Wanted to share an issue I had the other day concerning the latest firmware update causing my Phantom 4 battery to become "invalid."...And my less than satisfactory customer service experience.
Went to fly my Phantom 4 over the weekend.  Mind you,everything has been working great with my equipment since I purchased the aircraft. Have several DJI aircraft and never had any issues with them, until the other day. Upon powering on my Phantom 4, DJI Go informed me of a new firmware update.  Selected "update" and it went on to do the firmware download and update, like I've always done with all the updates in the past.  After it finished, I restarted my Phantom 4, and as soon as it finished warming up, I got a message "Cannot take off, battery signal error."  Further into the battery menu, it says "invalid battery." I rolled back firmware several times and restored factory defults in the assistant, but nothing would fix the problem.
I contacted DJI about my issue.  They replied the next day asking for all my information, where purchased, product description, what the issue was and asked for pictures or video of the error messages.  I sent them the information they asked for.  I got a reply back today and was told that because my battery was out of warranty, they can't help me and I have to buy a new battery.  I really do not think its right that I should have to buy a new battery, when the problem was caused by the firmware update.  Everything was perfectly fine with the battery until it made me update.  I sent them a reply to their email expressing my dissatisfaction with how they won't take care of this issue, considering this was a problem caused by the firmware update.  They basically told me "sorry but its company protocol they can't do anything about it".  I've spent thousands of dollars with DJI (Phantom 2, Inspire 1, Phantom 4, and a Mavic...And was planning on buying the Inspire 2)  I am not a very satisfied customer!  Thought I'd share this with everyone, and see if this has happened to anyone else.

Really sorry for the inconvenience caused, we'd love to help you escalate the case soon.
Would you please provide us your case number and the battery SN? thank you!

DJI Natalia Posted at 2016-12-15 01:34
Really sorry for the inconvenience caused, we'd love to help you escalate the case soon.
Would you please provide us your case number and the battery SN? thank you!

Hi Natalia,

The battery serial number is 082AD2R03100C8

The help ticket number is 360894

Paul

flightjunkie624 Posted at 2016-12-16 02:20
Hi Natalia,

The battery serial number is 082AD2R03100C8

Thank you for the information.
May I know have you tried to downgrade the firmware through the Assistant 2 on your PC then check again?

I tried downgrading and also re-upgrading the firmwares. I also tried a factory reset. None of this fixed the battery.