For decades, onboard generators have been the go-to option for topping-up batteries and running power-hungry appliances at anchor. But they come with drawbacks — noise, frequent maintenance, fuel consumption, and taking up valuable space. Now, high-output alternators and smart regulators offer a reliable alternative, generating power efficiently while cruising and keeping your batteries charged without disturbing the peace for you or the other boats in the bay.

How it works

When the owners of Geaux Girl, a Leopard 50 catamaran, were planning their electrical system, there was one big question:

Does it need a generator?

For Andre Cormier from The Yacht Rigger, who has completed numerous electrical system installations, the answer was simple: no. Let’s take a closer look at this system.

Instead of a genset, Geaux Girl was fitted with a high-output alternator, managed by an ARCO Zeus alternator regulator integrated with Victron components. “Crucial for this electrical design is a reliable and powerful energy system which is why we chose Victron as the foundation of the power system,” comments Andre.

Arco Zeus alternator regulator on Geaux Girl

The electrical system onboard Geaux Girl includes a 15kVA, 48V Victron MultiPlus-II, working alongside an isolation transformer to supply 230V shore power to the boat. The catamaran is also equipped with a 120V system, powered by two parallel 48V 5000VA MultiPlus-II inverter/chargers, providing a total of 10kW power. This dual-inverter setup allows the 230V system to handle high-power loads like air conditioning, hot water heaters, and an induction cooktop, while the 120V system runs lower-demand appliances without overloading the main inverter. “Victron’s price point and offerings on the 48V system side allowed us to create a powerful yet cost-effective system that eliminates the worry of overloading the inverter under normal use,” notes Andre.

230V and 120V Victron Multiplus-II inverter/chargers on Geaux Girl

Geaux Girl’s high power demands call for a reliable way to recharge the batteries while at anchor. That’s where its 4kW solar array comes in, making good use of its large stern arch. The 12V and 48V battery banks are charged independently through Blue Smart MPPT solar chargers, with three 12V 100/50 MPPTs dedicated to the 12V bank and five 150/35 MPPTs charging the 48V bank.

When the sun isn’t enough, the high-output alternator steps in to keep the batteries charged. In Generator Mode, the ARCO Zeus regulator boosts alternator output while idling, recharging the batteries while stationary.

When underway, the ARCO Zeus alternator regulator can be configured to limit charging at low RPM, ensuring the engine has enough power for propulsion when needed. At cruising RPM, it increases alternator output for charging the batteries.

Geaux Girl 48V battery bank

Here’s a look at Geaux Girl’s system diagram. If you’re interested in high-output alternator systems, you can find detailed system diagrams here.

Geaux Girl electrical system diagram

Monitoring

With a dual-voltage system, a large solar array, and a high-output alternator, it’s essential to have all the components working together—and to keep track of it all. “We decided to install two Cerbo GX to be able to monitor both systems at a quick glance on the nice displays,” says Andre.

The primary Cerbo GX is for the Lynx 500 BMS NG, ARCO Zeus alternator regulator, and the 230V system, while the secondary Cerbo GX monitors the 12V and 120V systems. Solar generation for both the 12V and 48V systems can be monitored simultaneously on the GX devices.

GX Touch 50 displays installed on Geaux Girl

The ARCO Zeus alternator regulator is connected to the Lynx Smart BMS NG, allowing it to receive real-time battery data, such as voltage and current, and adjust charging accordingly. This also enables real-time monitoring of alternator output and battery charge status on the Cerbo GX touch display, or from anywhere in the World via the VRM Portal. Here is a short video from ARCO Marine showing how this integration works.

Alternator information displayed on GX Touch 50

The ARCO Zeus alternator regulator can be monitored and configured through its dedicated ARCO Zeus App. Using the app, you can also switch between operational modes, and automatically log and share data for easy troubleshooting. If you’d like to learn more about the ARCO Zeus alternator regulator and the ARCO Zeus App, you can have a look at this short video, shared by ARCO Marine.

In today’s world, we can all agree that moving toward more environmentally focused solutions isn’t just a choice—it’s the way forward. If going fully electric isn’t an option, hybrid systems can bridge the gap. And if that’s not feasible, there are other ways. With a high-output alternator system, running a 50ft catamaran without a genset isn’t just possible, it’s practical. Smart energy management, efficient charging, and real-time monitoring make it easier than ever to enjoy life on the water without the noise, fuel burn, or maintenance of a generator. And if nothing else, the other boats in the anchorage will appreciate the peace and quiet.