Choosing which type of electric propulsion and battery bank to fit in your boat is a question of defining your requirements and fitting what's left into your budget (and your hull). Paul Sumpner reports


During the first lockdown in March 2020, my wife, Kay, and I began musing about the possibility of trying to be a bit greener in the forthcoming build of our 58ft 6in narrow boat Old Nick. The boatbuilder we had chosen – Ortomarine, based in the Droitwich area – already had experience of building electric narrowboats, and were very encouraging.

Which type of electric narrow boat

Making the choice of which type of electric boat was the first hurdle. We knew we wanted Old Nick to be electric but, as with all things in life, there were a number of different types of electric engine designs and we had to decide which one would be best for us.

See PBO news item: Worcester to Droitwich canal boat trials

The simplest is the ‘all-electric’ design, where you have a single electric engine, a big bank of batteries and a means of charging them. This design works well for vessels that are doing short trips and always returning to base at the end of the day, where they can plug in to the shore supply, ready for the next day’s cruising. A lot of day boats operated by hire companies are moving to this type of design and Ortomarine had already built two large all-electric trip boats.

For vessels that are cruising for longer periods, over greater distances, such as private holiday boats or continuous cruisers – boaters who cruise year-round – a different design is required.

What is parallel electric hybrid?

One of the first commercially successful designs was the Parallel Electric Hybrid, of which there are now a number of installations on UK canals. Ortomarine had already built six boats in this design.

In parallel hybrid systems, you have two engines; one diesel and one electric, which are linked via a special transmission system. Both engines can drive the prop  shaft, with the electric engine being used most of the time, but when the batteries get low or some extra horsepower is needed, for instance on a river section, the diesel can take over, or in some systems both engines can work together for maximum power.

What is serial electric hybrid?

With recent improvements in battery technology and electric engine design, a new, third type is now slowly starting to appear on UK narrow boats: the Serial Electric Hybrid.

Diagram of serial hybrid set-up

In a serial hybrid, there is a single electric engine driving the propshaft, but if the batteries start to get low, a small, quiet and efficient diesel generator can be started that will charge the batteries while still underway. With a good solar set-up (1,200W or more), the need to run the generator in summer months is rare and in the autumn/winter, a night or two on a visitor mooring in a marina, on shore power, will soon top up the batteries.

Taking all the above into consideration, it became clear that currently, it is just not possible to completely eliminate the use of diesel on a continuously cruising narrowboat. So the choice came down to the two hybrid solutions of which the Serial Electric Hybrid had some advantages, namely:

  • Quieter and more practical generator charging
  • When diesel is used for charging, more efficient, fixed rpm generator
  • Wider choice of electric engine manufacturers
  • Latest technology

There was surprisingly little information online about this technology being used in narrow boats, so it was a relief to finally discover one pioneering design. Narrowboat Shine was built in 2019 and fitted with a 10KW engine, 6KVA generator and a 48V 600Ah lead carbon battery bank. An article in a waterways magazine documenting Shine’s cruise from Teddington down the Thames to Limehouse really caught our attention, showing Shine completed the journey with 55% battery capacity left.

Which battery is best for my boat?

Charging two battery banks

There are basically four viable options for charging two battery banks on board: Battery switches, twin alternators, split charge diodes,…

This gave us a benchmark for Old Nick, proving that an electric serial hybrid could handle a hard day’s cruising without completely flattening the battery bank.

However, questions still remained, in particular the lead carbon battery technology which, until that point, we’d not heard of.

We consulted Ortomarine’s CTO, Rob Howdle, who confirmed they had good experience with lead carbons on a recently built all-electric trip boat. With confidence boosted, we contacted the UK offices of Leoch, manufacturers of the lead carbon batteries, which Ortomarine had used. Leoch has a very large range of batteries, covering all of the major technologies and the information they provided convinced us that lead carbons were the way to go.

We identified the following key battery requirements to power Old Nick:

  • A minimum of 48V, 600Ah
  • Batteries that can be used all year round
  • A regular depth of discharge” (DOD) of 50%
  • Life cycle of 3,000 or more discharges
  • Zero maintenance
  • Non-vertical mounting option for flexible use of space
  • Survive regular partial state of charge (PSOC)
  • Would not completely blow our budget

Feeding these requirements into the comparison table, it became clear that only lead carbon or lithium batteries would be suitable. If money had been no object, then lithium would probably have won the day, although there were some concerns, viz:

  • Each lithium battery has its own battery monitor system (BMS) inside, any one of which could fail
  • Some sources say it is better not to fit lithiums in series, but rather buy 48V lithium batteries (which are even more expensive)
  • Some popular lithium batteries state they should not be charged below 5°C, making their winter use on UK canals a potential problem.

See our comprehensive test of Lithium 12V batteries for boats.

Unfortunately, deciding to go electric had already stretched the budget to the max, so economies had to be made. Lead carbon ticked most of the boxes and, aside from depth of discharge and speed of recharge, matched lithium in most areas. They are heavier, but weight isn’t such an issue on a narrow boat as it would be on a sailing yacht and with the cost of a good LiFePo4 set-up being about three times dearer, there really was no doubt lead carbons were the best choice for us.

Impressive bank of Leoch 2V LC2 lead-carbon batteries

Studying the Leoch catalogue, it became clear that there were two ranges of 2V Lead Carbons: the LRC2 range that Ortomarine had previously used and a cheaper LC2 range that were lighter (12kg per battery) and 25% less cycle life (3,000 compared to 4,000 at 60% DOD).

We chose the cheaper ones, estimating no more than 300 days cruising per year and that the batteries would rarely go below 60% DOD, so it should be possible to get a minimum of 10 years of life out of the LC2 batteries (their design life is 12 years or more).

Battery comparison table

This table shows the key battery selection criteria that is useful for deciding which type of battery is best for any given application

Battery Technology Average







of cycles

Sealed lead acid £ 50% 200
Flooded flat plate (6V) ££ 60% 700
Flooded tubular plate (2V) ££ 80% 1,500
Gel cell £££ 60% 800
AGM £££ 60% 600
Lead carbon £££ 60% 3,000
Lithium £££££ 80% 4,000

Which engine system is best for my boat?

With the batteries chosen, attention turned to the serial hybrid system. There are now a number of manufacturers of inboard electric engines (Bellmarine, Lynch, Waterworld, Tema, etc) and a similar number of diesel generator manufacturers (Fischer Panda, Mase, Beta Marine, Westerbeke, etc).

Many companies are collaborating to provide a complete solution, but there was only one manufacturer who could provide the complete serial hybrid system: Vetus Marine.

Vetus markets itself as ‘creators of boat systems’ and that is exactly what they did for us. In addition to supplying one of their new E-Line electric engines, they supplied a 6KVA, 1,500rpm generator (GLX6,5SIC), one of their latest brushless bow thrusters 65kgf (BOWPRO65) and a whole list of other equipment including stern gear, tanks, calorifier, pumps, prop and driveshaft.

There are few companies that could have supplied this range of equipment and certainly none that has a competitive new electric propulsion solution.

Old Nick was the first boat in the UK to install one of the new E-Line engines, and we received excellent support from the Vetus team through the whole design and build process and are very pleased with the performance during commissioning and our first couple of outings.

We were slightly concerned about the 13in x 9in prop that Vetus recommended, as previous electric narrow boats have tended to choose larger props. As it turned out, Vetus had it spot on.

The company’s application engineer and sales manager joined us for a commissioning cruise in early December to carry out a series of tests to ensure that acceleration, braking (within one boat’s length) and most importantly the rpm versus speed versus current figures were all well within spec.

A table of the measured values during our sea trials

RPM 500 750 1,000 1,250
Volts 50.1 49.6 48.9 47.7
Amps 10.9 31.1 71.4 141
Temp 13 15 21 29
Speed (mph) 1.9 2.8 3.7 4.4

Which solar panels are best for my boat?

Another key component in any electric boat is the array of solar panels. The complete roof space area of Old Nick has been given over to the 12 semi-flexible 160W solar panels, which was no mean feat. Narrow boats typically rely on roof stowage for gangplanks, boat poles, boat hooks, antennas, chimneys and more. We fitted two 4G antennas either side of the hatch, used my own-design ‘quick fit’ temporary TV antenna solution and stowed the folding gangplank in a rear locker.

See: Solar Power – everything you need to know

In terms of performance, semi-flexible panels do not generate quite as much power as a similarly sized rigid panel, which can be tilted towards the sun. However, they look good, do not snag the ropes and can be walked on.

We really didn’t want to be constantly tilting the panels towards the sun to get optimum output and have, so far, been very impressed with the performance of our semi-flexible panels.

On inland waterways, your solar panels are in shade as often as in full sunshine, so Ortomarine intelligently split the 12 panels into three parallel sets. With one set at the front of the roof, the second set in the middle and the last set at the stern. This reduces the chance of ‘shadowing’ causing the power output of all three sets to reduce at the same time.

In full sunlight, each set of four panels (wired in series) will give 80.8V and 7.9A per set.

With the three sets in parallel, the voltage stays at 80.8V (which is within the safe limits set by the solar panel and MPPT controller manufacturers) but the current is tripled to 23.7A.

As Power = Voltage x Current you get three times the power: a whopping 1915W (80.8V x 23.7A).

Why I chose Victron energy management system

When you are completely reliant on electricity for propulsion and domestic living, having a well designed and proven energy management system is very important.

Ortomarine always uses Victron for this mission critical component and we were very happy with this choice, opting for a 48V 8KVA Quattro system. The Quattro takes care of switching between shore, generator and solar power sources, while also incorporating a multistage 48V battery charger and powerful inverter that can cope with the washing machine, induction hob and fan oven.

In addition to the AC circuit, there are three DC circuits on board: 48V for the engine, 24V for pumps and the bow thruster and 12V for lighting, the control system and NMEA 2000 network.

Victron DC-DC Orion units are used to create these additional DC circuits from the 48V battery bank and everything is monitored using the super smart Victron Cerbo GX. This little box brings together all of the data from the various Victron devices and displays a series of web pages that can be accessed on your phone/tablet/computer.

All of the data is also sent to the cloud (Victron’s VRM server) so you can remotely monitor all of the boat’s power systems and maintain an historical database of solar yield, battery status, etc.

On many boats, this would be seen as a very powerful and complete system, but Old Nick has another trick up its sleeve.

Ortomarine’s CTO, Rob Howdle’s background was designing industrial control and automation systems for heavy industry (oil and gas, pharmaceutical and shipping). He has put this experience to good use, developing an advanced vessel control system that is at the heart of every Ortomarine boat.

Called Ortomate, the control system is a central hub that monitors and controls all of the major systems on board.

Propulsion, power management, heating, lighting, tanks, security and connectivity are all monitored, controlled and then that data is stored in the cloud.

A central, dedicated, colour touchscreen display gives you a simple way to access all of the features of the system, where every function is only ever two button pushes away.

What is more, by installing a free app, you can walk around the boat replicating all of the Ortomate functionality on your smartphone or tablet, or you can remotely check on the boat from your office or home.

With the Ortomate system you get total control and peace of mind.

Real-world performance figures

See PBO news item: Worcester to Droitwich canal boat trials

After three months of living aboard Old Nick, due to a combination of winter weather and lockdown, we have only been out on the boat a couple of times, but initial indications have been very positive. After a four hour cruise, with next to no solar energy, the batteries only dropped to an 85% SOC, which would confirm we should be able to cruise for 1-2 days in the winter before running the generator.

Even more encouraging is that, with a better solar yield, we should be able to cruise every day without running the generator or needing shore power.

We estimate that this could be at least 6 months of the year, assuming 6-8 hour cruising days on normal canals. On really long days or when cruising on a river, it may be necessary to run the generator for an hour or two, but over the course of the year, we estimate a 70% reduction in diesel usage compared to a traditional diesel powered narrow boat.

With this significant reduction in diesel consumption, no gas and no solid fuel stove, Old Nick is about as environmentally friendly as a narrow boat can currently be.

Ortomarine, in keeping with their personal and company environmental ethos, have taken the brave decision that henceforth, only orders for boats equipped with some form of electric propulsion, will be accepted.

We could not be happier with Old Nick and have documented all of the design process and the equipment chosen on our blog ( which we hope will encourage and help other boaters to go electric either on a new build or refit.

As soon as we can cruise again, we’ll publish all of our electric engine, solar panel and battery performance figures in lots of different conditions. This should provide further evidence that electric serial hybrids can be used for continuous cruising and make a real difference to the environment.


Paul Sumpner has been in the marine industry since 1988 when, after finishing an apprenticeship with Marconi Underwater Systems, he joined Stowe Marine as a product engineer. After Stowe were purchased by Simrad, Paul left to run the UK office of C-Map for 10 years before joining Digital Yacht as their CTO. Paul and his wife, Kay, have always dreamed of living/working aboard a narrow boat. Follow their adventures at

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