Power 25 Brushless Outrunner Instructions
Thank you for purchasing the E-flite Power 25 Brushless Outrunner motor. The Power 25 is designed to deliver clean and quiet power for 25-size
sport and scale airplanes weighing 3- to 5.5-pounds (1.4-2.5 Kg), 15-size 3D airplanes up to 3.5-pounds (1.6 Kg), or models requiring up to 550
watts of power. It’s an especially good match for scale 25-size airplanes.
Power 25 Brushless Outrunner Features:
• Equivalent to a 25-size glow engine for 3- to 5.5-pound (1.4- 2.5-Kg) airplanes
• Ideal for 15-size 3D airplanes up to 3.5-pounds (1.6-Kg)
• Ideal for models requiring up to 550 watts of power
• High torque, direct drive alternative to inrunner brushless motors
• Includes mount, prop adapters, and mounting hardware
• Quiet, lightweight operation
• External rotor design, 5mm shaft can easily be reversed for alternative motor installations
• High quality construction with ball bearings and hardened steel shaft
• Slotted 12-pole outrunner design
Power 25 Specifications
Diameter: 35mm (1.4 in)
Case Length: 54mm (2.1 in)
Weight: 190g (6.7 oz)
Shaft Diameter: 5mm (.2 in)
EFLM4025A
Kv: 870 (rpms per volt)
Io: 2.4A @ 10V (no load current)
Ri: .03 ohms (resistance)
Continuous Current: 32A*
Max Burst Current: 44A*
Watts: up to 550
Cells: 10-14 Ni-MH/Ni-Cd or 3-4S Li-Po
Recommended Props: 11x8 to 14x7
Brushless ESC: 40-45 Amp
* Maximum Operating Temperature: 220 degrees Fahrenheit
* Adequate cooling is required for all motor operation at maximum current levels.
* Maximum Burst Current duration is 30 seconds. Adequate time between maximum burst intervals is required for proper cooling and to avoid
overheating the motor.
* Maximum Burst Current rating is for 3D and limited motor run flights. Lack of proper throttle management may result in damage to the motor since
excessive use of burst current may overheat the motor.
Determine a Model’s Power Requirements:
1. Power can be measured in watts. For example: 1 horsepower = 746 watts
2. You determine watts by multiplying ‘volts’ times ‘amps’. Example: 10 volts x 10 amps = 100 watts
Volts x Amps = Watts
3. You can determine the power requirements of a model based on the ‘Input Watts Per Pound’ guidelines found below, using the flying weight of
the model (with battery):
• 50-70 watts per pound; Minimum level of power for decent performance, good for lightly loaded slow flyer and park flyer models
• 70-90 watts per pound; Trainer and slow flying scale models
• 90-110 watts per pound; Sport aerobatic and fast flying scale models
• 110-130 watts per pound; Advanced aerobatic and high-speed models
• 130-150 watts per pound; Lightly loaded 3D models and ducted fans
• 150-200+ watts per pound; Unlimited performance 3D models
NOTE: These guidelines were developed based upon the typical parameters of our E-flite motors. These guidelines may vary depending on other
motors and factors such as efficiency and prop size.
4. Determine the Input Watts per Pound required to achieve the desired level of performance:
Model: Scale 25-size ARF
Estimated Flying Weight w/Battery: 4 lbs
Desired Level of Performance: 70-90 watts per pound; Slow flying scale models
4.0 lbs x 70 watts per pound = 280 Input Watts of total power (minimum)
required to achieve the desired performance
5. Determine a suitable motor based on the model’s power requirements. The tips below can help you determine the power capabilities of a
particular motor and if it can provide the power your model requires for the desired level of performance:
• Most manufacturers will rate their motors for a range of cell counts, continuous current and maximum burst current.
• In most cases, the input power a motor is capable of handling can be determined by:
Average Voltage (depending on cell count) x Continuous Current = Continuous Input Watts
Average Voltage (depending on cell count) x Max Burst Current = Burst Input Watts
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