It depends on three factors:-
1. Battery capacity:- Battery of Redmi4 is of 4100 mAh and that of Redmi4a is of 3080mAh. So, the batery of Redmi4 is 1.3 times that of Redmi4a . Or, for example, if battery of Redmi4a lasts for three days, then the battery of Redmi4 will last for four days approximately, provided the usage of phone is same.
2. Battery life- Every battery has a charging cycle, like 1000 or 2000 times. So, with period of time and with every charging of a battery, the battery keeps on getting weaker. Maybe the battery of Redmi4a is older than the battery of Redmi4. Or, the battery of Redmi4a has been charged more times than the battery of Redmi4. So, the battery of Redmi4a might have become weak.
3. Usage- the more one uses his/her phone, the more it consumes the battery. Maybe, the usage of Redmi4a is more than Redmi4, so it might be consuming more battery power than Redmi4.
I use phone for various purposes on a daily basis, so my phone battery does not long enough despite of it being a 3-month old phone. So, i need to charge my phone on almost daily basis.
Hope it helps!
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