December 11th 2017
By Mike Flaminio
A Reddit thread has some interesting observations on apparent performance degradation on some iPhones as the battery capacity decreases. This issue may be a means to extend battery life by reducing performance. If, however, an iPhone's battery is worn and holding a reduced charge, this could affect most of the time.
So, I did some research, and decided to replace my battery. Wear level was somewhere around 20% on my old battery. I did a Geekbench score, and found I was getting 1466 Single and 2512 Multi. This did not change wether I had low power mode on or off. After changing my battery, I did another test to check if it was just a placebo. Nope. 2526 Single and 4456 Multi. From what I can tell, Apple slows down phones when their battery gets too low, so you can still have a full days charge. This also means your phone might be very slow for no discernible reason. Check your Geekbench scores and see what you get if your phone is still slow!