the estimation.