We all know how Apple supposedly crank down the speed of their older phones to help compensate for reducing battery capacity with age, but I have a different problem. I had a Moto G5 which started to show low battery life (barely a day) with my standard useage. No problem, this phone has a removable battery so bought new (genuine) battery only to find it did not cure the problem.
Conclusion, maybe something failing in the hardware causing increase battery drain. Bought new phone, same model. Now, after a year or two I'm getting exactly the same symptoms on the new phone. Just put the brand new battery in, with the old one back on charge in the old body.
Seems like an odd problem. Any ideas?