Here's a handy tip for these situations. As soon as the aircraft enters RTH due to low battery, you can cycle the Mode Switch between any two modes (Sport & Angle, or RTH & Angle) and this will cancel RTH and return full control to you. At this point you better be heading back with dispatch because it will attempt to RTH again in about 30 seconds. If you still aren't at the LZ then cycle it again to buy a little more time. At some point however you will run out of power and RTH will no longer engage, and the aircraft will initiate an emergency landing and come straight down wherever it is.
Another scenario that can sometimes trigger RTH is lowering the landing gear after the 2nd Low Voltage Warning. I have had mine instantly enter RTH just as I was trying to land. As soon as I hit the Landing Gear Switch, the H Plus jumped into RTH and tried to climb away, even though I was only 3' from touching down. The voltage drop caused by actuating the Landing Gear motors is enough to trigger RTH when the battery is already low. This was a shocking surprise that has motivated me to lower the landing gear immediately when I get the 1st battery warning.
Late to comment on June thread... haven't flown the H520 in sometime and was cycling the batteries... and purposely bringing them down while watching volts... and triggered a RTH in driveway hover and a bit under a tree limb. Used to other platforms, quickly tried a few things to override... and was "after the fact" looking for an Emerg RTH override.
To clarify the procedure of toggling the RTH/Ang, Ang/Man...
In your scenario, with landing gear and close to ground. This procedure still worked and you regained control, and able to keep it low and land?
When cycling SW a 2nd time to add more time. Can this be done prior to RTH activating again or do you need to be on the ready to toggle when RTH is triggered? In other words, can you cycle at 20sec... 10 sec prior to 30 sec RTH trigger to initiate a new 30 sec counter?
I'm curious but I'll wait till an empty field to re-test to the lower level for a emergency RTH trigger vs a driveway with trees overhanging. Oh, and 1st test did result in a controlled landing... holding stick down for extended time (est 3-5 sec) also appeared to allow regain of manual control.
Incidently, Yuneec H520 manual (or safety manual) indicates 20% perfered minimal and 10% as max lower limit. The H520 RTH wasn't emergency triggered until somewhere in the 8-7% range which coincides to their 10% allowed low range. The drop from 16-8% is rapid compared to higher percentages. These low percentages are still comfortably above indicated voltage above the minimal LiHV per cell volts. It's lower than "Normally" desired but good to know limits and behavior.
Humorously, some have stated how H's RTH is quick... in comparison to other platforms it does have a fast reacting RTH and not the accustomed "cancel" on screen to delay.