Since One World Sailing Academy is heavily focused on vessel systems, along with the operation, maintenance, and management of those systems offshore, the following article will discuss many of the electrical systems we currently use aboard our vessel One World, our Amel Super Maramu 2000.
There are many good brands and system configurations available in the offshore cruising world, and there are certainly other systems that work well too.
The purpose of this article is not necessarily to say one system is the only correct choice, but rather to discuss some of the systems we currently use aboard our vessel, along with why electrical systems become so important in offshore and blue water cruising.
One of the first major systems aboard One World is the electrical system itself.
From the factory, the boat was designed as a European-built vessel, so it utilizes a 24-volt DC electrical system along with a 220-volt AC system.
In addition to that, we utilize 24-to-12-volt converters to operate many of the onboard electronics and accessories that require 12-volt power.
That includes systems such as:
- navigation electronics
- VHF radios
- radar systems
- chart plotters
- depth sounders
- forward-facing sonar
- Starlink
- various onboard 12-volt outlets throughout the vessel
Even on a 24-volt boat, there are still a significant number of components and accessories in the marine world that operate on 12 volts, so proper voltage conversion and power management become important parts of the overall electrical system design offshore.
One of the questions people often ask is: why use a 24-volt system instead of a 12-volt system aboard an offshore cruising boat?
One of the major advantages of higher-voltage DC systems is efficiency.
As voltage increases, amperage decreases for the same power demand, which means smaller wire sizes can often be utilized throughout various onboard systems.
In practical terms, many 12-volt systems require significantly larger wire sizes compared to equivalent 24-volt systems carrying the same electrical loads.
That becomes especially important on larger offshore vessels where wire runs can become quite long and electrical efficiency matters.
Overall, 24-volt systems tend to operate more efficiently for larger cruising boats with heavier electrical demands.
Those remaining 12-volt requirements are easily handled through the use of DC step-down converters.
On our vessel, we utilize Victron Energy 24-to-12-volt converters to power many of those systems.
Over time, I upgraded the original converters aboard the boat from smaller 12-amp converters to larger 20-amp converters in order to increase system capacity and allow additional room for future system expansion and electrical demands.
In addition to that, because the vessel was originally designed around European 220-volt AC power, there are some differences when operating the boat in the United States, where 120-volt appliances and utilities are far more common.
For years, we’ve handled that by utilizing portable 220-to-120-volt step-down transformers plugged into outlets in various locations throughout the vessel, which then provide standard 110/120-volt power for U.S.-based appliances and equipment.
That setup has worked well for us over the years, but we’re currently in the process of changing and upgrading that part of the system to create a more integrated onboard 120-volt solution.
To improve that setup, I recently purchased a Victron Energy 3000-watt inverter system.
The inverter utilizes 24-volt DC input and provides 110/120-volt AC output, allowing us to create a dedicated onboard 120-volt electrical system alongside the vessel’s original 220-volt system.
That inverter will feed a dedicated AC distribution panel with three separate 120-volt circuits.
One circuit will supply the aft cabin, aft restroom, and possibly the walkthrough cabin area.
A second dedicated circuit will feed the galley alone, including multiple outlets intended for higher-demand appliances commonly used in the galley.
And the third circuit will supply the forward cabin and forward head.
All of those new circuits will be wired as dedicated 110/120-volt systems.
So aboard the vessel, we will now have both 220-volt outlets and 110/120-volt outlets available throughout different areas of the boat.
Regardless of the specific power requirements of onboard equipment or personal electronics, we’ll be able to accommodate both systems aboard the vessel.
Our shore power system is configured around a 220-volt shore power inlet, which matches the vessel’s original European electrical design.
We also utilize an onboard transformer system, which gives us flexibility when connecting to different shore power standards around the world.
If 220-volt shore power is available, we can plug directly into that system. But we can also adapt the vessel to utilize 110/120-volt shore power by simply changing the plug configuration at the end of the shore power cord and switching the transformer input configuration accordingly.
That flexibility allows us to operate the vessel in marinas and facilities utilizing either 220-volt or 110/120-volt shore power systems.
We also carry multiple international shore power plug configurations that match various power systems used throughout different parts of the world.
In most cases, we’re simply changing the plug adapter itself rather than replacing the entire shore power cord.
In addition to that, the vessel is equipped with an Onan generator system rated at approximately 7 to 7.5 kilowatts.
It’s a 50 Hz, 220-volt generator designed to support the vessel’s primary onboard AC systems and overall electrical demands while offshore or away from shore power.
When operating, the generator is capable of powering virtually the entire vessel with some reasonable power management employed onboard.
That includes systems such as:
- air conditioning
- battery charging systems
- the inverter system
- dishwashers
- washing machines
- onboard outlets
- refrigeration systems
- and other AC-powered equipment throughout the vessel
In addition to the generator system, the vessel is also equipped with three 475-watt SunPower solar panels.
Those solar panels provide a significant amount of renewable charging capability offshore and have dramatically reduced our dependence on the generator during normal day-to-day cruising operations.
Under typical sunny conditions, the solar array is capable of fully charging the battery banks into float mode on a daily basis.
Because of that, the generator has effectively become more of a redundant backup charging system rather than a primary daily power source.
That level of charging capability becomes extremely valuable offshore, especially during extended periods at anchor or while living aboard full-time.
The vessel is also equipped with a 4,000-watt Magnum inverter system utilizing 24-volt DC input and 220-volt AC output.
We originally installed that Magnum inverter years ago, prior to converting the vessel over to lithium battery technology.
At the time, the boat was operating on AGM battery banks, and the Magnum inverter system performed extremely well for that setup.
In all of my years working on boats, I’ve rarely seen Magnum inverter systems fail. They’ve proven to be extremely reliable in the marine environment, which is one of the reasons I still continue to use and recommend them.
Had I known at the time that we would eventually transition to lithium batteries and expand into a larger integrated lithium charging ecosystem, I may have chosen a Victron Energy inverter/charger system instead—primarily because of how well Victron components communicate and integrate with one another.
But I’m also not someone who replaces high-quality equipment simply because another brand becomes popular or offers additional features.
The Magnum inverter continues to perform extremely well, and reliability offshore is one of the most important factors in any onboard system.
In my opinion, two of the best inverter systems commonly used in offshore cruising are Victron Energy and Magnum. Both have earned excellent reputations in the cruising community for reliability and performance.
One thing we currently do not run through the inverter system is the air conditioning.
At the moment, if we want to operate the air conditioning systems aboard the vessel, we simply run the generator.
In my opinion, that’s generally the more efficient approach for handling larger continuous electrical loads like air conditioning, rather than placing that demand directly on the inverter and battery bank for extended periods of time.
That said, modern lithium battery systems and inverter technology are becoming increasingly capable of supporting partial air conditioning loads for shorter periods of time.
It’s something I may expand into in the future.
One possibility would be configuring the system so the forward cabin and aft cabin air conditioning units could operate from the inverter system during evening hours in extremely hot climates while anchored.
That would allow limited overnight cooling capability without continuously running the generator.
So there are definitely multiple approaches to managing onboard air conditioning systems offshore, depending on vessel design, battery capacity, charging systems, and individual cruising preferences.
So far, since owning the vessel, I really haven’t found it necessary to run the air conditioning systems from the inverter and battery bank.
Even in warmer climates, our normal routine has been fairly simple.
If temperatures are high in the evening, we’ll run the generator and operate all three air conditioning units at maximum output long enough to cool the vessel down significantly.
Once the interior temperature becomes comfortable, we shut down the generator, turn off the air conditioning systems, and the boat generally remains comfortable enough throughout the night for sleeping.
Then in the morning, if necessary, we may run the generator again for another short period to cool the vessel back down.
In many ways, it becomes similar to overall onboard power management—you’re also managing onboard temperature and cooling loads efficiently based on conditions and actual needs.
So far, that system has worked very well for our style of cruising.
There certainly have been periods—particularly in places like Mexico during the middle of summer—where we’ve operated the air conditioning systems continuously for multiple days at a time.
But those situations are relatively uncommon for us because we generally avoid cruising in the hottest climates during the hottest times of the year whenever possible.
Still, as battery technology and inverter systems continue improving, the idea of selectively operating limited air conditioning loads directly from the inverter system during certain situations remains something I may eventually experiment with in the future.
As far as battery systems go, the vessel currently has a total of nine batteries onboard.
Eight of those batteries make up the primary house bank, while a separate dedicated battery is utilized as the engine start bank.
Our house bank consists of Battle Born lithium batteries utilizing 100 amp-hour batteries wired in a series-parallel configuration, creating a 24-volt 400 amp-hour lithium battery bank.
The lithium system has proven to be extremely efficient, lightweight, and capable of accepting charge very quickly compared to many traditional battery technologies.
One of the major advantages of lithium batteries offshore is their ability to utilize a much deeper discharge range compared to AGM, gel, or flooded lead-acid batteries.
That deeper usable capacity, combined with faster charging characteristics and reduced weight, makes lithium battery technology extremely attractive for offshore and liveaboard cruising applications.
When I originally purchased these Battle Born lithium batteries years ago, they were widely considered to be among the best lithium batteries available on the marine market at the time.
Since then, the lithium battery industry has evolved tremendously, and there are now many other highly respected and reliable battery manufacturers available.
Today there are multiple brands producing high-quality lithium batteries at significantly lower price points than what was available years ago.
Brands like WattCycle, along with several others, have become very popular and well regarded among many cruisers and boat owners.
If I were building the same system today, I might choose a different battery brand that offers a better balance between price, performance, and overall system value.
But regardless of the brand chosen, it’s extremely important to do extensive research before purchasing lithium batteries for an offshore vessel.
Not all lithium batteries are built equally.
Battery management systems, internal construction quality, thermal protection, safety features, low-temperature charging protection, and overall engineering quality are all critically important considerations offshore.
And price alone is not always a reliable indicator of quality.
Some expensive batteries may not necessarily be better, and some lower-cost batteries may perform extremely well when properly engineered and tested.
Another major advantage of lithium batteries is the dramatic reduction in weight compared to traditional battery technologies.
Weight matters tremendously on offshore cruising boats.
A typical 100 amp-hour AGM battery may weigh somewhere in the neighborhood of 90 pounds or more, while an equivalent lithium battery may weigh closer to 30 pounds or even less.
When we converted our vessel over to lithium batteries, the overall weight savings was substantial.
At the time, I calculated that we reduced the vessel’s weight by roughly 350 to 400 pounds simply by changing battery technology alone.
That’s a significant amount of weight reduction aboard any cruising vessel.
Another enormous advantage of lithium batteries is charging efficiency and charging speed.
Traditional flooded, AGM, and gel batteries typically utilize multi-stage charging systems.
In simplified terms, they usually begin with a high-rate bulk charging phase, followed by slower absorption stages where charging amperage gradually decreases as the batteries approach full charge.
By the final stage, charging rates may slow dramatically, sometimes down to only a small number of amps while the batteries slowly work their way toward full charge.
Lithium batteries behave very differently.
One of the major advantages of lithium systems is their ability to accept extremely high charging rates for much longer periods of time.
If a lithium battery bank is capable of accepting a 100-amp charging rate, it can often continue charging at or near that full rate almost all the way until the batteries are fully charged.
The result is dramatically faster charging times compared to traditional battery systems.
For offshore cruising, that becomes incredibly valuable because it reduces generator runtime, improves charging efficiency, and allows onboard systems to recover energy much more quickly while underway or at anchor.
Another major advantage of lithium batteries is usable depth of discharge.
This is one of the biggest differences between lithium battery technology and more traditional battery systems like AGM, gel, or flooded lead-acid batteries.
With many high-quality AGM batteries, a common recommendation is to avoid discharging the batteries below approximately 50% capacity on a regular basis in order to preserve battery life and longevity.
In practical terms, that means only about half of the rated amp-hour capacity is truly usable on a routine basis.
Lithium batteries are very different.
Many lithium battery systems are capable of operating at extremely deep discharge levels while still maintaining excellent cycle life and overall performance.
In real-world cruising applications, lithium batteries can often safely utilize a very large percentage of their rated capacity compared to traditional battery technologies.
The result is that within roughly the same physical battery footprint, lithium systems can provide nearly double the usable energy capacity compared to many AGM battery systems.
For offshore cruising boats where space, weight, and energy management are all critically important, that becomes a major advantage.
In the end, every offshore cruising boat is a little different, and every owner will have their own opinions about what systems work best for their style of cruising. The important thing is understanding your vessel, understanding your electrical demands, building redundancy where it matters, and creating a system that is safe, reliable, efficient, and manageable offshore.
In my experience, the electrical system aboard boats seems to challenge people the most in regard to developing a thorough understanding, and honestly, it has taken me many years and exposure to thousands of boats to develop a solid understanding myself—and I’m still learning because technology is always advancing.
I also view an offshore vessel’s electrical system as something that continues to evolve over time. Electrical systems are not necessarily permanent. As technology improves and better systems become available, I consider the electrical system aboard my vessel to be something that can continue to change and improve over time as advancements make sense.
The better you understand those systems, the more self-sufficient and confident you become offshore.