battery drain while in standby

Hi Anfizz, is your 6 Plus on iOS 10.3? I'm facing the same problem on my iPhone 6S. I recently upgraded to iOS 10.3, and I realised that there's a massive battery drain problem. My phone drained from 80% to 0% overnight even though it was idle the whole time (it used to drop no more than 20% overnight). Most times, my phone will feel warm even though it's just sitting on the table doing nothing. I think iOS 10.3 might be the culprit.

I have checked my battery usage. It shows that the top app that drained more than 20% of my battery was Facebook, which was used for a total of... 25mins on screen and 0min on background. The next few apps follow the same pattern: very little (less than 30mins) on-screen and background activity, but accounting for 10-20% of battery usage each. And the activity periods are consistent with my actual usage. So something doesn't quite add up in the battery usage data. It's like there's a core OS background activity that's constantly running (indexing files? iCloud?) and sapping energy without registering as an "app" in the battery usage screen—except indexing files, etc. usually take at most a whole day, and I've had this problems for a few days now.

Go to Settings > Battery when you wake up in the morning and see which app is using the most battery.

As with my reply above, check your battery usage.

I had the same issue and the only fix, which took my battery life back to normal, was turning off iCloud.