Elba 45 catamaran with 48V DC system without generator
Full Low Voltage Blue-Airco system powered directly by onboard lithium batteries
On a Fountaine Pajot Elba 45 cruising catamaran equipped with a 48V lithium battery bank, Blue-Airco designed a fully DC boat air conditioner system to provide comfort in every cabin and in the saloon. The units are powered directly by the 48V battery bank and, in this configuration, operate without starting the generator or adding load to the inverters, in keeping with the boat's energy architecture.
The challenge
The catamaran was already equipped with 48V lithium batteries. The request was clear: to power the air conditioning directly from those batteries, avoiding unnecessary conversions, reducing the load on the inverters, and containing noise and consumption.
On a boat of this type, the needs change from area to area: the cabins require quiet during rest, the salon must quickly reach a comfortable temperature, and the two hulls demand careful distribution of seawater and air. Therefore, it could not be a simple standard installation: an integrated system with the electrical system and with the way the spaces are experienced on board was needed.
Project details:
Boat
Fountaine Pajot Elba 45 – cruising catamaran, 13.45 m, Maestro version (owner's cabin + 2 guest cabins)
Boat builder shipyard
Fountaine Pajot
Geographical area
Mediterranean and later Tropics
Market
European recreational boating – cruising catamarans
System
Blue-Airco Full Low Voltage, entirely at 48V DC (unit and pumps)
Pumps
48V DC brushless seawater pumps, one for each hull
Power supply
48V onboard lithium battery bank
Objective
multi-cabin comfort powered directly by the 48V battery bank, with less dependence on the generator and without needing to start it to directly power the units
The Blue-Airco solution
Blue-Airco has built a system entirely at 48V DC, with units and pumps at the same voltage as the battery bank: in this way, the air conditioning directly uses the energy available on board, reducing intermediate steps.
The owner's cabin is served by a 10,700 BTU/h unit installed under the bed. On the port side, an 18,200 BTU/h unit serves the bathroom and salon, while the salon has a second 18,200 BTU/h unit to manage the larger common area. On the starboard side, the two guest cabins – aft and forward – are air-conditioned by two 10,700 BTU/h units installed under the beds.
The seawater pumps are also 48V DC, with a dedicated pump for each hull. The system is organized by zones: only the areas actually used are conditioned, adapting operation to external conditions and onboard presence, with a more rational control of consumption.
Why 48V DC makes a difference
With 48V lithium batteries, a system designed to work directly in direct current makes better use of the available energy. The advantage is not only technical: onboard it means more freedom of use, better consumption control, and less dependence on the generator, an important benefit for those living on the boat at anchor and seeking silent nighttime comfort.
Limiting the use of inverters also reduces losses, heat, and additional noise: air conditioning becomes part of the boat's energy architecture, not a separate load.
Onboard results
The system has made it possible to air-condition cabins and the salon without using the generator as a direct power source for the units. In automatic mode, the units quickly reach the set temperature; once stabilized, operation becomes steady and power consumption is reduced.
Estimated runtime in tropical conditions
| DC system runtime in tropical conditions (sea water at 32 °C) | Estimated runtime (60% ECO + 40% medium speed) | ||||||
|---|---|---|---|---|---|---|---|
| LiFePO4 lithium battery | Medium speed | ECO mode | Maximum speed | ||||
| Battery voltage | Battery capacity | Theoretical energy | Available energy (90%) | Air-conditioning runtime | Air-conditioning runtime | Air-conditioning runtime | |
| V | Ah | kWh | kWh | h | h | h | h |
| 48 | 100 | 4.8 | 4.32 | 1.6 | 3.6 | 0.9 | 2.8 |
| 48 | 200 | 9.6 | 8.64 | 3.2 | 7.2 | 1.8 | 5.6 |
| 48 | 300 | 14.4 | 12.96 | 4.8 | 10.8 | 2.7 | 8.4 |
| 48 | 400 | 19.2 | 17.28 | 6.4 | 14.4 | 3.7 | 11.2 |
| 48 | 500 | 24 | 21.6 | 8.0 | 18.0 | 4.6 | 14.0 |
The table estimates runtime with all five air-conditioning units and both circulation pumps operating simultaneously, assuming sea water at 32 °C and 90% usable battery capacity.
The noise level remains contained, especially in the maintenance modes: in ECO the owner describes it as almost imperceptible – a decisive aspect on a cruising boat, where air conditioning should improve the onboard experience, not disturb it. The technical support from Blue-Airco also contributed to the result, with practical advice to optimize the use of the system.
A solution for modern catamarans
The project shows how a 48V DC marine air conditioning system is a concrete solution for catamarans, boats with lithium batteries, and vessels that want to reduce dependence on the generator.
The value lies not only in cooling the spaces, but in integrating climate comfort and energy management: using available energy efficiently, keeping noise and consumption low, and offering the owner and guests a quieter and more autonomous experience.
For those designing a system on a modern catamaran, a Full Low Voltage solution transforms the air conditioning from a separate and demanding load into a coherent part of the onboard system.
Do you want to design a 48V DC system for a catamaran?
Blue-Airco supports shipyards, refitters, dealers, and boat owners in designing marine air conditioning systems at 12V, 24V, and 48V DC. Contact the Blue-Airco technical team to evaluate the most suitable configuration for your boat.