FAQ
TL;DR: For long tethers, push higher DC (e.g., 160 V ≈ 11 A) then step down on the drone; “It is EXTREMELY important to be mindful of safety issues.” [Elektroda, Anonymous, post #21679577]
Why it matters: This FAQ helps builders design safe, efficient drone tethers without frying electronics or overloading cables.
Quick-Facts
- Hover power cited: approx. 60 A at 6S (≈24 V) for a large quad; size your supply and wiring accordingly. [Elektroda, Anonymous, post #21679572]
- Example loss: feeding ~36 V over 100 ft of 10 AWG at 60 A can drop to ~24 V with ~720 W heat in cable. [Elektroda, Anonymous, post #21679583]
- Tether mass matters: 200 ft of high‑strand 10 AWG silicone wire weighs about 7.8 lb. [Elektroda, Anonymous, post #21679581]
- Safety must-have: automatic power cutoff if the drone stops drawing current. [Elektroda, Anonymous, post #21679573]
- Accuracy tip: add two light sense leads (Kelvin connection) to regulate voltage at the drone. [Elektroda, Anonymous, post #21679579]
Quick Facts
- Hover power cited: approx. 60 A at 6S (≈24 V) for a large quad; size your supply and wiring accordingly. [Elektroda, Anonymous, post #21679572]
- Example loss: feeding ~36 V over 100 ft of 10 AWG at 60 A can drop to ~24 V with ~720 W heat in cable. [Elektroda, Anonymous, post #21679583]
- Tether mass matters: 200 ft of high‑strand 10 AWG silicone wire weighs about 7.8 lb. [Elektroda, Anonymous, post #21679581]
- Safety must-have: automatic power cutoff if the drone stops drawing current. [Elektroda, Anonymous, post #21679573]
- Accuracy tip: add two light sense leads (Kelvin connection) to regulate voltage at the drone. [Elektroda, Anonymous, post #21679579]
Is a 100 ft, 10 AWG DC tether from 24 V batteries a viable option?
Yes, but efficiency and safety hinge on current. Pushing low voltage at 60–70 A wastes power as heat and increases risk. Using higher DC on the tether and stepping down on the drone reduces current and cable loss. Include fast shutdown if the drone stops drawing power. “Higher tether voltage lowers current” and improves practical wire size. [Elektroda, Anonymous, post #21679575]
How should I think about the amps so I don’t fry gear?
Keep tether current low by raising tether voltage, then convert down onboard. For example, ~160 V on the tether means roughly 11 A for a ~1.7 kW load. Lower current eases connector, fuse, and thermal limits. Add a circuit to immediately cut power if load disappears to protect people and equipment. [Elektroda, Anonymous, post #21679577]
What DC‑DC hardware tools can help me pick a converter?
Size a step‑down converter for continuous hover power with surge headroom. Use design tools like TI’s WEBENCH to explore topologies and magnetics. Validate efficiency and thermal margins, then derate for altitude and cooling. Add input filtering and soft‑start to prevent inrush trips. [Elektroda, Anonymous, post #21679573]
Can I just over‑voltage at the ground to compensate for 100 ft drop?
You can, but regulate using remote sensing. A Kelvin connection lets the supply hold the drone voltage constant as current and cable temperature vary. Without sensing, voltage rises on throttle reductions and can stress avionics. Keep sense leads light and twisted with the main pair. [Elektroda, Anonymous, post #21679579]
How bad is the heat in 10 AWG at hover current?
Example math in the thread shows ~36 V feed to get ~24 V at 60 A over 100 ft, burning about 720 W in the cable. That heat raises resistance, increasing drop further. Plan for thermal limits and avoid bundling the tether near delicate payloads. [Elektroda, Anonymous, post #21679583]
What safety interlocks should a tethered system include?
Use a guarded, touch‑safe tether connector, upstream fusing, and a fast load‑loss shutdown. Add ground‑side E‑stop and a logic path that switches to battery before releasing the tether. “Make sure to add a circuit so that when the drone stops drawing current, the source shuts down.” [Elektroda, Anonymous, post #21679577]
Can the tether also charge onboard LiPos during flight?
It’s tricky because charge control fights propulsion load changes. You’d need higher tether voltage than pack open‑circuit and active regulation of charge current and temperature. Many builders keep packs at float or bypass charging and just power the bus, then switch cleanly to battery. [Elektroda, Anonymous, post #21679579]
What is a Kelvin connection, in simple terms?
A Kelvin connection uses two thin sense wires tied to the load end of the main pair. The supply measures true load voltage at the drone and adjusts output to cancel cable drop. It improves regulation without heavier conductors. [Elektroda, Anonymous, post #21679579]
Could an AC tether be simpler than all‑DC?
An AC path works but adds rectification and bulk capacitance onboard. Many inverters internally create ~160 V DC before generating AC. Tapping that DC and sending it up the tether can improve efficiency and reduce onboard parts versus AC‑then‑rectify. [Elektroda, Anonymous, post #21679577]
How heavy is a 10 AWG silicone tether for this length?
One builder cited about 7.8 lb for 200 ft of high‑strand 10 AWG silicone wire. For a large platform with >25 lb payload capacity, that mass may be acceptable, but still affects climb and handling. [Elektroda, Anonymous, post #21679581]
Will a 230 V AC → 12 V 60 A SMPS at the drone work on a 100 ft 16 AWG tether (S550 hexa)?
It can, but 12 V at 60 A demands thick conductors if you run low voltage. Reduce current by sending higher voltage and stepping down onboard, and implement fast shutdown and touch‑safe connectors. Watch weight; S550 margin is tight. [Elektroda, Anonymous, post #21679575]
Can I drop the tether mid‑mission and keep flying on batteries?
Yes. Switch to battery first, confirm stable bus voltage, then release. Design the power path so the DC‑DC module isolates or disconnects before drop. This avoids brownouts and connector arcing on release. [Elektroda, Anonymous, post #21679577]
What happens if my voltage‑drop calculator assumes one conductor?
You’ll overestimate or misread the drop. Use round‑trip length for DC tethers. One user corrected an earlier 200 ft assumption error and matched other calculators afterward. Always verify tool assumptions. [Elektroda, Anonymous, post #21679585]
Any off‑the‑shelf references or kits to study before building?
Look at commercial tether systems like Blue Vigil and DIY write‑ups for architecture ideas. Compare where converters sit, release methods, and safety features to refine your design goals. [Elektroda, Anonymous, post #21679580]
Quick 3‑step: how to set up a regulated, safe DC tether?
- Choose high tether DC (e.g., 75–160 V) to cut current; size connectors and fuses.
- Add onboard step‑down to 6S bus with remote sense and soft‑start.
- Implement load‑loss shutdown, E‑stop, and battery‑first switchover before release. [Elektroda, Anonymous, post #21679577]
