At the end of April I published “One Year & 7300nm later; Most & Least Favorite Möbius Features April 17-30 2023” which was Part I of the first year review reporting on what has now been well proven to work the best for us and were our favorite features. Since that post we have put another thousand nautical smiles under our keel as we meandered our way up to our final destination for a bit at Tidewater Yacht Marina in Portsmouth VA just across the river from Norfolk Virginia. That passage totaled just over 8200 nautical smiles and we are going to push the Pause button and stay here for the next few months. If you missed it, I provided a more detailed update on this last leg of our latest journey in the previous post you can read HERE.
This will be Part II with our review of those things which have not worked out as well as hoped, our least favorite features and things to add/change to make Möbius even better than she already is. I’m delighted to report that our least favorite list is much shorter than our most favorites so this Part II will be much shorter than Part I.
As with Part I there is no implied ranking in the order of these items and I’ll group them as Design based or Equipment based.
DESIGN BASED CHANGES
I’ll start with Design based changes and note that given the enormity of this project and that we pretty much started from scratch, we have been pleasantly surprised at how few design decisions we and our brilliant Naval Architect Dennis Harjamaa made that we would have done differently. Even these are all best categorized as things that would be improvements to the current design and build. We have also passed on all these observations and recommendations to the new owners of the two XPM’s that are currently under construction in Antalya right now and to the builder for future new builds.
Extended SuperSalon/Pilot House
Depending on weather, this space is where we spend a majority of our time at anchor, especially for meals and evenings and it continues to be a joy to live in. However, we have come to realize is that it would have been very easy to extend the length of this superstructure by one frame which would have made this room about one meter or three feet longer.
If you click to enlarge the plan view from our design files and the rendering below, you can see the layout of the SuperSalon as it was deigned and built. 
As you can see, we had intended for two lounge chairs to go in the space to the side of the dinette table.
However, along the way we ended up deciding to install the two drawer style fridge/freezers inside the cabinetry on the Port side which is at the bottom behind the backs of the chairs in this rendering above.
When we moved aboard, we put two admittedly large comfy lounge chairs in as per the layout you see here, but after using for a month or so we found that this proved to be impractical needing to access the Fridge/Freezer drawers and so we have removed one lounge chair.
This is has been our setup ever since and works out fine but means that when we are having our nightly “dinner and a movie” time watching the large 50″ TV in the forward Port corner, one of us needs to be seated in either the Helm chair or on the settee with the table put down into “coffee table” height. Having that extra meter of length would have allowed each of us to have our own lounge chair which would make our evening entertainment time even more enjoyable and comfortable. I know, I know, poor pitiful us right?!
On the plus side we discussed this with Naval Yachts and with Chris and Sebrina when they were designing the layout for their XPM78-02 Vanguard and decided to add that extra meter and it has made their SuperSalon even better than ours.
Ventilation
We made natural or passive ventilation, especially when at anchor, a high priority as we were designing Möbius and most of the time it has worked well but when the weather is warmer but not quite hot enough to justify running Air Conditioning and when the winds are low ventilation in the primary living spaces, the SuperSalon and the SkyBrdge, are places where the ventilation can be improved the most.
Ventilation: SuperSalon
One of the many great things about being at anchor is that you know that all the wind is going to be coming over the bow and flowing aft so we took advantage of this to bring those breezes into the boat. There are three ways we bring natural ventilation into the SuperSalon area, two which bring the breezes into diffusers in the ceiling and a third with the air that flows through the large hatches in the Master Cabin and up into the SuperSalon. Ventilation via the Master Cabin flow through works well but the two independent ventilation systems for the ceiling diffusers do not provide as much ventilation as we had hoped. 
One of the ways the air enters the boat is through a series of slots cut into the roof overhang in front of the negatively raked front window which is highlighted in Red in this rendering. This location creates a slight high pressure zone that we wanted to take advantage of to help bring some fresh air inside.
This is what the real thing looks like. The space behind this grille connects through pipes into a large plenum or box in the ceiling overtop of the Main Helm Station.
In the ceiling overtop of the Helm station these five Black diffusers connect into that plenum and are adjustable to change the volume of air and the direction of the air flowing in. All good but there was supposed to be ducting used to bring the air from the grill box through to each diffuser and because this was not done all the air fills up the plenum and loses all its pressure and so there is not good flow of the air into the boat.
The second fresh air intake is located up here but is hidden from view when these three solar panels are in the closed or down position for when we are at sea.
Those three panels are mounted on a single frame that is hinged on its back side such that it can be lifted up and held in place horizontally like this. Very simple and quick operation to remove two locking pins on the front and lift the panel up and lock the support braces in place. Having the solar panels horizontal can also help increase the power when the sun is overhead.
This position creates this massive wedge shaped wind tunnel which directs air coming over the boat to flow through the “mist eliminator” grill my finger is pointing to which removes most of the humidity and airborne salt as the air flows through.
Similar to the forward Black ceiling vents this air flows through into a large plenum above these White diffusers you see here which directs the air down into the Salon.
Unfortunately, this system was built the same with with no ducting and so the flow rate is similarly compromised and produces much less air flow than expected.
Our interim solution for now has been to use this vertical rotating fan which works surprisingly well and is very quiet but longer term we will retrofit some ducting to the ceiling diffusers which should be much more efficient at bringing the breezes into the SuperSalon.
Ventilation; SkyBridge
Up in the SkyBridge there is excellent air flow available because each of the acrylic window panels are easily removable.
To provide great ventilation up in the SkyBridge we came up with a very simple and easy way to remove/replace each of the 8 side and 2 rear acrylic sheet windows so that we can open up or close in the SkyBridge as the weather changes and this has proven to work really well. To remove any of these windows you simply lift it up the bottom of each panel and as you can see here the bottom edge now just clears the cut down inner sidewall section of aluminium U channel that holds each panel in place.
The top edge of the panel slides up into the extra space at the top of these upper U channels so as you pull the bottom of the panel inside and down so it slides out of the upper frame channel you see here.
A good example of the KISS Keep It Simple & Safe approach we used throughout the boat and takes mere seconds to remove or replace a window panel.
Even though it is June 11th as I write this, the weather here in Portsmouth has been surprisingly cold, dropping down to 14C/57F last night for example. Brrrrrrrrrr!! So right now we have just removed one acrylic panel from each side and this allows us to slide the other three panels back and forth to block any wind or rain. In this photo I’m pointing at the edge of the acrylic panel that is behind my hand to the rear and the area to the front on the Right is wide open.
This different angle might show this opening a bit better with my finger again pointing at the edge of the acrylic panel with the open space forward. If we removed all 13 acrylic panels all four upper sides of the SkyBridge are open and air flows through. 
Very often too much breeze coming through especially through these three front facing windows so we tend to keep these in place all the time.
So once again, what’s the problem Wayne??!! Best description is the lack of the “Goldilocks” just right amount of ventilation up in the SkyBridge when we are at anchor. Too much if we remove these front three windows and not enough if they are left in place.
The problem is that with the wind coming over the bow, if these front windows are in place they deflect almost all the air down the sides of the SuperSalon and even if these side window panels are removed the airflow is such that it all flows straight back along the sides and too little air flows into the interior of the SkyBridge especially up at the front in the lounge area.
Fortunately I think that the solution is relatively easy to create. The idea would be to convert these glass panels from being permanently fixed in place to panels mounted into hinged frames so each glass panel can be open and closed. Perhaps this would only need to be done to the three front facing panels and leave the side glass panels fixed as well as being able to remove the upper side acrylic windows making it an even easier modification.
SkyBridge Windows View Obstruction
The SkyBridge on Möbius has proven to be our most favorite area for both helming the boat underway as well as lounging up there when at anchor so this is where we spend most of our time unless the weather turns cold and wet, which in the past two years has not happened much at all. The 360 degree views from up here are difficult to capture in photos but you’ll get some idea here with this view forward from the Lounge area.
and this view from the Upper Helm chair. So what’s not to like Wayne??
It may seem very minor to most, but when you are sitting down in the Lounge settee your eye level is the same height as the horizontal aluminium break between the lower glass windows and the upper acrylic sliding windows. So when I’m looking out that seemingly thin bit of aluminium gets in the way of your view and has become a pet peeve for me. You can sit lower or higher to see over/under this but the views would be so much better if your sight line was about 30cm/12″ higher such that you were looking through just the acrylic windows.
The best solution I think would be to build a raised platform about 30cm high for the lounge settee and table to sit on. This could be a welded AL platform but what I think I will do when I have the time is build a wood frame for the platform and cover with marine plywood as a first prototype and see how it works.
The floor of this raised platform could be covered with the left over vinyl flooring that has worked out so well in the other living spaces and there would be the bonus of having a very large storage space under the platform floor for larger and bulkier items such as deck/beach chairs and such.
That covers all the most significant design based changes of we have recommended for the next XPM78 boats which are built. Other minor ones are things such as decreasing the height of the stair risers, basically adding one additional stair step to each to make it easier to go up and down these stairs. The current ones are a bit too much of a step up and down for most people and not quite that Goldilocks just right height. Easily fixed during the build process but not something we will change on Möbius and instead see this as a feature rather than a bug by keeping us in good physical shape each time we use the stairs.
EQUIPMENT ISSUES:
The other area where improvements and changes would be recommended is with some of the equipment that is used in some of the systems onboard.
FireFly House Batteries
The most disappointing equipment issue has been my decision to go with FireFly Carbon Foam batteries for the large 1800Ah @ 24V house battery bank. If you’re interested in the fully detailed description of the situation you can go back and read the post I wrote back in August “No Fire at FireFly Batteries?” It really is a very sad and disappointing situation as these Carbon Foam type batteries are a fabulous solution for many boats and owners and I’m hopeful that another company will pick up the patents and start manufacturing more soon. The problem was not with the chemistry but with the lack of quality control at the factory which resulted in far too many of these batteries losing their capacity very early in their life.
In our case, the capacity loss began after about six months of use and has continued to slowly decline more and more ever since. On the good news front, we have been able to continue to use the boat full time every day with almost no problems using the existing capacity these batteries do have so it has not been disruptive to our day to day living and cruising. In fact we have only been plugged into shore power twice in the past year on some brief stays in marinas. This is all thanks to having so much capacity to begin with in the 24 individual 4V @ 450Ah batteries that make up our House Bank, as well as having so much solar from our 14 320Watt solar panels that brings the house bank up to 100% SoC each day. Plus anytime we are underway we have the two Electrodyne alternators able to crank out up to 9kW of power to charge the batteries if we need to go days without much sun.
This is another reason that we will be staying put here in Portsmouth so I can decide what to chose for the new battery replacements. Right now this is most likely to be some good quality AGM batteries or perhaps Gel based “traction batteries” but I’m still researching what the Goldilocks replacement choice will be. Lithium is what most people would think of but in our case they don’t make as much sense as we actually value the weight of our House Batteries providing part of our overall ballast and we have plenty or room as you can see above. There also appears to be growing evidence that one of the odd characteristics of both Carbon Foam and Lithium is that they prefer to NOT be kept fully charged to 100% all the time and I believe that this was part of what caused our batteries to fail prematurely. More research to follow and I’ll provide updates here whenever I make the decision on the new House Batteries.
Reducing Engine Room Extraction Fan Noise
One of the other equipment based changes we would make is to find ways to reduce the noise from the extraction fans which ventilate the Engine Room. These run whenever Mr. Gee is running to keep him supplied with fresh air and to exchange the air in the Engine Room frequently to help extract the heat and keep ER temperatures as low as possible. Not able to photograph the whole setup as it is welded into the hull and ER but you can see how the Red boxes are welded to the Aft Deck plate and then the Purple aluminium ducting runs in/out of the ER below.
The existing fans do the job very well and as extraction fans go they are not too loud. However, because the entry and exit grilles are located in these two vent boxes on the Aft Deck the noise they do make travels up into the SkyBridge and can be a bit distracting. One of those things you don’t notice so much until you do. I’m not sure how much this can be reduced but I will be researching fans that have been specifically designed to be quieter and look into whether moving the fans from inside the Vent Boxes to down inside the ER itself might reduce the decibels a bit.
Circuit Breakers as On/Off Switches
There are two circuit breaker panels on Möbius, this one on the Starboard/Right side of the Main Helm for all the 24 Volt circuits that are best accessed from there such as deck lights, navigation equipment, etc. These are all double throw circuit breakers so they control both the positive and negative sides of each circuit and this has al.l worked out very well. 
Then there is this larger panel with all the circuit breakers for the remaining equipment in all four voltages; 120V + 240V AC and 12V + 24V DC.
The issue is a minor one of convenience. Because there is a circuit breaker for each individual piece of equipment, no On/Off switches were installed where the equipment is installed. In most cases this is just fine but for things like pumps for transferring fuel and water, desk wash pumps and things like that, it would be handy to have an On/Off switch right there when you want to turn on a Deck Wash pump for example. This would simply save me a trip up to the circuit breaker panel so this is just a matter of convenience
Easy enough to solve the problem and I have purchased some nice On/Off switches to mount nearby these types of devices and just need to find the time to install them all.
Bosch washing machine
I’m not sure if this is a common problem with this model perhaps but our Bosch washing machine has failed three times since it was installed and has been very annoying to have to remove and repair. The first two times it was under warrantee but it failed again while we were making our way through the Bahamas and so is on my list of repairs while here in Norfolk.
What makes this particularly annoying is that none of the Bosch service technicians seems to be able to identify just what is causing the problem and they simply replace every circuit board inside and reinstall. 
Even worse, once the washing machine does quit it shows an error code on the LCD screen but as soon as you shut it off, it will not turn on again, not even the screen, until after the problem has been fixed. So unless you take a picture of the screen when it happens there is no way to turn the machine back on and figure out the problem! Fortunately I take photos of these error codes but even with that none of the service techs or my searches online can tell me what the problem is so I’m at a loss to know what to fix.
Will just need to break down and have them come out to the boat to replace the circuit boards for a third time but sure is annoying!
I should add that all our other appliances on the boat such as induction cooktop, oven, etc. are all Bosch and are working extremely well so no knocks to the company, just the lemon of a washing machine we seem to have lucked out with!
And that’s about it for the list of things which we’d recommend change on next builds and things we will be doing to improve what has already been a fantastic boat. Surprisingly few breakages in the time we’ve been underway and living onboard which says a lot for any boat and makes us VERY happy. About the best testament that can be given I think to ALL involved with converting our dreams into the reality that Möbius now is and we are eXtremely grateful to each of you and our special thanks to Dennis Harjamaa for his brilliant design work and everyone at Naval Yachts for their work building Möbius.
Hope this review of both what has worked the best and the least well will be of value to other boat owners out there or future ones. I know that I value first hand experience over just about all else and so glad to pass on what I’ve learned in our experience with Möbius so far. Please do let me know if there are other specific questions you have related to all this or of any kind and I’ll do my best to respond as quickly as possible.
Thanks,
Wayne
Hi
A couple of double thanks. Development is an ongoing “adventure”. Matching up this work with some of the original build decisions is fun
Now a couple of observations.
On the air flow. It S/B taken in at a high pressure point and EXHAUSTED at a low pressure point. I remember a very successful racing car which was famous for high cabin temps because a very famous and usually smart race engineer was trying to take air in at a low pressure point. Had he exhausted air where he was trying to intake it is likely he would have sucked the inside air out and gotten a very nice air flow. The speeds where in the high 190s so there is a difference BUT anyone working with airflow needs to understand the pressure differentials involved. The same car had the problem with air flow not coming in that you have on the side windows. The put a “fence” up to redirect the air. Worked but so would vortex generators which are now available is various sizes. These are not suggestions as I am not familiar with your air flows. I would say to pay attention to exhausting into low pressure areas and intake at high pressure areas. And watch how the air flow is attaching to various surfaces.
As for your appliance issue. We have very few repair persons left in any industry. What we have is part swappers who do exactly what is happening to you. No analysis of cause, just swap the failed part and maybe the cause will go away. The seven whys are forgotten. Or any other in depth cause analysis. Unless you luck on a true analyst the best you can hope for is a swap of the whole unit which will end up with the unit being scrapped. But the appliance is now out of warranty so that’s not likely to happen.
Added this to my “book”
Looking forward to next installment
PS The battery field is absolutely insane at this time with “breakthroughs” a bounding. “May you live during exciting times.”
Hi John and thanks as always for your thoughtful responses and suggestions.
Appreciate the air flow details and I think we have these addressed well in the case of the Engine Room but need to work on improving the ventilation in the SuperSalon and SkyBridge areas.
We share similar concerns about the “appliance industry” though the same symptoms seem to plague a LOT of other industries as well. For our Bosch washing machine I may see if I can just buy some new circuit boards and do the install myself but all a matter of so many ToDo list items and so little time!
Wayne
Hi Wayne, this feedback is great with one man’s hindsight being 20/20 vision for the next guy in line. One small point you may think about is space exists in the rear engine room access way to fit the exhaust fans. It does not make them quieter, but it takes the source of noise a good way from where it’s annoying. Not sure if this fits your double-engine room space design but it works for us. We have a 2 stage Delta T arrangement (same as yours I believe) fitted horizontally in this location with a fire damper inboard. p.s. still working on our launch, don’t yet see the end of all the jobs to do. Chris
Ahoy Chris and Sabrina! Hope you are enjoying your recent move to Antalya and that you’ll find it as super a spot to be as we did and that all will go as well as possible with getting Vanguard launched and fully seaworthy so you can throw off those docklines in the not too distant future and start enjoying all your hard work to realize your dreams of life at sea as a family.
For our ER fans, I agree that moving the location of the intake/exhaust spots would help and will see how I might be able to make this change now. This is not too big of a problem when we are underway just one of those things that once you notice you pay attention to it more and less noise is always a plus in any environment.
Sending all our best wishes to you both and all there in Antalya involved in getting Vanguard launched and off cruising.
Wayne
Hi, always a good read, thanks. As to the saloon chairs; we have Ekornes chairs with ottomans that fold up under the seat (electric) when not in use. Makes for lots more room.
We also have Firefly batteries. Have been lucky, no bad cells, but it has been quite a learning curve. They were working well a year ago when we got back to Newport after six months in the Bahamas. But after two months at a dock, on float, I thought they were totally shot. The full charge from zero SOC (twice) did the trick . I also switched to Wakespeed regulators so I could achieve target tail currents. My bank was already physically a 2 bank system, but functionally wired as one. I added a bank switch and now occasionally charge first one bank and then the other at >.4C. I have 900A @24v capacity and 300A charging capability. If you have no bad cells, I wonder if there isnt an opportunity to revive your bank.
Hi Greg & Lisa, thanks so much for these suggestions and am really enjoying our follow up since. We have a very similar setup with FireFly batteries and WakeSpeed regulators so most helpful to be able to compare notes with you and see what we can do to hopefully recover some or all of the original capacity of our FF House Bank. Looking forward to our continued discussions via Email and I’ll post updates as they happen here on the blog.
Wayne
Dear Wayne
Regarding the noise created by the engine room extraction fans: I made the observation, that reducing the supply voltage of a DC extraction fans somewhat (e.g. from 24V to 21V) does reduce the fan’s noise significantly. There is a VICTRON 24V-to-24V converter, where the output voltage is user-adjustable between 20V and 30V. When reducing the supply voltage, the fan will produce less airflow and its motor might run hotter.
Best regards, Markus
Hi Markus! Excellent suggestions re lowering the Voltage/Speed of our ER fans to reduce noise a bit. The challenge is as you noted that this would also reduce the volume of air flow and higher temps of the fans so for now at least I’ve decided to leave them running at 24V and see what I can do to find other ways to reduce the noise a bit more.
I also don’t want to overstate the current noise levels up in the SkyBridge as it not really very bad at all. Just one of those things that once you start paying attention you notice and exaggerate it more. So I’d classify this as trying to go from “good to great” in terms of noise levels and will keep working at finding ways to do so.
Thanks again for your suggestions and please do keep them coming as you think of more.
Wayne
You posted. “Circuit Breakers as On/Off Switches
all the 24 Volt circuits that are best accessed from there such as deck lights, navigation equipment, etc. These are all double throw circuit breakers so they control”
Why use double throw? Why not have one BIG FAT negative loop around, switch the positive and connect the negative to the closes BIG negative loop.
Less cable, and in some cases smaller cable with the same voltage drop?
Ahoy Jan. Very good questions and ideas re the negative DC wiring on Möbius. Being an aluminium boat we pay particular attention to all the electrical systems on the boat and keeping the hull isolated. This is the primary reason behind the decision to go with DPTH circuit breakers because they make it so much easier to trace any unintended grounds that might happen by being able to isolate and turn On/Off each individual circuit. As you noted it does use more wire this way but is well worth it for the benefit individual negative switching provides.
We do use negative DC bus bars and this helps reduce the length of the individual smaller wire runs so it has all worked out quite well for us and our use case.
Wayne
Hello Wayne – what AC frequency do you run the boat at – 50 or 60hz. I spent a long time trying to work out why my Samsung washing machine would not work in Antigua and bought spare PCBs etc. The solution was its a 50Hz washing machine (like most other european ones) and works fine on our genset (50hz) and inverters (50Hz) and shorepower in europe (50Hz) but misbehaved intermittently on shorepower in Antigua marina (60Hz). I have also known two other yachts complaining of this issue with other makes of machines and put them straight as well. In our cases, the solution in Antiguia is to unplug from shorepower to run the washing machine! Other equipment on board works fine with 50 or 60Hz including ovens, cookers, toasters, kettles, AC systems, battery chargers. But washing machines seem particularly fussy! If you have a eurpoean brand washer (Bosch) and run the boat at 60Hz then you might well get problems.
Hi Nigel, thanks much for your thoughtful response and questions. We setup our AC electrical system to run on both 50 and 60 Hz with all our 220V outlets being 50Hz and all our 120V outlets being 60 Hz. Relatively easy to accomplish by having all the AC come from the inverters in our Victron MultiPlus inverter/chargers which allow us set them up for these specific frequencies. On those occasions when we do have access to shore power it dictates the Hz on the boat as it bypasses the inverters so if the shore power is at 60Hz then our 220V outlets and consumers would be running at 60Hz as well. Not that much of a problem usually as you noted more and more AC consumers are happy to take either 50 or 60Hz but there are still some which do care and so the easy solution to this is to simply unplug or turn off the SP input on such occasions which is what we do as well.
As for our Bosch washing machine I was finlly able to get it to turn on and allow me to do more diagnositcs which led me to believe that it is the drain pump that is the problem. I removed this pump and it seemed to work OK when I connected it to 220V on my workbench but when installed in the washing machine it does not work and just makes a sort of ticking noise and does not pump any water out the drain. I’ve ordered a new one from England as it needs to be 230V @ 50Hz and can’t find any of these through North American suppliers and fingers crossed this will solve the problem when the new one arrives. I’ll keep you updated when that happens.
Thanks again for taking the time to let me know about your experiences with Bosch washing machines, much appreciated and helpful.
Wayne
I’m curious to know how / what data you used to decide to run your solar array with separate dedicated MPPT controllers for each panel.
Sorry to ask for advice here but thought that you would probably have a good rational answer…
I have 2 x 275W panels (Voc 38.5VDC) on my pilothouse roof but intermittent shading reduces the output well below its rated capacity. I am using a single 45A Morningstar MPPT controller with the 2 panels wired in parallel to feed the controller. (I initially set this up as a series array but after testing both arrangements, the overall daily solar output is much better in parallel vs series.)
It has been suggested that having 2 separate MPPT controllers, one for each panel, would significantly improve the solar power production but I cannot find much data to support this assertion. (I am running a 12 VDC house bank so the single panel Voc of 38.5 VDC should be more than adequate to feed separate MPPT controllers.)
-evan
PS. Our Firefly House Bank has been significantly improved by running a full discharge rapid recharge protocol.
Hi Evan, glad to share my experiences with MPPT controllers for solar panels. I decided to go with dedicated Victron MPPT controllers, one for each of our 14 320W solar panels to maximize the efficency of each panel and minimize the effects of shading on any of these panels. I’m not sure how much this setup increases the usable output or reduces the effects of shading but from what I read, going with dedicated MPPT controllers is the optimum setup and ours certainly seems to perform very well. In our case it also worked out to be slightly less expensive to purchase 14 of the Victron 100/20 MPPT controllers rather than 4 or 5 of the larger ones to run multiple panels. I also liked the added redundancy of having 14 independent solar power sources so these helped make the decision very easy in my mind. Hope this helps you with your decision.
Glad to hear that you are having success with keeping your FireFly batteries running at full capacity. I had similar success in the first year of using ours but they have now degraded substantially with two of the four 450Ah 24V banks having almost no capacity anymore and the other two declining badly as well. Fortunately with all the solar output we have been able to run for over a year by being able to fully recharge almost every day to 100% which allows us to keep the boat fully operational for daily live aboard use of all our systems. But once the days get shorter and we see less and less solar output that won’t be the case so I need to replace all our FF batteries before then. I will let you know what I decide to replace them with as that happens.
Wayne
Hi Wayne,
Thank you for your reply and information.
I thought I would share my findings in testing whether a retrofit of separate controllers would be warranted. My apologies if this is too long or too off-topic, or just plain way too pedantic; but it’s possible that someone could find this information interesting or helpful.
My situation is complicated by the fact that I have a seemingly quite functional single and rather expensive Morningstar MPPT controller being fed by 2 panels wired in parallel. My Radome and mast as well as VHF & AIS antennas all contribute to some unavoidable shading. I’ve been disappointed in the solar production of my system not coming close to its theoretical 550W
https://eheffa.zenfolio.com/img/s/v-10/p2021082506-5.jpg
Various “experts” on-line maintain that because of the very disparate optimal power curves of a shaded and non-shaded panel feeding a single MPPT controller it would be much better to have each panel installed with its own dedicated controller.
I’ve just had a few days at anchor (Winter Cove on Saturna Island) with an opportunity to carefully study the varying output of my panels with the plan to switch to 2 separate controllers while there.
Baseline State:
The most production I see under ideal conditions with the heading and sun angle such that there is no shading of either panel, (2 x 275W panels with Voc = 38 VDC wired in parallel) and at my latitude of 48°48’N in high summer is ~400 W (30 – 32 Amps at a nominal 12VDC ( ~12.5 – 14.0 V charging in bulk phase.) My MPPT controller is rated for 45A so output is not likely to be limited by the controller capacity.
In the absence of any real world data to draw on, it occurred to me that before tearing out my old installation and committing to 2 new separate controllers, I could test to see whether or not shading of one panel would degrade the output of the non-shaded panel and the total output of the system. I have breakers for each panel’s output so can switch the panels off & on independently & compare their individual optimized output to when they are both on together in parallel (I don’t know why I didn’t think of testing this before?)
Switching to independent controllers would only make sense if:
Independent PV Current Port (IPVIP) + Independent PV STB Panel Current (IPVIS) > Combined Panel Current (CPI) with a shared controller (CPI).
Is it true that IPVIP + IPVIS > CPI ?
Conversely, if IPVIP + IPVIS = CPI then there would be minimal value in switching to independent controllers.
Methods & Results:
When swinging to a heading where one panel is shaded & the other is in full sun in mid-morning, I found the following:
When independently feeding the controller with the non-shaded panel off, the shaded panel provided 1.5A. The non-shaded panel by itself with the shaded panel off, was producing 14A.
With both panel feeds on, in parallel, the total output was 15.5A which equals the sum of the 2 panels working independently. IOW, the combined output on a single controller was not degraded by the shading of one panel and the significant disparity in outputs between the 2 panels.
I repeated this later when there was a higher angle sun and with a 20A combined production, testing each of the panels separately with the controller dedicated to optimizing the production of each panel, the values were simply additive: 6A + 14A = 20A. (Note: I did give it some time to see whether the MPPT scanning protocol would optimize the output.)
To make switching from one MPPT controller to 2 separate MPPT controllers worthwhile, one should see the combined joint output with a single controller to be less than the total of the two independent outputs due to the single MPPT controller not being able to optimize the disparate power curves. That doesn’t seem to be the case in my application; so, there is no value in changing the setup now.
It’s possible that the Victron controllers would be better at finding the optimal power curve compared to my Morningstar controller, but that would be an expensive gamble to take the leap and try switching on pure hope…
So…the new unused and oh so compact and functional Bluetooth Victron, controllers go back.
If this was a new installation, it would make total sense to have each panel on its own controller but as a retrograde ‘upgrade’, the value doesn’t seem to be there.
(In fact, looking at the bigger picture… I am seeing ~ 190 – 200 Ah daily solar production under sunny summer conditions. Improving that by 20% (unrealistic as that is without more panels or eliminating shading) would only gain another 40 Ah or so. With a 9.5 KW generator on board and 2 AC chargers, I can produce that much power in 15 minutes of charging; so stepping back, it makes little sense to get too hung up on trying to extract an extra 10% solar production at a cost of several hundred dollars.)
My panels provide enough output so that there is no urgency to recharge in the morning and I can run the generator electively during daylight hours.
As much as the perfectionist in me hates to say it, the current setup is “good enough”.
Nothing beats real world testing and data in my opinion Evan and so getting this detailed report of your test results is extremely valuable for all of us.
I also think that your conclusion is spot on and makes the most sense for your situation of having an existing setup with a single MPPT controller for multiple panels. Your testing reflects my limited experiences as well which is that having a dedicated MPPT controller for each panel does offer more output and less reductions due to shading of one panel, BUT these improvements are too low to justify replacing a currently working setup with a single controller.
In my experience I have found it best to “do the math” or “run the numbers” for all such decisions so you can work out the net benefit and differences and use these to make decisions as to what is the best value and the best fit for your given situation and use case.
So I applaud your significant efforts to do this kind of real world and big picture evaluation and really appreciate you sharing it here for the rest of us to benefit from.
Thanks,
Wayne
Hi Wayne – what a great one-year-in series. Although I have a much smaller solar array (two 175w panels), I also used a dedicated Victron controller for each for the same reasons you shared. You can likely see the panels on the American Tug, Anomaly, berthed across from you at TYM as I write this (July 5), haha. I searched for info about XMP 78-01 out of curiosity when we arrived and am enjoying your blog. I’ll wave and say hello if I see you while we’re here (we’re Tom and Amy). Thanks for sharing your blog – as you say, it’s always great to learn from others’ experiences. – Tom
Hi Tom and Amy. Thanks for the greeting and sorry to take so long to see and respond to this kind note from you. As you may have seen we had our two Granddaughters and family aboard with us for the past week so things have been pretty busy here with lots of outings each day. They all left yesterday so we are back to being just the two of us onboard and please do knock on the hull if you wander over to this side of the marina. Othewise we can wave at you across the way on our evening sundowner times up in the SkyBridge or on the front deck.
Wayne