Drone Battery Requirements

What is different about the operation of a drone and hence what does this mean in terms of battery requirements? For a drone we are meaning an unmanned drone as used for photography or surveillance.

The fundamental parameters are:

  • Peak takeoff power
  • Flight time
  • Range
  • Peak power required to safely land
  • Reserve energy required for aborted landing
  • Accurate SOx parameters
  • Lifetime
Google delivery drone by Wing
America’s First Commercial Drone Delivery Service, Google Arts & Culture [3]

This post has been built based on the support and sponsorship from: Eatron TechnologiesAbout:EnergyAVANT Future MobilityQuarto Technical Services and TAE Power Solutions.

Just adding more battery energy doesn’t mean an ever increasing flight time / range [1].

drone flight time versus battery energy

Mass impacts power required for takeoff, level flight and maneuvering. More battery mass => larger motors => larger speed controllers.

Hence the key metrics are:

Thus determining Flight Time and Takeoff Power. Overall giving a total range.

This immediately brings a balance between power and energy as the fundamental cell physics is a trade between energy and power.

In simple terms the energy cell has thicker layers of active material, thinner current collectors and less of them.

This means the energy cell will have a higher electrical internal resistance meaning it will generate more heat based on I2R heating.

The energy cell will have poorer thermal conductivity in-plane and through-plane. Thus, it will need a higher temperature gradient to reject the heat.

Operating SOC Window

The battery operating window for normally operation and emergency use needs to be carefully determined to enable a safety reserve. This window will be determined based on power and energy requirements to operate safely [4].

Modelling of the vehicle and operational window is the best way to determine the energy and power envelope [5].

Accurate SOx Parameters

In order that the drone can accurately determine the flight time and safely land at it’s destination it needs to know the state of the battery pack. The battery state parameters (SOx) are:

  • State of Charge
  • State of Health
  • State of Power

These parameters are all estimated by the battery management system (BMS) from measured data and trained models.

This also relies on the quality of the battery pack design. All of the cells need to charge and discharge equally, the thermal management needs to deliver a uniform temperature within the cells and from cell to cell.

Lifetime

A critical parameter for any battery is the lifetime. Lifetime is normally described in terms of calendar and cycle life. As the cell ages the capacity descreases and the resistance increases. Thus impacting flight time and the power capability.

DCIR and ohms law

Power = volts x current, current is normally limited to a maximum continuous value by the power electronics, cables and connectors. As the battery resistance increases the voltage drops further for a given current. Hence, to deliver the same power the current has to increase.

From this you can see that there will be a maximum battery resistance at which the drone will be able to operate.

DJI have a recommended 200 cycle limit for their battery packs [2].

References

  1. A Guide to Lithium Polymer Batteries for Drones, Tyto Robotics
  2. Battery Maintenance Guide for DJI Enterprise Drones, DJI
  3. America’s First Commercial Drone Delivery Service, Google Arts & Culture
  4. Unmanned Aircraft System Operations in UK Airspace – Guidance, CAA
  5. Aiello, G.; Inguanta, R.; D’Angelo, G.; Venticinque, M. Energy Consumption Model of Aerial Urban Logistic InfrastructuresEnergies 202114, 5998.

Leave a Comment