What purpose does this serve? Can I plug it in to my computer and update all 3 battery firmwares at once?

Also, if you don't have one, the recharge times are awesome compared to charging via the Spark.

micro usb, you can update the batteries individually via USB yep.  have to use DJi Assistant 2 application.   as for what purposes it serves.. few things it can do.. update with it, use it to transfer videos and photos to PC off micro sd card, charge the spark.      charge times via USB vary depending on amount of amperage mostly.  so if you have a 2.4amp 5V charger, it will probably take about an hour to hour and half to charge.. lower amperage the longer charging takes.   

i personally carry around a Anker usb battery bank, i think one of there 20000mAh banks with 3 ports.  i use that when im out in the field or if im traveling, top up one of my batteries in between. i have 3 batteries, and charging dock. charging dock is by far fastest way.. completely flat battery charge up in ~50 minutes.  3 flat batteries in about 80-90 minutes, but if you're traveling to different location being able to top up is nice.

I believe the OP is referring to the micro-USB port that's on the 3 bank battery charger itself.  He's asking if he could have up to 3 batteries in the charger, plug the charger into a computer using the micro-USB on the charger, and update all batteries at the same time.  I don't think that's possible, but haven't tried it.  I've also wondered what that USB port is actually used for.  Not quite sure.

If you are referring to the micro usb on the 3 batteries charging hub, I read it somewhere that it was for updating the firmware of the charging hub. I have tried if able to charge any battery on the hub thru' the micro usb port (with a power bank) with the charging port on the other end unplugged, but did not success.

Second the Anker product line up! From the cables and the charger to the power banks.
Every mobile device that I own along will wall chargers is Anker

Did you mean the charger hub? The micro USB port is for upgrading the charger hub.

ImHereToCrash Posted at 2017-8-8 15:19
micro usb, you can update the batteries individually via USB yep.  have to use DJi Assistant 2 application.   as for what purposes it serves.. few things it can do.. update with it, use it to transfer videos and photos to PC off micro sd card, charge the spark.      charge times via USB vary depending on amount of amperage mostly.  so if you have a 2.4amp 5V charger, it will probably take about an hour to hour and half to charge.. lower amperage the longer charging takes.   

i personally carry around a Anker usb battery bank, i think one of there 20000mAh banks with 3 ports.  i use that when im out in the field or if im traveling, top up one of my batteries in between. i have 3 batteries, and charging dock. charging dock is by far fastest way.. completely flat battery charge up in ~50 minutes.  3 flat batteries in about 80-90 minutes, but if you're traveling to different location being able to top up is nice.

Hi there, the micro USB port on the charger hub is recommended for upgrading the hub's firmware at the moment. It doesn't support battery's firmware upgrading.

DJI Thor Posted at 2017-8-8 20:38
Hi there, the micro USB port on the charger hub is recommended for upgrading the hub's firmware at the moment. It doesn't support battery's firmware upgrading.

Didn’t realize that’s what he or she meant

Thanks everyone for the replies, and yes I was referring to the micro USB slot on the hub. Sorry for the confusion. Good to know that the hub can be upgraded.

Jestered Posted at 2017-8-8 18:21
I believe the OP is referring to the micro-USB port that's on the 3 bank battery charger itself.  He's asking if he could have up to 3 batteries in the charger, plug the charger into a computer using the micro-USB on the charger, and update all batteries at the same time.  I don't think that's possible, but haven't tried it.  I've also wondered what that USB port is actually used for.  Not quite sure.

The two USB ports on the charger are for charging your RC and phone/tablet while charging your 3 batteries.  excellent idea, I use it all the time.

lucsvette Posted at 2017-8-9 04:21
The two USB ports on the charger are for charging your RC and phone/tablet while charging your 3 batteries.  excellent idea, I use it all the time.

oops miss-read .. yes the Micro USB is used for updates to the charge station.

OK but how to update it ? When connected to my iMac, the charger hub isn't recognize by DJI Assistant ??