Dock 4 swaps batteries in 25 seconds. Now there are three of them to look after.

DJI launched the Dock 4 and the Matrice 5TD today. Every drone site has already covered the headline, so we will keep it short: the aircraft lands, the dock lifts out the depleted battery, drops in a charged one, and the aircraft is ready to go again. DJI quotes under 25 seconds for the swap and under 45 seconds from landing to takeoff. The Dock 3 charges its one battery from 15% to 95% in about 27 minutes, so on a busy site the difference is not incremental. It is the difference between a dock that flies in shifts and a dock that flies continuously.

The rest of the launch is strong too. The Matrice 5TD flies for up to 59 minutes, carries a 1280×1024 thermal camera, a 3,000 m laser rangefinder, integrated LiDAR and radar, and an independent flight termination system. The dock itself is rated to −40°C, up from −30°C on the Dock 3. With the AP1 parachute fitted, heliguy reports the aircraft meets C5/C6 in the EU and UK5/UK6 here. That matters for BVLOS applications here, and we will come back to it in a separate post once the paperwork is public.

But the battery swap is the part that changes how a dock has to be run, so that is what this post is about.

One aircraft, three batteries

A Dock 3 looks after one battery. It lives in the aircraft, it charges in the aircraft, and when it has done its 400 cycles you replace it. Everything you need to know about it is attached to one serial number.

A Dock 4 has four compartments and holds up to three batteries at once, because the swap needs an empty slot. The aircraft takes whichever pack is charged, flies it, and returns it to a bay. Over a month, the three packs rotate through every mission the site flies. Each one picks up its own cycle count, its own temperature history and its own wear. None of that is attached to the aircraft any more. It is attached to the battery, and the battery moves.

That has three consequences for an operator.

• Cycle counting is now per pack, not per dock. DJI rates the Matrice 5TD battery at 400 cycles. Three packs sharing the work will reach that figure at different times, and the one that has been doing the heavy lifting will get there first. If you track cycles per dock, you will replace all three at once, or you will miss the one that is tired.
• Which battery flew which mission becomes a question. Today the answer is always “the one in the aircraft”. With a Dock 4 it is one of three, and when an evidence pack or an incident review asks about the battery on a particular flight, you need the record to say which pack it was and what state it was in.
• Storage conditions count against the warranty. DJI’s spec sheet is specific on this: time spent above 35°C counts toward the battery’s cycle life, and keeping cumulative time above 35°C under 100 days in any 12 months is what preserves the 400-cycle rating. With one battery in a Dock 3 that was a footnote. With three batteries sitting in a cabinet for most of the year, it is a maintenance obligation.

A warmer cabinet, with more in it

The Dock 4 draws up to 2,000 W, against 800 W for the Dock 3. It charges two packs in parallel, and it allows charging up to 60°C where the Dock 3 stopped at 45°C. All of that heat is managed by a compressor air conditioner inside a sealed IP56 cabinet.

In July we wrote about a Dock 3 whose climate system failed silently overnight with a battery inside, while its console reported Normal for twelve hours. On a Dock 4 the same fault has three batteries to cook instead of one, more heat to get rid of, and the same console. The failure mode has not changed. The cost of missing it has roughly tripled.

DJI has also added a sensible backup: during a power cut, the stored batteries can run the dock for about 4.5 hours each, and the dock can keep swapping if at least two packs are loaded. But the spec sheet is clear that charging, air conditioning and the wind gauge heater all stop during an outage. A dock that keeps flying on battery power while its cabinet warms up is a dock you want to know about quickly.

A second box to watch

The Dock 3 had its RTK base station, Ethernet and 4G built in. The Dock 4 moves all three into a separate O4 Ground Station, which also carries the video link. It is a good piece of engineering, with its own 45-minute backup battery and an IP67 rating, but it is a second device with a second power feed, a second temperature range and a second way for the site to go offline. If the ground station drops, the dock has no RTK, no network and no video. Readiness checks that only look at the dock will say it is fine.

What does not change

The Matrice 4D and 4TD do not fly from a Dock 4, and the Matrice 5TD does not fly from a Dock 3 today. Heliguy reports that 5TD support on the Dock 3 may arrive in a future firmware update, but DJI has not confirmed it. So nobody’s existing fleet is upgraded by this announcement. For the next couple of years most UK operators will run Dock 3 sites, Dock 4 sites, or both, and the maintenance evidence an authority asks for will need to cover both the same way.

Dock 4 reports through FlightHub 2 and the DJI Cloud API, which are the same channels Dock Pulse reads today. We will validate the Dock 4 telemetry, and the per-pack battery data in particular, as the first units land with UK customers. If you have one on order and want to be part of that, tell us.

The short version: Dock 4 turns a dock from a thing that charges one battery into a thing that manages a small fleet of them. That is exactly the kind of job that should not depend on someone remembering to look. It is what we build.