I've been using the Galaxy Z Fold 7 as my daily driver for the past few days. Although I used it briefly when it launched last year, I have now had the chance to use the phone regularly. It has already changed one of my expectations about Samsung's upcoming flagship foldable phone, the Galaxy Z Fold 8 Ultra.On paper, the Galaxy Z Fold 7's minuscule 4,400mAh battery does not inspire much confidence. It has the same battery capacity Samsung has used in the previous four generations of Galaxy Z Fold series phones. Yet it powers a larger 8-inch foldable display and a bigger 6.5-inch cover screen.Compared to Galaxy S Ultra phones, which feature 5,000 mAh batteries, the Galaxy Z Fold 7 seems like it should have a clear disadvantage in terms of battery life.I assumed I would need to charge the Galaxy Z Fold 7 twice a day, or at least recharge it more often than I charge my Galaxy S26 Ultra. That seemed especially likely if I used the inner display for web browsing or watching videos. Thankfully, that has not been the case.My daily usage includes web browsing, reading a lot of news (for work), using shopping and banking apps, and checking work-related emails and chats. I also use wireless Android Auto in my car for about an hour during my daily commute. None of this is unusually demanding, but it could strain an ultra-slim phone with a large screen and a small battery. Galaxy Z Fold 7 battery life on a typical day – Source: Asif Iqbal Shaik / SamMobile The Galaxy Z Fold 7 has so far consistently lasted through the day on most days. It has been a pleasant surprise, and it is a good example of the job Samsung does in optimizing a phone's hardware, software, and power consumption. The battery capacity may look below par, but its real-world endurance exceeded my expectations.This experience has made me more excited about one rumored Galaxy Z Fold 8 Ultra feature: its larger 5,000mAh battery.If the rumors are accurate, the Galaxy Z Fold 8 Ultra could fix a major complaint that many Galaxy Z Fold users have had for years. A 5,000mAh battery would bring it in line with Samsung's Galaxy S Ultra phones. More importantly, it would give users greater confidence that the phone will last through a typical day on a single charge, or even two.Battery capacity is only one part of the equation, though. The Galaxy Z Fold 8 Ultra is also rumored to use the more power-efficient Snapdragon 8 Elite Gen 5 for Galaxy chip.Another rumor claims that Samsung will bring faster charging to the Galaxy Z Fold 8 Ultra. It is expected to have 45W wired charging and 20W wireless charging. If that turns out to be true, it would be the fastest charging ever offered on a Samsung foldable. Galaxy Z Fold 7 Deals Samsung Store Samsung's foldables have come a long way in terms of design, durability, display reliability, and performance. After using the Galaxy Z Fold 7, I feel Samsung's battery optimization deserves more credit than it usually gets, and it has me very excited for the upcoming sequel.