Samsung j7

[Zameer27]

Battery is downing too fastt.. some time it may switch off when it become 30%Battery. 

[Anonymous]

same matter

[Ashwin98]

Try recalibrating your battery...
First clear cache partition from recovery mode
Then head to dialer *#0228# and select quick start. A warning message will appear, then select Okay and your fuel gauge will be reset.
Drain your battery to 0% and charge completely in switched off condition to 100%( It takes nearly 3 hrs)
I think this may help you...

[Samsung_Support3]

Dear Samsung Member,

Greetings from Samsung Customer Support!

Please visit this mentioned link to resolve your device battery drain issue: 

https://www.samsung.com/in/support/mobile-devices/samsung-mobile-battery-drain-issue/

For further assistance, register your concern in Samsung Members Application (Open Samsung Members Application > Get help > Send Feedback > Error report/Ask questions).

Thank you for writing to Samsung.

Warm Regards,
Samsung Customer Support