A teardown of the iPhone 5s and 5c was done by iExperts, an Australian phone repair site. Both the iPhone 5s and 5c have more compact logic boards than the iPhone 5.
The iPhone 5s has an extra cable connecting the Touch ID sensor to the charging port assembly.
The iPhone 5s battery is slightly smaller than what was previously reported based on FCC disclosures — 5.92 Wh, instead of 5.96 — and the iPhone 5c battery is 5.73 Wh, as expected.
Apple Japan is printed on the batteries for the new phones, a first. Switches in the new phones now have extra coating “that should help hold them together to prevent the failures prevalent in the other models.”