Can you set the batteries discharge in the DJI Mini 4K?
Just got a Mini 4K, went out on a lovely sunny day … and found my charged battery flat 
I’ve searched the various responses here, but can’t find anything on the Mini 4K
Looked in the Fly app, but not spotting anything ?
No
What was the charge percentage as DJI batteries will self discharge to around 60% over a week or so to protect them
When did you charge it
Not sure what the percentage was … don’t actually know where to find it 
I’d charged the battery to the full four lights when I got back from previous flight, and left it in the drone.
I think it was only a week before I went out for another flight … and found the battery was completely flat, no lights at all
And this is the second time it’s happened, which has got me worried there’s something wrong
Luckily I’d bought another battery, and it was still fully changed (4 lights), so it wasn’t a wasted trip, unlike the first time 
How old is the battery ?
Is there any chance that the drone was still switched on when you stored it ??
A battery will go into hibernation mode if left for a long time but normally a week is nowhere near long enough for that to occur.
Have a look at AirData and upload your flight logs - you can see the battery data. 
Got bought the drone at Xmas, no idea how long it sat on the shelves in the Amazon warehouse