Are you thinking about building or upgrading your own electric watercraft with a jet drive? Whether it’s an adrenaline-pumping e-surfboard (electric surfboard) or a larger boat, everything starts and ends with one crucial component: the battery.

Choosing the right battery can be quite intimidating because the market is full of technical jargon. If you pick the wrong one, your watercraft will either be too heavy or it will run out of power way too quickly.

To make things easier, we’ve simplified the whole science behind lithium-ion batteries into the two main options used today.

1. Cylindrical Lithium-Ion Batteries: The Kings of Lightweight for E-Surfs

If you are building an electric surfboard (e-foil or jet surf), your biggest enemy is weight. The heavier the board, the harder it is to maneuver, and the more energy it takes just to stay on the water.

This is where cylindrical lithium-ion batteries come into play (they often look like slightly larger versions of regular AA batteries, but they are much more powerful, such as the 21700 type).

• Why they are great: They have an extremely high energy density relative to their weight. This means you get a lot of power in a very lightweight package.

• Ideal for: Electric surfboards where every gram counts. They make jumps, sharp turns, and carrying the board to the water much easier.

2. Larger Square (Prismatic) NMC Batteries: For Raw Power

If your project isn’t a small board, but a larger, high-performance system (like a RIB boat with a jet drive or a smaller speedboat), cylindrical cells won’t cut it. You need something heavier duty.

For these setups, larger square (prismatic) NMC lithium-ion batteries are the way to go (NMC stands for Nickel Manganese Cobalt).

• Why they are great: These lithium-ion batteries are built for heavy workloads. They can continuously deliver massive amounts of current (amps) for a long time without overheating.

• Ideal for: High-performance systems where weight isn’t the primary factor, but brutal torque and long runtime at high speeds are essential.

What to Look Out For During the Build? (Safety First)

Choosing the cells is only half the battle. When you start assembling a lithium-ion battery pack for a jet drive, you absolutely must follow three golden rules. Water and electricity don’t get along very well.

1. Perfect Waterproofing (IP67 or IP68)

The battery will be on the water. Even if it is sealed inside the board’s compartment, condensation or stray drops will occur. The battery enclosure must be 100% waterproof. Any contact between saltwater and a lithium-ion battery can cause a short circuit and destroy the system.

2. High-Quality BMS (Battery Management System)

The BMS is the “brain” of your battery. It’s an electronic circuit that ensures individual cells don’t overdischarge, overcharge, and—most importantly—overheat. Jet drives put an enormous load on the system, so you need a smart BMS that will shut things down in time if something goes wrong.

3. Cooling

High current means high temperatures. Tightly packed lithium-ion batteries in a sealed box heat up fast. Consider passive cooling through aluminum heatsinks or even a water-cooling loop that utilizes the water you are riding on.

Summary: Which One Should You Choose?

• Choose smaller cylindrical lithium-ion batteries if you are building an e-surf and want agility and lightweight handling.

• Choose larger square NMC lithium-ion batteries if you are building a larger, heavier, and high-performance system that needs massive, constant power.

Building your own electric jet driven vessel is an incredibly fun project. Just take your time with safety and insulation planning—your battery will thank you with a long lifespan!

Do you have any questions about wiring or choosing a correct battery for our jet drives? Contact us and let us help you!