Solved:
Since the last update which I did in March 2018, my battery had to be charged twice during the day at work and I keep all apps closed with data turned off.
I had been using Outlook on my Samsung Galaxy S4 for a few years with 6 email accounts.
After reading the posts here, I decided to uninstall Outlook.
I updated Gmail and all my accounts are moved over.
Wow! !!!
My battery is back to normal even with data turned on all day.
At the end of the day my phone was still at 60% instead of having to charge twice. Outlook also wiped out my contacts when I uninstalled it. I had to re-sync my contacts with my Google account. Outlook sucks! Use any other email client.
By the way, my phone is not running warm or hot.
It's running cool like it should be.