RC Basics: Batteries, Motors, ESCs, Servos and Radios
Cars, boats, planes, helicopters and drones all run on the same few parts: a battery, a motor, a speed controller, servos and a radio. Understand those once and every model makes sense. This guide explains each part, how to choose it, how the numbers on the label work, and how to keep LiPo batteries safe.
By Kyle HilsonUpdated: October 202615 min read
The RC system at a glance
Every electric RC model follows the same chain. You move a stick or trigger, the transmitter sends that position by radio, the receiver passes it on, and the ESC and servos turn it into motion.
| Part | Job | Key numbers |
|---|---|---|
| Transmitter (TX) | Reads your sticks, sends commands | Channels, protocol, model memory |
| Receiver (RX) | Receives commands, outputs signals to ESC and servos | Channels, protocol, telemetry |
| Battery | Stores the energy | Voltage (cells, S), capacity (mAh), discharge (C) |
| ESC | Controls motor speed from the throttle signal | Max current (A), voltage range, BEC output |
| Motor | Turns electricity into rotation | Brushed/brushless, kV, size, max power |
| Servos | Move steering, rudders and control surfaces | Torque, speed, size, digital/analog |
Nitro and petrol models replace the battery, ESC and motor with a fuel tank, engine and throttle servo, but keep the radio, receiver and servos.
Transmitter, receiver and binding
Almost all modern hobby radios use 2.4 GHz with frequency hopping. Each brand has its own protocol, so a receiver normally works only with transmitters of the same system. Binding pairs one transmitter with one receiver, after which they ignore every other radio around them.
- Channels: a car needs 2 (steering, throttle), a basic plane 4, a helicopter 6 or more. More channels leave room for lights, retracts or gyro gain.
- Model memory: computer radios store settings for each model, so one transmitter can run your whole fleet.
- Telemetry: some systems report battery voltage, temperature or signal strength back to the transmitter.
- Fail-safe: what the receiver does when it loses signal. Always set it: throttle to neutral or off.
Step-by-step: binding a transmitter and receiver, types of RC controllers and understanding RC transmitters.
Batteries: LiPo, NiMH and Li-ion
| Type | Cell voltage (nominal) | Strengths | Weaknesses |
|---|---|---|---|
| NiMH | 1.2 V | Robust, tolerant of abuse, safe | Heavy, less punch, slow to charge |
| LiPo | 3.7 V (4.2 V full) | Light, high power, the hobby standard | Must be charged and stored correctly; fire risk if damaged |
| LiHV | 3.8 V (4.35 V full) | A little more voltage and power | Needs a charger with an HV mode |
| Li-ion | 3.6 V (4.2 V full) | High capacity, long flight times | Lower current; suits long-range planes and camera drones |
Reading a LiPo label
A pack labelled “3S 5000 mAh 50C” has three cells in series (3 × 3.7 V = 11.1 V nominal), stores 5,000 mAh, and is rated to deliver 50 times its capacity in amps: 50 × 5 A = 250 A in theory. C ratings are often optimistic, so treat them as a comparison between packs of one brand rather than a hard figure. More cells mean more voltage, and with the same motor, more rpm and speed. Capacity sets run time; C rating sets how much current the pack can deliver without overheating.
LiPo safety and charging
- Use a balance charger and plug in the balance lead, so every cell is charged to the same voltage.
- Charge at 1C unless the maker allows more: a 5000 mAh pack at 5 A.
- Never leave a charging LiPo unattended, and charge in a LiPo bag or metal box on a non-flammable surface.
- Don’t go below about 3.0–3.3 V per cell under load. Set the low-voltage cutoff on your ESC and use a timer.
- Store at about 3.8 V per cell. Full or empty packs age quickly; most chargers have a storage mode.
- Retire damaged packs. Swollen, dented or punctured packs must not be charged or used.
Warning: a swollen LiPo cannot be repaired. Puncturing or “venting” it is dangerous. Discharge it safely and take it to a battery recycling point. Our article on swollen LiPo batteries explains how.
Charging questions come up for every brand; for example, charging non-Traxxas batteries on a Traxxas charger and how long to charge an RC car battery.
Brushed and brushless motors
Brushed motors use carbon brushes to switch current inside the motor. They are cheap and simple but wear out and lose power when hot or wet. Brushless motors switch current electronically through the ESC, so they are more efficient, more powerful and last much longer. Almost every hobby-grade model now uses brushless power.
What kV means
The kV rating is how many rpm a motor turns per volt with no load. A 2,000 kV motor on 3S (11.1 V) spins about 22,000 rpm unloaded. Higher kV is not “more powerful”; it means faster spinning with less torque. Match kV to the job: high kV for small props or gearing, low kV for big propellers, large boats and heavy crawlers. Our article on understanding RC electric motors goes deeper, and for planes see sizing an electric motor.
Inrunners have the spinning part inside the case and suit cars and boats with gearing or water cooling; outrunners spin their outer case and suit propellers directly.
ESCs: speed controllers
The ESC takes the throttle signal from the receiver and controls how much power reaches the motor. It also usually powers the receiver and servos through a built-in BEC (battery eliminator circuit).
- Current rating: choose an ESC rated above the maximum current your motor and prop or gearing draw, with some margin.
- Voltage range: the ESC must handle your battery’s cell count.
- Calibration: teach the ESC your transmitter’s neutral, full throttle and brake points after binding.
- Programming: cutoff voltage, brake strength, timing and reverse are set by program card, app or stick programming.
- Cooling: car ESCs use fans, boat ESCs water cooling; heat is what kills ESCs.
How-to articles: how a speed controller works, setting up an RC speed controller and programming a car ESC.
Servos
A servo is a small motor with gears and a position sensor that moves to the angle the receiver tells it. Steering in cars, rudders in boats, control surfaces in planes and the swashplate in helicopters all use servos.
- Torque (kg·cm): how hard it can push. Big tyres, large rudders and big planes need more.
- Speed (seconds per 60°): how quickly it moves. Helicopters and racing cars need fast servos.
- Size: micro, mini, standard and large-scale; check what fits your model.
- Gears: metal gears survive crashes and big loads better than plastic.
- Waterproof: for boats and bashers that see water.
More detail in our RC servo guide and what a servo does in an RC car.
Nitro, gas and turbine engines
Glow (nitro) engines burn a methanol, nitromethane and oil mix, ignited by a glow plug that stays hot once running. Petrol engines in large-scale models use spark ignition and a two-stroke petrol-oil mix. Both are tuned with needle valves on the carburettor: the high-speed needle sets the mixture at full throttle, the low-speed needle at idle and acceleration. A slightly rich setting runs cooler and safer than a lean one. Turbines are small jet engines with their own electronic control unit and fuel system, used in large jets and some helicopters.
See the basics of RC engines, and the vehicle guides for engine types used in cars, planes and boats.
FAQ
What does 2S, 3S or 6S mean?
The number of LiPo cells connected in series. Each cell is 3.7 V nominal, so 2S is 7.4 V, 3S 11.1 V and 6S 22.2 V. Check that your ESC and motor are rated for the cell count before plugging in.
Can I use any receiver with my transmitter?
Only receivers using the same protocol as your transmitter. Many transmitters support several protocols, and some third-party receivers support popular protocols, but check compatibility before you buy.
Is brushless always better than brushed?
For speed, efficiency and lifespan, yes. Brushed motors are still fine in budget models, crawlers and scale boats where smooth low-speed control and low cost matter more than power.
Why does my ESC beep and not run the motor?
Beeps usually signal a missing or wrong throttle signal (not bound, throttle not at neutral, reversed channel), low battery voltage or a calibration step. Look up the beep codes for your ESC model; most manuals list them.
How should I dispose of an old LiPo?
Discharge it fully with a charger’s discharge function or a battery discharger, then take it to a battery recycling point. Never put LiPos in household waste.
All 10 articles in this guide
Every article below goes deeper into one question from this guide. Open a group to see its articles.
Batteries, motors, ESCs and radios 10
- Are LiPo Batteries Dangerous? A Guide to Safe Handling and Use
- Choosing the Best RC Glider Motor
- How Does a Speed Controller Work
- How to Bind an RC Transmitter and Receiver
- How to Fix Swollen LiPo Battery
- Mastering RC Servo Control with Our Comprehensive Guide
- Optimizing RC Outboard Motor Electric Performance
- The Ultimate Guide to Remote Control Jet Engines
- Ultimate Guide
- Understanding RC Transmitters Radio Control Guide
About 20 years in RC. Mostly boats in the NAVIGA Mini Eco Expert class, with many self-made parts; also a King Motor Baja 5B, a home-built electric plane, home-built nitro planes he has flown, and an RC helicopter. More about SwellRC
