Selecting Electric Power Setups John Hoddinott, 21 May 2015

Components of the Setup ●Brushless Motor ●Electronic Speed Controller (ESC) ●Battery (Usually LiPo, but could be NiCad, NiMH, LiFe, etc) ●Propeller ●Connectors/Wiring

Why Brushless Motors? Brushless motors offer several advantages over brushed DC motors (according to Wikipedia!): ●high torque to weight ratio ●increased efficiency ●increased reliability ●reduced noise ●longer lifetime (no brush and commutator wear) ●reduction of electromagnetic interference

Size Matters!

Why is the Setup Important? ●Performance ●Efficiency (longer flight times/smaller & cheaper batteries) ●Safety

Getting it Wrong!

Some Definitions V - Voltage (Potential Difference) in Volts (V) I - Current in Amperes (A) P - Power in Watts (W) P = V x I (Ohm’s Law) RPM - Rotations per Minute kV - RPM per Volt mAh - milliamp hours (a measure of battery capacity) C rating - A measure of the discharge (or charge) rate of a battery as a multiple of its capacity

My Process 1.Estimate Power Needed 2.Decide on Maximum Flying Speed 3.Calculate Ideal Thrust 4.Calculate (or Measure) Maximum Propeller Diameter 5.Select Preferred Battery Voltage 6.Find a Setup 7.Test/Check the Setup

Step 1 - Estimate Power Model Type or Flying StyleExample Power Range in Watts (W) per pound (lbs) Trainer/Powered Glider/Scale Light Aircraft/Vintage Mentor, Habicht, Cub, Junior Sports/Scale Warbird/Bi-PlaneWot4, Mustang, Gemini Aerobatic/Pattern Ship/Warm Liner Yak 54, Angel, Blaze D AerobaticShock Flyer, AddictionX Hot Liner/Pylon RacerSpeedy, Nemesis

Step 2 - Flying Speed Model Type or Flying StyleTarget Flying Speed (mph) Trainer/Powered Glider/Scale Light Aircraft/Vintage Sports/Scale Warbird/Bi-Plane Aerobatic/Pattern Ship/Warm Liner D Aerobatic Hot Liner/Pylon Racer

Step 3 - Thrust How much thrust do we need to fly? Less than you might think!

Step 3 - Thrust to Weight Examples Aircraft (full size)Thrust to Weight Cessna Concorde0.373 BAE Hawk0.65 Harrier1.1 Typhoon1.07 Space Shuttle1.5

Step 4 - Propeller Diameter Bigger is better (usually)

Step 5 - Battery Voltage Use Ohm’s Law to calculate the battery voltage that provides the desired power with sensible current level. P = V x I Therefore V = P / I But what is a sensible current level?

Step 5 – Battery Current Capacity Battery current capacity is calculated by multiplying the pack capacity (in mAh) by the C rating. Example – a 2200 mAh pack rated to 25C can produce: 2200 x 25 = 55,000mA = 55A

Step 5 - Connector Current Capacity Deans - 100A XT Series - 30/60/90A EC3 - 60A EC A JST - 3A

Step 6 - The Setup Using the data we now have (power, flying speed, thrust, propeller diameter and voltage) we now have all the information to find a setup that works. But how? Get on the internet and search!

Step 6 - Typical Motor Specs Nominal Voltage (V) LiPo Cell Count Typical Motor kV Typical Stator Diameter (mm) Typical Motor Weight (g) Typical Prop Diameter (inches) – 2210 – 100Under – 3025 – 2006 – – – – – – – – – – – – –

Step 6 - Some Good Web Sources AXI Motors Hacker Scorpion Power Systems Eflite Emax

Example Setup for Seagull E-Pioneer

Example Setup for the Yak e

Step 7 - Testing Physical Testing Using a Watt Meter

Step 7 - Testing Testing using ESC Data Logging Capabilities

Step 7 - Testing Testing using a Calculator Tool (e.g. eCalc)

Summary 1.Estimate Power Needed 2.Decide on Maximum Flying Speed 3.Calculate Ideal Thrust 4.Calculate (or Measure) Maximum Propeller Diameter 5.Select Preferred Battery Voltage 6.Find a Setup 7.Test/Check the Setup 8.Charge Batteries 9.Go Flying!

Thank you That's it, I'm off ohm... That’s it,I think you’ve heard Amp’le from me. I’m off Ohm...