Sorry that I wasn’t able to write up this weekly update and get it posted on my “regular” schedule of each Sunday and I’ve kept you waiting till now but hopefully the wait will have been worth it as I take you on a deep dive into the DC charging system on Möbius.
On Sunday, Christine and I took the afternoon off to go explore some of the area around our new “home town” of Finike, which is something we should do more of I’m sure as boat and book work completely consumes us otherwise. We have rented a little Fiat minivan for a few weeks so we wanted to take advantage of that and my super researcher partner had found a cool sounding little restaurant on a river about 20 minutes drive away from the coast here.
It was a wonderful treat for us both and we spent the whole afternoon sitting at this table for two at this tiny little restaurant on the riverbank in an equally tiny little village off a side road. You can see that I timed the shot to catch one of the kids jumping into the cool waters that the village had created with a small rock dam to slow down the flow. We have found several of these little riverside restaurants during our years here in Turkey and this one was the Goldilocks just right, just for us being so small and remote.
Fresh roasted trout dinner with the full compliments of fresh salads, fries, Turkish baked bread and sauces plus a well chilled bottle of Merlot made for the perfect getaway afternoon for us both. Total bill was an exorbitant USD 30 but heck, we’re worth it!
We weren’t the only ones chillin’ ourselves waterside as Barney enjoys his very own pool on the aft deck where he can survey his Kingdom while staying well hydrated.
Yes, that’s the bow of our Tender “Mobli” which when on deck serves double duty in providing the shade for Barney’s pool.
Möbius’ Charging System Trifecta
Back in September 2019 I wrote the first Tech Talk to outline the overall design we came up with for the Electrical System and this is an updated version of the schematic I created of the overall system.
As per this week’s title I believe that we have put together the perfect trifecta of components to make our Goldilocks 24 Volt charging system consisting of;
24 x FireFly Carbon Foam 4v cells
Just 10 of them shown here and these have been well covered in many previous posts.
2 x Electrodyne 250A @ 24V AC PowerHead E250-24 alternators with remote rectifiers mounted out in the Workshop (see photo below)
2 x WakeSpeed 500 Smart Regulators with the 2 red remote Electrodyne rectifiers mounted alongside
I have written several articles in the past as these components were being installed and if you’d like more details on that here are links to some of those past postings:
NOTE: Just to be clear for anyone who might wonder, Christine and I have purchased all of the equipment I’m discussing here and none of this has been sponsored or otherwise paid for. indeed this is true for ALL of the equipment on Möbius and covered in this blog. We are simply BIG fans of companies who produce products that really work in our eXtremely real world and especially the people at these companies who stand behind their products from the beginning of our work with them to design systems, install them and all the way through to their support as we move into commissioning and putting all these systems to work.
So we are delighted to feature such products and the people behind them here on the Möbius.World blog.
Meet Big Red #1 & #2
As I wrote in those past posts, I’d known Electrodyne alternators since I was working as a HD construction mechanic in my youth and Electrodyne alternators were the ultimate choice for large construction and mining diggers, railroads, trucks, busses, emergency vehicles where they often ran 24/7 for weeks or months. They are literally built like tanks and each one weighs 40kg/90 lbs!
I had initially worked with Pete Zinck until he retired in 2018 and turned things over to his Production Manager Dale Gould and who could not have been more helpful and responsive to my many Emails and requests.
As you can see Dale is also a very hands on guy! Here he is making the final checks and tightening the remaining nuts on finished alternators awaiting packaging.
Dale continues to be super supportive as I commission the whole charging system on Möbius and I can not recommend Electrodyne and Dale highly enough.
What we ended up choosing are two identical Electrodyne E250-24 models which are de-rated down to 250Amps @ 27.5V @ 3750RPM which would give each one a maximum output of almost 7kW (6.875) for a combined output of almost 14kW. As I covered in last week’s posting about the drive systems for these massive alternators, I chose some ratios for the pulleys such that their max speed will be about 3200-3400 RPM for even longer life.
These “PowerHead AC alternators” have several unique characteristics that made them just right for me and Möbius:
- Brushless so no brush springs or brushes to wear out
- One moving part (rotor)
- Everything other than the rotor is external; No built in regulators, No built in rectifiers.
Why go to such extremes? In a work; HEAT, which is the largest factor in shortening an alternators output and lifespan. Rectifiers can produce more than half the total heat within an alternator so by removing these and going with industrial grade 3 phase bridge rectifiers I can reduce the internal head of the alternator by more than half AND control the heat of the rectifier bridges outside the ER and with their own fans.
With only one moving part, the spinning rotor so MUCH better airflow through the alternator stator windings and rotor. The Goldilocks alternator for an XPM; consistent high output with low heat and low maintenance.
Each PowerHead is “double headed” housing two separate AC Alternators inside, one on each end. Having two of these Electrodyne units means we have 4 alternators in total.
With no rectifier or regulator built into them, each PowerHead only puts out AC current, everything else to convert this AC current to DC is external.
As you can see in these photos, there are six large cables to carry the AC output out of the Engine Room and over to ……
…… these two red external rectifiers which are mounted outside the Engine Room under one of my AL Workbench tops with thermostatically controlled fans to ensure they are always running nice and cool and at maximum efficiency. All the heat Mr. Gee generates stays in the Engine Room which is why I designed the ER to be just that; and ENGINE (only) Room.
Q&A with Dale Gould from Electrodyne:
** Feel free to skip to the end of this section if you are not interested in a deep dive into the inner workings of how these Electrodyne alternators work.
For those of you interested in more details on the unique way these Electrodyne PowerHeads work, I asked Dale a series of questions and he kindly answered them as follows. I’ve added some photos I took when I was taking these alternators apart and painting them, to help illustrate these Q&A.
** Before you ask, Yes, of course I took these Electrodyne alternators apart! When I don’t understand how something works or I am otherwise curious, this is what I do.
Wayne’s Q: In working with the two Electrodyne E250-24 PowerHead alternators you built for us, I’ve noticed that they are built quite differently that any other alternators I’ve worked on. Can you tell me a bit more about how you build these and why?
Dales A: When looking at the inside of an E250-24 you will notice that the Electrodyne’s are built completely opposite of a normal alternator. The rotor spins around a stationary stator rather than the rotor being inside the stator (Claw tooth design). The reason we do this is to achieve more power. By having a larger stator inside the unit that can hold larger sized wire we can achieve higher outputs. We have fine-tuned the size of the magnet wire to the amount of turns per coil to achieve certain outputs at various voltages. We also use an individual lamination stack made up of either 54 or 64 laminations depending on unit and voltage. This helps us reduce eddy currents and allows us to dissipate heat more efficiently. This method is also used in our rotor lamination stacks.
Wayne’s Q: I understand that these are permanent magnet or PMA alternators so can you tell me why there are still Field Coils and what their role is?
Dales A: The field coil is essential to all units as it works in tandem with the stator to achieve the voltages, output, and current desired. Each field coil has also had extensive testing with different turns of wire at different thicknesses for the highest performance. Even though the rotor has magnets in it a field coil is still necessary.
The field coil is what supplies the magnetic field in the alternator. On certain alternator applications such as yours, Electrodyne will add permanent magnets to the rotors to aid in additional magnetism to achieve higher outputs and a lower turn on speed.
Wayne’s Q: Most alternators, even high output ones I’ve used in the past, their cases are typically made from aluminium and are much smaller and lighter than these beautiful cast iron beasts you make. Can you explain the reasoning behind this?
Dale’s A: The housing we use is cast out of ductile iron for two reasons. Extreme durability and magnetization. When the unit is first powered on and magnets are introduced to the rotor, we magnetize the housing. This also contributes to higher outputs as the whole housing now acts as a magnet itself. Electrodyne uses an insulated grounding method for its alternators so nothing goes to ground unless specified by the customer. Having an insulated ground system allows for the Electrodyne’s to be either negatively or positively grounded.
Wayne’s Q; I chose to go with your Electrodyne alternators largely because you not only removed the regulators but the rectifiers as well so I can mount these as separate units outside of the alternator cases and outside the Engine Room. The rectifiers like this one here also have their own thermostatically controlled fans. This dramatically reduces the amount of heat being generated inside the alternator cases but there is still some, so how do you keep these PowerHeads running even cooler and for so much longer than other makes?
Photo Dale provide from the Electrodyne factory showing the rotors being machined.
The fan spinning will pull air from outside and cool the two major components of the alternator (stator & field coil), simultaneously ejecting that air out and keeping the inside free of excess heat buildup.
Finally, on a remote rectifier system like yours, we remove the diodes from the top of the alternator and give them their very own fan cooled housing. The E-2281 is mounted with a fan that keeps the diodes cool while under load. The diodes used on Electrodyne’s are extremely important and need to be able to withstand constant abuse. The diodes act as a check valve for electricity, turning the AC current the alternator produces and eliminates the back and forth alternating current to a straight-line direct current. Our diodes are rated to a 900-ampere capacity and offer a high load dump capacity as well. Ensuring that electronic equipment such as regulators are not damaged when the unit is powered down.
Wayne’s Q: As I looked more closely I can see that these PowerHeads are not just heavy in weight they are truly Heavy Duty as well. With our focus on Maintenance (Lack thereof) and longevity this was another big factor in my choosing to go with Electrodyne alternators so can you give me some details of how you have designed and built these alternators to be so long lasting?
Dale’s A: The Mechanical parts Electrodyne uses are made for longevity. The bearings used are class 3 ball bearings and needle bearings that have a 20,000-hour rated life. The reason we use such long lasting mechanical components is for duration of life for the alternator. When an Electrodyne is purchased peace of mind should go along with it. Minimal failure rates are key to the Electrodyne advantage. With a brushless design we can eliminate parts from wearing over time.
Mounting the Red Monsters:
If you read last week’s post you know all the details of how I’ve designed and mounted each Electrodyne to be driven differently so here is a quick summary.
Big Red # 1 is up top, resting on the large flat mounting surface cast into all Gardner 6LXB Crankcases and then driven by a cogged tooth rubber belt being driven by the crankshaft pulley. This drive setup has a 2.15:1 ratio, meaning that the alternator rotates at 2.15 times the RPM of Mr. Gee’s crankshaft.
Big Red # 2 is down lower where it is bolted directly to the side of the AL crankcase to align with the gear driven PTO or Power Take Off on the bottom front corner of all 6LXB engines. I modified a jack shaft to connect the two very solidly together as you can see here. The drive ratio for this alternator is fixed by the internal gears driving the PTO shaft at 1.80:1 so this alternator #2 will spin a bit slower than #1.
No Generator = Best Generator?
I am often asked how Möbius can be completely self sufficient electrically without having at least one if not two stand alone diesel generators as would be typical of most other passage making boats and trawlers. First part of the answer is that the 4.48kWh from our 14 solar panels is enough to keep our 43.2kWh battery bank fully charged most days and the second part is that if not, the combined output of these two Electrodyne alternators are able to add up to 12kWh of their own.
Designing our charging system this way eliminates the need for a separate generator and aligns perfectly with our SCEM priorities of Safety/Comfort/Efficiency/Maintenance to give us the best generator of all; none!
To be fair and technically correct I guess it can be said that we do in fact have a generator onboard, and a 12kW one at that! Just not in the traditional sense nor with all the traditional cost, noise and maintenance.
Electrodyne Output Details:
I’ve received quite a few questions about the numbers behind our charging system so let me provide the following info to help answer these:
Here is a scan of the graphed results of the test runs that Dale did at Electrodyne of our E250-24 PowerHead alternators.
(Click to enlarge this or any other photo)
Using this graph I can see the output of each alternator when they are spinning at any RPM as well as how much power they need Mr. Gee to provide to do so.
Using those numbers, I have put together this simple spreadsheet to show the output of each Electrodyne alternator when Mr. Gee is spinning them at different RPM’s and the combined total output at the bottom.
For example, when Mr. Gee is running at 1000 RPM, we have a total output of 363 Amps @ 24 Volts or 8.7kWatts and at our typical cruising speeds he is running at about 1500 RPM and there is up to 478 Amps/11.5kW available from the two Electrodyne alternators. Hence, anytime Mr. Gee is running, we have more charging power than we would ever need whether we are in tropical climates or the polar regions.
The Secret Sauce: WakeSpeed 500
I very purposefully refer to our charging setup on Möbius as a SYSTEM and each of the three components of our system are important and neccessary members of the team.
But what I think has really turned this into an eXtremely good system is the “brains” of the system; our two every “smart” WakeSpeed 500 Regulators. It is not at all hyperbolic to call these regulators “advanced” as they do on their cover and let me explain a bit more about why these are the true Goldilocks factor for our charging system on Möbius.
And don’t take just my word for how truly revolutionary and smart these WakeSpeed regulators are! Here are some reactions from others MUCH smarter and more qualified than me as to how well these worked when they installed WS500’s on their boats:
“The notion of using current, as well as voltage, to regulate charging has always been the holy
grail for intelligent battery charging. With WakeSpeed Offshore’s new WS500 Advanced alternator
regulator, we now have that ability.”
Rod Collins — from www.marinehowto.com
“The WS500 also has a bunch of whiz bang features, but the cool thing is all most of us have to
do is install a shunt (if not already present) and replace our stupid regulators with this smart one
— and the even cooler part is that because this regulator is designed right — measures and
acts on net charge current — we don’t need to spend hours reprogramming it to get around its
John Harries — from www.morganscloud.com
Just as with Dale at Electrodyne it was the people more so than the electrons that mattered most. From the beginning, I was able to work directly with the two brains behind the smarts of WakeSpeed, Al Thomason and Rick Jones who created this amazing product. Al and Rick are both veterans of the marine charging world and are founders and inventors of WakeSpeed. Even better, Dale, Al and Rick all teamed up and worked together with me to do more testing on the combination of Electrodyne alternators being controlled by WakeSpeed 500 regulators charging FireFly Carbon Foam batteries! Does not get any better than that and I can’t begin to thank these guys enough for putting up with my incessant Emails and questions. Thanks guys!
The key features that make these WS500 regulators such a Goldilocks fit in our charging system are that they monitor and use a combination of system voltage, current in/out, alternator and battery temperature and alternator RPM to continuously adjust the Electrodyne’s to be the Goldilocks output for the FireFly Carbon Foam batteries at all times. Until WakeSpeed came along all our previous regulators could only use voltage to monitor and adjust the output of the alternators whereas the true indicator of what’s going on battery charge wise is the current (amps) going in/out of the batteries.
It was also not lost on me when I first started researching them several years ago, that WakeSpeed had already created custom profiles for FireFly Carbon Foam batteries and this was one of the examples that told me that these Carbon Foam batteries met my Tried & True test that I require for all our critical systems on Möbius or any XPM.
The other Goldilocks factor for our installation is that both my WS500 regulators can be “daisy chained” to work together and automagically synchronize the outputs of both Electrodyne’s by using both WS500’s to perfectly meet the needs of our FireFly house bank and everyone plays nicely together.
Sound difficult? It normally would be and would require additional relays or switching devices, but not with the WS500’s. All I do is plug a standard ethernet cable (white cable in this photo) into the RJ45 jacks in each WS500 and they become one big happy charging family.
Without going into too much detail here as there is lots available elsewhere that I will link to in a moment, it is the use of current (amps) going in/out of the batteries that adds the previously missing secret sauce to ideally optimized charging systems. Prior to these WakeSpeed 500 units, regulators were correctly called Voltage Regulators because that is what they monitored to control the charging output of an alternator. This obviously works because generators and alternators have been using voltage regulators for over 100 years to do their job. BUT, voltage by itself is not a very accurate way of determining the state of a battery and what we really care about is the amps flowing in/out of a battery to provide a truly accurate and just in time determination of what the batteries need from the alternator which ranges from everything they’ve got to nothing at all.
Some other great people have done a MUCH better job than I ever could at not only explaining their perspective on WS 500 regulators, they do so having installed these on their and other boats so they are speaking based on my favorite kind of knowledge; eXperiential. Here are links to these great resources so you can learn more from these others:
- Steve “Seabits” Mitchel review and installation WakeSpeed WS-500 regulator review – SeaBits If you are not currently subscribed to Steve’s Seabits blog I highly recommend doing so. His articles are some of my most valued resources.
- Luis Soltero post on Panbo.com How Wakespeed’s WS500 alternator regulator solves complex charging issues, now with NMEA 2000 UPDATE – Panbo
- Ben Stein’s review of Louis’ eXtremely interesting setup on his boat “Bliss” where he is using WS500 regulators to control not only his boat’s electrical needs but one with a SeaKeeper 5 gyro and NO generator. Bliss: 100hp diesel powers trawler, SeaKeeper, and huge battery bank – Panbo
- Last but not least, a big thanks to Rick Bell at Off Grid & Marine Energy Systems where I purchased our two WakeSpeed 500 regulators. Rick was a big help in answering questions and providing eXcellent after sales service for the WS Configuration Utility Pro version as part of my purchase.
WakeSpeed Setup: Have it Your Way
These WakeSpeed 500’s not only have the electronic smarts to do all of this, they have been put together in a package that I think is just brilliant. It can be as simple or as complex as you’d like to configure these regulators. For example, if you want to KISS the setup to your system, there are a set of 8 DIP switches inside each WS500 case and you just flip these to a pattern of On/Off and you’re done.
Rick and Al and their crew at WakeSpeed also get a gold star from me for their documentation. NOT an easy award to get nor one that I am able to hand out very often I can assure you. For example, how well done is this Quick Start card?! Clear, concise, colour coded and shows you everything you need to know to connect and configure on one page! Connect the wires, set the DIP switches once and you can leave it at that for most installations.
Adding to this already impressive feature list, WS500 regulators also provide me with these very valuable benefits that would otherwise not be possible or not easily obtained:
- Adaptive Idle Technology™ which allows me to set the WS500 to control alternator loads based on
engine RPM. We can use this at both ends of the spectrum; when getting underway, doing close quarter manoeuvring and such we would typically have Mr. Gee at lower RPM’s and want all of his available power for moving the boat and don’t want or need any loads from the alternators. But if/when we want to add the output of the Electrodyne’s to our solar charging when at anchor, we can turn on our “Gardner Generator” by dialing up the loads on Mr. Gee at lower RPM’s to produce high outputs from the alternators to charge the batteries faster. This keeps both the batteries and Mr. Gee very happy.
- Zero Output Technology™ enables the regulator to limit output to
loads when batteries require discontinued charging. This is particularly valuable for Lithium battery installations but this will be very handy with our large solar outputs when we don’t want or need any output from the Electrodyne’s when we are on passages.
More Goldilocks Gold
At the opposite end of the KISS spectrum, for those of us who might want to “geek out” more and really customize our charging system to be a truly Goldilocks setup, the WS500 regulators have more than 100 parameters that can all be adjusted and tweaked to get that just right, just for your boat’s charging setup. While this an get you “into the weeks” of minute details of charging systems there are several tools and utilities to make these adjustments relatively easy and quick to do. WakeSpeed is also to be commended for doing everything with open standards and being equally open themselves and we are already seeing a rapid growth in the number of companies making batteries, alternators and other components who are building custom profiles with all the specific settings for the WS500 to use. This method of having profiles, which are just small text files, that can be freely shared and easily uploaded into any WS500 via SD cards, USB cables, WiFi interfaces, etc. makes these WakeSpeed regulators a truly Goldilocks solution. You can see a list of some of these profiles and other technical documents HERE on the WakeSpeed web site.
Real World Data Coming Soon
I am still finishing up the final wiring of the WakeSpeed 500’s and the Electrodyne alternators so I have not been able to run this charging system and gather the real world data of all this at work; yet! But do stay tuned as I get this and the other critical boat jobs finished so we can take Möbius out on more trial runs and start to log all the data from this charging system and put some real data behind all this work to design and build our Goldilocks charging system. I’m waiting on some parts for Mr. Gee to arrive from the UK and complete a few other jobs that are keeping us tied to the dock here in Finike but I’m hopeful that we will be able to head out by the end of September and as soon as we do I’ll be posting updates for you that provide the proof of how all our systems are performing, including the charging system you now know all about.
Hope it was worth the wait of an extra few days for this week’s Möbius Update and that you found this latest posting to be of interest and value. Either way, I would be most appreciative of any and all questions and comments you can provide in the “Join the Discussion” box below.
Your Feedback Wanted: More Q&A type content and more Video?
On a related note, I’ve received some good suggestions that I start doing some Question & Answer sessions in some of these blog posts so if you have some questions that you would like to see me cover in a Q&A section, please type those into the box below and I will start to gather them together and post some answers to them in future blog posts.
I have also been receiving more requests to also start creating more video based content to cover the boat now that it is more finished and to consider including some Q&A sessions in those videos so let me know your thoughts on that and if there is enough interest, Christine and I will do our best to start creating more video content to post here and on YouTube.
But Wait!!! There’s more! Speaking of video content, if you have not already seen it, be sure to check out the great little video segment “The Drone Report” which Christine just published last week based on her first solo test piloting of our DJI Mavic Mini 2 drone. She’s a fabulous story teller in any medium and you can see that clearly in the suspenseful context of her first drone flight. You will also get a great hi-rez aerial tour of the Finike Marina and Möbius so it will be well worth a few minutes of your time. CLICK HERE and enjoy!
Now that the belts were upgraded from multi-v -style to toothed belt, which is a great upgrade btw, next candidate for it-just-makes-so-much-sense would be the alternators, or one of them to keep another as a spare / backup.
Those beasts of alternators pushing 10kW at around 55% efficiency (from the graph above, with heat effects etc might subtract 5% more), means total load of 18kW on main engine, thus 8kW lost as heat, or around 2 liters per hour, as waste.
Whereas using a modern permanent magnet alternator (eg RFL RFDC-10) same rpm, same powerpoint means around 90%+ efficiency, 1kW lost as heat, or around 250 milliliters per hour, as waste.
When running 24/7, in a day this is 42 liters, on a three week long passage this accounts to almost 1000 liters of diesel.
Hi Andy. Yes, I remember us discussing last year the merits of multi V vs toothed or cogged belts for driving the one alternator and water pump. At the time I already had two multi V pulley’s for the Electrodyne’s so I was going to go with that and I think that would have worked well too. However when I was doing my research on my go to McMaster Carr website, to figure out the other pulley’s I would need to adapt to the crankshaft and the Jabsco water pump I found these fabulous cogged pulleys and the ingenious Quick Disconnect or QD bushings that Martin makes so it became a much better choice to go with them and it all worked out eXtremely well and I REALLY like this belt drive system that I now have running on the front of Mr. Gee. No slippage, no axial loads, no belt tensioning, no tools 10 second belt change and all for a great price so what’s not to like!?
And while I know I can always count on you to help me spend my $$$ 😉 I’m equally as pleased with my choice of Electrodyne alternators coupled to the WakeSpeed 500 regulators. I researched different alternator options for over 2 years all together and I did consider some similar to the RFL FRDC-10 permanent magnet ones you referenced. But as with all such decisions as I outlined in my previous decision making process article, I try to take the big picture view that takes all the aspects of the decision into account. Efficiency is certainly a big factor in my decision making but not the only one as I also need to account for things like maintenance, longevity, tried & true performance, etc. So when I took everything into consideration the Electrodyne E250-24 were the best choice for Mr. Gee and Möbius and I remain very happy with that decision. I don’t have the space here to go through all the factors in my Electrodyne decision but let me offer the following for you and others who are interested.
In addition to efficiency I also took into consideration things like the physical dimensions of the alternators as to how they would fit onto the Gardner and what kind of mounting and drive system I would need to come up with to use the PTO and/or crankshaft on Mr. Gee. Another factor which affects all my decisions is the “Tried & True” qualifications of any given bit of kit I’m willing to install on Möbius. As I mentioned in the article, I had a long history with Electrodyne alternators from back in my days working on HD trucks and construction equipment as well as on other people’s boats and so I was able to “go with what you know” vs products which do not have the that test of time and in marine based environments. It is much more subjective of course, but it would be disingenuous of me not to note that the people behind a product also factor into my decision making. As I briefly noted in the post, Dale and his crew at Electrodyne were willing and eager to work closely with me to come up with an alternator and charging system that was that just right Goldilocks type of fit for me and Möbius, so that helped to make this a very easy decision.
Responding briefly to the extrapolated numbers in your comment, it seems to me to be a bit of a spurious comparison to take a theoretical best case set of numbers from the RFL web site where you quoted “90+ % efficiency” and try to compare that to the “worst case” real world set of numbers from the Electrodyne graphs and then want to subtract another 5% for “… heat effects, etc.” to get down to 52.5% (55- 5%)?? I couldn’t find any real world graphs on the RFD site and I’m not quite sure what they define as “half load” but I think that their efficiency #’s are likely best case “peak efficiency” measurements and that actual real world numbers would be a bit less to say the least. Conversely ,the Electrodyne graph I published came directly off of a one hour run on their test bench, loaded to 27.0 volts so all losses including heat are already taken into account such that I think these numbers on the graph are as close as is possible to the actual performance they will deliver here on Möbius and why I included this graph in my post.
I think we must also be reading the Electrodyne graph differently as their peak efficiency @ 1500 RPM is about 70% and at when they are delivering about 10kW combined/5kW each, when loaded to 27.0 volts as per the graph, each alternator would be putting out about 185 Amps (5kW/27A = 185.2). As I read the graph, at 185A they would be running at about 2000 RPM which would equate to about 67% efficiency. It may be unfair of me to do so, but even being very generous with what the actual efficiency of the RFL or other PM alternators would be in the same real world circumstances, I think it would be closer to 80-85% at best. If so, the difference in efficiency between these two different alternators is closer to 13-18% (80-85% – 67) compared to the 38+ % you came up with. That is a pretty huge difference I think. While I must admit that I don’t understand what numbers you were using to calculate the fuel burn rate on a Gardner 6LXB (??), nor how you got to a “waste of 42 liters per day” (??), it certainly seems like a big stretch to come up with a total of 1000 liters of “wasted fuel”.
I’m sure we could debate this and come up with different “math” ad infinitum Andy but at the end of the day what matters most is that the decisions we all make are the Goldilocks, just right, just for us ones and I hope that you and others now understand the logic behind my decisions, however flawed you might see it. Of course I too need to wait to see what the actual numbers are for the charging system on Möbius once I have collected more data from our ongoing sea trials and use underway in the coming months and years and I look forward to bringing all of that to all of you here on the blog as we cruise the world.
My sincere thanks to you Andy and others who question my decisions and make alternative suggestions as they are eXtremely helpful in forcing me to go through my logic again and see if a given decision still makes sense and passes the Goldilocks test. That is a huge value to me and I hope these discussions are also helpful to others out there striving to make their own Goldilocks choices. So thanks!