Charged up my iPad to 100% on Saturday. Tossed it in my bag (which I carry around with me), and haven’t used it until this morning. Pulled it out of the bag, and the battery is at 6%.
Is this normal?
I realize that cellular, Wi-Fi, and Bluetooth use energy - but is that level of drain to be expected?
No, I guess. My iPad Pro (WiFi only version) typically looses about 5 (most of the time) to 10% max of its charge when not in use over night.
What I have noticed on previous builds of the OS that it looses substantially more of its charge when the pencil is being attached to it. Apparently that has gotten better, though, with recent builds.
I would try the usual stuff: restart the iPad, check for battery draining app acitivity. Try to narrow it down step by step.
Agree I would say my battery is largely similar. I don’t have cellular but do leave the pencil attached.
age of the device? my 2017 10.5 iPad Pro start to drain a little faster that it used to, nowadays.
do the battery panel in settings says something?
About a year old.
I think I found the problem. Dropbox apparently decided that it needed to run all day (no idea why - there wasn’t anything that wasn’t synced), and that seems to have depleted my battery by over 80% in just over 48 hours.
I turned off all of its permissions, and battery life seems to be more reasonable. I drop 10% or so in standby mode every day, which is to be expected.
ouch that’s weird.
Glad you found the source of the problem 
Okay, I have a similar problem, but with an iPad Air 5 and M1 chip. It drains pretty quickly. Just to test it out, I monitored the battery levels and discovered:
I do attach the Pencil to the iPad in storage, but I would think when the Pencil gets to 100%, it would stop drawing power. I checked the Battery section of Settings to see what apps were drawing power. They were:
Why is OmniFocus drawing so much power? Is there a setting I need to change? This is not the vaunted battery life I heard so much about!
Leaving the Pencil aside…
It’s almost certainly syncing at regular intervals, so it’s using wi-fi / cellular - and those radios use power. That said, I would also suspect that there’s stuff running in the background that’s not reflected in those stats. I wonder if things like iCloud syncs (calendars, mail, etc.) get reported in those stats?
Also, was this iPad ever moved / jostled so that the screen might think it’s an appropriate time to power on? Did it receive any iMessage notifications / other alerts that would turn on the screen? I remember my girlfriend’s iPad sitting next to the bed and turning on CONSTANTLY throughout the day as she was texting back and forth with people on her iPhone. Every time that display comes on, it’s a battery drain.
Thanks for the thoughts. I have since done some online research and disabled update in the background for all apps. Looking into Notifications. I will run another test to track battery drain now. As to jostling, it pretty much stays in my bag unless I am using it.
Do you think the Pencil is contributing?
Don’t know, but some battery devices discharge on their own over time. And if that happened, I would suspect the iPad would immediately “top it off”. I would test with and without if I were in your shoes. 
The Pencil needs battery. But I have it attached to my iPad all the time. That should not be the issue.
A battery loss of about up to 10% per day when not in use can be normal depending on the background activity and the quality of your connection, though. And yes, the pencil needs power. But you should leave it connected. The power management works just fine, I think. There are a lot of fried pencils out there because its battery died after the pencil had been forgotten by its owner… 
One more question regarding your power usage data: What does the Activity graph look like? The dark blue colums indicate activity with the screen turned on, the light blue ones indicate activity with the screen turned off. Do those columns reach 60 minutes in many hours even with the screen turned off (that should not happen)? If so, something might be stuck.
So, what to do?
The easy one: Turn the iPad off and back on again.
Given your suspicion with regards to OmniFocus. You never know… Deleting OmniFocus, turning the iPad off and back on again, installing OmniFocus again, may be a good idea, too.
Try to find other processes that might be stuck and deal with them.
If everything fails: reset the iPad.
A reminder: it is normal that your iPad uses power, even when not in use. With your description in mind, I am not 100% sure, if you have an issue or if not…
Whenever mine has drained unexpectedly in my bag, I find the cover to be the culprit. If the final 1/4 flap on the cover isn’t completely “adhered,” the screen comes on every time anything moves in the slightest.
I recognize that may not be what’s happening here but I wanted to add another possible factor to the mix.