I had some Test and Tuning flights with my quadcopter. There was no Battery low from my Taranis, but from my Pixhawk. Pixhawk entered RTL mode and tried to land about 10m away from the initial arming point which was very near to a brand new car. I had no chance to do anything, every stick input was ingnored. Furthermore the descending speed was set to 0.3m/s but it was much faster. Quad landed hard and flipped over with spinning rotors what caused damages.
Is there no chance to takte over when in Battery Failsafe/RTL?
The parameters are set right but the Quad descends like a stone. It was a windy day, could that cause such a problem?
Any ideas to make Battery Failsafe more safe or gently?
My Radio Telemetry (Flight Deck) at Taranis showed Battery Failsafe, RTL. I don’t think that it was signal lost, there was no alarm from Taranis and I was very near to my Quad. I’ll download the data flash log and post it. All what really worked was the emergency stop to stop the rotors spinning, but it was too late to rescue them
You said that your Quad descends like a stone。I think that was the main problem。When the battery voltage is too low，the propeller cannot Provide enough tension。
So maybe your battery warning voltage is too low。
13.2V on a 4S is seriously dead, except perhaps on really old or very low C-count batteries. Every battery is a bit different on the fall-off voltage. What I would recommend is start super conservative, say 14.4V or so, fly it until the FS kicks in. then recharge, and see how much of the mAh you put back. You can slowly lower the FS voltage until you are putting back 75% to 80% of the rated capacity.
Along this line - I would be really interested in seeing a somewhat smarter battery failsafe routine. We fly some long endurance quads using very low C-rated batteries, rated at 6C continuous and 10C burst. They have amazing energy density, but the voltage sags dramatically with current load, so if we use a battery failsafe voltage that is safe for hovering flight, it will be tripped really early during climbs. What I would like to see is a FS voltage level that is a function of the current load, such that lower voltages are OK if the load is high. Perhaps this would complicate things too much for the regular user. What I would probably do is set a failsafe voltage for hover (what we do now) and have an option to add a non-zero slope to account for voltage-sag under load. By default the slope would be zero, but advanced users could add a slope suitable for their system, at their own peril of course.
You can switch to using this sag corrected voltage for failsafes by setting BATT_FS_VOLTSRC to 1. Might be worth having a look at logs first to see how good a job its doing of correcting for sag first tho.