Navigating the Hybrid Drive Explorer Yacht Experience: A Reality Check
- Chris Leigh-Jones
- May 3
- 5 min read
A year after our handover, a sense of normality has finally settled in. Alarms are reduced to manageable levels, working practices are established, and we can begin to enjoy our journeys with hard-won reliability paramount. A major design feature of Vanguard is its hybrid drive, a spin-off from the rise of lithium battery technology and electric propulsion. So, what has that experience been, and where do we now see the benefits, if any?
Let's begin by focusing solely on the equipment, setting aside the issues with Naval Yachts. Praxis Automation designed our system, a well-established company with an excellent reputation for reliable products throughout the commercial marine world. This technology is new in our yachting world; I know of only Sarp and Arksen, who have also fitted it on vessels similar to Vanguard. So, there needs to be an expectation of a learning curve in how the equipment performs. For as long as their products have been in the field, Praxis has "owned" this role, visiting the vessel and working with us remotely as issues arose. Without this backup, we would have failed. So, breaking the system down into its parts:
Batteries.
Our batteries are huge by most standards: 21 kW.H. for the house and 120 kW.H. for the power batteries - more power than the average minor God of antiquity.
3 by 7kW.h MG Systems LiPO house batteries. We have electronically limited the maximum charge rate to 2kW and comply with MCA survey requirements for enclosed batteries in engine room spaces. House Batteries - Solar power, Power Batteries, Generators, or Shore Power can recharge house batteries. They are LiPO from MG Systems and have proven utterly reliable, even capable of recharge from a total discharge (that has happened twice).
Power batteries, also LiPO, have been a blessing, although they have exhibited teething troubles. At 600VDC and with such a capacity, they are not to be trifled with. Batteries perform best when actively used; leaving them for long periods needs preparation. Charging them is easy with a generator capacity of 50kW, though they must also be glycol-cooled for high charge and discharge rates. Battery voltages can wander and should match before connecting at the DC Bus bars.
Power batteries located as 2 banks in the engine room. They are designed as their own battery room with a dedicated emergency exhaust and water/glycol cooling. Running away on one cell will not propagate to the others. The connection itself can be tedious with multiple attempts. The alternative is akin to placing an iron bar across a starter battery, only at 600VDC. Cell voltages can drift apart and must be returned in line by an occasional forced recharging. Our lives became much more predictable once we established a battery management regime. There is a methodology to this that we have now well documented for future reference and owners. The flip side of this complication is that near-limitless power becomes available. We can operate a kettle, dishwasher, washing machine, HVAC, Oven, and hair dryer simultaneously and without the inevitable restrictions or matrimonial recriminations that ordinarily follow on a yacht of limited size. We are free at anchor or underway; it is as easy as pie!
Hybrid Drives
Motor/Generators are large by most standards, power or generate at approximately 50kW, though the speed changes between these modes. We had problems with installation, but these have been remedied. They have proven to be reliable and silent. One small downside we had not envisaged is the loss of some 5-8kW through the Esco Power drive and having them constantly rotating when the engines are running. This would have little consequence with a powerful engine installation, but Vanguard's engines are small, and that 5kW is noticeable. We retain the option to change the engine rating to "M2" for some additional motive force (currently M1), though that would also entail a change in propeller specification. I'm not sure we will go there yet; it's simpler to charge on two engines and run on just one when the batteries become nearly full.
Charging uses redundant high-power inverters connected to Praxis Green power batteries. We can control the system from the engine room or the helm stations.
Solar
Perhaps our biggest self-delusion. We installed 6.5kW of solar capacity but did not fully grasp the very negative effect of shading. After much consideration, readjustment, and general playing around, we moved maximum output from 1.10 kW to close to 2.0 kW and daily energy input from 4 kW.h to over 11 kW.h. A hard-won battle, but less than we expected from our naive starting point.
Solar energy is occasionally useful, but it is not good enough to exist permanently at anchor in an energy-hungry design without running generators for a short duration every few days. It did, though, save us once when we anchored off a remote island in Greece and lost our house battery charge.
Victron provides all our house electrical needs for 240 and 24VDC, including solar. Multiplus inverters can be bypassed and we carry a spare 1000 amp MG Systems bus bar.
The sun came up, and so did our batteries! One great tangential benefit is the Victron Cerbro controller, which oversees solar and other house electrical systems. It has provided great insight into its operation and has proven reliable throughout.
Final Thoughts and Reflections
Our hybrid installation creates a more compact engine room in a small space. It eliminates the need for two additional generators yet provides the same level or greater redundancy and in total silence.
It takes time to learn this system and to limit the unexpected events, but the effort is worthwhile. My wife, Sebrina, loves the freedom from power rationing, allowing her to use all the conveniences of a modern land-based home. I like the assurance of silent anchorages and a certain freedom from range anxiety.
We can slowly motor for 50 miles on an electric drive, but it will not help save the planet.
A design plastered with solar panels will produce little more power than a few efficient and thoughtfully located, shade-free panels.
This technology, including in-line, direct coupled motor/generators, improved control software, and battery technology (cost, power density), is constantly developing, promising a fertile playground for future yacht designers.
Lastly, NEVER believe a marketing pitch that electric drives offer "ocean crossing" potential. One head sea and you're toast. Ocean crossing potential is only available from a good hull, sails, or a large diesel fuel tank. Such marketing claims are dangerously untrue, but Hybrid Power Yachts offer many other, more subtle benefits.
Chris Leigh-Jones
Further reading
Boat International: Their "Technology" section frequently covers hybrid propulsion https://www.boatinternational.com/technology
Professional BoatBuilder Magazine: Technical articles on marine systems, including hybrid propulsion https://www.proboat.com
Marine Propulsion & Auxiliary Machinery: Professional journal covering propulsion technologies https://www.rivieramm.com/publication/mpam
Praxis Automation Technology: Information on their MEGA-GUARD HYBRID systems https://www.praxis-automation.com/products/mega-guard-hybrid/
Arksen Yachts: Technical information on their sustainable vessel designs https://arksen.com/technology/
IEEE Xplore Digital Library: Search "hybrid marine propulsion" for peer-reviewed articleshttps://ieeexplore.ieee.org
DNV GL Maritime: Classification society with technical reports on hybrid systems https://www.dnv.com/maritime/
Electric & Hybrid Marine Technology International: Magazine and annual directory https://www.electrichybridmarinetechnology.com/
Chris,
If you have time, I would appreciate hearing more about "the loss of some 5-8kW through the Esco Power drive". Thanks.
Patrick