Many customers have the same question when purchasing an underwater thruster:

“What else do I need besides the thruster to make it work?”

In fact, a complete underwater propulsion system is not just a thruster. It requires a properly matched ESC, battery, controller, and connection accessories. Only when all components are correctly selected can the thruster operate safely and efficiently.

What Components Make Up a Complete Underwater Propulsion System?

A basic underwater propulsion system usually includes:

• Underwater Thruster

• ESC (Electronic Speed Controller)

• Battery

• Controller or remote control system

• Power cables and waterproof connectors

Different applications, such as ROVs, underwater robots, electric boats, and kayaks, require different system configurations.

1. Underwater Thruster

The thruster is the power output component of the system. It generates thrust by rotating the propeller.

When selecting a thruster, you should consider:

• Operating voltage

• Maximum power

• Continuous power

• Maximum working current

• Thrust output

• Application environment

For example:

Small ROVs and underwater robots usually use 12V or 24V thrusters.

Electric boats, kayaks, and larger marine equipment often require higher-power 24V or 48V thrusters.

The thruster voltage must match the battery and ESC voltage. Using an incorrect voltage may damage the motor or controller.

2. ESC (Electronic Speed Controller)

A brushless underwater thruster cannot be connected directly to a battery. It requires an ESC to control the motor.

The main functions of an ESC include:

• Controlling thruster speed

• Adjusting power output

• Protecting the motor and electrical system

• Receiving signals from remote controls or control systems

Simply:

Battery → ESC → Thruster

The ESC converts the battery’s DC power into the three-phase signals required by the brushless motor, allowing precise speed control.

3. How to Properly Match an ESC with an Underwater Thruster?

When selecting an ESC, three factors are especially important:

(1) Voltage Matching

The ESC voltage range must cover the operating voltage of both the battery and the thruster.

For example:

A 24V underwater thruster should be paired with a 24V battery system and an ESC that supports the same voltage range.

Using excessive voltage, such as:

24V thruster + 48V battery

may cause:

• ESC overvoltage damage

• Motor overheating

• Reduced service life

Therefore, always confirm that the thruster, ESC, and battery voltage are compatible.

(2) Current Matching

Besides voltage, the ESC must also be matched according to the thruster’s current requirements.

Many users calculate current using this formula:

Current (A) = Power (W) ÷ Voltage (V)

For example:

A 1000W, 24V thruster:

1000W ÷ 24V ≈ 42A

This value represents the theoretical maximum input current and can be used as an important reference when selecting an ESC and battery.

However, it is important to understand:

The actual operating current is not always equal to the calculated value.

The actual power consumption of a thruster depends on factors such as:

• Propeller load

• Water conditions

• Rotation speed

• Control method

• Motor efficiency

For example:

APISQUEEN AQ1121 underwater thruster:

• Maximum power: 2000W

• Operating voltage: 48V

Theoretical calculation:

2000W ÷ 48V ≈ 42A

However, during actual operation, if the thruster is not running at maximum load, the current can be lower. Under certain test conditions, the operating current may be around 22A.

Therefore:

• Maximum power represents the highest output capability of the thruster

• Test current represents actual power consumption under specific conditions

• ESC selection should be based on maximum power and possible peak current, not only the test current

Generally, it is recommended to choose an ESC with a continuous current rating higher than the thruster’s maximum working current and leave some safety margin for more stable long-term operation.

(3) Choosing the Right ESC Type

Common ESC types used with underwater thrusters include:

Square Wave ESC

Features:

• Lower cost

• Simple control method

• Suitable for general applications

Disadvantages:

• Higher motor noise

• Less smooth low-speed control

FOC ESC (Field Oriented Control)

FOC is a more advanced motor control technology.

Advantages:

• Quieter operation

• Higher efficiency

• Smoother low-speed performance

• Lower heat generation

It is suitable for:

• Underwater robots

• ROVs

• Research equipment

• Applications requiring low noise

For example, the APISQUEEN AQ1121 thruster uses a built-in FOC ESC to provide smoother and quieter operation.

4. What Other Components Are Needed Besides the Thruster and ESC?

Battery

The battery determines the operating time of the propulsion system.

Common options include:

Lithium-ion Battery

Advantages:

• High energy density

• Lightweight

• Longer runtime

Suitable for:

• Unmanned boats

• Long-duration underwater operations

LiFePO4 Battery

Advantages:

• High safety

• Long cycle life

• Stable performance

Suitable for:

• Electric boats

• Fishing boats

• Cruising applications

When selecting a battery, make sure:

• Voltage matches the system

• Capacity meets runtime requirements

• Maximum discharge current is sufficient

Controller

Different applications require different control methods.

Remote Control

Suitable for:

• Electric boats

• Kayaks

• Recreational applications

PWM Control

Suitable for:

• ROVs

• Arduino projects

• Pixhawk systems

Automatic Control Systems

Suitable for:

• Unmanned boats

• Intelligent robots

Power Cables and Waterproof Connections

Since underwater thrusters operate in wet environments, reliable connections are essential.

Pay attention to:

• Cable size

• Waterproof connector quality

• Electrical insulation protection

For high-power thrusters, properly sized power cables are required to prevent overheating and power loss.

5. Common Underwater Propulsion System Configurations

Underwater Robot / ROV

Recommended configuration:

• 12V or 24V underwater thruster

• Properly matched ESC

• Lithium battery

• PWM control system

Suitable for:

• Underwater exploration

• Camera systems

• Research projects

Electric Kayak / Small Boat

Recommended configuration:

• Dual thruster kit

• 24V or 48V battery

• High-current ESC

• Remote controller

Compared with a single thruster, dual thrusters provide:

• Higher thrust

• Forward and reverse movement

• Left and right steering control

High-Power Unmanned Boat

Recommended configuration:

• High-thrust thruster

• FOC ESC

• Large-capacity battery

• Automatic control system

Suitable for:

• Long-distance cruising

• Autonomous boats

Summary: Complete Propulsion System = Thruster + ESC + Battery + Control System

A reliable underwater propulsion system requires proper matching between all components:

✅ Thruster, battery, and ESC voltage must be compatible
✅ ESC continuous current rating should be higher than the thruster’s maximum working current with safety margin
✅ Control method should match the application requirements
✅ Battery capacity should meet the required runtime

Choosing the right combination of thruster and accessories ensures more stable operation, higher efficiency, and longer equipment lifespan.