Apple's latest smartwatch model isn't that different from Series 4, but its 40mm version is apparently hiding a component that's dramatically different from its peers. iFixit has discovered that the smaller Series 5 watch uses a battery encased in metal instead of in black foil pouch like typical lithium-ion batteries. Its larger 44mm sibling is powered by one of those standard batteries. The teardown website found a patent that could explain the change: the new metal casing is apparently more space efficient and can free up valuable real estate for a small device.
That might be how Apple was able to give its battery life a boost, even though the size of its battery compartment isn't any different from its predecessors'. Using metal as a pouch also leads to a battery that's stronger and more puncture-resistant. While iFixit wasn't sure what metal Apple used to make the casing, the patent says the layer could be made of aluminum, nickel, steel or other alloys. Whether Apple is planning to use the design for its phones and laptops isn't clear -- but using it on a small device seems to be a good way to test it out.