Chosen Solution
iPhone 6 Plus won’t hold charge more than 4 hours normal use
Your battery is most likely at the end of its life. To be certain, use a battery utility, such as coconutBattery (for Mac) or 3uTools (for Windows). Anything less than 75% of design capacity will require replacement. You can also use the Battery Health Diagnostic (Settings\Battery\Battery Health (Beta)) in iOS 11.3 and above. It will tell you what the health of the battery is. Once the battery reaches below 80% of design capacity, iOS will throttle performance if the phone experiences an unexpected shutdown. You can read more about this at the following Apple Support page (https://support.apple.com/en-us/HT208387). If you have access to a USB Ammeter, you could use that to determine if the phone is really drawing current when it says it’s charging.
