iApplebytes confirms iOS 13.5.1 has a worse battery life, geekbench 5 battery test is a intensive test. On my iPhone 11 i got around 9-10hours of screen on usage and on geekbench
Apple iPhone 5c - Battery Life - AT&T
Use Low Power Mode to save battery life on your iPhone or iPad – Apple Support (UK)
iOS 10 is a pleasant surprise for the iPhone 5 and 5C | Ars Technica
iOS 12.4.5 battery life test (Video) - Geeky Gadgets
iPhone 13 battery life tested: All four models compared | Tom's Guide