Drone and robot batteries: weight against runtime
Drones and robots share a battery problem: the battery is both the fuel and part of the load. Every gram of battery must be carried, and every watt-hour of energy must be worth its weight. This article explains that trade-off and how to size within it.
Layered pack cross-section — the site's recurring diagram motif. It is a schematic, not a photograph of a product, factory or customer project, and it is not presented as a photograph of this company's factory.
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The weight-energy trade, stated plainly
A battery's energy grows with its size and weight, but the device that carries it grows heavier too, and a heavier device needs more power to move. For a drone, that means more energy spent on lift; for a robot, more energy spent on locomotion. Beyond a point, adding battery adds almost as much consumption as it adds energy, and the runtime gain flattens. A buyer should therefore size from the device's measured or specified power draw, not from the largest pack that fits, because the largest pack is rarely the longest-running one once its weight is counted.
Energy density is the figure that describes this trade: watt-hours per kilogram, or per litre, for the pack as a whole, including its protection, wiring and housing. A pouch Li-polymer pack generally offers high energy density for its weight, which is why drones favour it; a cylindrical Li-ion pack offers a different balance of density, robustness and cost, which suits robots with more space. Compare packs on whole-pack energy density, not on cell figures alone, because a pack's housing and board dilute the cell's density, and different packs dilute it by different amounts.
Peak current: the hidden constraint
Average power sizes the energy; peak power sizes the current rating. A drone taking off, climbing or manoeuvring draws bursts far above cruise draw; a robot accelerating, lifting or climbing draws surges above its average. The pack's maximum continuous discharge current, listed per model, must cover the worst burst with margin, not just the average. A pack that covers the average but not the peak will sag, cut out or overheat under load, behaving as if its battery were empty when it is not.
The detail packs on this site illustrate the range of current ratings a buyer will meet: 50A on the 12V 100Ah solar pack, 100A on the 12V 200Ah pack, 30A on the 48V e-bike pack, 10A on the compact 12.8V battery, 5A on the garden-tool pack and 3A on the single 18650 cell. Those are per-model figures, and a drone or robot buyer should compare the device's peak draw against the exact pack's figure, not against a family average or a neighbouring model's rating.
Runtime sizing, done honestly
Runtime follows from usable energy divided by average power draw, with a reserve for landing or for task completion. A drone's average flight draw is higher than its bench draw, because wind, manoeuvre and payload all add load; a robot's average draw depends on how much it moves against how much it waits. A buyer who sizes from a bench test will be disappointed in the field. The honest method is to size from the device's measured or specified average draw in real use, allow a reserve — for a drone, enough to land safely; for a robot, enough to finish the task or return — and then check that the resulting pack fits the weight budget. If it does not, the device, the payload or the mission must change, because no battery chemistry repeals the trade-off.
Space is the final check, and it is often the binding one. A drone's battery bay and a robot's body are designed around function, so the battery cavity is frequently irregular. A pack that is electrically right but mechanically too large fails just as surely as a pack with the wrong voltage. Send the cavity dimensions with the inquiry, and where no listed pack fits, the custom route designs a pack around the cavity rather than forcing a catalogue pack into it.
What to send for a drone or robot inquiry
State the device type, its all-up weight or mass, its motors' peak and average draw, its required runtime or flight time, its battery bay dimensions and its connector. Those facts determine the pack; a request for a drone or robot battery without them is a request for a guess, and this site does not present guesses as recommendations. Add the documents needed, noting that certificates are available upon request, and whether the pack must match an existing outline or can be designed fresh.
Testing runtime before you commit
Runtime claims should be tested before a pack is committed to a fleet, because a bench figure and a field figure differ, and the difference is where disappointments live. A test plan need not be elaborate: define the mission, fly or run it, and measure. For a drone, the mission is a realistic flight — take-off, cruise, manoeuvre, hover and landing, with the intended payload and in representative wind. For a robot, the mission is a realistic task cycle — movement, sensing, waiting and manipulation, in the proportions the job actually uses. A pack that passes a realistic mission will pass the job; a pack that passes only a bench discharge may not.
Measure honestly. Record the pack's starting charge, the mission duration, the energy consumed where the device reports it, and the ending voltage or remaining charge, and repeat the mission at least twice to check consistency. A single good run proves little, because wind, temperature and payload vary; two or three consistent runs prove the pack's behaviour for that mission. Temperature deserves a specific note: cold weather reduces usable capacity and increases internal resistance, so a pack tested in summer will disappoint in winter, and a fleet that flies or works year-round should be tested in the cold as well as the warm.
Compare packs on the same mission, not on headline figures. Two packs with the same capacity can differ in runtime if their discharge ratings, weights or voltage behaviours differ, and the mission test reveals those differences directly. A heavier pack that stores more energy may still lose on runtime if its weight raises the device's power draw, and only a mission test shows that trade. A lighter pack with a lower capacity may win on a short mission and lose on a long one, and the mission test shows where the crossover lies.
Finally, test the charger and the turnaround as part of the mission. A drone or robot fleet's productivity depends on how fast packs recharge and swap, not just on how long they run, and a pack that runs long but charges slowly may deliver fewer missions per day than a shorter-running pack that charges fast. Measure the full cycle — mission, swap, charge, next mission — and size the fleet's pack stock from that cycle, not from runtime alone. A fleet planned on the full cycle will meet its schedule; a fleet planned on runtime alone will discover its bottleneck on the first busy day.
What to send us now
Send one message with your device type, the space the pack must fit, the voltage and capacity you need, the peak current if it matters, and the model description if a page on this site already matches. Add the documents you need — certificates are available upon request — and whether you need a listed model or a custom design. Use the contact page or write to [email protected], or call +86-755-25629920. A specific message like that is what turns a range of hundreds of models into a short, answerable question.