Something running in the background is a software issue. Trying to solve that by throwing more hardware is the most expensive least efficient way to solve your problem
Upgrading to a bigger battery won’t solve whatever is draining your battery
While that is all true, it does give more time to realize what is going on, so I can address the issue, without leaving me in a bad spot.
On days with normal battery usage, how is having more battery life ever a negative? Long travel days, which may also have heavy map usage, leave users outside of normal patterns and often with unpredictable access to charging. Having a long battery life would ease stress around those days and be preferable to carrying a battery bank.
Those days are not the norm. So having a heavier phone 90% of the time so that 10% of the time can be less stressful is not efficient. Just attach a magsafe battery pack those days and you have full day battery life.
Upgrading to a bigger battery won’t solve whatever is draining your battery