Many customers ask the same question after purchasing a water thruster:

“I already have a car battery or an electric vehicle battery. Can I use it to power my thruster?”

The answer depends on several factors. A battery can be used with a water thruster only when its voltage matches the thruster requirements and its continuous discharge capability is sufficient.

Although car batteries, electric vehicle batteries, and lithium batteries can all provide power, they are designed for completely different applications. Understanding these differences can help you choose a safer and more suitable battery for your propulsion system.

First, Check the Thruster Voltage

Before choosing a battery, always confirm the operating voltage of your water thruster.

A 12V thruster requires a 12V battery system, a 24V thruster requires a 24V battery system, and a 48V thruster requires a 48V battery system.

Using an incorrect voltage can cause problems. A battery with insufficient voltage may prevent the thruster from reaching normal performance, while excessive voltage may damage the ESC or motor.

For this reason, voltage matching should always be the first consideration.

Can You Use a Car Battery for a Water Thruster?

A car battery is designed mainly for starting engines. Its biggest advantage is that it can provide a very high current output in a short period of time.

For example, a typical 12V car battery may have a capacity of 45Ah–100Ah and can provide hundreds of amps during engine startup.

However, starting batteries are not designed for continuous deep discharge. After the engine starts, the alternator takes over the power supply, so the battery normally does not need to run electrical equipment for several hours continuously.

For this reason, a car battery is suitable for testing or short-term use, but it is not the ideal choice for long cruising applications.

For example, if you have a 12V water thruster with a maximum working current of 42A, and you use a 12V 100Ah car battery:

100Ah ÷ 42A ≈ 2.4 hours

This is the theoretical maximum runtime at full throttle.

In real use, because users normally do not run at full throttle continuously, the actual runtime may be longer.

However, repeated deep discharge will shorten the battery lifespan. Therefore, car batteries are better used as temporary power sources rather than permanent propulsion batteries.

Are Electric Vehicle Batteries Better?

Electric vehicle batteries are designed for a very different purpose. Unlike car starter batteries, they are built to continuously power electric motors.

This makes them much closer to the working conditions of a water thruster.

Electric vehicle batteries are commonly used for applications such as kayaks, small boats, fishing boats, and underwater robots because they can provide stable power output for longer periods.

Traditional electric vehicles often use lead-acid batteries. They are affordable and easy to find, but they are heavier and have a shorter cycle life compared with lithium batteries.

For example, a 48V 20Ah lead-acid battery paired with a thruster requiring 20A:

20Ah ÷ 20A = 1 hour

At normal cruising speed instead of continuous maximum throttle, the actual runtime may reach around 1.5–2 hours depending on conditions.

Why LiFePO₄ Batteries Are Recommended

For most water thruster applications, LiFePO₄ (Lithium Iron Phosphate) batteries are the preferred option.

Compared with traditional lead-acid batteries, LiFePO₄ batteries provide a higher energy density, lighter weight, more stable voltage output, and much longer cycle life.

However, many users only focus on battery capacity (Ah) and overlook another important specification: continuous discharge current (A).

Both parameters are important.

Ah determines how long the battery can run the thruster.

A determines whether the battery can provide enough current to make the thruster work properly.

How to Choose a Battery for a 24V Water Thruster?

For a 24V thruster system, we normally recommend a 24V LiFePO₄ battery.

The battery should meet:

• Voltage: 24V
• Continuous discharge current: at least 100A for dual thruster systems

The calculation method is simple:

Runtime = Battery Capacity (Ah) ÷ Thruster Working Current (A)

For example:

A 24V 100Ah battery powering a dual thruster system:

If the two thrusters consume around 90A at maximum throttle:

100Ah ÷ 90A ≈ 1.1 hours

This means the system can run for about 1 hour at continuous full throttle.

During normal cruising, where the throttle is adjusted and maximum power is not used continuously, the actual runtime is usually around 2–3 hours.

Single Thruster vs Dual Thruster Battery Requirements

A dual thruster system means two thrusters are installed. The advantage is that the left and right thrusters can operate at different speeds, allowing easier steering.

For example, APISQUEEN U5 dual thruster or U92 dual thruster systems require around 90A at maximum output.

A suitable battery should provide:

24V voltage and at least 100A continuous discharge current.

For a single thruster system, the power requirement is lower.

A single thruster with a maximum working current of around 45A can use:

24V battery + continuous discharge current ≥50A

With a 24V 100Ah battery:

100Ah ÷ 45A ≈ 2.2 hours

In normal use, the runtime can reach around 4–5 hours depending on speed and load.

Battery Capacity Reference

For a 24V system:

These values are calculated based on continuous maximum throttle operation.

Actual runtime depends on boat weight, water conditions, speed, and throttle usage.

The Most Important Things When Choosing a Battery

A common mistake is choosing a battery only by capacity.

A 100Ah battery does not automatically mean it can power every thruster.

You also need to check:

• Is the voltage correct?
• Can the BMS provide enough continuous current?
• Is the battery designed for high-current discharge?

For example, a dual thruster system requiring 90A cannot perform properly if the battery BMS can only provide 50A, even if the battery capacity is 100Ah.

Remember:

Ah determines runtime.
A determines performance.

Both are equally important.

Final Recommendation

Car batteries can work for short-term testing, but they are not designed for long-term water propulsion.

Electric vehicle lead-acid batteries are affordable and suitable for lower-power applications, but they are heavier and have shorter lifespans.

For users who want reliable long-term performance, especially for kayaks, electric boats, and underwater robots, a LiFePO₄ lithium battery is usually the best choice.

Choosing the right battery will not only improve the performance of your water thruster but also protect the motor, ESC, and the entire propulsion system.