PowerBox for Sailing Boats

Wall-Mounted 12-Volt Power Supply with Replaceable 18-Volt Batteries

A compact, wall-mounted PowerBox was developed to provide a reliable 12-volt power supply on a sailing boat. Instead of using a conventional 12-volt lead-acid battery, the system is powered by replaceable batteries from the Bosch 18V tool battery platform.

The PowerBox supplies the navigation instruments, mast-mounted displays, masthead light, and dimmable LED lighting inside the boat. An additional 12-volt connection is available for future devices or temporary equipment.

All switches, fuses, electrical connections, and electronic components are integrated into a custom-designed, 3D-printed enclosure. Waterproof connectors allow the individual devices to be connected securely and disconnected when required.

Initial Situation

Many small and medium-sized sports boats do not require a large or complex electrical system. Nevertheless, a limited number of essential devices still need power, including navigation instruments, mast displays, navigation lights, and interior lighting.

Installing a comprehensive marine electrical system is often difficult to justify for such a limited power requirement. As a result, many boats use improvised solutions consisting of individual batteries, loose wiring, separate switches, and inconsistent connectors. These systems are often difficult to maintain, unreliable, and hard to extend.

The previously used 12-volt battery was heavy, inconvenient to transport, and difficult to charge. It required a separate charger and could not be replaced quickly while on board.

There was also no central unit combining the power supply, switches, fuses, and connections. This made the wiring difficult to understand and complicated maintenance or future modifications.

The objective was therefore to develop a solution that:

• replaces the existing 12-volt battery

• uses lightweight and easily replaceable batteries

• centralizes the switching and protection of all connected devices

• provides clear and structured wiring

• uses waterproof external connections

• can be permanently mounted to the wall of the boat

• can be extended with additional 12-volt devices

Defined Solution

A permanently installed PowerBox was developed around a replaceable Bosch 18V tool battery. The battery can be removed within seconds, charged outside the boat with a standard charger, and replaced with a fully charged spare battery when necessary.

Because the connected devices operate at 12 volts, a DC-DC converter was integrated into the enclosure. It safely reduces the battery voltage from 18 volts to a regulated 12-volt output for the boat’s electrical equipment.

The individual devices are controlled through separate switches. The connected systems include:

• navigation instruments

• mast-mounted displays

• masthead light

• dimmable LED interior lighting

• one spare 12-volt connection for additional equipment

Each electrical circuit is protected by an individual fuse inside the PowerBox. This provides separate protection for the wiring and the connected devices. All external devices are connected using waterproof plugs. The connections are clearly assigned, can be disconnected individually, and allow components to be removed or maintained without modifying the internal wiring.

In addition to the active battery mount, the PowerBox includes a dedicated holder for a spare battery. If the installed battery runs out, the power supply can be restored immediately without requiring access to a charger on board.

Result & Added Value

The PowerBox replaces the previously distributed and improvised electrical setup with a central, permanently installed power unit. Switches, fuses, voltage conversion, and external connections are now combined in a single compact enclosure.

The main advantage is the replaceable battery system. The battery can be removed easily, charged using an existing Bosch charger, and replaced with the spare battery when required. There is no longer a need to carry a heavy and inconvenient 12-volt battery between the boat and a charging location.

The centralized design makes the wiring easier to understand and maintain. Each device has a dedicated switch, fuse, and connector. This makes it easier to identify faults, disconnect individual systems, and replace components.

The integrated fuses protect the individual electrical circuits, while the DC-DC converter provides a stable 12-volt supply for the connected equipment.

The dimmable LED lighting also improves comfort below deck. The brightness can be adjusted to the situation while keeping energy consumption low.

The additional 12-volt connection makes it possible to connect another device in the future without rebuilding the entire system.

The result is a compact, modular, and practical electrical solution that meets the limited power requirements of a sports boat without the cost and complexity of a full marine electrical installation.

Technical Design

The PowerBox enclosure was individually designed and produced using 3D printing. Its dimensions and internal structure were adapted to the available mounting space, switches, connectors, battery interface, and electrical components.

The enclosure is permanently screwed to the wall of the boat. This provides a fixed installation and prevents the unit from moving when the boat heels or is exposed to waves.

The replaceable 18-volt battery connects to the system through a compatible battery adapter. A second mount securely stores the spare battery next to the PowerBox.

The enclosure contains:

• the battery connection and power input

• a DC-DC converter from 18 volts to 12 volts

• separate fuses for the individual circuits

• wiring for the switches and outputs

• connections for the waterproof plugs

• the control system for the dimmable LED lighting

The DC-DC converter is the central technical component between the 18-volt battery and the 12-volt equipment. It reduces and regulates the input voltage to the required operating voltage. The external switches allow the connected devices to be controlled individually. Devices that are not required can be switched off completely, preventing unnecessary battery consumption. Waterproof connectors are used between the PowerBox and the boat’s electrical devices. These protect the contacts from moisture while maintaining detachable connections. Individual cables or devices can therefore be replaced without removing or rewiring the complete PowerBox.

The modular design also allows future modifications. The currently unused 12-volt output can be assigned to another device, while switches, fuses, and connectors can be replaced individually when required.

Components and methods used: 3D printing · CAD design · Bosch 18V battery system · DC-DC converter · 12-volt electrical system · Fuses · Waterproof connectors · Dimmable LED lighting · Prototyping and practical testing