The problem is simply that the small form factor doesn't allow a big battery. So the iPhone 12/13 mini simply have a bad battery life compared to the bigger iPh

The problem is simply that the small form factor doesn't allow a big battery. So the iPhone 12/13 mini simply have a bad battery life compared to the bigger iPhones. The reason why we have such big smartphones is that the ratio of screensize (2d area) to battery size (3d volume) is better for bigger smart phones.