Last week I was doing some high speed tests of the Phantom 4 in Sport Mode.  I was more focused on flying the craft and trying to keep it as low as possible and fly a straight line, (harder to do than you think in Sport Mode.... man its fast....)  when I suddenly get a 30% battery warning on screen and immediately the P4 goes into a "RTH" flight plan.  

The problem with this is that I had launched the Phantom 4 some distance back on the lake and before I could process what was happening,, the Phantom 4 was already flying toward a forest of trees on a bluff high above the lake. Desperately, I looked at the DJI Go app for the setting to reset my "Home Point", but, could not find it quickly.  (I damn sure know where it is now under aircraft on the first page of settings)  Worried my "RTH Altitude" was not high enough, I made a decision to keep the Phantom 4 at a high altitude and try to race the boat back to the original launch site. (I still had 25% battery life)  Racing the boat back I kept the altitude high, however, at about 15% battery life it reached the RTH point and began to fight to descend.  I realized I could only keep it at altitude for a short time and had better find a landing area nearby on the shoreline near the RTH point.  So, thats what I did.  Gliding her over to a lake home with a nice yard I set the Phantom 4 down with less than 10% battery left.

My question is this.  Why did this happen? When I fly in Phantom Mode I get the 30% battery warning and maintain full control over the Phantom 4.  Did the same thing after this flight without any issues.  30% Battery warning in Phantom Mode,,, time to bring her in.  Complete control and no automatic "RTH" sequence.  Was this a "glitch" in the software, a battery issue, or, is the Phantom 4 supposed to automatically initiate a "RTH" sequence when flying agressively in "Sport Mode" and it reaches the 30% battery level?  I checked the manual and cannot find anything on this issue.  Smart Return Home was turned On in the DJI Go app.  

Hi!

Maybe it entered in ''Low battery RTH'' mode, but strange you should have 10 seconds to cancel it. Look also here http://forum.dji.com/thread-54671-1-1.html.

Where is your critical battery voltage set, in the Go app under battery info?

RedHotPoker

My critical battery is set at 10% before initiating "RTH" and it (the DJI Go app) didn't give me the option of canceling "RTH",, just gave a "low battery" warning and "RTH" error.  For comparison sake, I am typically in Phantom mode and the 30% battery warning is always my time to bring it in cue.  This is the first time I've been flying in Sport mode to my knowledge when the 30% battery warning comes on.  I was hauling ass... shaking it down over the water in Sport mode for pretty much the entire battery trying to get a feel for controlling the Phantom 4.  Between scanning my DJI Go app and the sky for where the P4 was in altitude from the water, I didn't realize I was as close to 30% battery power as I was when the warning came in and the "RTH" initiated.  Bottom line was I didn't want it to do that... Very tense 10 minutes went by waiting for it to clear a tree filled bluff and figure out whether I was going to be able to catch it in the boat, or, locate a area along the shoreline to land it.  I'm simply seeking to understand why it did that,, can I stop it in settings,, is it just a automatic thing when flying in Sport Mode??

I now have a Dead Phantom 4 because of this issue.  I suggest that anyone who is going to be flying for extended periods in "Sport" mode be concious of the possibility your Phantom 4 may develope a "battery error" and automatically RTH without your input or ability to control.  Not a problem if your home point is not changing, but, a huge problem if your flying from a moving boat.  Trying to reset your "Home Point" from the DJI Go app will not work.  However, switching from Sport to Phantom mode may help you regain control of your Phantom should this "unauthorized RTH" occur.  I believe it is caused by the increased load placed on the battery during intensive flying in "Sport" mode. The battery becomes too hot and senses failure telling the P4 to return home.  If you like to fly and film over the ocean, especially while flying in Sport mode, you need to be aware of this issue and prepared to handle it.

I had the same issue yesterday... i was filming off a yacht and to keep up i had it in sports mode the whole time... at 46% it automatically went into rturn to home and my phantom lights were all red. I had the scare of my life because the home point was the ocean at that point. After battling the drone i finnaly got it to land on the yacht but i was shaking for a hour after that. Everyone be very careful with sports mode. You can lose your drone.

There are multiple different automated RTH modes. Don't forget the "smart RTH" which estimates the amount of battery required to get home - the "H" in a circle on the battery bar. If the algorithm decides that you are so far away and need 30% or 46% or whatever to get home, it will do so. I believe this is "smart RTH" but I may get my terminology wrong. You can turn this off, unlike the Low Battery RTH (which you can just set to a certain percentage). Critical is 10% and just starts landing.

The three RTH modes are

1) Failsafe:- where it will RTH on loss of control signal for more than three seconds. RTH can be cancelled when signal resumes.
2) Smart RTH:- which is initiated when you push and hold the smart RTH button on the controller, or the RTH icon on screen. RTH can be cancelled if needed.
3) Low power RTH which monitors the power required to get home and triggers it when it gets to the 'H' mark. This takes no account of wind speed. RTH can be cancelled.

If battery hits critical point (default 10%) then it will land, although you can manoeuvre by pushing left stick up to hover then guide it to the safest spot to land.

I had the same problem and it caused a crash.  At 30%, and within 60 feet of home base, RTH was initiated and the drone descended into a bush that was just below it.  I was confused by the 30% RTH warning and didn't respond quickly enough to stop the drone from hitting the bush.  Anyway, this problem went away after a firmware/software update months ago.