Cell Phone Battery Life Issues

[vortalexfan]

Greetings everyone, I work a 3rd shift custodial job cleaning bathrooms at a local Amish Themed Restaurant and Gift Shop that also has an Inn attached to it, and when I'm working I like to listen to either music or podcasts on my phone and I usually use blutooth earbuds when I'm doing this, but sometimes I forget to charge my earbuds at home before going into work and so I have to just listen to my stuff using my phone's built-in speaker turned up all the way so I can hear it above the sound of the toilets being flushed (they have vacuum break flush valves on some of the toilets that when they flush they are loud enough to drown out the audio even when using earbuds unless I use "noise cancelling" earbuds.)

Anyways, I've noticed that my cell phone which is an iPhone SE 3rd Generation model, has a strange issue with it where, when I listen to my Podcast app or Music app on my phone with earbuds, the phone runs as cool as a cucumber and only drains about 20% of the battery over the course of a 5 hour shift from a full charge, but when I use the phone's built-in speakers the phone runs hot, and is dead by the end of the shift from a full charge.

What's different between the two operating modes that would cause that much of a difference in battery drain/battery life in my cell phone?

Any help with this issue would be appreciated.