iPad adjusts brightness when it reaches full charge I recently put some iPads up around my office building as conferance room markers.  They're plugged in to USB outlets, and seem to be charging fine.  The screen stays on all the time, running Eventboard Pro.  

The problem is that in order to keep the battery from running down while plugged in, I adjust the screen brightness to around 75%.  But, whenever I come back to them later in the day, they brightness slider is back at 100%, causing the battery to drain.  Usually when I arrive in the morning I have to go around the building, manually turning on and lowering the brightness.  Autobrightness is turned off on all of them, and I'm pretty sure the outlets are fine, as it charges during the day with lowered brightness.

Is this auto-adjustment in brightness a known issue, or is there some hidden setting I'm missing?  The iPads are all updated to the most recent iOS as of April 1st, and it's a mix of iPad 2s and New iPads.

If I need to provide any other information, I'll be happy to do so.  Thanks for looking!
First, to directly answer your question, no, there is no hidden setting that is causing your brightness to increase without your input. The only to settings related to brightness as of iOS 6 is Auto-Brightness (which you have disabled), and the brightness slider. As far as I'm concerned, it must be a bug.

So it looks like you have a few sub-par options. 


USB outlets are really nice, but in the long run, they may not be a good solution for you. Even though the original power supply bricks that come with iPad, stick out of the wall, and can be in the way, they do supply enough energy to keep the iPad charged, and even charging despite high battery consumption at the same time. 
Bring one home to see if you can replicate the problem with original charging apparatus. If this is the case, you may consider scheduling an appointment, and taking it to one of Apple's Genius bars. Perhaps they are aware of a bug or will have an idea as to what is going on. 


One side note, I have seen extremely strange behavior when an iOS device is given "bad" power. If the USB outlets are questionable quality, there is a far-out chance this is causing it. That said, most of the behavior I have seen from "bad" power comes from touch screen activity, and this would mean that each device was used in between times that you checked on it.

Either way, my recommendation would be to use the included chargers with your iPad if that is at all possible.