Help! iPhone irregular battery percentage after replacement

[3:16]

I replaced a battery on old iPhone 5 the percentage skips from 100% to 98 % in just 2 minutes and decreases fast until below 40 % and slow after that

Time since last full charge
Usage 5 hr 29 min
Standby 8 hr 11 m
Currently at 29%
What could be the problem?

 

[ab22]

Most likely a faulty battery.

 

[Trader05]

Full charge and completely drain a few times. See if it normalizes, if not its the battery.

 

[maerz001]

Wait, you get 5:29 h SOT with that? And have still 1/3 battery left. So we are speaking about 7h SOT with empty battery.

What do you expect? Thats more than good

 

[3:16]

Second full charge
Usage 5 hr 18 min
Stand by 40 hr 8 min
Currently at 19 %
Still battery % does the same remains still at certain % for 15 min and then quickly drop 2-3 % in 2 mins .

 

[Aneef]

don't be obsessed with the battery % if it is giving you decent SOT overall

 

[MacCheetah3]

You can do a calibration as @Trader05 alluded.

Battery Calibration

All newly-installed smart batteries should be calibrated as soon as possible. This helps your phone or laptop get an accurate reading on the battery’s state of charge.

www.ifixit.com

Nonetheless, as @maerz001 and @Aneef noted, the performance itself is not bad — in fact, it’s practically as expected — and don’t get concerned, obsess watching the details.