My battery was draining very fast even when UNUSED and in LOW POWER MODE. This was happening even in AIRPLANE mode (i.e. overnight, unused, in Airplane and Low Power Modes both enabled).
I got the phone services and the service guy told me the problem was the U2 chip, so I paid to have it repaired. But now it should have the new U2 chip, but it still drains the same (i.e. very quickly).
Can the battery be the problem of fast draining too?
The guy that repaired the U2 chip now tells me the battery is the problem, but now I doubt everything he says.