Pillar guide
Marine battery systems for yachts: sizing, technology & integration
Everything you need to know about energy storage for sailing and motor yachts, from LiFePO4 technology and capacity sizing to modular architecture and real-world autonomy. The complete guide from JOOOL’s engineering team.
Definition
Why energy storage is the foundation of yacht electrification
Every benefit of a hybrid or electric yacht : silence at anchor, autonomous hotel loads, reduced generator runtime, electric propulsion, depends on one thing: the ability to store sufficient energy onboard to meet demand between charging opportunities. Without adequate battery storage, even the best energy management system cannot deliver the experience sailors expect.
Battery technology has transformed what is possible in the past decade. The energy density of modern LiFePO4 packs is high enough to fit meaningful capacity into the space and weight budget of a production sailing yacht. Charge cycles are long enough that a battery bank installed today will outlast the vessel’s first decade of operation. And the management systems have matured to the point where the battery bank is genuinely maintenance-free under normal operating conditions.
JOOOL’s Battery Pack range : 21, 27, 32 and 38 kWh modules, is designed specifically for marine integration: compact, modular, IP65-rated, and built around the safest available lithium chemistry.
CHEMISTRY
LiFePO4: why it is the only chemistry for marine use
Not all lithium batteries are equal. The chemistry determines safety, cycle life, operating temperature range, and end-of-life behaviour. For marine applications, where the consequences of a thermal event at sea are severe, chemistry selection is not a specification footnote. It is a fundamental design decision.
NMC (Nickel Manganese Cobalt) and NCA (Nickel Cobalt Aluminium) chemistries offer higher energy density than LiFePO4, they pack more kilowatt-hours per kilogram. This is why they dominate electric vehicles, where weight is critical. But they are also more prone to thermal runaway under stress: overcharge, short circuit, mechanical damage, or extreme temperature can trigger a self-sustaining exothermic reaction that is very difficult to extinguish.
LiFePO4 (Lithium Iron Phosphate) has lower energy density but is intrinsically thermally stable. The chemistry does not support thermal runaway. It is non-toxic and cobalt-free. It tolerates overcharge and elevated temperatures far better than NMC. For a battery bank installed in the hull of a sailing yacht, inaccessible, potentially exposed to heat, and far from emergency services, this stability is decisive.
The storage unit
JOOOL Battery Pack: 21 to 38 kWh
JOOOL Battery Packs are modular, high-density marine storage units designed for seamless integration with the OneBox. Available in four capacities, they stack to deliver up to 152 kWh per OneBox — or up to 456 kWh on a three-OneBox installation.
Safe and cobalt-free battery technology with no thermal runaway, ensuring reliable and eco-friendly marine energy storage
Built-in fire suppression system activating at 80°C for enhanced onboard safety beyond industry standards
Voltage Interlock Loop ensures secure operation with integrated hardware safety protection
Advanced Battery Management System providing real-time cell balancing, temperature, and health monitoring
Scalable battery architecture up to 152 kWh per module and adaptable to various yacht configurations
Zero maintenance required under normal operating conditions for long-term reliability
| 21 kW | 27 kW | 32 kW | 38 kW | |
|---|---|---|---|---|
|
Nominal energy (kWh)
|
21.5 kWh | 26.9 kWh | 32.3 kWh | 37.7 kWh |
|
Nominal voltage VDC
|
205 | 256 | 307 | 358 |
|
Weight (kg)
|
200 | 245 | 290 | 335 |
|
Length (mm)
|
760 | 885 | 1,030 | 1,165 |
|
Height × Width (mm)
|
770 × 275 | 770 × 275 | 770 × 275 | 770 × 275 |
|
Cooling
|
Air | Air | Air | Air |
|
|
|
|
QUESTIONS
Everything you want to know
Up to 4 Battery Packs in parallel per OneBox module, for a maximum of 152 kWh per module. With up to 3 OneBox modules running in parallel, total system storage can reach 456 kWh.
The EPMS monitors each pack continuously. If a pack falls below operating parameters, it is isolated automatically and the system continues operating on the remaining packs. JOOOL's worldwide service network handles replacement.
Ready to size your battery bank?
Contact JOOOL's engineering team for a custom system sizing or explore the full product range and reference yachts below.
