This is the first of the Tech Talk style of articles I promised in THIS previous posting. Many of you have been asking for a more in depth and technical look at the What, Why and How of all the various major systems required for an XPM boat such as Möbius. And not to worry, I will continue to do the weekly progress updates and then as my time permits, I will also post these Tech Talks for a bit of a change of pace and a different look at these boats.
Note that there is a tag in the blog for Tech Talks so you can filter on this whenever you want to have just these articles show up on your screen. These Tech Talk articles will also be a bit different in that I will update them if things change or there are other additions or edits to improve them so much like your author here, these will be a continuous work in progress.
As with all my writing on the Möbius.World blog please keep in mind that the context for all my writing and all our decisions is always and only, what is “just right, just for us” as we are living on our all aluminium XPM78 eXtreme eXploration Passage Maker. As in our past boats, this will be Christine and my full time home as we double-hand** our way around the world’s most remote locations at all latitudes from polar to equatorial with equally eXtreme degrees of Safety, Comfort, Efficiency and Low Maintenance.
** We were both formerly single handed sailors until we met, fell in love and married in our 60’s and are now about to set off “double handing” our way around the world on our new XPM78 Möbius.
If you would like to learn more about our use case THIS previous post has the full explanation.
And before I go any further please keep the following in mind about all these Tech Talk articles:
- These are NOT recommendations on what YOU or any other boat owners should do or what equipment you should buy.
- I am NOT suggesting that our choices are “the best” I merely hope to explain OUR (Christine and my) logic and why we believe that these are the Goldilocks “just right, just for us” choices in the design, installation and equipment aboard XPM78-01 Möbius.
- I am NOT an expert nor do I have any qualifications or certifications in any of these topics and while we have enlisted the help of true experts, engineers, designers and naval architects throughout the design and build process please only use the information provided in these Tech Talks as additional information to assist you in developing YOUR OWN opinions, ideas and designs.
· These Tech Talk articles are intended to generate lots of questions, suggestions, and ideas. I hope to learn as much as you do by writing these Tech Talks and more so by responding to your comments and provoking more good discussions.
· In doing so we can all contribute to the wealth of information and knowledge already out there for all of us to access and learn from. Indeed this is the primary purpose and value of these articles, so don’t be shy and please add your contributions to the “Join the Discussion” box below. I only ask that you keep the above notes in mind and of course keep the discussion respectful, polite and on topic as you always have.
As mentioned in our use case overview and in many previous posts, we have four fundamental principles or priorities which we have used throughout the entire design and build process to guide our decisions. These are Safety, Comfort, Efficiency & Maintenance. We strive to keep the first three as high as possible and the last one, Maintenance, as low as possible. I will therefore add a “SCEM Review” section for each system’s Tech Talk and summarise how each system contributes to each of these fundamental priorities and principles.
All right, with all that out of the way, lets dive into the details of the What, Why and How of the XPM Electrical System.
ELECTRICAL SYSTEM OVERVIEW
The Electrical System on our new boat can best be described as a DC Battery Based electrical system meaning that ALL of the electrical power consumers on the boat, both AC and DC, get their power from the large 24 volt “house” battery bank. This is in contrast with many other boats that could be characterized as “AC Based” boats because their systems are optimized for AC inputs from onboard generators and shore power. Both models work well and the question is not which system is “best” but which system is best for a given boat, owner and use case.
Given that by design and use case there is no generator onboard Möbius and shore power is rarely available as we live on anchor almost all the time, a DC Battery Based boat is the just right, just for us solution.
Our large 24 volt 1350Ah battery bank is charged from either the +5kW bank of 14 solar panels and/or via the two large alternators, 250A @ 24V each, 12kW total, driven off the main engine when on passage.
This is very much a “world boat” so all four of the most common voltages are available onboard at all times. 24V DC and 220V 50Hz AC are the primary voltages we use and 12V DC and 120V 60Hz AC outlets are located throughout the boat as well for devices and guests which require these voltages
There will be shore power connectors at the front and rear for those infrequent occasions when the boat is hauled out for maintenance or to leave for extended times for trips back to be with our three Grandkids and other family and friends. These shore power connections come aboard through a Victron Isolation Transformer primarily to ensure we have no connection from the boat to shore side grounding wires and gives us the significant advantage of being able to plug into any shoreside power from 100-240 Volts @ 50 – 60Hz.
BASIC ELECTRICAL SYSTEM COMPONENTS:
- House Battery Bank: 18 FireFly Carbon Foam L15+ 450Ah @ 4V batteries connected in three 24V banks 6S3P (6 Serial 3 Parallel) = 1350Ah @ 24V = 32kWh
- 220 Volt Inverter/Chargers: 3 Victron MultiPlus 24V 5000W 120A
- 120V Inverters: 2 Victron MultiPlus 24V 3000W 70A
- DC-DC converters Victron Orion 24V to 12V 70A
- Engine Alternators: 2 Electrodyne 24V @ 250A = 6kW each = 12kW total output.
- Both with remote rectifiers and remote “smart regulators”
- Battery Monitor: Victron BMV 712s for monitoring each of the 3 battery banks and the overall DC electrical system.
- Augmented with Maretron monitoring
- Solar Panels: 14 each 96 cell 360W = 5.04kW peak total
- MPPT Controllers: 14 Victron SmartSolar 100/30 MPPT controllers
- one per solar panel
- Engine Start Battery: 2 FireFly G31 110Ah Carbon Foam batteries in series 110Ah @ 24V
I hope you have found this first of my Tech Talk articles to be of some value and I would be most appreciative of any and all comments and suggestions on ways I can improve them. With this Electrical System Overview done I will next dive into each of this system’s components and I think it is appropriate to start with the true center of or Electrical System; the House Bank batteries and then progress through each of our Charging Sources which are solar and engine alternators.
Please add your comments, questions and ideas in the “Join the Discussion” box below each post.
I think that makes sense. We have a smaller bank of Firefly batteries (6 x110 Ah) in Parallel. We have had these for 2 years now with excellent performance.
I note a small typo in your schematic Diagram. (Alternators labeled ‘250V’. I think you meant 250A…?)
Your decision to go with DC based system makes very good sense.
Forgive me for asking what you may have outlined already. Are you planning on going with a DC watermaker or AC?
Correct Evan and really appreciate getting your experiences with these Carbon Foam batteries. I am working on a full article on our decision to go with FireFly and will go into more details then.
Thanks for catching the typo on the alternators, I will correct the illustration soon.
I have not covered watermakers on the blog much yet so you didn’t miss anything. We had a DC watermaker, Spectra, on our previous boat and liked it a lot. However I want a much larger output on the XPM as we use water for ballast equalisation as the fuel gets used so will need to go with 220V AC for the new watermaker that has an output of about 50USG/200L per hour output. This was included in the calculations of the electrical system so we can power this no problem and AC motors tend to be MUCH more reliable and long lasting than DC in my experience. Going with an AC watermaker also lets us have one that is entirely made from “off the shelf” standard commercial items so much more cost effective to purchase and maintain.
For watermaker modular unit made from “off the shelf” widely available parts is a way to go. Much easier to maintain and fix, if and when problems arise. I have heard good things about Cruise RO and Seawater Pro systems, but there are others similarly designed systems.
One thing to note, definitely get an 230 VAC driven pump, and do get a VFD to drive this. This way you can control the motor so much better, and control the soft start and soft stop and torque limits and all that. It will make your pump and motor last so much longer, and a quality VFD from 1st tier brand like ABB or Siemens cost less than one set of watermaker filter, and 10x less than new pump + motor.
Same applies to anchor winch / windlass, 230 VAC VFD driven motor gives soft start and smoothest control of torque possible, and multispeed control for fast anchor dropping/recovery.
Hi Andy. Not doing as well as I would want to in keeping up with responses to all the great questions and comments here on the Mobius.World blog so I’ll need to beg your continued patience with my slow response times to some. Picking up on this latest one regarding the watermaker we are in heated agreement about the many advantages of going will all stock components regardless of which company we end up purchasing from. If I were not so short on time I would go full DIY and just buy the components and build one here in house but we will probably go through a watermaker company and have the advantage of their nicely done control panel. I KISS my watermakers making them all mechanical, no automation, etc. as I like to be in direct control and be able to dial them in to just right production as things like salinity and sea temp vary. And given the high volume we need, 200l/50USG per hour, the high pressure pump motors need to be 22V AC anyway and completely agree with your list of benefits of AC vs DC motors.
We are still making up our minds on AC vs DC for the windlass and even the bow thruster as I can make good arguments for both. So you’ll have to stay tuned to find out which way that goes.
Definitely go with 230 VAC bow thruster as well, and make it VFD-controlled with industrial components as well.
Those are designed for 24/7 operation, and you can find spares everywhere as they are used everywhere in all sorts of uses from conveyer belts to water pumps to air compressors. And prices are so reasonable nowadays that you can buy spares, though they rarely fail.
Then wire analog potentiometer joystick for proportional control. Could not be more simple.
And wiring savings alone 230 VAC vs 24 VDC will save you a long penny. I won’t even calculate, but 24 VDC cable needed will be a beast, whereas 230 VAC all you need for say 5 kW bow thruster is pretty normal extension cord thickness dirt cheap rubber cable.
ABB ACS150 or Siemens Sinamics v20 -series VFD’s I can highly recommend. Been using them at work for years, highly reliable, quality units.
Thank you for a very interesting post.
What is the usable range of the carbon foam batteries: 50% like lead acid or?
A bit more than that I think and as a big bonus they don’t need to be taken full every time, only once in a while/week/month.
But sometime they need to be taken full, and they are only highly efficient and accepting a lot of charge below this, below around 70-80% SOC, so there’s that. Not a problem while on passage, but solarcharging is not 100% straightforward…
I enjoy your blog. Thanks for sharing all this info. Couple of questions from a newbie here so forgive my ignorance.
1) Why no wind turbine? On face value it would make sense with a DC setup to complement your solar over night. Too noisy? Doesn’t fit the ‘comfort’ spec?
2) is it possible to get an ‘at anchor’ wave motion power generator? (Does such a thing even exist?) Ie drop a second mini anchor that pulls a line attached to a small turbine that then turns as the boat moves up/down?
Quite right Andy that the ability of Carbon Foam batteries to be able to be in any PSoC for almost any amount of time with no adverse effects on them is a very big bonus and one of their features which convinced me they are the best choice for us and the XPMs. As per some of my answers below, we aren’t concerned about high charge rates and I have sized the overall system such that the expected 15-21kW of daily solar output will easily be able to keep the house bank fully charged most days.
Hey Carl. I will get into all the details on the CF batteries in the next Tech Talk posting but one of the big features of these batteries is that they have almost the same usable capacity as Lithium. In both cases it isn’t recommended to go below about 20% DoD and they don’t start to lower the CAR until about 90% so that gives them an actual usable capacity of about 70%. These CF batteries can also be charged at much higher rates, 1C and so assuming you have that much charging capacity (we don’t) then you can charge them very quickly. In our case fast charging isn’t a priority as most of the time we are using solar to charge the batteries so there is no concern about having a motor running for long periods of time as would be the case with a genset. And when we are underway with up to 12kW output from the two alternators, we are usually going for many hours, often many days and weeks non stop so if anything we need to cut back the alternator outputs to next to nothing as the solar is working at the same time whenever the sun it out, which hopefully it often will be when we are underway as well.;)
I think that one of the great advantages of the Carbon Foam over typical AGM’s is that in gloomier environments when Solar may not keep up so well, and / or when one would prefer to not run a generator excessively..(.i.e. that extra hour going from 92% to 100% SOC), one is not obliged to bring them back up to 100% SOC to keep them healthy. Normal AGM’s will sulphate and be damaged by not being careful to regularly bring them back up to 100% SOC.
Quite right on these advantages of the Carbon Foam batteries and they were all substantial factors in our decision to go with this battery tech. We don’t have a generator so no concerns about the typical long run times required to bring most battery types up to 100% SoC although with the amount of solar output we have the house bank batteries will get to 100% most days I think. But as you noted, the ability for CF batteries to be at PSoC for long periods of time with no detrimental effect on the battery health means that even if we do find ourselves going with extended times in low solar locations, the health of our batteries will not be adversely affected and are also immune to killer sulphation.
I’m sure you e thought of this in infinite detail, but do you have sufficient air cooling to the two alternators? Do you have alternator temp sensing from the regulators? Normal engine room heat could shut them down if they don’t have specific cooling…..
Dealing with heat for the alternators was one of my top priorities and I’ll cover this in more detail in an upcoming Tech Talk about them. Short summary is that we reduce the heat generation dramatically by removing both the rectifiers, which are the source of a huge percentage of heat in alternators and the regulators, and mount these outside the engine room entirely. So the only thing producing heat in the alternator is the actual AC power generation of the spinning stator. Being mounted out in the relatively cool Workshop area, four external rectifiers, two per alternator, are not battling the heat of the ER and in addition each rectifier will have a thermostatically controlled fan mounted on top.
Combined together with some very cool new external smart regulators we think these alternators will have no problem putting out the full 6kW x 2 capacity as much as needed.
You mention above “… and shore power is rarely available as we live on anchor almost all the time, …” and I was wondering why you then want the complexity and cost of shore power at all. You always have your solar panels to charge the batteries – also in a marina and on a hard stand (except if the hard stand is covered). If you want shore power anyway, I would use a Victron Skylla Charger (100 A charging capacity, universal 90..265 VAC input) with the chargers output directly connected to the 24 V bus bar. Input and output of this charger are galvanically isolated, you could remove the isolation transformer. On this model, charge current can be regulated to limit shore power. You could then exchange the 3 (230 VAC) & 2 (120 VAC) Victron Multi/Quattro Inverter/Charger with Phoenix Inverters – they are significantly cheaper since they don’t have the battery charger function (which you now have replaced with the above Skylla charger). With this modification you would make your system even “more DC”.
If you exchanged your 14 individual 100/30 MPPT SmartSolar charge controllers for 7 individual 150/35 MPPT SmartSolar charge controllers you could connect 2 solar panels in series to each controller and have less hardware there as well (I am assuming the output voltage of a individual solar panel is in the 50..60 VDC range).
Skylla Battery Charger http://www.victronenergy.com/upload/documents/Datasheet-Skylla-Charger-24V-universal-input-and-GL-approval-EN.pdf
Phoenix Inverter 230 V/50 Hz http://www.victronenergy.com/upload/documents/Datasheet-Phoenix-Inverter-1200VA-5000VA-EN.pdf
Phoenix Inverter 120 V/60 Hz http://www.victronenergy.com/upload/documents/Datasheet-Phoenix-Inverter-3000VA-120V-EN.pdf
SmartSolar Charge Controller MPPT 150/35 http://www.victronenergy.com/upload/documents/Datasheet-SmartSolar-charge-controller-MPPT-150-35-EN.pdf
Thank you for your most interesting blog.
Thanks for the very thoughtful response and suggestions Markus, just what I was hoping these Tech Talks would produce and very much appreciated.
While we don’t use it often, we do want to have the option of using shore power, mostly when we are going to be leaving the boat for an extended time to get some Gramma Grampa time and get to visit friends and family who we can’t on the boat. In those situations we will still use solar as our primary source of keeping batteries topped up and also providing whatever limited amount of AC needed when we are not onboard. However we always want to have a backup, or two, to cover the ever possible/probable “accidents” or other unexpected events and so we would use the shore power to provide such a backup.
Like you, I have spent quite a bit of time considering the pros and cons of going with a combined inverter/charger MultiPlus setup vs using dedicated chargers and inverters. If I were to go this way I would chose pretty much all the same Victron components you so kindly included with all their links. I would however still keep the Isolation Transformer as I believe this is a critical bit of kit in my estimation. The galvanic isolation can be looked after by other units but it is the isolation of the grounding wire (green/yellow) that concerns me most and which I would not want to be plugged into any shore power without.
My current choice however is to go with combined inverter/chargers using the MultiPlus units. There are quite a few components which individual inverters and chargers have in common and so you end up with a lot of duplication with the individual units vs the Multi’s. Going with individual chargers and inverters is also quite a bit more expensive if you want to end up with the same amount of output, especially on the battery charger side.
The MPPT situation is interesting and I originally had a setup along the lines of what you suggested with 2 solar panels per MPPT but it actually works out cheaper and more efficient to go with a dedicated MPPT for each solar panel. Wiring also ended up being a bit less and very straightforward this way and the whole solar setup becomes a bit more efficient with less impact from shading. You’re quite right that this does have more hardware components, 14 vs 7 MPPTs but I have plenty of space to mount them on their own “wall” down in the Basement and have a nice neat and tidy layout setup for them.
You obviously have a lot of time and experience with these systems so please do push back if you feel that there is a better setup for our use case. We have not yet put in the Victron order but will do soon so I’ve still got time to make a few changes if needed.
Thanks again for the well thought out suggestions!
I guess that designing the electrical system must have been more of a philosophical exercise for you than anything else – there are so many choices and most are neither wrong nor entirely right. But after all, the electrical seems to be a very fundamental system, that’s maybe why you cover it first in your series of tech talks.
I am not criticizing your system layout, I understand now that you want:
a) AC shore power
b) to use combined inverter/chargers instead of dedicated chargers and dedicated inverters
c) to use an isolation transformer for any external AC power source
One issue comes to mind with multiple inverter/chargers in parallel and that is with limiting shore power.
The “power assist” function of the Multis have a minimum shore power amperage below which the function is not working. The minimum amperage is per unit (per Multi). Having 3 Multis in parallel might result in a too high minimum amperage and the shore power supply might still be overloaded at the minimum setting.
There used to be a spreadsheet on Victron’s website which answered these question for all the different models but it has now been transferred to their professional website, to which I have no access. See article on http://www.victronenergy.com/blog/2018/04/20/multiplus-quattro-inverter-chargers-improved-current-limits/
Best regards, Markus
Well you said you were going DC based system.
Now if you went for a seperate charger and inverter, as Marcus suggests then you are. The AC and DC consumers are fed from the battery – the battery is charged from solar, engine or shore. Same if plugged in a marina or out at sea – the AC devices always take power from the batteries. It’s all quite easy to understand day to day.
But if you use Victron Multis, that changes to a hybrid system. At sea the AC power comes from the batteries via inverter function. On shore power, the AC devices take power from the shore. Excess shore power is used to charge the batteries. And if the shower power is not enough, then the Multis flip the other way and boost the shore power. Its all quite complex, sometimes the Multis take the shorepower offline temporarily preferring to deal with an AC surge themselves, sometimes they trip out if they dont like “ripple current” coming from a low battery, occasionally they get overloaded. They need managing. They certainly need “dialling in” to a new shore power. Start low and wind up the load on the shore until you see the shore voltage drop. They have the power to overload many marinas and the voltage drops away. 220V becomes 180v very quickly in some.
So in your system, the only time the battery charger is used is when you are on shore power. Would you ever need it charging at 360 amps in this situation as you will probably be there at least overnight. 50/100 amps would probably be enough unless you think that you will behave differently and become a power guzzler when plugged in – like having aircon on full all day long???
The Victron inverter/chargers are very good and smart – but at times I think they are too clever and they need watching. I find myself checking the voltage/current gauges and double thinking whats going on. I know what they do on my boat and what to expect- but I have never tried to explain them to my wife or yachting friends who sail with me! I would say the electrics would be the thing that would stop me lending my boat to a friend!
I get overloads, too much “ripple current” and other reasons to reset the inverters from time to time. For me that involves a trip into the engine room to flip off/on the blue boxes maybe once every two or three days.
My setup is explained somewhere else on here. I am slightly more AC based than you (having an AC genset which I want to flick on and have charge batteries fast ) but in your situation, when I read Marcus’s comments I thought they were very sensible and thought that seperate inverters and smaller charger might be simpler and work better
These inverters will have the ability to flatten your battery in 2 hours if the AC power demand is there. In my case, I decided to fit a high and low power AC power rail putting the big consumers on the high rail that only came live when the shore or generator was powered up (bit of electrical relay trickery in a box). I am not sure how you would handle this. I think you might need some way to control whether big consumers were allowed on. Big as in air conditioning, cooking hobs, watermaker.
The type of scenario is you are plugged into shore, leave aircon running when you go out, get back to find shore power tripped out, inverters have run your battery totally flat.
There is one surprising thing with Victron Multis (in my 10 year old set up anyway) – you can switch them to inverter/charger, you can switch them to charger only or you can switch them off. But when you switch them to charger only or off, you don’t get shore power going through to the AC consumers in the boat – you get dead sockets in your boat.
When I lay up my boat, I cant risk leaving the inverter on as it would flatten battery if the shore power went off. So if I want a dehumidifier on or an alarm or light, it has to be wired off the isolating transformer (before the Multis) as the sockets in the boat will be dead.
Hi Markus, thanks for this and your other most thoughtful and considered responses. Much appreciated.
We are still undecided about whether going with combined inverter/chargers or with stand alone chargers and inverters is going to be the best fit for us. As with many other systems and as you and others have noted here, there are good arguments, pros and cons for each setup. Given our extremely rare use of shore power the charger side of this equation is a smaller factor in our decision than for most others so we will almost always be providing all our AC from the batteries via the 120V and 220V inverters. Even when we are plugged into shore power we will usually just use the shower power AC as a backup to our solar charging system and leave everything running the same as when we are at anchor with no AC input.
To your point (b) above regarding combined vs individual chargers and inverters I am still undecided. As a result of having such low needs for shore powered battery chargers I am still considering going with dedicated inverters and a smaller number of dedicated battery chargers than if we were to have the five chargers within the MultiPlus combos. You and others here have pointed out additional aspects of these two setups and this whole discussion is just as I hoped would happen and be the high value of producing these blog posts and articles so thanks to you all and please keep your thoughts, critiques and questions coming.
Thanks too for reminding me to look more closely at the minimum shore power amperage scenarios with multiple MultiPlus units in parallel and I will be checking that and your link.
I see the beauty of having one panel per controller, and potential efficiency gain in difficult shading situation. However, two panels next to each other should not get that different shading, right?
Also wouldn’t using 7 vs 14 MPPT controllers roughly halve the wiring needed – 7 positive and 7 negative leads to panels vs. 14 each – not counting the very short inter-panel leads? Also by connecting two panels in series vs. one and doubling the panel voltage ohmic losses not only halve, but drop by 75%, and idle/”zero power” losses in also controllers halve, and their internal DC-DC converters run on better efficiency due to higher conversion ratio? I find it hard to believe you end up getting _more_ efficiency with more controllers, plus they surely cost more for more boxes, or are the smaller boxes so much more affordably priced?
Lets consider 360W panel, with assumed 36V Vmp (mp = maximum powerpoint) and thus 10A Imp. Lets estimate 15M cable for each string, so 30M total per string. 2.5mm2 cable, resistance is 7.5 ohm/km, so for 30M loop 0.225 ohm.
14 panels parallel. 14 * 30M, 420 meter cable needed. Ohmic loss 0.225 ohm * 10A * 14 strings = 31.5W, over 8 hrs charging = 0.25 kWh lost per day heating cables
7 strings of 2 panels parallel. 7 * 30M, 210 meter cable needed. Ohmic loss 0.225 ohm * 10A * 7 strings = 15.8W, over 8 hrs charging = 0.125 kWh lost per day
Plus losses from the controllers. One Bluesolar 100/30 uses 12Wh per day each for idling loss, so 14 pcs is 0.16 kWh.
Maybe the losses are not really that significant, but amount of cable needed is I think. Depends on routing and maybe my rough estimate of 15 meters per panel is way off, but still there is not better cable than no cable.
I think splitting the inverters and chargers separately is sensible thing to consider, and keeps the system layout elegant. Then there is three clearly separate systems, which can be sized and optimised individually:
– DC-system with batteries and dc-distribution, including solar charging subsystem. Always powered on
– Shore charging AC-system, feeding only ever the charger charging the batteries. Only energised when needed, ie. tied to shore power
– Inverter driven AC system, can be optimised and split to few according to various different load levels and different voltages/frequencies needed. Only energised when needed, and only the number of inverters needed
Simple, elegant, intuitive, efficient. Might even save some money, as a bonus.
Hi Wayne, I see you have one 24-12v converter. Is there a back-up? We run two on Play d’eau with a further 12v battery in case both fail.
I guess with battery made out of 4V cells, you always have a backup by hooking power leads from the middle of the pack?
1) What is the claimed efficiency for Electrodyne alternators?
If they are “traditional” type with “traditional” voltage regulation, they are most likely in the 50-60% range. This drop-in replacement 450A brushless alternator claims 80%, which is pretty significant difference:
Not only efficiency of producing electrons, but also way less cooling needed and thus improved lifetime or equipment.
Permanent magnet alternators, as found in wind turbines and such, can get to very high 90’s efficiency, but they need more complicated controller. Though not any more complicated than MPPT for solar. In fact, Victron solar controllers have been used successfully with such alternators, though this is not officially supported.
2) What drives the need for every panel having own MPPT-controller?
Of course shading etc can be handled individually for each panel, but then again say having two nearby panel per controller in series, or three? This would reduce part count, cost, amount of wiring, losses in the wiring and also improve MPPT efficiency, as MPPT controllers and their internal voltage converters tend to operate more efficient with higher panel voltage and thus higher panel/battery voltage ratio. You would still have a plenty of redundancy, if you had 3-7 MPPT controllers.
Of course having each panel controlled individually means nice accurate realtime tracking of what each panel produces, that is a nice bonus!
I have a similar DC based setup on my sailing yacht – 71ft ketch – except that i have a 9kw genset instead of solar panels. Only run it about 1 hr a day max. I have 3x 3000w Victron inverter/chargers so can charge quite fast. And I have all electric cooking etc. which will run on inverters but I tend to use cooking or water-making times for the genset run. Bit extra alternator on main engine.
Anyway couple of things I have experienced are
1. The inverters have a surprising consumption in the dormant mode – about 1 amp each. So 5 inverters on standby 24 hours a day will use 125Ah – or about 10% of your battery capacity in 24 hours for nothing much! I find this a bit frustrating. I guess this will be more than offset by your steady solar trickle which I dont have.
2. I have 1000 kw hrs of Lifeline AGM gel cells at 24v. They are good but I am on the third set now – seem to have a 5 year life with my set up. Anyway in practice 3 of my inverters will push 160/170 amps into these batteries and this will warm the batteries especially in later years. So if you are going with bigger inverters, make sure your batteries will take a long run of 360 amps in practice without cooking especially if they are all packed tight together with little ventilation.
3. I don’t think my charger/inverters are very good at the equalisation thing – not much you can do with them as far as I can see. But maybe Victron have improved this over the last 10 years.
125Ah at 24 VDC? That is 3 kWh per day? That is almost Tesla -class vampire drain…
That is far from efficient, better shut down those inverters or at least most of them when not in use…
It seems Victron inverters (both Phoenix and Multiplus) consume somewhat linear percentage of their nominal rating as vampire drain. 5000W consumes 30W, 3000W 20W but 2000W “only” 11W and 1600W 10W.
So it would most likely make sense to have a small 24/7 inverter for those 24/7 loads that are likely to be rather small, and only switch on the “big iron” when needed.
I should have said 1000 amp hrs of Lifeline AGM gel cells at 24v (not 1000kw hrs!!!!).
8 batteries at 70kg each. Changing them is tough on the back.
Maybe change them to something lighter next time 🙂
– 1000Ah 24V Lifeline AGM is 8 x 70kg, 560 kg total.
– 1000Ah 24V Battleborn brand Lifepo is 20 x 14 kg, 280 kg total. Though with deeper SOC capability, you could get same amount of usable amp/watt-hours from 500Ah, so 10 x 14 kg, 140 kg total.
– Lets not go there, but a “known brand” EV lion module is 25 kg and 220Ah 24V. 5pcs is 1100Ah and 125 kg total, or 50/75 kg for similar usable amp/watt-hours, so literally 1/10 weight. These will still burn when your boat is already sunk and at the bottom of the ocean, though, so there’s that. Lifepo above won’t have this “slight” issue.
And Battleborns have a 10 year warranty, so you wouldn’t need to change them every five years if not for defects. And you should be able to drop in replace your current batteries with them.
All this is definitely in the category of, IMO! The area most likely to evolve in the near future is the means to store the energy. Tesla’s new “mysterious” battery patent is one area to watch.
EV-batteries are a slightly different use case though. Weight is ultra critical, have to have very good power density whereas boats care more for energy density, and have to charge crazy fast and take fast, deep cycles.
But for sure (all) progress on battery front will eventually benefit boaties as well 🙂
I’ve noticed where several large yacht proposals use hydrogen with fuel cells. That is NOT a viable option here as there is essentially no production and distribution network at present. Could be we’ll see some sort of hydrogen availability at favorite ports of call for big yachts, maybe starting with the Med and Car?
Interestingly there’s some big bucks being gambled on a distribution network within the US for hydrogen – fuel cell over the highway trucks. Something like 600 current truck stops proposed for conversion to having an additional 15 minute hydrogen refill capability for a truck.
Back to reality. Watch the battery technology.
Not really 100% relevant here, but there is a house in Sweden built by inventor Hans-Olof Nilsson, that is driven by solar energy with hydrogen energy storage instead of batteries for the winter months. Pretty fascinating:
Fun to watch things like fuel cells, hydrogen and battery tech in general evolve all right John. And I’ll throw in small nuclear to the mix as well! But as you note, back to reality and we’re busy getting our Carbon Foam battery based system all setup and installed.
I have 3x 3000w Victron Multis inverter/chargers on a 24v / 1000 amp hr bank of Lifeline AGM gel batteries. Its OK – but almost too powerful for the batteries. The specs say it should be fine, but in practice it is charging too fast (heating up batteries that weight >500kg) and looking for greater DC stability when dealing with big AC startup loads.
I am sure the carbon foam batteries are better but will they take the even bigger loads that you propose? The specs will say yes – but in practice?????
My gut feeling is to go fewer/smaller inverters and/or bigger batteries.
Hi Nigel. I hope to post a Tech Talk articles on our whole battery setup on Möbius and it will get into this in great depth but re your points here, the CF batteries are real tanks and can take just about anything you can throw at them. They are able to be charged and discharged at 1C with no adverse effects and so in our case that would be 1350A so way more than we would ever need to take out or be anywhere close to be able to put in. So yes, our house bank will be able to take much higher loads than we expect to use in charge/discharge rates. When you look at the numbers I think you’ll see that we have in fact done just as you proposed in terms of the ratio between inverter/charger size and battery bank size. Once I get the TT on Batteries up, hopefully this weekend, see what you think and comment on that please.
How can I post a picture here in the discussion?
Since your are still in the design phase of the electrical system, I would like to send additional thoughts on a slightly different electrical layout for XPM78 Möbius.
Maybe you can upload to imgbb or similar and post a link here?
Andy’s suggestion (thanks) seemed to work well and got your diagram with thanks Markus. Christine has been back in the US for the past 3 weeks and she looks after all the blog issues so I’ve asked her to look into posting pictures and uploading other files in this comment section and will see if we can improve. Glad there is this link based method that can be used in the interim.
Below are my thoughts for a boat with no AC generator and rare use of shore power. The layout pays attention to simplicity, cost and some component failures.
https://i.ibb.co/DWMsShL/XPM78-ELEC.jpg links to a single line electrical diagram (no negative wires).
Switches, fuses, control panels, monitoring equipment, 24-12 VDC converters, sub busses, etc. are not shown.
– The horizontal line is the 24 VDC bus with 2 batteries (B) connected to it on the very left and 1 battery on the very right.
– The 24 VDC bus is split into 2 using an automatic charging relay (ACR) with remote control and manual override.
– Items shown above the 24 VDC bus are electricity producers and items shown below the 24 VDC bus are electrical consumers.
– GREEN is the normal 24 VDC, ORANGE is the alternate 24 VDC.
– BLUE is AC power (single phase).
Now for some individual components:
– You have chosen your batteries already and I have included them on the diagram. However…
My choice would be a large 12 x 2 V GEL battery on the GREEN side and a smaller battery on the ORANGE side.
those are available from 280 Ah to 2’700 Ah – so no shortage of battery power when you can handle the weight.
Why GEL? High capacity without paralleling, maintenance-free and sealed, 12-15 years useful life, they deal well with tropical temperatures
no need to recharge them immediately after use (resistance to sulfating) and their charge acceptance is quite high (0.15..0.5C).
They are however very sensitive to overvoltage.
– RED is an ultra-capacitor (C) replacing a starter battery to drive the starter motor (S).
– Universal input 100 A battery charger with adjustable shore power limitation. The neutral (green/yellow) wire from shore terminates at the charger.
Unstable shore power does not propagate into any of the AC (or DC) buses.
– I would not use 120 VAC/60 Hz circuits at all, and therefore only install 230 VAC/50 Hz inverters.
Most devices that plug in (like chargers for guests laptops, etc.) can handle 100-240 VAC 50/60 Hz.
– I could not resist and included a DC generator with keel-cooling and the same type alternator (A) used on the main engine. But I know your answer to this one already…
Best regards, Markus
Apologies to you and others for my slow response rate of late, been running flat out here with the build and just not enough hours in the day for all I would like to fit in but I can assure you I DO read them all and I DO ponder and think about them all. Typing up my responses is the challenge and I thank you for your very well thought out comments as I know this all took a lot of your precious time. Much appreciated and thanks for your continued patience.
I’ll do my best to make some quick comments to yours:
I’m also behind in getting more Tech Talk articles posted but the next one, which I hope to post this weekend will cover the whole House Battery Bank setup in much more detail and you can see what you think then.
We had originally thought similar to you and originally designed the boat for three banks of six each of 2V OPzV Gel batteries. They are as you mentioned super robust and used in many industrial applications so very well proven. However I’ve decided that the Microcell Carbon Foam batteries are the best fit for us; not affected by PSoC for indefinite periods of time, 60-70% usable capacity, able to be charged and discharged at 1C, no sulfation and perhaps the highest factor for me, extremely high fault tolerance for most any scenario that would likely kill any other battery type. Many won’t agree but I now have enough people using these for enough years to feel that they are now ready for “prime time” use in the real world and they are the best fit for us and the XPM use cases.
Re having 120V/60 aboard, we have enough “legacy” equipment ourselves plus enough that our guests have to make having inverters onboard to provide a 120V system throughout the boat. There won’t be as many of these outlets but there will be some in each cabin and in my workshop. We just feel that the convenience is worth the cost.
A DC generator could certainly be added at a later date and may well be an option that other XPM owners will want to go with. For Möbius we will try our current setup with the CF batteries, solar panels and dual high output alternators on the main engine for the first year or more and see how this works.
As I like to stress this is just the combination and choices that Christine and I think fit us and our use case best and other boats and owners will certainly make different choices, exactly as they should.
Again, thanks for all the thought you put into this Markus and please don’t hesitate to push back with your perspectives on this and other systems as we get into them on the blog.
This might be challenging to arrange though. Quote from FF battery manual:
“If deep cycling, ideally once or twice per week, the batteries
should be charged at a current of 0.4C or more”
0.4C is 540A or 13 kW.
“For applications lacking fast charging capability, contact OPE or Firefly USA for alternative restoration procedures.”
Would be interesting to hear the alternative.
Very nice and well though out system and nice diagram!
– Having just single AC voltage and frequency is a way to go. If something does not work with 230VAC/50Hz, it is much easier to replace than running multiple AC-busses. Almost everything is universal voltage nowadays anyway.
– I really like charger only and charger terminated AC shore power thinking, and I absolutely think it is the only reasonable way to go with an aluminium hull boat, to lesser degree with steel only. This will eliminate so many things and failure modes that could possibly go wrong with stray currents, safety and also power quality onboard.
– what is your reasoning behind splitting bus to main DC-bus and alternate, and division between them? It makes mostly sense to me, but wouldn’t you want to have engine starting connected to alternate bus and windlass to main bus? Maybe have bus select option DPDT-switch for those?
– would the automatic charging relay work reliably with relatively low charging current from PV-panels? There might be some problems there, and not the least with inter-battery balancing currents, which if left unrestricted might raise to huge levels.
– would you really need the super capacitors for engine start, in addition to having two separate battery systems – there should be more than enough punch from batteries for starting? I would myself have a totally separate dedicated starting battery connected to absolutely nothing else and trickle charged via AC-connected trickle charger, and then have a spare air starter as a backup. Heck, maybe just have an air starter as main starter for cool starting sound, and always keep two scuba bottles topped of so starting would never fail or run out of air.
– In a boat with substantial AC-capacity and triple redundant inverters, I would go with VFD-AC-driven windlass and bow thruster and water maker and scuba compressor and AC and fridge and heat pump heating and everything else with big loads, simply to keep wiring light and because of soft start capacity of VFD. Makes starting loads to systems so much less and thus improves reliability and life time of motors and especially seals, and gives much better totally smooth proportional control of torque and speed.
I will surely think of more, but lets start with these. This is a fascinating subject to discuss, and there is not only one right way of doing things, except maybe for shore power charging mentioned above 🙂
Please find below further thoughts regarding the electrical system. I don’t claim superiority over other layouts and would like to add that my layout would be different for a twin-engine boat/multi-hull and totally different when an AC generator is integrated (there I would use Victron’s QUATTRO).
Electrical equipment failure seems to be related to stress on an individual component. Naturally, you want to avoid equipment failure and therefore avoid stress. With stress I mean running the equipment at close to maximum rated power but also abrupt voltage/current changes (shocks/spikes). I identify the engine starter, anchor windlass and the AC inverter as “stressors”. Bow thruster, water maker, scuba compressor, etc. could be added to that list.
– The capacitor completely eliminates the engine starter as a stressor. Several engine starts are available from such a capacitor’s single charge. They fully recharge using probably 20 A in a short time even if the supply voltage is way below the normal 24 VDC. Capacitors don’t age and can be installed directly in the hot engine room next to the starter – batteries don’t like that environment. As a back-up and with some effort it should be possible to start Wayne’s engine by hand.
– The AC inverter is always powered by DC; the other mentioned stressors can be powered by AC or DC. If they are powered by AC, you might want a backup AC supply. The triple inverters are not really redundant – after one inverter fails, AC power is initially unusable until the remaining inverters are reconfigured by software. Therefore, I would power the essential anchor windlass from DC but isolate it from the main DC system using the 3rd battery, which has enough capacity (450 AH) to support the high amperage of a powerful windlass.
– The Automatic Charging Relay (ACR) can be left in AUTO mode to make the 3rd battery useful and part of the big battery bank. The ACR AUTO mode considers the voltages from both sides of the split bus before it closes the relay and opens the relay again under certain voltage conditions.
Sure, I am not a fan of paralleling batteries and their associated problems with charging/equalization currents, etc. but the splitting of the 24 VDC bus in a normal and alternate part by the ACR seems to be an acceptable compromise. Remember, you always have full control over the split system since the ACR can be remotely/manually opened/closed if desired. Now that I think about it, there are quite sophisticated possibilities to control that ACR in various situations (using a PLC for example). The split 24VDC bus prevents that a short/overload tears down the entire electrical system.
– Issue with solar charging priorities (solar-over-alternators or solar-over-shore) with good results and simple to implement: by adjusting/programming the alternator/shore power output to 0.2 volts lower than the solar output.
– Please note that this alternate layout does not require to operate any switches in normal operations.
– I know DC generators are difficult to source and a hassle to maintain but there is an interesting argument for such a generator in addition to a large solar array especially for the high latitude cruiser. But I save that for another time.
I agree that this is fascinating to discuss, but let’s not get lost in the details (like where to place switches and fuses, etc.).
The overall layout must be robust and survive the inevitable failure. It is indeed complicated; too much of anything (equipment, complexity, electronics, etc.) is in itself a risk even if cost did not matter (they very much do for mere mortals).
Don’t buy yourself a problem, best regards.
Quick note on starter motor stress for battery, most likely starter motor current is 100A-200A or something like that. For 1350Ah bank, this is less than 0.2C, so basically nonexistent stress. For separate dedicated 110 Ah battery this is a bit more, but even 2C is almost nothing for the battery, might even be mildly beneficial removing sulfates.