September 28

Electric Planes RC Motor Installation

This section will attempt to explain how an electric planes rc motor installation is accomplished. This will involve installing the motor, ESC (Electronic Speed Controller) and Lipo battery.

Schematic: Motor/ESC/Lipo installation using internal BEC circuit
Schematic: Motor/ESC/Lipo installation using internal BEC circuit

The above diagram shows the arrangement of components for your Outrunner powertrain when using an Electronic Speed Controller (ESC) with its own built in Battery Elimination Circuit (BEC). The alternative arrangement uses an ESC without internal BEC. Instead you will use an External Universal Battery Elimination Circuit (UBEC) as shown in the diagram below.

Motor/ESC/Lipo circuit with UBEC receiver supply.
Motor/ESC/Lipo circuit with UBEC receiver supply.

In this arrangement the output from the “Green” UBEC (Yes, I know it says BEC in the diagram!) goes to the battery input socket on the receiver to supply the necessary 4.8 – 5.0 volts required to energise it. All ESCs provide a Black, Red and White or Orange three wire arrangement to the receiver. As you now have a +5.0V supply from the external BEC circuit, you do not need the Red (+) wire from the ESC.  Remove this wire from the small black plug and tape it back to to the black and white/orange leads. Use a sharp modelling pin or the point of a modelling knife to lift the plastic retaining lug so that you can slide the gold plated sleeve from its location. If in doubt, get someone familiar with electric flight to show you how to do this.

Most ARTF trainer kits come with the necessary motor mounts for either glow or electric installations. Follow the manufacturers instructions carefully to ensure the correct installation of your motor. If possible, get help with this as a secure motor installation is essential for safe flying.

Preparing Motor & Speed Controller

Motors are usually supplied with the necessary male bullet connectors attached to the three leads projecting from the casing ( If not, you will need to solder three x 3.5mm male bullet connectors to these leads with heat shrink sleeve covering the part of the plug that does not slide into the female connector. To understand the current rating of different wire sizes and connectors go to my post on this subject here)  Some also supply the mating female connectors for the output leads from the ESC. You will need to solder three x 3.5mm female connectors to the ends of the ESC output leads. There are plenty of videos on YouTube showing you how to solder electrical connections. Again, you will probably find someone in your club who will be happy to help you with this exercise. IMPORTANT: DON’T FORGET THE HEAT SHRINK SLEEVE OVER THE FEMALE CONNECTORS to prevent shorting between motor phases!

It is important to learn how to solder if you have chosen to go down the electric flight route. There will be many instances where you will be required to make soldered electrical connections. One of these arises when it comes to coupling the input wires of the UBEC along with the power supply leads of your ESC to the appropriate MALE side of the ESC to Lipo plug and socket set. This may be a Deans type, a XT60 type or Male and Female bullet connectors.

I have listed these three types as they are the most popular ones for the size of Motor, ESC and Lipo that we will be using for our trainer. The Deans connectors have been popular for a long time but more lately the XT60 connectors are becoming more common. In some instances the simple Bullet connectors can be more appropriate but necessitate two connections to be made instead of one.

Soldering Your Connectors

You need to make your electrical connections as safe as possible with the least chance of causing a short circuit across the Lipo. Convention stipulates that a connector on the Lipo should be fully shrouded. this means soldering the Female version of your connector pair to the Lipo and the Male partner to the black and red leads from the ESC.

When soldering your leads to a Deans connector you will see that the solder tags are arranged in a “T” formation. The convention is to solder the “RED” lead to the top of the “T” and the “BLACK” lead to the upright stem of the “T”. Be sure to slide lengths of heatshrink of the appropriate colours over the leads as far away from the solder joint as possible before making the joint. If you allow them to get too close, they will shrink from the heat of your soldering and you will not be able to slide them over the joints.

XT60 connectors are normally marked with a “+” sign on the plastic body square end to denote the position of the “RED” lead. The negative or black  lead goes to the terminal nearest the shaped end of the casing. Once again, don’t forget your heatshrink before soldering as explained above.

A tip is called for here. When soldering to either Deans or XT60 connectors it helps to plug a Male and a Female together before starting to solder. This ensures the metal parts remain exactly where they should be within the plastic shrouds irespective of the amount of heat being applied. If you don’t do this it is possible for the heat to melt the plastic shroud and for the metal parts to become displaced, rendering the assembly un-useable.

If using bullet connectors, ensure you put the “FEMALE” part on the “RED” lead  of your Lipo with heatshrink sleeve right to the top of the socket. The “MALE” part goes on the “BLACK” lead and has heatshrink sleeve to the point where the mating female part reaches when they are fully engaged. Below is a photo of this arrangement.

Lipo with Male & Female Bullet Connectors
Lipo with Male & Female Bullet Connectors

Needless to say, the mating parts are soldered to the ESC leads in reverse, i.e. “MALE” to “RED” lead and “FEMALE to “BLACK” lead.  Once the solder joint has cooled you can slide your length of heatshrink over the joint and shrink it into place either with your soldering iron or a heat gun.

Exceptional care must be taken not to bring the bare wire ends together when soldering to Lipo leads. I find it helps to bare only one end at a time and complete the soldering and application of the heatshrink shroud before moving on to the other lead. That completes the method of installing an electric planes rc power train.

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  1. By Michael on

    Great site full of useful info.
    One suggestion:

    The stated use of 3.5mm bullet connectors is rather misleading for people who don’t understand electronics.

    As you know, there are different sizes of wires and connectors, each being capable of carrying different amounts of electrical current. Use of wires and connectors that are too small for any particular current can result in fires and/or damage to the radio system or model.

    I suggest that the above instructions are edited to emphasise this point?


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