5,000 NAUTICAL MILES AGAINST THE TRADES WITH AN ELECTRIC MOTOR
by Keith Dickey and Rebecca Frontz
This is part two in a five-part series. See the links below for other parts:
Part One: Part One: 5,000 Miles Against the Trades with an Electric Motor
Part Two: Installation Overview
Part Three: The Charging/Discharging System
Part Four: 48V Discharging/ Electric Motor Usage
How do two 30-something-year-olds convert a 43-year-old sailboat to electrical propulsion and then beat nearly 5,000 nautical miles eastward in the Caribbean?
There is nothing easy about repowering a boat, let alone an old one, but add an electric motor and it feels increasingly overwhelming. The layout of a traditional
sailboat is not intended for an electric motor, of course, and the systems are not compatible. It is not simply a plug-and-play situation or a swap like-for-like affair — but it is achievable. While every person and boat would encounter different challenges, we hope that sharing our experience in detail might help someone plan for their own electric conversion.
Out with the old
As described in our initial article, “5,000 Nautical Miles Against the Trades with an Electric Motor” in last month’s publication, our 1979 sloop-rigged Pearson 424 came with its original reverse-mounted 60hp Westerbeke and V-drive. Once we determined it was time to repower, regardless of what would be installed in its place, we needed to get the ol’ leaky diesel out of the boat. With the crane at the shipyard being expensive and charging by the half hour, we prepped Vagari while she was still docked in her marina slip to save time and, therefore, money. We disconnected all electrical components to the diesel engine and loosened all bolts holding it in place. A three-quarter-inch double-braided line was wrapped around the engine with a shackle placed at the top.
We then called for a tow to the shipyard across the channel in Kemah, Texas. In an effort to keep expenses as low as possible, the goal was to spend 30 minutes or less at the shipyard’s work dock using the crane. We requested that the tow stay on standby to move us from the work dock as soon as possible once the old engine was out. We also asked a friend of a friend, who was a contractor, to stand watch, as the shipyard required this. A nice bottle of rum was accepted as payment for his time. We advertised the 40-something-year-old diesel for free online if you could be present with a truck at the shipyard at the time it was lifted off the boat. This meant the engine went straight from the boat to the truck without touching the ground, keeping the time the crane was in use to a minimum. Luckily, we had a taker.
With Vagari at the work dock and the crane lowered, we attached the crane’s chain to the engine via the shackle on the rope. The engine was carefully lifted through our aft companionway with absolutely no spare clearance on any side. With it tilted just right, it slipped through without having to remove any of the beautiful teak trim of the companionway. The Pearson boatbuilders in Rhode Island in the 1970s either planned this perfectly or it was sheer luck. Either way, we felt fortunate. Our bimini
was already folded back to allow for easy movement once it squeezed through the narrowest part. With the Westerbeke removed, the tow pulled us from the dock right at the 30-minute mark and moved us back across the channel to our marina slip engineless. Once back in the slip, we removed the old V-drive. This proved to be a much easier feat, as it was much smaller and did not require a crane.
Preparing for the change
With the diesel long gone, it was time to plan the installation of the 20kW Electric Yacht motor. The motor consists of two 10kW motors stacked together working in
unison to rotate two pulleys that then spin a one-inch shaft. The one-inch electric motor shaft would then directly connect via a coupling system to the existing oneand-a-half-inch propeller shaft.
The first step was dry fitting the electric motor into the old V-drive compartment under the aft cabin sole. We decided it would be a tight fit, but doable without any large modifications. We first built struts for support and to serve as attachment points for the motor mounts. They were built out of three-inch by quarter-inch mild steel flat bar coated in an epoxy and then painted. We were comfortable using mild steel, as this is an area of the boat that, by necessity, is dry, given that it houses an electric motor.
While building the struts, we had a custom coupler machined. At the time, the electric motor shaft terminated below the aft motor, only providing two inches of vertical clearance. This meant a typical Buck Algonquin coupler with a four-inch flange could not be used. Importantly, our motor is designed to shut down if it experiences markedly increased torque (e.g. from a fouled prop), and we did not take this into consideration when designing our initial coupling system. We would painfully learn that our custom-built coupler, which lasted four years, would fail us and this whole process of connecting the electric motor shaft to the boat shaft would need to be redesigned. As it happened, this occurred at what was likely the most inopportune location of all our cruising. Perhaps, we shall delve into that in more detail at a later date. Suffice it to say, our recommendation is to discuss the aspect of shaft coupling with the motor manufacturer to ensure your coupler can withstand the force needed to allow for the electrical motor over-torque protection to activate.
In with the new!
Once the struts were built and the coupler machined, we placed the electric motor into the old V-drive compartment. Before securing it, we tightened the coupler to align the two shafts and we then adjusted the motor mounts and bolted them down. This order of operations allowed us to precisely align the shafts while in the water
without any special equipment.
Each 10kW motor came with its own “computer,” which is essentially a 48DCV to variable AC voltage inverter. We were able to mount them in the same old
V-drive compartment. Once we studied the wiring diagram, we measured out the necessary length of 4/0 wire and acquired all the needed lugs. There was one problem. We did not have the tools needed to cut or crimp said thick wire. Thankfully, our local West Marine did and they graciously let us hang out in the store for an hour cutting and crimping. Voila!
Battery challenges
Our next big challenge was determining how best to power the motors — AGM versus LifePO4 batteries. The sheer weight of and physical space needed for AGM batteries to reach the amp-hour storage we wanted was extreme. Roughly, 400 usable amp-hours would have weighed approximately 2,000 pounds. Meanwhile, LiFePO4 batteries had their own challenges, the biggest being the cost. At the time that we needed the batteries, four years ago, each 48V 100Ah battery retailed for approximately US$5,000. Despite the hefty price tag, we decided LiFePO4 batteries were our best option and we were determined to decrease the cost by cutting out the middleman. We located a LiFePO4 battery manufacturer in China and researched the process for importing the batteries ourselves. We shared our motor specifications with the battery manufacturer to ensure the batteries and associated battery management systems (BMS) were appropriate for our motor needs. Acting as the importer of record and filing all your own paperwork is not for the faint of heart. However, we deemed the effort worth it as the total cost of our four 48v 100Ah batteries, shipping, and all other associated fees to import was approximately the cost of one and a half batteries in the States at the time.
Like many things, not everything has gone to plan pertaining to the batteries. We initially ordered three batteries from the manufacturer in China. Shortly after, wedecided we wanted a fourth identical battery and had one shipped over. Unfortunately, our fourth battery never quite acted like the others. It seemed like it had fewer amphours, as the BMS would engage prematurely in comparison to our other three identical batteries. Over time, this issue worsened and we finally got to the bottom of it while out cruising. After some testing, we discovered one individual cell within the battery had gone bad. Interestingly, the difference between our first received shipment and the manufacturing of the second was the start of the Covid pandemic. We wonder if the pandemic affected the quality of the product as the manufacturer was shut down off and on or if it was simply bad luck. Either way, a learning point for us is, while we saved on cost, we forfeited having a usable warranty. In theory, the manufacturer offered a two-year warranty, but logistically working directly with an overseas manufacturing company during a pandemic to discuss next steps or a warranty proved to be impossible. We’ve made the best out of the situation and are actively converting the bad 48V 100Ah battery into a 12V 300Ah battery by rewiring the good cells and using a new 12V BMS. As a bonus, we have a couple spare cells and a spare BMS for our three other 48V batteries.
Trimming the boat
With the motor installed, the batteries obtained and secured in the old engine compartment, and the system wired, we were left with one big hurdle that we did not anticipate. The boat was now significantly bow-heavy.
When converting our system, we should have considered the weight difference when swapping from a half-ton diesel to an 80-pound electric motor. Furthermore, we considered the weight difference when choosing LiFePO4 versus AGM batteries in terms of moving the batteries around to install them and finding the physical room. However, we forgot to take into account how the overall weight change from one system to another would affect the boat. As mentioned in last month’s article, we got a little creative. We cut out our forward water tank and turned it into storage. Additionally, the anchor chain on a Pearson 424 typically lives in a forward deck locker. We chose to extend the chain pipe through the deck locker into the locker at the foot of the V-berth and farther down into the forward section of the old water tank. This moved weight lower into the boat and slightly more aft. We also store heavy items in our cockpit lockers and installed our diesel generator in the aft cockpit locker. With all of these changes combined, we remedied our problem.
Next: Charging
Even with all of this effort, we still had work to do. The system was in need of a way or multiple ways to charge our new battery bank. The charging setup has proved to be the most time consuming and expensive. There was plenty to learn and, after some trial and error, we are happy with our current system. Next time, we’ll share the nuances and our learning regarding this. If you have any questions or are interested in a more detailed discussion, email us at [email protected]
This is part two in a five-part series. See the links below for other parts:
Part One: Part One: 5,000 Miles Against the Trades with an Electric Motor
Part Two: Installation Overview
Part Three: The Charging/Discharging System
