Batteries for drones

The battery supplies energy for propulsion, electronics and payload and is usually the heaviest single part of a drone. Drone batteries are ready-made packs of several lithium cells with a high-current connector.

Form factor

For batteries the finished pack, for cells the format such as 18650, 21700 or pouch. Cylindrical cells are mechanically robust and standardised; pouch cells are lighter but sensitive to pressure.

C-rate

Continuous discharge current as a multiple of capacity: continuous current divided by capacity in Ah. For cells the value is usually calculated from continuous current and capacity; promotional peak C-ratings on labels are not continuous values.

Continuous current (A)

Current the battery or cell can deliver continuously without overheating. It must exceed the total current of all motors in hover, with a margin for manoeuvres.

Energy (Wh)

Stored energy in watt-hours, nominal voltage times capacity. It is the best figure for comparing flight time and determines the rules for shipping and air travel.

Weight (g)

Weight of the pack or cell. It feeds directly into energy density and is often the largest single item in a drone's take-off mass.

Capacity (mAh)

Charge in milliampere-hours. On its own it says little about flight time, because what matters is energy (Wh) relative to weight.

Nominal voltage (V)

Average voltage during discharge according to the manufacturer. Together with capacity it determines the energy (Wh).

Cell count (S)

Number of cells connected in series. It must suit the motor and the ESC and, together with the cell chemistry, determines the nominal voltage.

Connector

High-current connector on the pack, such as XT90, AS150U or QS8. It must match the drone's power circuit; anti-spark versions (marked S) dampen the spark when connecting.

Energy density (Wh/kg)

Energy per kilogram, decisive for long flight times. For Tattu and Herewin packs, the figure in the product name is higher than the recalculated value (probably the cell value); use the recalculated value for comparisons.

Cell chemistry

Chemical system of the cells, such as LiPo, LiPo HV, semi-solid LiPo, Li-ion or lithium metal. LiPo delivers high currents, while Li-ion and semi-solid cells store more energy per kilogram with lower current capability.

First, cell count and connector must match the motors and ESCs. Flight time depends on energy in Wh relative to weight, not on capacity in mAh alone. LiPo packs deliver high currents and suit FPV and heavy-lift drones; Li-ion and semi-solid packs store more energy per kilogram and suit long-range and survey drones. The pack's continuous current must cover the total hover current with a margin. The energy density in the product name is often a cell value; the recalculated pack value is what counts.

For transport, lithium batteries must meet the tests of the UN Manual of Tests and Criteria, Part III, subsection 38.3 (UN 38.3) (IATA passenger leaflet, revision 3, February 2019).

Air travel (IATA leaflet): spare batteries up to 100 Wh in carry-on baggage only; above 100 up to 160 Wh only with airline approval and at most two spares, also carry-on only; above 160 Wh only as dangerous goods cargo under the IATA Dangerous Goods Regulations. Many drone batteries in the data exceed 160 Wh.

Protect spare batteries against short circuits, for example in the original packaging or with taped terminals (IATA leaflet). Airlines may impose stricter rules; check the current version before travelling.

For Tattu and Herewin packs the Wh/kg in the name is higher than the recalculated value; rankings use the recalculated value.

How do I calculate a battery's energy?

Nominal voltage in volts times capacity in ampere-hours gives watt-hours.

Can I take drone batteries on a plane?

It depends on the energy. According to the IATA leaflet, spare batteries up to 100 Wh may go in carry-on baggage, above 100 up to 160 Wh only with airline approval, and larger ones only as dangerous goods cargo.

What is a semi-solid battery?

A lithium battery with a partly solid electrolyte. It usually stores more energy per kilogram than LiPo but delivers less peak current.

What does the C-rate mean?

Continuous current as a multiple of capacity. Promotional peak C-ratings on labels are not continuous values.