RC Plane Project

The primary goal of this project was to harness the skills I had acquired from my previous endeavors and channel them into a complex and ambitious undertaking. I opted for an RC plane as the ideal project, as it posed a considerable challenge, exceeding the scale of anything I had previously constructed, and afforded me the opportunity to indulge in my passion for aviation.

Additionally, through this project I aspired to gain a deeper understanding of radio transceivers due to their ability to facilitate long-range communication, surpassing the limitations of Bluetooth. Moreover, I wanted to become proficient in using PCB software. To achieve this, I manufactured both the RC controller and receiver PCBs that would be needed for the RC plane.

The Learning Process [EasyEDA]:

When I first started with PCB design, one of my biggest challenges was finding the right software. I initially tried the tool that comes bundled with Fusion360, but it wasn’t exactly beginner-friendly. After some trial and error, I landed on EasyEDA. It seemed like a great fit, until I realized it couldn’t export accurate 3D models—a problem I only discovered when I tried designing a case for my controller. Luckily, KiCad can handle precise 3D models, and someone had even created a simple file converter for EasyEDA files (you can check it out here: easyeda2kicad). Despite this hiccup, EasyEDA still turned out to be pretty useful, especially with its extensive library of parts for building circuit schematics.

One of the coolest things about PCB design is working on the schematic—it’s like creating the blueprint that everything else is built from. The connections you establish in the schematic get highlighted in the PCB design tool, making it easier to see how everything is supposed to link up. Personally, I found the schematic phase to be super rewarding. It’s where you really get into the heart of circuit design, learning as you go rather than just memorizing symbols and connections. It’s a hands-on approach that makes the process both educational and satisfying.

As I got deeper into the world of PCBs, I learned a lot about how they’re manufactured and the design principles behind them. One thing that stood out was how important trace length and width are. The current running through a trace creates heat due to resistance, so you need wider traces to handle more current without generating too much heat. Too much heat could even melt the trace. But at the same time, you don’t want traces to be too wide, or they’ll take up too much space on the board. It’s all about finding that balance.

RC Plane [Components]:

Building the RC plane opened the door to a whole new level of components—far more powerful and professional than anything I’d worked with before. One of the biggest upgrades was switching from the familiar 9V alkaline batteries to a high-powered 11.1V LiPo battery. This jump wasn’t just about more power; it required extra caution, especially when charging, since LiPos demand careful handling.

The power boost was essential for driving the brushless motor, which spun way faster than any motor I'd used in past projects. It was a game-changer, reshaping how I approached electronics. While I was initially nervous about handling such powerful components, those nerves quickly turned into excitement.

Brushless Motor:

Choosing a brushless motor for this project was a no-brainer due to their superior power-to-weight ratio and overall performance, essential qualities for an RC plane. Brushless motors outshine their brushed counterparts in every aspect, generating less interference, managing heat better, and squeezing more performance from a given battery size.

The 1, 400KV A2212 brushless motor ended up being my choice for the RC plane, although I initially aimed for the 2700KV version. Unfortunately, during testing, the 2700KV motor used to much power due to the size of the propeller being used being quite big, and fried itself. Despite this setback, the 1, 400KV motor proved to be sufficient for the task at hand. (KV essentially denotes the revolutions per minute (RPM) the brushless motor generates per volt supplied. For example, a 1, 400KV brushless motor will spin at 1, 400 RPM with 1 volt and at 14, 000 RPM with 10 volts.)

The reason I opted for this specific brushless motor was its decently high KV rating and its compatibility with both 3S and 2S LiPo batteries. For this particular project, I utilized 3S LiPo batteries. This motor was capable of lifting 800 grams (or generating 7.84532N of thrust), while the plane weighed 700 grams. An ideal thrust-to-weight ratio is usually 0.5:1, this motor provided a higher ratio of 1.143:1, a thrust to weight ratio that was not optimal.

ESC 40A:

The ESC I picked for this brushless motor was a 40A model that played well with 2-4S LiPo batteries. What made it a star player were its extras: it came with a 5V power wire, a digital pin, and a ground wire. These little add-ons were a lifesaver, making it super easy to power up the control board using the LiPo battery as the power supply and to gain full control over the brushless motor.

The specified Amps capacity, in this case, 40A, doesn't necessarily need to be exact for the motor, as long as it offers around 10-20% more power than what the brushless motor requires. Typically, the motor won't overheat even if the Electronic Speed Controller (ESC) is capable of delivering far more Amps than the motor's power rating because the motor only draws the necessary power it requires to function.

An unforeseen challenge emerged when utilizing a larger propeller for the RC plane. This sizable propeller escalated the torque requirements on the motor. Consequently, as the motor's RPM surges, it necessitates more power to maintain that RPM. The high Ampere rating of my ESC (high compared to the power rating of the motor itself), allowed the brushless motor to draw far more power than its design could handle. This was primarily due to the propeller demanding excessive power to spin at 29, 970 RPM (the maximum RPM of the 2, 700 Kv model), leading to the unfortunate frying of the motor.

LiPo Battery:

The three-cell LiPo battery I chose for this project holds a hefty 3, 3000mAh capacity and a rating of 30C. I would have opted for a smaller capacity if I could, but limited local options led me to this larger battery (which was the only LiPo battery I could find tailored for RC planes)—I couldn't source any LiPo batteries from abroad.

The battery's size is critical; it tends to be the heaviest component of the plane, significantly impacting its flight characteristics. Before delving deeper into how a LiPo battery works, understanding LiPo terminology is key.

RC Plane [GASB One]:

The GASB One airframe was my go-to choice because the design files were easily accessible and ready to 3D print using lightweight PLA (LW-PLA). I decided not to create my own RC plane in CAD for two reasons: first, I don’t have a strong interest in aerospace engineering, and second, I lack the necessary expertise to dive into that level of design.

RC Plane [Test Results]

The maiden flight of the plane didn’t go as planned and ended in failure for a few key reasons. First, the propeller was too large for the plane, which threw off the balance and performance. On top of that, the pusher configuration (where the propeller is mounted at the rear) made it awkward and tricky to launch by hand, making it difficult to give the plane the necessary push to fly. Additionally the weight distribution of the aircraft was slightly forwards which I planned to address by 3D printing the back from a heavier PLA material.

In the second iteration of the plane, I made key improvements by reinforcing the front for more durability and adding weight to the back to restore the center of mass. Unfortunately, this version never got the chance to take flight. I wasn’t able to test it in time, and finding a smaller propeller proved difficult, which delayed further progress.

RC Controller [Component Analysis]

An overview:

At the core of the RC transmitter lies the Arduino Pro Mini (using the ATmega328P chip), which acts as the brain of the entire system. Each part of the circuit is assigned to a control pin, allowing the Arduino to both receive inputs and control outputs using its digital pins. Take the toggle switch, for example—when you flip it on, it closes the circuit between the ground (GND) and the digital pin connected to it. The Arduino detects this change and updates the switch's state from 0 to 1, essentially tracking whether it's on or off.

That approach works well for simple components like LEDs, but what about something more complex, like a potentiometer? To read the potentiometer’s real-time position, the Arduino applies a constant voltage across it. This voltage then flows through the potentiometer and into the Arduino’s analog input pin. The Arduino can then measure the change in resistance based on the voltage it reads. Here’s where some basic electrical physics comes in: by comparing the initial voltage and the one at the analog pin, the Arduino can calculate the potential difference and, assuming a steady current, figure out the resistance using Ohm’s Law (R = V/I).

What makes the Arduino really handy is its ability to map a large range of values into a smaller, more manageable one. In the case of the potentiometer, it can convert the wide range of possible resistance values into a practical scale, say from 0 to 260, making it much easier to work with.

This ability to monitor real-time data from all components and convert it into digital signals is what makes the Arduino so powerful. It continuously packages up accurate information about each component in the circuit and sends it to the NRF24L01 module, which wirelessly transmits the data to the receiver on the RC plane.

NRF24L01:

During the initial design phase of my RC transmitter, I made the mistake of assuming that I could randomly assign any pin to an Arduino digital pin. This misguided assumption led to a complete failure of my PCB. Once I dug into how the Arduino communicates, it became clear why this approach didn’t work.

The Arduino Pro Mini has four main communication pins: RXD, TXD, MOSI, and MISO. RXD and TXD are often reserved for serial communication (they are part of the UART interface), while MOSI (Pin 11) and MISO (Pin 12) are typically used for communicating with external components like the NRF24L01 wireless module. Unlike simple components that just need on/off digital states, the NRF24L01 requires actual data exchange for wireless transmission, which is why it interfaces with the MOSI (Master Out Slave In) and MISO (Master In Slave Out) pins. Since the NRF24L01 is a transceiver—capable of both sending and receiving data—it uses both these pins for bidirectional communication.

However, the NRF24L01 doesn’t work alone; it needs to be synchronized with the Arduino. This synchronization happens via the SCK (Serial Clock) pin, which pulses at around 16MHz, ensuring that the Arduino and the NRF24L01 stay in sync during data transfers.

HT7333:

The NRF24L01 operates on low power consumption, specifically accepting only 3.3V. As the Arduino Pro Mini supplies roughly 5V, this necessitates the inclusion of a voltage regulator. The HT7333 perfectly fits this role, being both small, capable of accepting up to 12V and specifically designed as a 3.3V voltage regulator, ensuring compatibility while maintaining a small footprint within the setup.

The HT7333 is a three-terminal, low-power, high-voltage regulator that uses CMOS technology. The series has a very low quiescent current, which is usually around 3.5A. It accepts input voltages of up to 12V. The device delivers a lot of current with a very low dropout voltage.

To filter out AC noise, suppress rapid voltage changes and improve feedback loop characteristics, capacitors are placed at the input and output terminals of the HT-7333. (In this case the capacitor was placed right next to the NRF24L01 rather than the output terminal). Generally it’s good practice to couple voltage regulators with capacitors to improve the stability of the voltage regulator.

Joysticks:

The analog joysticks utilized in this project rely on 2 potentiometers to define the stick's coordinates at any moment. Leveraging the Arduino's capability to interpret potentiometer resistance as numerical values and subsequently map these values to coordinates, we achieve precise joystick functionality, accurately translating potentiometer readings into corresponding coordinates.

RC Controller [PCB]

Designing the PCB for the RC Controller stood as a crucial milestone in this project, consuming a week of dedicated effort. This step was particularly pivotal as manually connecting all the connections on a breadboard would have been both messy and unreliable. It marked my first time utilizing PCB software, providing an invaluable learning experience.

In the early stages of designing my RC controller, I sketched out the essential components: joysticks, a microcontroller, a radio transmitter, buttons, and switches. I wanted to pack in as many features as possible to give the controller maximum functionality. At the same time, I made sure to focus on ergonomics—shaping the PCB like an actual controller to ensure it was comfortable and easy to use. Looking ahead to future projects, I also added the option to include an accelerometer/gyroscope module.

When I had to redesign the circuit and untangle the connections in the schematic (to pinpoint issues), I decided to change my approach. Instead of manually connecting points with wires, I used "NetLabels." By assigning matching IDs to points that needed to be linked, I was able to streamline and declutter the entire schematic. This made troubleshooting and refining the design so much easier and cleaner.

The RC controller case was designed to be as comfortable as possible to hold whilst protecting the internal electronics.

RC Receiver [Component Analysis]

The Arduino Pro Mini is the powerhouse of this board, packing impressive processing power into its tiny frame. Its compact design makes it perfect for embedding into a PCB, which is exactly what it was made for. But that small size comes with a catch: if you want to use it on a breadboard, you’ll need to manually wire each pin to control your components, which can be a bit tedious. With this PCB, though, everything is streamlined. It establishes seamless communication between the Arduino Pro Mini, the NRF24L01 (with the same voltage regulation setup as the controller), and all the external components, tying the whole system together.

This board was also designed specifically for easy connection to the ESC (Electronic Speed Controller), and by extension, to a brushless motor. You’ll notice the three pins shown in the image above, which are dedicated for this purpose.

FT232RL:

The Arduino Pro Mini, because of its exceptionally small size, doesn't come equipped with an onboard serial port for direct communication with the ATMega328P chip. As a result, an external Serial Port module, such as the FT232RL, becomes necessary to facilitate communication with the Arduino Pro Mini.

RC Receiver [PCB]

Designing this PCB was much less of a challenge compared to the RC controller. It needed fewer components, and the experience I gained from working on the RC controller made designing this PCB a lot easier.

My main goal in designing this PCB was to create a versatile tool that simplifies the connections to the Arduino Pro Mini, can draw power from various sources, and supports seamless wireless data reception—while avoiding common issues along the way. Compactness was also a priority. I wanted to make sure the PCB wasn’t too bulky, so it could easily fit into any model without affecting its form or functionality.

This PCB has become an essential part of my toolkit, making project development much smoother by integrating all the necessary circuitry in one place. It not only adds a level of professionalism to my projects but also drastically cuts down setup time. Its small size offers even more benefits, as it takes up minimal space for electronics. This means less filament is used during 3D printing, which reduces costs—especially when a complete reprint is needed due to dimensional errors in the model.

📖THEORETICAL INFORMATION PAST THIS POINT

THEORY: How Planes Fly

It's crucial to understand that air behaves similarly to a fluid medium, albeit less dense than water or other liquids. Objects lighter than air experience buoyancy within it, akin to floating in water, while heavier objects tend to fall or "sink" through the air. For heavier objects to remain aloft, they require lift, an upward force. In aircraft, the primary source of lift is provided by the wings.

Understanding how wings generate lift requires examining their airfoil, which represents the two-dimensional cross-section of a wing (bearing in mind that a wing is a three-dimensional object with finite length). To better understand the physics behind lift generation, let's break down the key components of an airfoil:

1. Leading Edge: This is the front part of the airfoil.

2. Trailing Edge: Located at the back part of the airfoil.

3. Chord: A straight line connecting the leading and trailing edges.

4. Angle of attack: The angle between the chord and the direction of airflow is called the angle of attack.

5. Mean Camber Line: This line is drawn midway between the upper and lower surfaces of the airfoil. Camber refers to the curvature of the airfoil. A symmetrical airfoil has zero camber.

Lift is generated by creating a pressure difference between the upper and lower surfaces of the wing. The higher pressure underneath the wing, relative to the lower pressure above it, creates an upward force, thus generating lift. As the aircraft accelerates, the airflow over the wing intensifies, accentuating this pressure disparity and consequently bolstering lift. This principle underscores the critical role of velocity in attaining optimal lift during flight. (Shear stress acting on the wing also contributes to lift, but not significantly)

To elucidate further, consider the mechanics at play: the air pressure beneath the wing exerts an upward force on the wing, while the air pressure above the wing exerts a downward force. If the pressure beneath the wing surpasses that above it, the cumulative upward force prevails, resulting in lift. Trying to imagine air as water can provide a clearer visualization of the phenomenon.

Now, a pertinent question arises: how does the airfoil of a wing create a pressure difference between its top and bottom parts?

The pressure difference between the upper and lower surfaces of the wing creates an upward force through a combination of factors:

Bernoulli's Principle: According to Bernoulli's principle, an increase in the speed of a fluid (such as air) results in a decrease in pressure. As the airflow over the curved upper surface of the wing accelerates, its pressure decreases. Meanwhile, the airflow along the flatter lower surface moves at a slower speed, resulting in relatively higher pressure. This pressure difference contributes to the upward force on the wing.

Newton's Third Law of Motion: The downward momentum of the air molecules deflected by the wing's shape generates an equal and opposite reaction, resulting in an upward force on the wing. This is essentially Newton's third law of motion in action.

Coanda Effect: The Coanda effect describes how a fluid tends to adhere to a curved surface. As the airflow follows the curvature of the wing's upper surface, it creates a region of low pressure above the wing, contributing to lift.

Combining these principles, the pressure difference between the upper and lower surfaces of the wing results in a net upward force, known as lift, enabling the aircraft to overcome gravity and stay airborne.

THEORY: NRF24L01

The NRF24L01 itself is a compact transceiver module that operates using the SPI protocol (or the RF24 library if you're using Arduino). Inside, it has everything from frequency synthesizers and a crystal oscillator to amplifiers, modulators, demodulators, and an Enhanced ShockBurst protocol engine. Operating at a low voltage range of 1.6V to 3.6V, it’s known for its energy efficiency—consuming less power than a typical LED!

This module operates in the 2.4 GHz ISM band and supports data rates between 250 kbps to 2 Mbps. When used in open environments with a lower baud rate, it can achieve a range of up to 1 kilometer, but that’s only true for the version of the module with an antenna (like the NRF24L01+PA+LNA). Without the antenna, the range is significantly shorter. It’s also worth noting that the module can utilize 125 different channels (spanning from 2.401 GHz to 2.525 GHz), which means you can set up a network of up to 125 devices in the same area, each on a different channel. Each channel can handle up to 6 simultaneous connections, allowing the module to communicate with multiple units at once.

Enhanced Shock Burst protocol: The Enhanced Shock Burst protocol (ESB) is a basic protocol that allows for two-way data packet communication including packet buffering, packet acknowledgment, and automatic retransmission of lost packets. The ESB protocol is used in the NRF24L01 as it is able to provide radio communication whilst consuming a small amount of power.

Frequency Synthesizer: A frequency synthesizer is an electronic circuit that generates a range of frequencies from a single reference frequency. (I presume it’s used to create a 125 distinct channels from the 2.4Ghz frequency.)

THEORY: FT232RL

The FT232RL Module derives its name from its core chip, the FT232, boasting an impressive array of functionalities. Among its capabilities, it excels in converting serial data from USB to TTL (Transistor-to-transistor logic), and can conveniently regulate voltage from USB to 5V and 3.3V. Remarkably, this chip operates without the need for any external hardware or firmware.

One of the key components of the FT232 is the UART Controller, which block converts the USB data format so that it can be sent over the UART (universal asynchronous receiver / transmitter) data lines RX and TX. This controller is programmable in FT232 IC to make the CBUS and DBUS pins (TXD, RXD, RTS, CTS, DTR, DSR, DCD, RI) pins to function as normal GPIO (GPIO: General Purpose Input Output pins, a generic pin whose value consists of one of two voltage settings (high or low) and whose behaviour can be programmed through software) pins. By factory default these pins will function as control pins for USB to UART communication.

Interesting to note as well that the FT232 does not have a SCK pin, which is due to the way USB works. SPI doesn't need any 'Baud' (a unit of transmission speed equal to the number of times a signal changes state per second. For signals with only two possible states one baud is equivalent to one bit per second.) rate since it is a synchronous protocol.

The connection between the FT232 and Arduino is established by linking the SPI (Serial Peripheral Interface) pins on the Arduino to the corresponding pins on the FT232. For transmitting data from the Arduino to the FT232, the TX (Transmit) pin on the Arduino is connected to the RX pin on the FT232, facilitating data reception by the FT232. Conversely, to receive data from the FT232, the RX pin on the Arduino is connected to the TX pin on the FT232, enabling data transmission from the FT232.

Although this setup enables communication between the FT232 and Arduino, these pins alone cannot upload code to the Arduino. Uploading code to the Arduino necessitates wiping the EEPROM (Electrically Erasable Programmable Read-only Memory) Memory, a process that occurs when the Arduino is reset during code upload. To facilitate this reset, the RST pin on the Arduino is linked to the DTR pin on the FT232, allowing the FT232 to reset the Arduino while uploading code.

THEORY: Brushless Motor (Outrunner BLDC)

In the image, you'll notice the label indicating "10T, " where 'T' signifies Turns. This refers to the number of times the internal wiring wraps around the armature of the motor. As a general rule, higher turn motors tend to offer greater torque but lower RPM.

Understanding why this occurs requires delving into the function of armatures in a brushless motor, illustrated in the accompanying picture. These armatures serve as the core element. Essentially, wire is wound around these armatures to act as electromagnets, which is crucial for the motor's operation. As the number of windings in these small electromagnets increases, their magnetic field strength intensifies (Hence, higher toque). A higher number of turns in a brushless motor means more wire, which in turn increases the resistance. As a result, the motor's RPM per volt decreases due to this added resistance in the system.

Brushless motors are renowned for their efficiency owing to the absence of brushes that succumb to friction. Instead, these motors rely on a clever configuration involving a central assembly of armatures surrounded by a moving part equipped with permanent magnets. These magnets are strategically arranged in alternating north and south polarities.

The magic happens through an external circuit or Electronic Speed Controller (ESC). This system rapidly toggles the polarity of electromagnets—shifting between north, south, and neutral states (needed to prevent repulsion between the electromagnets). This orchestrated interplay generates attraction and repulsion forces between the permanent magnets, and hence generating movement.

Visualizing the intricate process solely through words can be tricky. Picture a north pole (NP) permanent magnet. When one electromagnet switches to a south pole (SP) to bring the NP permanent magnet next to it, the other electromagnet next to it, transitions to a NP to attract the SP permanent magnet.

This dual shift not only draws the SP permanent magnet close to the NP electromagnet but also boosts the speed of the NP permanent magnet by pushing it away with a repelling force generated by the NP electromagnet. This orchestrated movement repeats rapidly as the electromagnets' polarities change and are turned on and off at various positions, creating a continuous and controlled motion. (Refer to the image on the left for a visual aid in understanding this process.)

It's fascinating to think that this intricate dance of magnetism unfolds in less than a second, driving the motion within the brushless motor. For this dance of magnetic forces to function flawlessly, the brushless motor always reverts back to a predetermined position when powered on, ensuring its smooth operation and precision.

THEORY: ESC

The Electronic Speed Controller (ESC) functions as the intermediary between the motor and the power source, typically a LiPo battery in our setup. Its primary role involves regulating the motor's rotation speed by dispatching precisely timed electrical signals (The Throttle unit in the ESC manages this, sending signals that either close or open gates. We'll delve deeper into these gates shortly for a clearer picture.). The pace of these signals can be adjusted to accelerate or decelerate the motor, based on the input received from the digital pin on a control board.

These timed electric signals are transmitted through the three wires linked to the brushless motor. Intuitively one may assume that these wires are GND, 5V and a digital pin, but they are not. To first understand how the ESC works, it's essential to understand what each wire within the system is used for.

The wires in the brushless motor connect to clusters of electromagnets nestled inside. Due to how the permanent magnets are arranged, we can activate for example, three electromagnets at once, lining them up as either north or south poles whenever needed (Reversing current each time to change polarity). This cool arrangement lets us control these electromagnets using just one wire, turning them on or off easily. We repeat this setup across other groups of electromagnets, creating three distinct groups, each tied to its own wire. This setup isn't just nifty—it makes the motor super efficient. Only two wires need power at any given time to get the motor moving, no matter the size of the motor. Plus, it makes things simpler for the ESC circuit.

Now that we've got a handle on how the wires function, understanding the ESC operation should be a breeze. Essentially, as shown in the image on the left, each wire (or group of electromagnets) is linked to two gates, which are controlled by the microprocessor. When one gate closes, it sends a current through the electromagnets in a way that generates a north pole attraction. The other gate, when activated, sends a current in the opposite direction, creating a south pole attraction.

Now, an intriguing question surfaces: how does the microprocessor discern when to activate or deactivate specific groups of electromagnets within the brushless motor, and determine the polarity these electromagnets should assume?

There are two primary methods to achieve this. The simpler approach involves strategically placing hall-effect sensors—typically 120 or 60 degrees apart—between the electromagnets. These sensors offer a HIGH or LOW signal, determined by the passing magnet's polarity, providing the microprocessor with crucial information to initiate the next commutation sequence.

The second method harnesses electromagnetic induction. When a permanent magnet passes by a deactivated coil (or electromagnet), it induces a current in the coil, causing a voltage drop in the ESC. The ESC registers this change and uses it to calculate the timing for the next commutation sequence. Both methods showcase the ingenuity behind how the microprocessor coordinates the motor's precise movements.

THEORY: LiPo Battery

The 'S' denotes cells, determining voltage; more cells equate to higher voltage as they are connected in series. A single LiPo cell delivers around 3.7V, thus a 3S battery totals 11.1V. The battery's capacity, specified as 3, 3000 mAh here, denotes the amount of current it can supply for an hour before complete discharge, meaning it can provide 3.3A for an hour. Consequently, the higher the mAh, the longer the battery's operational duration.

Lastly the ‘C’ rating defines the maximum current that that can be drawn from the battery (any higher than that, and it will cause the battery to degrade at a faster pace), so for example for our battery the battery can output a maximum current of (capacity of the battery in A rather than mA * the charge: 3.3A * 30) = 99A, hence this means that at that rate the battery would fully discharge in, ((3.3A * 60 (mins) * 60 (secs) [Total current that the battery will output, recall “3.3A for one hour”])/99A / 60) 2 minutes. Keep in mind that nowadays, it's common to find two C Ratings: a Continuous Rating and a Burst Rating. The distinction lies in their endurance levels: a Continuous Rating denotes the maximum current draw a battery can sustain continuously, while a Burst Rating indicates the ability to endure that draw for brief 10-second bursts. Typically, the Burst Rating surpasses the Continuous Rating, albeit batteries are generally compared based on their Continuous Ratings rather than their Burst Ratings.

Now that we've clarified the terminology surrounding LiPo batteries, let's explore their function, delving into the underlying technology and chemistry. Lithium Polymer batteries represent an advancement from Lithium-ion batteries, operating on the same fundamental principles. What distinguishes them is the utilization of a solid polymer electrolyte (SPE), as opposed to the liquid lithium-salt-electrolyte (like LiPF6) in an organic solvent found in Lithium-ion batteries. Currently, LiPo batteries utilize highly conductive semisolid (gel) polymers as their electrolyte. LiPo batteries are widely used, as they have a higher specific energy (specific energy is energy per unit mass (Joule/Kg)) compared to other lithium battery types, making them ideal for weight-sensitive applications, such as in RC planes.

The typical structure of a Lithium cell comprises of four primary components: the positive electrode, negative electrode, separator, and electrolyte. Even in cells with a liquid electrolyte, the separator typically consists of a polymer material, such as a microporous film made of polyethylene (PE) or polypropylene (PP), thus incorporating a "polymer" component. Further division of the positive electrode reveals three constituents: the lithium-transition-metal-oxide (e.g., LiCoO2 or LiMn2O4), a conductive additive, and a polymer binder like poly(vinylidene fluoride) (PVdF). Similarly, the negative electrode material may consist of these same three components, albeit with carbon replacing the lithium-metal-oxide.

Similar to other Lithium-ion cells, LiPo batteries operate based on the principle of intercalation and de-intercalation of lithium ions between a positive electrode material and a negative electrode material, facilitated by a liquid electrolyte that serves as a conductive medium. To prevent direct contact between the electrodes, a microporous separator is positioned between them, allowing only ions to migrate while preventing the movement of electrode particles.

Intercalation refers to the reversible inclusion or insertion of a molecule or ion into materials with a layered structure. Examples of such materials include graphite and transition metal dichalcogenides, where metal dichalcogenides have the formula ME2, with M representing the transition metal and E representing sulfur, selenium, or tellurium.

The role of the anode and cathode in a battery is to store the lithium. The electrolyte carries positively charged lithium ions from the anode to the cathode and vice versa. During charging, a voltage is applied to the cathode, marked as (+), prompting lithium atoms to release electrons and transform into lithium cations. These cations then migrate towards the anode, marked as (-), where they capture electrons once again. This process effectively charges the battery.

Conversely, during discharging, the process reverses. Lithium ions move from the cathode to the anode, causing an accompanying flow of electrons from one terminal to the other, thereby generating electrical current for external use.

Critical to the battery's functionality, the separator serves to impede the flow of electrons within the battery, permitting only the movement of ions. This selective permeability ensures the efficient operation and longevity of the battery by preventing internal short circuits.