Energy Source Requirements Part 1 – Calculations
Calculating Required Battery Capacity
Desired flight time: 45Mins (Obtained from flight plan)
If continuous load is 9.5 amps, to be sustained for 45 minutes:
- 45 mins = 0.75 hour
- 9.5 amps for 0.75 hour = 7.125 Amp Hours
- LiPo batteries are usually nominated in mAh, therefore 7.125Ah = 7125mAh
The MINIMUM USABLE battery capacity required for this flight – IN IDEAL CONDITIONS – is 7,125mAh
Additional Considerations
There are a number of considerations we must take into account when determining the required battery capacity for a flight. The following are only intended as an example:-
- We can only use 80% of the nominal capacity if a battery
- We have to make a ‘Reserve Fuel’ safety allowance for the flight. For example, allow 20% additional capacity
- Flight conditions will never be ‘ideal’! We need to make an allowance for changing weather conditions, for example a headwind occurring during the flight. For example, allow 20% additional capacity
A More Realistic Battery Size
| Consideration | Capacity mAh |
| Minimum usable battery capacity – ideal conditions, no allowances | 7125.00 |
| Add additional capacity for reserve fuel (20% of 7125 = 1425)) | 8550.00 |
| Add additional capacity for weather (20% of 7125 = 1425 ) | 9975.00 |
| Determine the NOMINAL capacity to ensure required capacity is 80% of nominal capacity | 12468.75 |
Realistically, we require a battery with a nominal capacity of 12,468.75mAh (12.5Ah) to be able to conduct this mission in one flight, even though in ‘normal’ conditions we would only use7125mAh (7.125Ah).
All we have done is calculated how much power we need for the mission in ideal conditions, made an allowance for reserve fuel, an allowance for bad or changing weather, and ensured that we do not discharge the battery past it’s lower limits.
A Condor battery is only 5000 mAh! This aircraft would have to do multiple flights to complete this mission, as it is not possible to fit a bigger battery to the aircraft.
Double the battery capacity does NOT mean double the flight time, as the bigger battery is heavier then the smaller one!
Managing the Energy System
The battery and the complete energy system must be inspected and checked off in the pre and post flight inspections.
The aircraft configuration must be inspected and checked off in the pre and post flight inspections
Any hazards will be addressed in the risk assessment, and identified hazards monitored throughout the flight