I love my Mavic Pro but the charger that it came with has me charging each of my three batteries one at a time . . though I know the charger holds up to four batteries.

I did find this charger that I have found to be great !!!   It charges all the batteries and the controller at ONE TIME.
https://www.amazon.com/exec/obidos/ASIN/B01N7FYBDL/mavichelp-20

Now I also found this device for cycling and drawing batteries down to 50% for storage . . . so far . . it has been doing a very good job as well . .
http://phantomangel.rocks/

Worth looking into these two devices . . good luck !!

That's been around since they first started to sell the Mavic . Also the Mavic batteries have a selectable self discharge setting for storage built in to the smart feature that is more than adequate .  That device may be useful if you need to discharge fast before going on a flight but then hovering for a few minutes would do the same .

Yessss you can through the DJI APP set your batteries to discharge after a preset number of days . . but it takes 3 dayyys for the batteries to discharge . . the Angel take 20 - 30 minutes . . or less . .  (per battery) .  . . and your done.  

Zorrr2@aol.com Posted at 2017-7-20 12:41
Yessss you can through the DJI APP set your batteries to discharge after a preset number of days . . but it takes 3 dayyys for the batteries to discharge . . the Angel take 20 - 30 minutes . . or less . .  (per battery) .  . . and your done.

As Ryd said, it might be useful for a

"Hurry honey we have to leave the country in 20 minutes or the IRS will take my drone too" kind of scenario.

So save your money and discharge with few minutes of hovering or...