Power boost – Lithium Batteries on a sailboat

Installing lithium batteries onboard sailing vessel Bagabodna - Amel Samtorin

Our sailboat battery upgrade to lithium, and adding much more monitoring is part of our projects in making Bagabonda, our Amel Santorin, as autonomous as we technically can.

This is a post in our series of upgrades and more we plan on Bagabonda. It’s a rather technical article rather than a post about our voyages and adventures. Want to see those stories? Click here.

Our hang for autonomy

Where the anchor drops, the office pops, has been a concept we discussed earlier. But to achieve that, we need to ensure that our systems onboard Bagabonda are built so that our dependency on shore systems is minimal. Power and water are two of the main attention points we’ve worked on since we resolved the internet connectivity issue.

Today, after months of planning, we started one of the larger projects onboard: the upgrade of our lead batteries to lithium and adding a better management system for power and power generation.

Where does the power on board Bagabonda originate from?

In our Amel Santorin, we charge the batteries in four ways before this upgrade:

  • A shore power charger. In a marina, we connect a cable to the shore power, which feeds into the charger that adds power to the batteries. When we bought Bagabonda a few years ago, she had a Cristec smart battery charger installed that we will remove today in this project.
  • Solar Panels: in 2022, we installed an arch and two solar panels of each 335W, feeding the batteries. This was done up until now with a Victron MPPT that would feed its power directly into the battery bank.
  • When the engine is running, we have the alternator (just as you have in a car with a combustion engine) that will generate power as long as the engine is on.
  • And last but not least, despite its age, our Amel has a unique system that will generate power when under sail. We can keep the propeller running in the water while we move forward under sail. The propeller will move a dedicated alternator and will generate power.

One of three big upgrade projects

Gaining autonomy on Bagabonda is a multifaceted endeavor, encompassing three major projects designed to ensure our life at sea is as self-sufficient and sustainable as possible.

Bagabonda Sailing vessel at anchor in Cabrera (Spain)
  • Generate our power
  • Produce our drinking water
  • Have broadband internet access offshore

The comprehensive upgrade of our power systems stands as a cornerstone among these initiatives. By enhancing our ability to generate, store, and manage power more efficiently, this project empowers us to use our resources wisely, minimizing our dependency on shore-based utilities and enabling longer, more sustainable periods at sea.

Parallel to this, our communications project aims to secure reliable internet access, crucial for both our professional commitments and staying connected with the world, regardless of our location.

Completing the trio of autonomy-enhancing endeavors is the installation of a water desalinator, a game-changing addition that allows us to produce our own fresh drinking water from the sea.

Together, these projects form the backbone of our strategy to achieve unparalleled autonomy on Bagabonda, setting us free to explore the oceans while maintaining the comforts and necessities of modern living.

As both the communications/internet project and the water-making depend on the power we can generate on board, we started this winter with this largest (and most expensive) of the three pillars on which our autonomy rests.

The Upgrade Initiative

Our ambitious project aimed to transition from lead batteries to lithium ones and introduce a sophisticated power management system. This upgrade wasn’t just a technical enhancement; it was a leap toward a sustainable and efficient energy solution aboard Bagabonda. We tackled this extensive and costly endeavor by choosing Almerimar, Spain, as our base, marking a pivotal point in our journey toward autonomy.


In Almeria, we met Spencer from Alamar in person. His reputation preceded him through the blogosphere of sailors. As this gentleman has no shortage of work on boats, we were happy he could squeeze in our rather substantial project in his planning. Working with him was not only the only reason those projects actually got where it is now, but his insights and hands-on thinking allowed me to learn my ship and its techniques even better.

During the project, Spencer would discuss ideas with me, and we decided on the direction to take. Do we need an extra charger for the starter, what bout we can isolate the engine power, and so on It is not only a project that added security and autonomy to our Amel Santorin, It is very much adjusted to the way we will use her.

When in this post, I write ‘we‘, basically know that it’s actually Spencer with a bit of assistance from my end 😉

Battery System Overhaul

The heart of our project was the battery system upgrade. The four old lead-acid batteries, barely providing 8V and far past their prime, were replaced with advanced lithium batteries. This switch significantly increased our energy storage capacity from a meager 160Ah to a robust 600Ah and introduced efficiency and reliability into our system. With lithium batteries, we could utilize nearly the full capacity, a stark contrast to the 50% limitation of lead-acid batteries.

Much of the job was to separate the starter battery from the house bank. In the past, not having that separation, we had run into a situation where a charger drained most of our battery power and had us call for help to get the engine started again.

Our new Lithium batteries delivered on board Bagabonda

Furthermore, individual connections to a power distributor enhanced our control, allowing for selective battery usage and maintenance. In the old setup, we had a metal bar linking the batteries connected in parallel with a metal bar. Years ago, most installations on ships would be done this way. However, it gave us no insights into the individual batteries and would put a higher weight on the units at the beginning and the end.

We connected each new lithium battery to a Victron power-in manager. The extra cool effect that now has is that a faulty or short-circuited battery can be isolated without moving it around. The combination of BMS and this Lynx system, leading to the shunt, is another game changer.

Our old lead-based bank

Four batteries x 108 AH = 432 AH, but since lead batteries can only be discharged for 50%, we had about 216Ah. Considering the batteries were worth approximately 75% of their expected power, we had about 160Ah. The starter and house batteries were not separate, so we used that capacity for both.

Our old battery bank aboard Bagabonda
The old battery bank aboard Bagabonda

Our new lithium-based bank

Four batteries x 150Ah = 600Ah, which we can use almost wholly. These are house batteries, and we added a new lead battery to act as the starter battery. So our house bank went from 160 Ah to about 600Ah.

Installing the new batteries

Separated starter battery

We discovered the hard way during the summer of 2023 that having the house and starter batteries are the same leads to unforeseen issues. When I left our Torqeedo battery charging in the 12V system this summer, I came back on board to find the batteries depleted beyond the point where they could deliver enough power to start the engine. Ending with the marineros of Portocolom having to bring us to the shore to get that sorted out.

One of the core deliverables of our power project was the ‘separation of powers’ onboard Bagabonda. Having lithium on a sailboat is only one achievement; ensuring we can rely on the starter battery is another.

With the old batteries beyond their useful lifespan, we added a new 12V lead-based battery that would serve as the starter battery. It receives power from the alternator, and we added a separate battery charger (a small Victron Blue Smart IP22 Charger) to ensure these could be charged separately. When the starter battery is full and receives more power from the alternator, it will feed this back to the house batteries via a battery-t-battery charger (Victron Orion-Tr Smart DC-DC Charger Non-Isolated ).

This is where we discovered that our Lucas alternator wasn’t behaving as we expected. It took us some time to figure out, as we were still building the new energy system. Thanks to some local help, we could have it tested the same day, and pretty soon, we had the alternator charging our brand-new shiny starter battery.

Integrating Smart Technology

Introducing batteries equipped with a Battery Management System (BMS) and Bluetooth connectivity modernized our setup. This smart technology enables us to monitor each battery’s status and manage them remotely, an upgrade from the rudimentary voltage checks of the past.

The core of the new system: Victron MultiPlus-II

After a couple of good conversations with specialists in Portocolom and with Spencer in Almerimar, we decided to go for this Victron MultiPlus-II 12/3000/120-32. This system sits centrally in our new setup. It manages the shore power (and charges our batteries) and provides 220V/110V on board Bagabonda.

While we try to eliminate all systems that need 220V and 110V if there is an equivalent in 12V, not all devices have a good substitute. Our water heater (yes, of course, we have warm water on board) works on 220V, as does the extra heater we use on the few very cold days in Spain.

Those on a boat know that not all marinas provide the same amperage regarding shore power. We’ve all been a that point where we insert the cable from the boat in the shore power plug and hear the ‘poof’ or ‘click’ of the breaker in the box on the shore. That’s why we added the Victron Digital Multi Control. A switch in the galley allows us to decide what maximal amperage is that we will draw from the port.


Bagabonda now has multiple sources of energy we can use to store in our new lithium batteries on a sailboat:

  • When in a marina, we can use the shore power there
  • The solar panels
  • The alternator, when the engine is on
  • A second alternator that is driven by the propeller when under sail
  • A very small portable AC power generator

We have been in doubt about adding a wind generator, but most sailors we spoke to complained about the noise they generate. So, at this point, and especially since we’re in the sun-rich Mediterranean Sea at this moment, we decided not to add a wind generator at this point. When we plan to sail north (or south), we might revisit this choice.


With the ship having its primary power source in the 12V battery system, we seek, when possible, to buy 12V systems rather than 220V (110V) systems commonly used at home. Fortunately, our needs, and the ones of truck drivers and RV owners, made a market of many home appliances that can run directly on 12 V.

At the same time, we have some projects running to remove the transformation from some devices. Many appliances we use in our home actually take the 220V/110V AC and convert it into 5 or 12V DC internally to make the system work. We try to change these ourselves so they can run off the DC system without us having to change 12V to 220V, only to have it transformed inside a printer or charger converted back to a lower voltage in DC. It brings its challenges (and we void most warranties), but it keeps the power consumption under control on board.

In our old setup, we had a very weak inverter that we integrated in the chart table, allowing us to charge a computer occasionally. That one will become a spare part now for use in emergencies, as we will end up with a power line providing 220V over the port side of the boat in the cabins and the galley.

The Victron Multiplus is made so we get the right balance of power: it will first draw from shore and solar before it takes energy from our lithium batteries. And when we need more power than the shore and solar can deliver, it compensates with electricity from our new house bank.

System Monitoring and Management

Another core part of our upgrade was installing the Victron Cerbo GX system. This advanced monitoring unit is now the central intelligence of our power setup, allowing for real-time tracking of energy production, storage, and consumption. Its integration into the Victron Remote Management (VRM) platform means we can oversee our system’s status from anywhere, ensuring Bagabonda’s energy system operates smoothly and efficiently.

On our Amel Santorin, we installed the Cerbo GX in the chart table area, meaning we have to bring the communication cables from the engine room (where our batteries and the inverter/charger are placed). Those of you who have installed or replaced wiring on a boat know this is one of the more time-consuming moments in any boat project. Thanks, however, to the help of Bill, who manages a reference library of Amel installations and datasheets, we had the right clues to find all relevant cable conduits.


Once we had the cables in place, we gained an insight into our power management that we could, up until now, only dream of. It shows the power we draw from the shore, the energy generated by the solar, and how much we use on the DC circuits (12V) and the AC circuits (220V). It also gives a status on the battery and an idea of autonomy at the current power consumption.

The Victron Cerbo GX and the Victron Cerbo GX Touch on Amel Santorin Bagabonda
Victron Cerbo GX Touch onboard Bagabonda

But no night vision?

The cool thing about the touch screen is that Victron allows us to see the beta version of the new displays (as the picture shows). For a boater, however, there is one disappointment that I hope Victron will address before release: the screen allows the dark and bright mode but has not (in the beta we use) thought about a night vision mode that sailors need. At night, we switch all systems to screens that only show black and red colors, so our night vision is not impaired after consulting a screen.

Remote Monitoring

Since we also installed a more intelligent IP network on board, we can now view the situation of our power system on board, even while we are away from the ship. And since our Ruuvi sensors talk to the Cerbo system, we can even see the temperature and humidity.

Boat mess

Did I already tell you that when I do a project on Bagabonda, especially one where I need to open panels, it requires me to move stuff around and generates a huge mess? Here’s what I mean:

Solar Power Optimization

Our pursuit of autonomy also led us to address our solar power generation issues. After discovering improperly crimped connections, we meticulously revised every link between our solar panels and the MPPT controller. This effort rectified our power generation woes, ensuring a steady and reliable charge to our new battery bank even on cloudy days, a testament to our commitment to harnessing renewable energy effectively.

While devoid of the day-to-day intricacies, this extensive project represents a monumental step towards achieving a higher degree of self-sufficiency on Bagabonda. By enhancing our power storage with lithium batteries, optimizing solar energy generation, and incorporating intelligent monitoring and management systems, we’ve set a new standard for living and working at sea. Our journey towards energy independence not only underscores our commitment to a sustainable seafaring lifestyle but also ensures that wherever the anchor drops, our office indeed pops, powered by the sun and the sea.

We have no affiliations with any of the above brands or professionals. We are happy with our choices and will update our experiences on our blog here. But please, do your research before engaging in an expensive and complicated project like the one we did here.