Aberration; Powerplant design

For an overall discussion of this design go to: SHEWAC Aberration

In my prior blog on Aberration, I promised to write a discussion on the propulsion system and the whole powerplant design. It is probably most useful to describe the whole powerplant design process to see how things eventually came together. That makes it a long story, but should be an interesting opportunity to go down a design process rabbit hole. It should be particularly interesting to young engineers since it will be a good example of the normal life of an engineer, which is always a combination of hard thinking, reliance on experience and the realization that often the answers are out there once you really start to look.

I am not a powerplant designer, but do spend an extraordinary amount of professional time dealing with powerplant failures. This has allowed me to get a sense of where powerplants fail, not in the electronic or mechanical sense, but rather in the systems or operational sense.

I had a pretty good idea where I wanted to end up, and to a large extent expected to fit off- the-shelf equipment to make it happen.

In this regard I had decided I was going to use twin 10kW Torqeedo outboards to power the boat and let the chips fall with regard to speed. This was a rational decision, because I cared more about reliability than speed. Having said that, my evaluation of the Torqeedo reliability is not based on hard numbers, but is based on a rational approach. I was going to create a complex system and felt that by going with the most established player for propulsion, hopefully, I would be able to connect with them for help when things did not work out. From various industry angles I was referred to Todd Simms of Torqeedo and when I first spoke with him I got the impression that he understood what I was trying to achieve. Todd uses a lot of the stuff he sells on his own boat, and therefore was able to make suggestions from both the supplier and the user side.

Todd provided a proposal for a propulsion package consisting of the outboards, 240V AC chargers, and the batteries. He also specced a twin engine throttle and some other minor stuff.  I then had some discussion with him about chargers and inverters and solar panels. He did not push specifics hard, but did point in the direction of Victron. I was reasonably familiar with Victron gear, but had mixed experience with it over the years. Regardless, again, Victron is a top player in the charger/inverter/solar controller game and the use of Victron gear would allow me to reduce suppliers on the charging and conversion end with a similar ability to find them when you need them.

As far as the Torqeedo package is concerned, Todd offered two types of batteries. They were both Lithium Ion batteries but one type was a conventional huhum battery that Torqeedo had been using for a number of years and the other battery was the actual battery pack for the BMW EV, which had been licensed to Torqeedo for marine use. Both were 48VDC nominal systems, with the huhum batteries consisting of 24VDC units. Todd noted that the BMW battery was a little lighter, and the latest of the latest as far as controller technology was concerned, while the other batteries were just less sophisticated. The other batteries actually had a little more capacity than the BMW batteries for the same price. I went for the simpler batteries because I felt that reducing complexity would be an advantage in the complex system that I was putting together. In essence, the battery packs could only be scaled in .75 hour run time increments. I went with 1.5 hours because a 2.25 hour setup would add too much weight and too much cost. I also figured if needed, I could bleed for another pack later.

The batteries would have to be charged with dedicated Torqeedo chargers and I could choose four or eight 1700W chargers.

This resulted in my first conundrum. Relatively speaking those puny chargers were ridiculously expensive, and if I were to run on the generator alone it would limit the outboard output to four times 1700W, basically 6.8 kW, instead of 20 kW. Eight chargers just was stupidly expensive, and I decided to stick with four chargers.

For the record, this package ran about $40,000, with about 40% engines, 40% batteries and 20% for other stuff.

I then figured: What if I can get a 48VDC generator package? Those packages exist and are actually quite nicely put together. I suggested this to Todd and he said that if I wanted one cheap they had one in the Torqeedo warehouse because they could never get it to work with the batteries. At the time it seemed like a dismissive comment to a technologically sound idea, but today I realize that it makes sense noting that the batteries need to be charged at a variety of DC voltages depending on their charge state and that is difficult to do with an off the shelf DC generator. Later on it became apparent that there were other good reasons for going with an AC generator package.

At that point I started to do a deeper think about the charging. Lithium Ion charging is new territory to me, but in discussions with Todd it became apparent that these Torqeedo chargers were needed to allow the batteries to reach maximum charge. I could feed other DC power to them as long as they shut down before maximum charge was reached. To think about this a bit deeper, as long as the outboards are running, the batteries are just power sinks and any voltage that gets added to the system that is less than the maximum charge voltage does not affect the batteries.

Hence the solar panels can be added with proper controllers, and I could add Victron charger/inverters that would add further power to the system when running the outboards on the generator.

At this stage I started scratching out one line diagrams. This is an early version:

I had decided to fit the vessel with substantial 110VAC capacity with the intent of running the entire vessel on AC, except for typical 12V stuff like bilge pumps, FW pressure pump, anchor windlass and nav gear (and the chair lift, which uses dump truck components, hence 12V).

With running the entire vessel on A/C I could forego a gas powered stove, which I consider to be a significant hazard in boat operations (and would also result in a reduction in weight and nuisance).

My load analysis showed that my maximum house load would be around 10 kW 110 VAC, so I sized the system for two Victron 5kW charger/inverters to provide 10 kW to the house. This also provided me with 10kW DC additional charge to the battery/outboards.

At this stage I also realized that I could design the whole system with a complete port and starboard split. In essence, I could run the vessel on one side alone. That is nice, but what is even more valuable is that two identical systems are a huge help in trouble shooting. In pursuing that, I also split the AC panel to port and starboard with a charger/inverter for each side and half the solar panels for each side. (Really experienced hybrid power system designers may note there is a downside to this, but I will not go into that here)

I sized the roof and figured I could fit about 4 kW of thin film solar panels on the roof, but then became really confused about what solar panels and controllers to purchase.

In effect I was stalled by a lack of knowledge on the finer details of chargers/inverters/solar controllers/solar panels.

I had not yet talked to Victron and decided to give them a call. On the internet I discovered that calling Victron would not work since they worked through a dealer network. That made me less than happy. Dealers can be weird. They may have strange alliances and are more likely to go out of business.

However, in searching for my local dealer I found Tekris in Point Pleasant. This operation is run by Chris Hanrahan, who answered the phone when I called the company.

Chris is a very experienced rectifier/inverter specialist and more recently his business had become very much involved in fitting solar on RV’s and motorhomes. He had not done a lot of boats, but was familiar with the higher power charger inverters that I would need and the thin film solar panels that are typically installed on moving equipment.

I agreed to stop by with my dirty one line diagram, and, when we met, he specced the whole inverter/charger/PV panel/controller system out. He did this pretty much by heart, while also providing buckets of insider knowledge on the latest and greatest in that technology.

A few days later he provided a price and at that stage I had pretty much all the fancy pieces in place from just two suppliers! I circulated an updated one line diagram to Todd, Chris and Scarano and everybody was aboard.

This is the “As-built” one line diagram, which, in concept, is unchanged from that moment.

The cost of the solar and charger inverter package came to about $18,000 with about $11,000 of that consisting of 36 Xantrax 110W thin film solar panels.

I cannot overemphasize how important it is to keep the number of parties in a project like this to an absolute minimum. Too often there are too many players, and, when things become difficult, you get stuck in pass the buck yoga. The world is littered with unsuccessful tech projects that never ran because the players became confused about who is supposed to do what, when to whom.

In this case I was particularly lucky because, as the one line shows, there is a very clear split between the Torqeedo supplied components and the Tekris supplied components. They have separate functions and, if needed, can operate independently. If there is dependent operation in a system, it becomes extremely important that one party assumes the full responsibility for getting the system to work.  For example, if I had bought the PV panels from a different supplier, any operational or installation problems would have to be resolved between two suppliers. Moreover, at this stage, I was relying on suppliers who were supplying things they had gotten to work before.

I then selected a diesel generator to round out the system and chose a shore power lead rated at 50A. I picked the Fischer Panda 15kW mini as the lightest and least expensive generator that could do the job. ($16,000). I chose 50A/240VAC shore power since it appears to be the most readily available shore power lead in the boat’s cruising area. One of our very smart long ago M&O interns (now a very experienced engineer), suggested a shore power transformer. I decided against that, and may live to regret that, but at this stage I am not convinced I need it.

Both the shore power and the generator are about 12kW feeds, and the Torqeedo chargers and the Victrons together total out to about 16.8 kW. In other words, if I ran all chargers I would pop the generator breaker (and the shore breaker if I was running on shore power).

While building the boat, I had not fully gotten my head around this issue, but the flaw became evident during the maiden voyage and I will discuss that later.

To keep the 12VDC system charged, Chris supplied a Victron 110VAC to 12 VDC charger that can charge the generator start/chairlift battery and the nav syst/house/anchor windlass battery. This charger, in theory, was a stand alone product and did not need to be Victron, but in keeping with the minimal supplier approach, it made sense to not even consider any other chargers, and, again, that turned out to be a good decision.

Meanwhile, the construction of the boat was taking place. All the stuff had arrived and we looked at the pieces, cables, connectors and often minimal instructions and received valuable input from Todd and Chris as we moved along. I had expected that we would need a visit from Todd and Chris during the build process, but, remarkably, everything was resolved by phone and text/photos. Again, this easy resolution is related to the limited number of suppliers. More suppliers, more confusion and more communication, not unusually to a point when there is all communication and no building.

These discussions did result in some auxiliary component exchanges. One particular example had its own charm. The outboards are each supplied with a throttle controller.

They are rather dinky looking components and Todd had suggested that I purchase the Torqeedo twin throttle unit; A lovely bit of industrial design that would look really sharp in the wheelhouse.

However, when we started laying everything out we noticed that this gorgeous unit only had one small display. The display would show battery charge but showing left and right battery bank displays would, at best, require a lot of screen back and forth manipulation and would fly completely in the face of port and starboard independent system operation. We sent the unit back (and I saved about $1,600) and used the throttles that came with each engine. These throttles are both left handed, and when mounted next to each other don’t look so hot, but to see battery charge and consumption on both sides simultaneously is absolutely essential. I’d like to add that these displays are not backlit, which is a design outrage for boating equipment, and I hope that in Mod 2 they will be backlit (Maybe Torqeedo will send me two of those units then and I will delete this comment). In Mod 2 it would also make sense to allow the throttle handles to be flipped from one side of the control to the other so two units next to each other will look a little sexier with a left facing and a right facing handle rather than two left facing handles. In design God is in the details…., and Mod 2.

In laying out the 240VAC/110VAC panel, the chargers and the big in-line water heater are all 240VAC, and then the rest of the house is 110VAC including a smaller 110VAC 1500 W in line water heater.

There were various reasons for this water heating arrangement, but the end result is actually rather charming. The boat only has electric in-line water heaters, no engine loop or tank heaters. There are various reasons for this. Most of all, tanks are heavy and these in line water heaters weigh nothing and are very inexpensive. In the final arrangement any faucet aboard the boat can get a nice 1500W warm water trickle for handwashing and dishes powered by the batteries (nothing better than a slow trickle there, so new boaters don’t empty the water tank while volunteering for the dishes). But for a shower you need to run shore power or the generator. That larger water heater is in line with the smaller heater so there is a 9,000W in-line water heating system for the shower. Strictly speaking, that means showers can never be truly solar powered, but I hope to be forgiven for that bit of greenwashing.

The actual purchase of the AC panel became somewhat frustrating. The common marine breaker panel suppliers could not provide a good (and economical) solution, and Chris Kane, the Scarano systems engineer, suggested we use home style square D panels. These panels are very reliable and often used aboard commercial vessels, but I think these grey mild steel boxes with their chinky doors are too ugly to even live in a home basement.

This resulted in a trip to Lowe’s where Chris and I spent some time pulling Square D panels out of boxes and came to the conclusion that those grey metal boxes are not needed on a boat and that the guts of those boxes and the breakers look quite nice when covered with a Garolite NC cut face panel over a plywood back panel that serves as the mount for the bus and breakers.

One huge advantage is that the cover panel can be made nice and big which really makes working in the box much easier. With a plywood back panel the wires can be routed beautifully too, since clips can be fitted where they work best.

In summary, I had spent about $74,000 on propulsion system components that would be comparable to a twin diesel propulsion package of about 20 hp each plus a sizable generator or very large alternators with a big battery bank. I did not do a direct cost comparison, but a rough estimate would indicate to me that in comparison such a package would run about $40,000, but would have a bunch of very significant disadvantages. One is noise, the other is maintenance, another is the cost difference between buying 110VAC home style and DC marine style appliances, and another is the need to carry more fuel and to refuel more often. In essence, the surcharge for this electric arrangement and its advantages is about $34,000 on a boat that in essence is a $500,000 boat. That surcharge for this type of vessel is an absolute no-brainer for a client like me. The math changes if I were looking for a faster vessel. With present technology it is not possible to get more speed. The added cost of installing more powerful propulsion diesels is small and therefore will likely be selected by a customer who is not interested in zero noise, vibration, fumes and emissions.

One could also select a gasoline outboard package at a much lower cost, but personally I would never want to have such a set-up, since it would include a gasoline generator and other unpleasant consequences that I will not further elaborate on here.

In May 2021, the boat was ready for her maiden voyage where all components had been trialed except the solar panels which would not be commissioned until Chris Hanrahan would attend aboard the vessel in New Jersey. He would also commission the entire Victron communication and remote control system, and we would rely on local controls on the Victron equipment for this trip.

The 48V batteries had been charged with the Torqeedo chargers and the 12V batteries has been charged with the Victron charger. We had also tested the generator with the chargers on (but at near full battery charge only). The 12V batteries were cheap Walmart lead acid batteries that I had bought new to start the original Yamaha outboards for the post purchase trip from Rhode Island to the Scarano yard in Albany NY back in July 2020. The outboards mysteriously gave up the ghost halfway in that trip and since that time those batteries had sat on the shelf in the yard. I was too cheap to purchase proper deep cycle batteries, and actually felt I did not need them because the batteries would be continuously charged by the Victron 110VAC to 12 VDC charger. As such, those batteries actually served more like car batteries than boat deep cycle batteries with the anchor windlass and chairlift basically functioning equivalent to a starter motor.

Anyway, we left and it did not takes us long to figure out that we could not run all chargers when the battery voltage dropped and every charger came on line. In other words, the generator would poop out. That meant we had to take the Victrons off line, but when we did that, we would lose the 110VAC system. (Melting the ice in the freezer! Never!) A deep think made us realize that we should not use the Torqeedo chargers when running the outboards (not a big deal because the batteries were not really charging). Conversely when we got to the dock we could charge with the Torqeedo chargers to get a full charge, but then we could not use the Victrons when the shore power was hooked up, because the shore power breaker would trip and with the Victrons off line we lost 110VAC service again.

All very confusing and requiring a deep think for a solution.

Meanwhile, halfway into the trip, in the afternoon, we got a nav system low voltage alarm. We used a multimeter to check the voltage at the battery, because we had not yet bothered to study the 110VAC to 12VDC Victron charger manual, and found a ridiculously low voltage on the battery of around 8 volts. Yes, modern electronics can run on very low voltages.  But we decided there was little to worry because we still had a nicely charged generator start battery and we could do some swapping if needed. The generator start battery voltage we could read on the generator display and was only 11 or so volts. Were both batteries bad? But even then, should the generator 12V DC alternator not provide charge? Did we cook the generator alternator with the Victron charger?

Where was that alternator on the generator? (We took the cover off, but did not stop the generator in case we could not restart it.) We could not find it. The manual did not describe the alternator at all (the manual is far from useful). We called Chris Kane and asked him, he checked with Fischer Panda who told him that this unit did not have an alternator and the starting battery needs to be charged by alternate means.  Well, by good luck and coincidence, we did have that. Or did we? Out comes the Victron manual and Chris Abel, one of our crew who is a retired unlimited USCG Chief Engineer (again nothing beats being lucky), crawled between my legs while I was driving (by hand; no autopilot), and started to play with the tiny display panel on the Victron inside the control stand.

Long story short; we concluded the Victron was dead. A classic case of infant mortality. And, already on the maiden voyage, we had discovered one fatal flaw in Rik’s perfectly redundant system.

No 12VDC charger, no nav system, no generator start, no anchor windlass, no nav lights, no sailing at night. We’d better find a marina. This is where the cover of the Hitchhiker’s Guide of the Galaxy comes in. (Don’t Panic)

Since we had gobs of 110VAC, all we needed was a cheap K Mart style battery charger. So we pulled over at the Newburg Yacht Club went to Autozone and got a $80 plug in battery charger.

It was actually too fancy, since it auto sensed whether the battery to be charged was 6V or 12V, and the little bastard kept concluding that an 8V charge must belong to a fully charged 6V Battery and simply stopped charging. How we fixed that is also a long story, but we will save that for another time. Meanwhile for $80 the whole system now actually became fully redundant. We charged the nav battery, regained running lights and ran through the night.

The Victron charger was eventually replaced with a new unit under warranty (but Victron made me pay for the travel and installation time for the mechanic) and we keep the Autozone charger aboard for a backup.  To this day I am actually still not sure how healthy those Walmart batteries are. Some day I will have to do a discharge test on them.

All of that is much easier, since now the Victron monitoring system is online. Chris Hanrahan took care of that in Red Bank and also reprogrammed the big Victron Charger/Inverters. Their charge capacity is now limited and we can now run everything at the same time, without popping breakers.

What is actually quite amazing is that, once all the pieces are in place, configured and the bugs are shaken out, Aberration’s propulsion and power system is muuuuch easier to run, maintain and troubleshoot than a comparable IC plant. This actually surprised me, but even now, still in the early stages of shake down, I would feel much more comfortable to hand this boat to another boater. The instructions are much simpler than pointing out all the bells and whistles on a comparably equipped and outfitted IC boat, and if things become confusing, it is possible to fall back to a very basic set of instructions to get the boat home.

A quick note here on Victron and Torqeedo. I provide some modest criticism in this blog (and there are other things that bothered me), but that needs to be balanced against many things that I really like about this equipment. The best way to figure out if a certain piece of equipment or equipment supplier can do the job, is to ask the user if they would buy that gear again. In this case there is no doubt, based on what I know so far; Hell yes!

And the same goes for the builder; Scarano Boats. Building custom boats is hard, really hard, but working with shipyard professionals like John Scarano, Rick Scarano, Keith Duffy, Chris Kane, Will Hempel, John Thorne, Brian Burke and all the others on the crew whose names escape my much abused brain, allows us to get over the bumps and grinds without too many bruises and with a deep sense of mutual accomplishment that is so rare in our normal lives.

Let me finish with an engineering insight. In the very first blog on Aberration I made reference to a question by Ethan Wiseman asking how fast the boat can run on generator alone. I suppose I can figure that out once we are doing a long run where the boat will essentially run on generator alone. Weirdly, that is such a rare condition that it is hard to figure out by trial, since, even on a cloudy day, the mixture of solar charging, tides, wind, bottom growth, varying house loads, different chargers kicking in at different times, and many other variables make it a continually moving target. This is a measure of the hybrid complexity of propulsion systems like this. However, based on experience so far, I am incredibly comfortable with answering 6 knots. Some days more, some days maybe a little less, but on average and on most days 6 knots. Sounds fuzzy, and it is, but that does not make it inaccurate, and, in this regard, Aberration is no different than the nationwide hybrid powers systems that we are developing today, which are much more difficult to describe than the power systems we have been used to for the last 100 years or so. However, if it is well put together, from a consumer point of view, you don’t really notice it.

But from an engineering point of view, we always need to make sure that we can quickly analyze what we put together. If we can’t, when things go wrong, they can go very badly wrong. Compexity in component configuration is OK, but make sure it can be quickly untangled.