6S Power System: The Numbers Behind 19.76 Minutes of Hover

A UAV's flight endurance isn't measured by mAh alone. Motor efficiency, propeller geometry, ESC response, voltage regulation, even the cooling solution, all of it factors into the equation. Let me break down piece by piece how we got to 19.76 minutes.

Battery choice: 22.2V 6S, 5000 mAh, 40C

RC Masterflight 6S 5000 mAh Li-Po. The 40C discharge rating delivers the high power needed at takeoff without voltage sag. Because it's 6S, the motors produce more torque. The battery weighs 720 g, roughly a third of our total weight. We also tried 4S, and hover time dropped to around 13 minutes; the extra half kilo of the 6S was worth it.

Two-tier power distribution

The Holybro PM07 power module distributes the high current from the battery to the four ESCs while supplying a clean 5.2V to the Pixhawk. That part's easy. The real problem is the Raspberry Pi 5's 5V/5A draw. The PM07's BEC output can't deliver that current. What happens when it can't? The Pixhawk reboots and the Pi drops out too. We hit this once in workshop testing and lost three hours of recording. We added the Pololu D24V50F5 as a separate line. High efficiency, low heat loss. Without this BEC, the Pi 5 wouldn't stay stable on any long mission.

MN4010 580 KV + 1055 carbon-filled

T-MOTOR MN4010 580KV. Optimized for a 6S battery and 10-inch propellers. Each motor puts out between 1.5 and 2 kg of thrust; our total flight weight is already 2.4 kg. So we're working with a comfortable margin. For propellers we went with 1055 carbon-filled. It doesn't flex like the plastic alternative. No thrust loss on sudden maneuvers. We used plastic 1045s in our first attempts; there was a noticeable response lag on fast maneuvers, and on one of them the tip even developed a small crack.

Hover time

19.76 min

Hover throttle

45.9%

Hover efficiency

68%

Max thrust duration

3.2 min

Two scenarios, two tables

At hover we draw 12.9 A total, 53.2 W per motor. In the max-thrust scenario it's 80.8 A total, at 74.7% efficiency. Knowing these two tables ahead of time is critical for us; we plan the order of missions on competition day around these numbers. If we try to finish a target-detection mission at full throttle, our hover budget burns through fast.

If the battery runs low

The PM07 module reports live voltage and current values to the Pixhawk. When the battery hits a critical level, failsafe kicks in (like RTL, autonomous return-to-launch). The buzzer gives an audible warning. It's set up so the vehicle can look after itself even if the pilot's attention slips. For us this is a soft safety belt; we hope we never need it, but we're ready if we do.