I’ve been a big fan of Victron electrical components and the company for a long time since discovering them when I first bought our previous boat sv Learnativity in Sidney British Columbia back in 2005. She was and still is a 1994 all steel 52’ Bruce Roberts designed cutter with a raised pilot house and was wonderfully overbuilt by a local builder in Sidney. After searching the world for my Goldilocks sailboat at that time, and my first boat ever, it made me smile to eventually find her a few miles the closest thing I ever had to a “home base” when I was growing up which was Victoria BC on Vancouver Island. I am an “Army brat” having been born into a military family in the sense that my Dad was a chef in the Canadian Army Service Corps and so we moved about every 2 years to a new base somewhere in Canada or Europe and I never grew up with an understanding of home being a building. Instead, home for me was wherever my family was and that’s remains my model to this day. A big reason why living full time aboard a boat has worked out so surprisingly well for me I guess.
I spent the next two years doing a major refit to make her fully outfitted and up to the task of being sailed single handed around the world as that’s where I was headed. Part of this refit was a major upgrade to all the 1994 based electrical and electronic systems and that’s how I got to know Victron equipment. Learnativity was a word I had invented many years earlier and seemed like the just right name for this crazy adventure I was bound and determined to pursue. Amongst the endless list of things I learned over these past 13 years is how much of your safety and comfort at sea, and at anchor, depends upon electricity and so I gained a whole new appreciation for the value and significance of having a rock solid electrical system on any boat I was going to captain Möbius offers me an amazing new and rare opportunity to design and build the best possible electrical system based in large part on my past experience as well as what I am able to learn from others. There is a plethora of choices of manufacturers and we have the wonderful problem of too many good choices, but going with what I know to work well, and seeing them do things such as this support and adoption of Signal K, is why I’ve decided to go with Victron equipment on Möbius for things such as chargers, inverters, isolation and DC to DC transformers, solar MPPT controllers and battery monitoring systems.
** Just to be clear, and as with all decisions we make for designing, building and outfitting Möbius, what is “just right” is also “just for us” and not meant to imply that our choices should be what you or others do. I have no affiliation with Victron or any other manufacturers so my interest here with these postings and this blog is simply to share our experiences and thinking as so many others have done on their blogs and books and sites which have played a huge part in our learning and decision making.
OK, dismounting from this horse named Tangent, let me get back to the point of this article and my reference to Victron. Because I had such great experience with the Victron chargers, inverters, isolation transformer and battery monitors on Learnativity Christine and I have specified all Victron equipment for our new boat Möbius. I will write much more in future posts about our thinking and planning for the overall electrical system on Möbius in future posts, but I wanted to put this short one up after just reading this new posting on the Victron blog about Victron’s recent decision to join and support an open source initiative I’ve also been following for the past few years called “Signal K”.
I will let the article’s author John Rushworth tell you all about Victron’s decision in his article I linked to above but to put this in context for myself and other boat builders, owners and enthusiasts out on the water in any form of boat, as John writes, Signal K is about the development of a free, modern, Open Source, universal marine data exchange format. A more comprehensive description is the one on the Signal K website:
“Signal K is the next generation solution for marine data exchange. It not only allows for communication between instruments and sensors on board a single vessel, but also allows sharing of data between multiple boats, aids to navigation, bridges, marinas and other land-based resources. It is designed to be easily used by Web and Mobile applications and to connect modern boats to the Internet of Things”.
Whether you are a boater or not I think we have all known the frustration of not being able to share data of many forms with others because the data is saved or transmitted in a format that is not compatible with the ones we are using. If we use the analogy of electricity this would be the ongoing frustrations and limitations any traveller knows when your physical plugs don’t match up be they AC plugs in the wall and at the ends of the cords on our electrical devices, or data connections such as USB, DVI, HDMI, serial, RJ45 and the list goes on almost to infinity it seems. And the data itself can be incompatible with other data as well which might be analogous to 120 vs 240 AC voltages, or 50 vs 60 Hz power. Standards are the answer to most of these issues but having worked within the international standards worlds of IEEE and ISO for almost 20 years in a previous life, we used to have the not so amusingly say that “The great thing about standards is that we have so many of them!”. Still an all too real problem today and one which I’m personally dealing with on my personal devices such as my Nexus phone and Lenovo laptop which both use the newest iteration of USB C for all their data and some power connections. USB-C is great, small, reversible, fast, covers data, sound, video and power. BUT of course it doesn’t help when my other devices and cords use previous versions of USB A, B, mini, etc. As I said, we ALL know this all too well.
In the marine world these challenges have been and continue to be with both the physical connections and the data formats and transmission standards. The advent of NMEA 0183 was a huge leap forward from a mostly all proprietary past and this was then updated to NMEA 2000 or N2K as it is often abbreviated. I went through this transition on Learnativity and learned a great deal not the least of which was a great desire for the next leap forward to whatever the next standard would be. As you may know and will read in John’s article, while NMEA 2000 has been and remains a huge help with interconnectivity of the many devices on our boats, it has some significant limitations not only technically but with the standard itself being quite closed and limited to development and improvements mostly by the manufacturing community. Kudos to this community for the truly immense and difficult work they have done and their solutions have really revolutionised setting up and maintaining and using electrical devices and signals on our boats. However if there were to be a truly “open standard” which anyone could support then as history has clearly demonstrated I think, such a standard would progress much faster and benefit far more people, companies and organisations. And THAT is what Signal K, amongst several others, is all about.
The biggest challenge I would opine, lies within the “amongst several others” part of that last sentence. For standards themselves are NOT the true solution, the ADOPTION of standards is when things really improve. Going back to the electrical standards while it is very helpful that within one country or region there is usually a common standard for the AC plugs and receptacles, but as soon as you travel outside these areas you quickly experience the “many standards to chose from” problem and you end up carrying a whole bag full of just power adaptors to go along with your bag full of USB adaptors and converters. What would be REALLY revolutionary and powerful is to have ONE standard become the defacto standard for all these and that is what Signal K and more so this Victron support outlined in this article above is all about.
You don’t need to know the intricacies of the Signal K standard itself, I certainly don’t, to appreciate the potential of having this, or any other standard for that matter, become a defacto standard. A standard that would be adopted by all manufacturers and available to all of us to use and benefit from. Hence my excitement and support for Victron in joining forces with Signal K by choosing to adopt it and support it within their product development going forward.
I certainly have no idea if Signal K is up to this daunting challenge, nor that it will be widely let alone universally adopted by manufacturers. As you’ll read in the article it is very much undecided if the manufacturing community will adopt Signal K and the Signal K standard itself is still very much in the early stages of development but all great journeys are born out of such small steps. I can however appreciate the promise and do my best to promote and encourage things like Victron’s adoption and support for Signal K and hence this posting so you too can be aware and consider ways you might assist with realising this form of electrical and data nirvana.
Have you already decided on which batteries you are going with, as this will greatly affect the choices on said Victron equipment? They also make batteries I know, but seem to be quite on the expensive side, though good.
There is a good blog and youtube channel on one narrowboat fellow using all Victron including their lithium batteries: https://twitter.com/journeyjono/status/988122005063991296
Really what I am interested to hear, are you going with lithium or legacy batteries? I personally would not ever go to lead acid again, and it is not just me:
https://www.gonewiththewynns.com/product/lithium-batteries “Want to know what our #1 recommended upgrade is? Lithium Batteries.”
https://svdelos.com/brands-we-love/ “Delos is now 100% powered by Lithium Batteries”
Also this site is a treasure trove of information on subject: http://electrodacus.com/
And Victron also: https://www.victronenergy.com/blog/2015/03/30/batteries-lithium-ion-vs-agm/
Hi Andy, great to have you aboard for this journey.
The DC system is extremely critical on Möbius as she will be a battery based boat for all her electrical power both AC and DC. We are rarely in marinas or otherwise connected to shore power and we will have no generator so our house batteries are where all the power comes from for everything on the boat. This has been a fundamental part of our use case definitions as I outlined in an early “Mission Impossible” post and it is almost literally true that we designed the boat around the batteries as they are housed in a dedicated compartment that is built into the hull and their weight is being used in lieu of any other form of lead ballast.
The immediate answer to your question is that we will be using lead acid batteries as these suit our use case the best. No question our use case is different than many, but after great deliberation and running lots of numbers and spreadsheets, for our situation, lead acid is the clear winner and the best overall value by far. You seem to be very interested in batteries and let me repay some of your kind sharing of links by suggesting one for you if you have not seen it already over on the Attainable Adventure Cruising site. https://www.morganscloud.com/2018/05/05/battery-options-part-1-lithium/ John and many others on the site are very experienced cruisers and their articles are very well researched and thought out based on all their experiences so they are an excellent source for very real world exploration of most aspects of cruising and I think you might find the same if you have not already visited.
I mention John’s recent series on Battery Options as it generated very large and valuable comment streams from other cruisers with their countless years of experience with a wide range of different batteries on different boats and use cases, and many of them match up well with my battery experiences on boats.
I have not ordered our batteries yet as we delay all purchases as long as possible to take advantage of the typical combination of many system parts rising capabilities and declining costs, but I do know pretty much all the details of the batteries we will be using other than the brand so I’m happy to share the details.
Our house battery bank will consist of twelve OPvZ type batteries which are 2Volt lead acid Gel cells. The OPvZ term is a standard nomenclature for these kinds of batteries which are used for applications such as fork lifts and rail and are often referred to as “traction” batteries. Being an industrial and international standard means that it would be much easier to find replacement batteries if/when needed in most parts of the world and the sizes are all the same so we have been able to design around these batteries from the beginning. OPvZ and other batteries of this type are produced by many different manufacturers including Victron so we have lots of choices and range of prices for these.
Each 2 volt cell has a C20 rating of 1700Ah and C100 rating of 1955Ah and combining 12 of them in series creates a total capacity of 52 kWh. There is no question these fit well with the eXtreme nature of many aspects of Möbius as each cell has a L x W x H measurement of 277 x 215 x 855mm and weigh 110Kg/245 lbs which adds up to 1320Kg/2910 lbs so you can see why it is not too much of a stretch to say that we designed the boat around the batteries! These are located pretty close to the center of the boat in a dedicated sealed “void” within the integrated tankage that makes up almost all of the aluminium hull below the WL. They sit very low, with their bottoms just above the top edge of our massive 25mm thick keel bar that is about 300mm high down the center and help out in keeping our metacenter
The other factor which makes lead acid the best choice for us is that we have an equally eXtreme amount of solar generated by the 14 solar panels up top. As with the batteries we have not ordered the panels yet and the output may go up by the time we do but at this point in time each panel is rated at 360 Watts so we’ll have a total rated output of about 5kWp. With this much solar our DoD (Depth of Discharge) will be very small most days and so unlike most situations these batteries will be topped up almost all the time when at anchor. Underway we have about 9kW of output from two 24v alternators on the main engine which will also keep the batteries fully charged and allow us to run all the systems on the boat when underway as well. This type of use case puts the cycle lifetime of the batteries up at the very top of their range and I would expect to get 15-20 years from these batteries.
Hope this answers your questions and be glad to field more if you have them. I will be writing up a whole post on these batteries and other posts on our design of the whole electrical system on Möbius so stay tuned for those as well and thanks for your contribution here, much appreciated.
Friends don’t let friends invest in legacy technologies 🙂
I understand choice of batteries is somewhat personal opinion and all that, but this is something you should consider once more, as you are building from the scratch and have no history ballast to drag. Especially so when you have selected to go with Victron, that supports Lithium batteries officially – their own batteries or others with integrated/external BMS.
In the links I posted earlier, there is good comments like this from Gone with the Wynns: “Want to know what our #1 recommended upgrade is? Lithium Batteries.”, but best thought trough is the one from Dacian Todea, who has lived off grid for many years now (and in Canada of all places) and depends on his batteries and solar for almost all his electricity needs:
Lithium and in particular LiFePO4 is a better long term investment than Lead Acid batteries.
–LiFePO4 has 2000 to 8000 cycles (70% to 100% DOD) vs Lead Acid 250 to 1200 cycles (20% to 50% DOD).
(This means you can get LiFePO4 with half the Lead Acid capacity since LiFePO4 can be discharged deeper and does not have to be fully charged as Lead Acid).
–LiFePO4 has a charge / discharge efficiency of 95 to 98% vs Lead Acid just 50 to 75%.
–LiFePO4 will cost about the same as Lead Acid with 2x capacity.
(A half capacity LiFePO4 will perform the same or better do to ability to discharge deeper and stay discharged with no effect on life cycle and do to better charge / discharge efficiency)
–LiFePO4 protected with Solar BMS can last 20 to 30 years where a typical Lead Acid will only last 4 to 6 years.
–LiFePO4 can be 5 to 10x better value than Lead Acid over the life of the battery
–The cost benefit are not the only benefits.
– LiFePO4 can be installed indoors with no need for external venting since it does not produce flammable Hydrogen gas as Lead Acid.
– LiFePO4 even at the same capacity as Lead Acid is much smaller and lighter (in some applications this can be important).
– LiFePO4 is maintenance free (AGM also claims that but in solar applications you probably need an expensive (1 Liter/kWh) gasoline or diesel generator to recharge the battery if there are more than two consecutive cloudy days else the battery life will be drastically affected)
Building the same kind of battery capacity you are planning with lifepo’s, you would take say 2 x 400Ah (because deeper DOD) in parallel and 8 in series. 16 cells would weight bit over 200kg and cost 7-8 k usd. Or with same money/weight, you could have much more capacity. Building from smaller (and light) cells, you could carry a spare or two in extremely unlikely event of cell failure.
With lifepo there is no fire risk, they can literally be punctured with a nail without setting fire.
Main benefit is in my opinion ability to accept charge fast in most any DOD, so generator if needed can be run highly loaded for minimal time, high roundtrip efficiency (you are not wasting 30-40% of power) and high cycle life. Only drawback I see is lifepo’s is they don’t take abuse kindly, but then again same goes with say main engine. You run it once without oil and/or coolant, and thats it. But then again BMS protects your battery automatically, so provided everything is set up correctly, you end up with low voltage cutoff at the worst case.
It is hard for me to find even a single good/strong argument for going with lead batteries, now that it is year 2018. I have read John’s article, he has good points and good thinking behind his opinions, but so does Dacian above. Everyone has to decide for themselves, but given the facts decision should be pretty easy. Plus it speaks something that every single EV car out there manufactured this year will have lithium battery in and same goes with every single electric boat or ship which there are tons being built all around the world.
ps. Going with Victron, I would also set up everything to run on 48VDC. This whether you go with lead or lithium. That little what needs 12/24VDC can be run via voltage converters, what you lose in efficiency you gain many times back in higher efficiency for heavy loads and much thinner cables.
pps. I personally would not even go with lifepo’s on my next boat, but use EV car -type batteries (possibly salvaged, car batteries are really well constructed), but that I must admit that they are for not yet anywhere near ready to be used without some pretty deep knowledge on battery technology, but that field is also progressing crazy fast with home batteries and ev cars becoming commonplace. But this progress will take few years, before they are ready for prime time in boats. But it is already possible:
These are the kind of lifepos I am talking about: https://www.ev-power.eu/Winston-40Ah-200Ah/WB-LYP400AHA-LiFeYPO4-3-2V-400Ah.html#tab2
Hope my longer writing did not disappear, as this came visible here before the earlier one…
Was my longer writing really lost? A bit of a bummer if it was.
Just wanted to add that on Morgansclouds article I think John was initially going to go with lithiums, main thing stopping him was his existing installation which would have been had to be redone. With new install from scratch there is no such historic payload. I think this is something you should consider once more, could even split the bank in two, have a bit smaller critical load bank on 24VDC with lead acids to give peace of mind, and then a bigger 48VDC lifepo house bank to keep house loads happy!
I really see no single reason to go with lead acids, now that it is 2018. Lifepos have matured to a point that they are very reliable and supported by equipment manufacturers like Victron, and they should outlast any lead acid by at least a decade or so.
Hi Andy, looks like all your messages came through fine and I do appreciate you taking so much time to send along your thoughts and research. I don’t dispute much in the articles you reference but as with most things, the answer to “What is best for ……???” is “It depends”. Depends on context or what I refer to as use case and in our use case lithium simply do not make the cut. To many risk factors for our kind of situation for example, they are much more fragile than lead acid batteries, much more difficult to source in remote parts of the world, still have a potential danger factor, however small if the BMS or other components fail, and they are much more expensive overall in our use case.
You are quite correct when you say “I really see no single reason to go with lead acids” and that is the case for us too. There are a multitude of reasons why they are the best choice for us as I’ve tried to lay out in previous posts. With the kind of world cruising we do to extremely remote parts of the world and needing to be extremely self sufficient we tend to only go with very well proven systems and lead acid has served us very well for over 100k of nautical miles so in part we are also going with what we know works well for us. Lithium batteries certainly are maturing and advancing as you noted but for us they are still too “new” and unproven. In the future lithium may well become the defacto standard battery type in boats although if we were talking about 10-15 years out I think it will be some other battery type or electrical source which will have taken over. Right now the carbon foam batteries are showing very good promise and if they continue to live up to their results over the past few years I could see them easily taking over, but as I say in the longer range future I think it will be a very different breakthrough in electrical storage that will emerge.
It is a similar logic for us when considering the 48v setup you mentioned. Too much complexity with too little benefit for our use cases so we will go with 24v for our house bank and most systems. We will supplement this with a small number of 12v outlets for devices which still prefer or insist on this voltage.
In the here and now though of building our new boat, we’ve made what we think is the best choice for us and our use case scenarios and that’s what I think we all strive for. Time will tell how well our system works so stay tuned for when we can start to provide the real world data which is all that matters.
Thanks again for all your input and ideas here Andy. I hope lithium, or whatever batteries you chose for your next boat or upgrade work out to be just right for you.
Thanks for very thorough and thoughtful response. You have clearly though this through, and whichever way you choose, the choice will be well thought and right for you – and in the end it must be as you are the one maintaining the end result!
Just two things I wanted to clear. When talking about lithium batteries, lithium ions are the new unproven and somewhat dangerous technology – see Boeing 787 and Tesla fires. Lithium iron, lifepo batteries on the other hand are mature, 100% safe, robust, reliable, and offered by ready to plug and use in boats by Victron, Relion etc. They have already been used in boats for years and in offgrid solar for more than a decade.
And the cost. Lifepo batteries are already cheaper for same usable capasity, as they can be discharged twice more than same nominal capacity lead acid. I quickly calculated 7-8k usd for your battery using lifepo, surely your lead acids will cost (much) more? Have you calculated a ball park figure?
But so much about batteries, lets next start discussing other aspects!
Quite right Andy, we each need to find solutions that work for our unique situations. Even when the specific use cases can be the same, the individuals involved are not, we all have our own preferences, risk tolerance, maintenance skills, etc. and so “best” is always a totally relative term and each combination of situation and individuals is unique.
I’m quite clear that LiFePO is much different than other forms of lithium based batteries and they are much safer but they as still relatively “fragile” in my estimation compared to lead acid. Not only the batteries themselves but the overall system with monitoring, charging and discharging the batteries. While LiFePO has a much larger range in most measurements they are not very tolerant of even one case where this range is exceeded be that over charging or over using their capacity. So in our use case where we are most often very remote and far from any form of assistance or supply, we put a high value on the independence that comes from being extremely self reliant. A big part of that is our ability to deal with most any problem that comes along and be able to fix everything ourselves. In the case of the Winston cells is would be possible to carry a spare cell or two and carry extra BMS boards, shunts, and the like, however unless you go with a single manufacturer’s complete solution, you end up with a relatively complex system which can be difficult to maintain and trouble shoot, as well as being many times more expensive.
The other piece of our puzzle that factors into the overall decision is that because we are going, by design, with no generator and no shore power, we are most often relying on our large solar bank to charge our batteries. While we have a very generous amount of solar it is not such that we could take advantage of the high rate of charge/discharge which lithium batteries have as one of their strong points. Our scenario is that we have a steady daytime supply of power for charging our batteries and we will couple this with a very large overall battery capacity such that we do not take our batteries SoC down much each day and the solars easily replace this the next day. To me a battery based system is all about this In/Out/In balance and in our case the high charge/discharge feature of lithium does not work as well as the low charge/discharge balance we will have with the system I’ve outlined. We are also very conservative in our calculations overall and in this case our calculations on watts per day we’ll actually use, and watts per day we will actually put back in and we plan for the worst case combination and then add a fudge or safety factor on top of that. This has worked well for us in the past and taught us the very high value of “over engineered” or over built for critical systems in our boat. Electrical certainly is up near the top of that list of mission critical systems along with steering and propulsion, and I’ll get to those in future posts and look forward to an equally engaging discussion with you and others on that too.
There are not a lot of couples or boats which spend all their time on the hook (at anchor) like we do and I very much appreciate the value of lithium’s features for most others. It just does not fit our use case as well as a large lead acid bank supported by a large solar bank. Our math then becomes different as well and for us the lead acid solution is much cheaper and a much better fit so that’s what we plan to do.
I hope I have not come across as being overly defensive or inflexible in this discussion Andy. I’ve enjoyed it and learned from it a great deal and I will remain open to any and all alternatives right up to the time we need to place the order for any system. Your comments and questions have motivated me to do even more research on our electrical system and to consider more options and run the numbers again, which this type of feedback loop is a big part of why I wanted to put in the time to create and maintain this blog. So please keep them coming as your time and interest allows, I’m already most appreciative of your contribution to Project Goldilocks.
I promised to stop discussing batteries and move to other subjects, but there is still one more thing I just feel like I must add.
Your use case of charging only on solar with no generator and shore power is almost the most challenging possible for lead acids, and also the use case where characteristics of lithiums would benefit the most. Reason being in end of the charging curve, near 100% DOD, lead acid batteries will be accepting very limited charge/current. Typical value for charge acceptance when near full is few percents of the Ah capacity in amperes, for this discussion lets say around 1-3% out of you 1800Ah capacity, so around 20-50A of charge acceptance, or maximum around 1.3kW of charging power for 24VDC battery – and this will taper down even more as battery nears full. Considering the efficiency of lead acid batteries, you end up with around maximum 1kWh usable power to and then from batteries during night time, per good solar hour. And with lead acids it is critical not to (almost) ever exceed this, otherwise your batteries end up not full after the cycle and sulfation follows which kills the batteries very quickly.
This is of course when solar is optimal, when it is cloudy or day is shorter, the amount of usable power will be little less. So in short, I fear you end up losing a lot of usable capacity of your PV system and it will be a bit of a challenge to get battery full every cycle – and as this will never happen every time in practise, battery lifetime of five years is a good estimate. Maybe you can live with such a constrained amount of power compared to system sizing, but it is definitely something that has to be taken into an account
What can you do to help this? You will need try to move big loads to when sun shines – or when motoring, but that is not the discussion here – and minimise night time consumption. You could install a wind generator to trickle charge 24/7, this would help a lot with getting batteries full. And/or you could have a smaller lithium battery as a buffer sized to accept all the available power from PV cells during the day and then trickle charge the bigger lead acid bank 24/7 with high efficiency switch mode DC-DC charger keeping it full and happy. This would then not be critical component as such, as it could easily be bypassed and also it could be sized much smaller.
Sorry for me continuing this discussion when I already promised to stop, but I feel this is a subsystem of critical importance, and will at least in part dictate the future day to day use pattern a lot.
Hi Andy, sorry to take so long to get back to your latest comments and suggestions. No need to ever apologise for feeling strongly about such things Andy. As per your ending comment, electrical systems are indeed of critical importance, and even more so in our use case of needing to be so eXtremely self reliant so I welcome all your comments and concerns as they motivate me to check our decisions all the more closely which is good
The shortest answer is that when we take everything into account, including the declining acceptance rates of lead acid batteries, the benefits of lithium, which are significant, are not benefits which we can take advantage of and the overall system we have put together with a very large gel cell house bank, along with oversized engine starter battery bank and a third windlass/bow thruster bank, along with a very large solar array is one we can optimise for a just right fit with our use case. A slightly longer answer follows …………………………………
Your initial comments about lead acid batteries having the characteristic of a greatly reduced acceptance charge rate in the last 15-20% to being fully charged is well known fact and no arguments there. In contrast lithium batteries are the polar opposite and one of their great strengths is their very high charge acceptance rate, over 1:1 to rated battery capacity, right up till almost fully charged. With Christine and I having been full time liveaboards for decades now, we are very familiar with this acceptance charge rate limitation of lead acid batteries and have also learned how to work around them. So you can rest assured, that while our solution would not be what you’d want on your boat, we think our choices of the various components of our electrical system on Möbius is what will work best for us.
Batteries are but one of many elements of the overall electrical system and we take a systems approach to each of the many systems on Möbius. As we do so, we also factor in other elements such as safety, maintenance in both effort and time, durability and overall value (not just cost). In our case while we are quite aware that lithium would jump up to the top of the choice chart if measured by charge acceptance rate, when we add in our other factors our choice of large industrial versions of either Gel or AGM batteries rise to the top.
To your specific points about charge acceptance rates, your figures don’t quite match up with our experiences with lead acid of all types and seem to be worst case to the extreme. We have zero experience with lithium so can’t weigh on that but we have a lot of our own experience along with doing a LOT of research to gain insights and focus primarily on those who have first hand experience and in use cases as close to ours as possible. Based on all this we believe that by having the combination of a very oversized total capacity battery bank or 1700-2000 Ah being fed by an even more generously sized bank of solar cells putting capable of producing about 5kWp that we can easily be energy neutral and have fully charged batteries at the end of most days. Let me provide the figures I’m using to reach this conclusion and so you can check them against yours.
Factoring reality into some of these basic numbers and using worst case scenarios to be very conservative in our calculations we anticipate our maximum daily 24 hour consumption to be 300-400A so at 24 volts that would be between 7.2-9.6kWh. Based on the real world data we have from very similar solar setups and boats as Möbius, when taking into account all of the system losses, inefficiencies and shading it is realistic to expect an overall average of about 60% of panel output. Panels which experience little to no shading would be “derated” to about 85% of their Wp and the other panels with more frequent shading would be derated to about 30% or their rated Wp. To work out a daily total output from solar panels our experience and that of most others averages out to 5-7 hours per day of these derated outputs. In our case, after running some initial computer based shading tests on the boat in different locations we estimate that our typical solar output to average about 3.1kWh and thus using the 5-7h/day estimate we can reasonably expect 15.5 – 21.7kW per day.
And finally, using these same numbers to look at just the batteries, this would mean that our DoD each day would range between 16-21% or in the inverse our SoC would range from 79-84%. Such “underuse” of our batteries total capacity add dramatically to the cycle time numbers of these batteries and give us much longer overall battery bank lifetime. These are extremely conservative estimates extrapolated from our real world experience on admittedly very different boats, but very real none the less and so most days in most places our actual numbers would be better than these estimates. So when we put all these numbers together, which again is ONLY taking into account the “electrical numbers” of our overall calculations on determining the best batteries for Möbius, we think that our goal to be energy neutral is very probable and that we can expect to have long lived batteries.
Getting back to lithium and charge rates, with our primary charging source being our solar bank, we would simply not really be able to take advantage of their extremely high acceptance rate so this is not as significant a factor as it would be for others. Similarly the much higher weight and size of lithium are not any advantage to us on Möbius as we have designed integrated sealed and vented battery boxes into the hull and our batteries are serving double duty as “lead ballast” so their weight is all “good weight”. Given the choice of paying for lead to pour into the bottom of the boat vs having large heavy lead batteries do double duty and serve the same role, our large lead acid batteries become a “feature” not a “bug”.
After a LOT of research into house bank batteries overall, both reading and listening, my overall conclusion about lithium batteries, rightly or wrongly is as follows:
• Going the DIY route with lithium can be much cheaper and you can put together a very good system BUT at the cost of requiring very high electrical and electronic skills and expertise, a lot of complexity with the mandatory BMS systems and charging regulation and a LOT of time required for tinkering, actively managing and trouble shooting. I am a very big DIY guy but this would not be a good choice for me.
• There are a few, basically MasterVolt and Victron manufacturers who have whole systems for lithium batteries which mitigate most of the issues with the DIY route but come at a significantly higher cost, quite understandably so.
• While LiFePO in particular has become much more manageable and has much higher safety factors, the consequences however remote, of lithium batteries which do fail is higher than we are willing to accept. I fully expect lithium systems to continue to evolve at an ever increasing rate and become safer, cheaper and easier to maintain but they are not there yet for our use case and preferences.
• From my perspective, lithium batteries are far less durable than lead acid in the sense that they have a very low tolerance for misuse and mistakes. By most reports they have almost zero tolerance for being taken below 20% SoC or overcharged in that they can not usually recover from even a one time occurrence. Lead acid, are much more tolerant of such abuses and mistakes and can usually be recovered from multiple occurrences of such situations over the years in a boat. To be clear, this is mostly human error I am talking about and I am painfully aware of just how “human” I am in this regard so again lead acid fit me better.
You went on to make some very good and creative suggestions on other ways to deal with the low acceptance rate issue, and they would work but again they don’t fit well with us. We have had great success with wind generators on our previous boats, particularly the big KISS unit we had on Learnativity. We may look at adding one on Möbius once we get some real world testing in on how well we are treating and charging our batteries but right now the relatively small contribution and wind generator would give us, comes at too high a “cost” in the form of added complexity, maintenance and noise so we will set sail without one for now.
Your idea of having a smaller lithium bank to store up the excess of solar output during the day and then use this to trickle charge the batteries at night via a DC-DC charger is intriguing and would work quite well I think. But again, at too high a cost for us both literally with the added batteries, charging, BMS, etc. this would require and more so the added maintenance trouble shooting and that ever present possibility of a very bad scenario if something did fail with this lithium bank. My general “rule” is that I never mix battery types of any kind on the same boat, too much trouble managing multiple charging profiles, complexity and costs with multiple charging elements, and the like.
Please understand that I am NOT trying to convince you or anyone else that lead acid batteries are better than lithium nor the other way around. I’m simply hoping you can see that when we take a systems based approach and factor in all our use case and personal priority factors, the overall setup and system we have devised will be able to maximise the benefits and minimise the limitations of Gel or AGM lead acid batteries.
At the risk of starting an even larger and longer discussion, I will note that it is a very similar set of logic reasoning and systems based approach to the overall boat propulsion system which has led us to going with a super efficient single diesel engine coupled to a CPP prop rather than going with an electrical hybrid of some kind. While she will be resplendent in her raw aluminium silver coating, with our use case we believe that Möbius will be one of the “greenest” boats traversing the world’s oceans. But we will leave that for another time!
I see great many positives for having the small lifepo-buffer for at least part of the solar array:
1) You’ll be able to utilise the power output from connected panels much, even multiple times better. Depending on sizing, could be 2-10x more kWhs.
2) You’ll have 100% separate, independent, fully redundant source of power no matter what, to use navigation equipment etc and start the engine. Think lightning strike, small fire, broken hose in bad place, hull breach, something severe enough to temporarily or permanently cripple the main battery bank
3) You’ll save money, per kWh, over lifetime of system. This can be debated, but when all figures are calculated together, will stand I am pretty certain
4) You’ll get real world experience and data of using lifepos, without much risk. Worst case you can always disconnect the buffer and its like it never existed
5) These lifepos will most likely outlast the lead acids
6) In small part this will help me win the bet for a bottle of Scotch, that your next battery system will something based on lithium, should you accept this bet 🙂
Understand your argument for considering a smaller bank of LiFePO batteries as a “buffer” Andy but for us LiFePO takes itself out of consideration due to several ways it runs very counter to many of our fundamental priorities such as:
* Safety, the risk and collateral consequences of a failure within the BMS system or charging systems is too high for us.
* The complexity and fragility of the BMS is too high.
* The amount of time spent expertise required to adequately monitor and troubleshoot this additional whole system onboard is too high.
* Adding another whole battery and charging system onboard.
* Too little real world experience yet to know how well a LiFePO system will work in the long term.
And I guess there is also the “devil you know” factor in that we know all the various forms of lead acid batteries, charging, monitoring and maintaining very well and feel most comfortable in putting our trust with the system we have designed for Möbius.
5B) will make your lead acids last much longer due to better charging profile, especially more frequent charging to 100% full. I would predict 20%-50% more lifetime, but this is hard to estimate and even harder to measure, as there is no reference to compare against
** Safety, the risk and collateral consequences of a failure within the BMS system or charging systems is too high for us.
What is the main risk you see here – especially safetywise? Is it fire risk or something else – as lifepos dont have the fire catching tendency Boeing and Tesla have made the lithiums famous for?
Worst that could happen I see is for this extra battery to disconnect maybe due to LVD or HVD and go dark, but then it would be one connector away from bypassing completely.
Is there some other major risk you see here, if we talk about a small buffer battery of few hundred Ah, not the main bank?
** The complexity and fragility of the BMS is too high.
** The amount of time spent expertise required to adequately monitor and troubleshoot this additional whole system onboard is too high.
If we make it simplest possible (not necessary the cheapest though), we just take a ready battery from say Victron (with inbuilt BMS) and hook it to Victron solar controller connected to one or two panels, thats it and nothing else is needed. Wired in 30 mins, configured in another 30 mins, set and forget for next 10 years. Victron solar controllers even have this ready configurable option called “streetlight” -mode, which would then trickle charge the main battery bank only during the night. And monitoring would be via same Victron interface as rest of the Victron equipment needs anyway, some more variables to monitor yes, but not overly complex. Same app and same connection (bluetooth nowadays, also canbus possible) for sure.
BTW Lifepo batteries can still be used quite fine, even if BMS fails, which in itself is extremely rare as there are no moving parts in BMS and they are very simple electronics. LVD and HVD still need to be configured to chargers and inverters, but this is the same with any battery chemistry including lead acid. BMS is really mainly needed for cell balancing during final topping up charging, which can be also quite simply done manually with multimeter and some small load resistor/lamp etc, in contingency for sure.
** Adding another whole battery and charging system onboard.
But complexity we are talking here is fairly limited, and as a risk-reward tradeoff quite manageable and should I say favourable to much tougher choices like single/twin engine decision etc.
** Too little real world experience yet to know how well a LiFePO system will work in the long term.
There is decades of data on lithiums in general, around a decade of real world experience in using Lifepo batteries for offgrid solar and half a decade at least in using it onboard boats, with overwhelmingly positive results and relatively few problems. At the same time, there are decades of experience onboard boats with lead acids and their associated issues – I have myself had my fair share. I think the balance is already quite equal here, and already at the point of slowly starting to tilt to one side…
Here is a nice video I put together on the proposed complete buffer battery system, very compact for 5 kWh capacity:
Not really, I did not make the video but it is very well made and a solid looking setup. Interesting to watch for sure.
Another even more advanced system is the current leader of the field Batrium, which nowadays can even talk to Victron “natively” over canbus:
We’re tuned to similar channels apparently Andy. Saw that 123Smart BMS video last month and sent it over to a friend who is considering lithiums for a refit he is doing on a Lagoon 500 sailing cat. While very nicely done typical of most Dutch companies this also provides a good illustration of why lithium is not a good fit for us and Mobius. Too fragile and too complex for our use case. We think about lightening strikes for example, which while rare in terms of direct hits are very common nearby in many of the places we have traveled and close enough to take out electronic equipment onboard. One time in a marina in Fiji for example, where Mother Nature regularly puts on some incredible lighthing shows, a bolt hit a sailboat that was up on the hard about 400m from where we were docked in the water and the lightning traveled down the mast of this boat and then turned sideways and shot through about 30 boats including ours. No immediately obvious effects but apparently the EMF was enough to take out quite a few of our electronics once we tried to power up and navigate. There is no getting around having electronics onboard out boats and more all the time I’m sure but we evaluate each one we do put on board very carefully to determine if this electronic item is really warranged and if there are non electronic alternatives. So when I see that whole layer of BMS circuit boards sitting atop those lovely Watson LiFePO batteries, I go through this same evaluation and add this to our decision on battery type and conclude that LiFePO is not a good fit for us.
As I’ve tried to emphasize previously, most systems on boats are very personal decisions and each of us needs to decide what is best for us so I am not trying to convince you or anyone that LiFePO battery systems are “bad”. Rather, when I take a holistic systems view and consider all the characteristics of the various options for our electrical system and test these against our use case scenarios, an oversized housebank of 2v gel cells, kept topped up by equally oversized solar arrays, is the winning combination for us and Möbius.
I understand the concern for fragility of electronics, but I feel quite strongly (having an electronics background both for work and hobby) that BMSs are not any more fragile than solar charge converters or inverters. In fact having a lightning hit an aluminium boat, solar chargers, radars and radios etc are at most risk, as they are and must be directly connected to outside of nice and very well protected faraday cage the hull forms. In addition, BMSs are at least a magnitude of less complexity than those, having very little and very simple electronics inside. Basically a power supply, an ADC for voltage and temperature measurement, a mosfet controlling the bleeding resistor and some sort of bus for communication, and the bus is even being replaced by wireless BT in newest units. With wireless connection there is one less path for lightning to damage.
Also as BMSs are not directly connected to main power path, I find it extremely unlikely for them to be affected by lightning, much less than the battery cells themselves, and when we talk about direct hit, any electronics is fragile whether it is a battery of any chemistry or any other piece of equipment or instrument.
Same concern for lightning goes to other equipment as well. For example I just don’t see how lightning could fry hydraulic automatic pump hidden inside massive aluminium hull, especially when you have a dual redundant system with two of everything. I had a good discussion on this subject with the Man himself when I visited Circa. Aircraft get hit with lightning all the time, and it is very rare for them to be crashed because of it – though they take this very seriously in design and inspection of damage. Just some perspective.
I think we are in agreement here Andy that as you noted “any electronics is fragile” when it comes to being affected by lightning strikes. I did not mean to imply that BMS systems were any more at risk than other electronics, I just pointed out that fragility is one of the factors I take into consideration when deciding what equipment is best onboard Möbius. Something our experience at sea has taught us is that any electronics are at risk during lightning storms and that simply disconnecting them from circuits and turning them off, while reducing the risk does not eliminate it. We have had devices stored below in a steel boat affected by distant lightning strikes and so while we take typical precautions such as placing our portable electronics inside a microwave, shutting down systems, etc. we are aware that electronics are still at risk and hence our reasoning in factoring this into our equipment selection decisions. If there is an equally viable alternative to an electronic device we are likely to go with that instead and we also try to not bring devices onboard which are not really neccessary. It is challenging to think of a boat such as Möbius being “simple” we do our best to follow a KISS or Keep It Simple & Safe approach as much as we possibly can and pretty much as you said “… take this very seriously in design”.
We use surge these protectors from Phoenix Contact at work. Never had anything protected by those break:
Devices itself have taken quite many hits, both natural (lightning) and man made (swithing transients from HV lines). They take small hits multiple times, but a big hit destroys the protector while protecting the device connected, bit like a fuse really (though technically quite different). The HV electric switching station is harsh environment for electronics, not a lot survives without surge protection. Because of excellent grounding, they do take a lot of direct lightning hits all the time.
Thanks so much for this link Andy. I’ll check them out. We are just now getting into the detailed BOM for the electrical system so will add these to our list of possible items to include.
Excellent videos on subject of solar charging and also some quite fancy stuff like new Victron management over bluetooth:
Thanks Andy, I’ve been watching Jono’s Narrowboat blog for awhile now. Very interesting guy and does a great job of very methodically detailing his work. Well worth following.
From your posts I understand that you do not have a generator (nor shore power) supporting the electrical system on MOBIUS. I also read that the boat has provisions for some “upgrades” at a later state (e.g. active fin stabilizers). I wonder if you have reserved the space to install a generator in the engine room?
The reason I am asking is that you mention you love the tropical climate (20/20 rule) and your high tolerance for heat and humidity. But if you nevertheless decide to run the air conditioning when it gets too sticky at anchor on a windless day, would the substantial batteries/solar support that and for how long? I guess you could always start the Gardner engine and supply electrical power through the 2 alternators. How would you deal with such a situation and what is your position on air conditioning in general? Best regards.
Excellent questions Markus and I’ll do my best to give you as short a summary of my answers as I can, which is always a challenge for me and then elaborate much more on our overall electrical and HVAC systems in future posts.
You are correct that we have purposely designed Möbius and her systems to have no reliance on a generator or shore power. This is mostly a consequence of our life style and use case and not any comment on either of these well proven and effective options. In our case though we are hardly ever in marinas or docks preferring to be anchored well out or being the only boat in the Bay whenever we can so shore power is not an option for us. Having said that we will be wiring the boat with a shore power connector, isolation transformer and the other necessary equipment so that we could plug in whenever we might want to leave the boat for longer periods of time or when conditions might dictate so we are not eliminating the ability to connect to shore power but we are designing the boat’s electrical system with the assumption that there is no shore power and no generator.
The no generator decision is similar in that we have had generators in previous boats and they have worked well and been valuable. However I think that for most of us full time world passage makers and live aboards, a generator falls squarely in the “necessary evil” category in that there has not been much of an option but to have one if you are going to be without shore power for long periods of time. However with the dramatically improving solar power option and overall electrical component efficiency we believe they are now a very viable option with enough installations and time to have proven themselves worthy of a place on a boat designed to be as self reliant and independent as Möbius.
After a lot of research to confirm this in our minds, we have designed the whole electrical system and the boat itself to some extent around this approach of being a “battery based” boat wherein batteries will be the primary source of electrical power on the boat and we will use inverters to meet all our AC power needs. Our 24v house bank batteries will be kept charged primarily from our 3 large solar banks and with 2 high output engine mounted alternators for backup and charging on passage. Based on the experiences of others we’ve talked to and our research and calculations we feel quite confident that we will be able to generate more power than we use and thus meet all our electrical needs and keep our batteries fully charged most every day. Of course reality wins out over theory every day so we won’t now for sure till we’ve been living aboard for the first year or so but we have done our best to base our decisions and do our calculations with as much real world data we’ve been able to find as well as what we have from our own personal experiences to date.
Thus we do not anticipate needing to add a generator in the future and I have not reserved any dedicated location for one. However the Workshop on Möbius is very generous and I have gone over it with the same question you ask of some future owner or other boats which might be built off this design wanting to install a generator and there are several ideal locations in the Workshop where a good sized generator could easily fit and be installed rather easily along with all the attendant components such as exhaust and cooling. One of the many benefits of an all aluminium boat is the ease with which changes or additions such as this can be made. In the case of adding a generator there is plenty of room, most likely on the Stbd side of the Workshop to add a generator and weld in a sturdy supporting framework for it should that ever be wanted.
The fundamental numbers on these components are:
• 52kWh 24v House Bank based on large industrial OPzV 2v gel cell batteries. If we consider up to 50% max DoD that would give us about 26kWh usable capacity.
• Additional battery banks for 24v main engine start and front bank for 24v bow thruster & windlass
• Twin 24v alternators on main engine, 195-240A each = 9.4-10.5kWh
• 14 solar panels 360W each = 5kWp Derated to 61% after analysing losses in system and running shading models = 3.1kWh x 5 hour solar day = 15kW/day
As for the other kind of AC, air conditioning, we will certainly have a very good AC system in Möbius and this is part of the overall electrical, plumbing and systems design. We are going to use a chiller system to circulate chilled coolant through heavily insulated PEX tubing going to a multitude of small radiators in all the living spaces which have DC “muffin fans” on them to circulate the cold air. We will have this same system serve double duty as one of our heating sources by simply having this same system connected to the diesel boiler when it is heat we want in higher latitudes.
A related option which we have not made a final decision on yet is that we may also install a hydronic based in floor heating system which can also do some degree of double duty for some additional cooling of the insides in more temperate climates. More on that if we decide to go forward with this option that has a lot of appeal and advantages.
Finally getting down to answering your latter questions on Air Conditioning we think that based on the numbers above we would be able to run the air conditioning whenever needed. One of the most common situations for AC is often on long passages through very hot and humid areas and with the added increase of the amount of salt in the air coming aboard and being thrown up around us. In that situation with the large alternators, battery bank and inverters we would be able to easily run the AirCon and all the other AC loads such as induction cook top, washer, etc. while underway. On anchor we think that our house bank and solar setup will be able to run the AirCon as well and even if relatively heavily used we would be good for at least a week. Two interrelated factors are enabling this; extremely effective insulation and using the AirCon intermittently to cool the boat down and then shut off. We learned the value of “living in a thermos bottle” as I some times put it on our last boat Learnativity which was an all steel 52’ Bruce Roberts design boat that had 3-4” of sprayed in place closed cell foam shaved flush with the frames and covered with 3/8” plywood. Such high insulation did just what a thermos does; kept the insides cool when it was hot outside, and warm inside when it was cold outside.
I should also mention that the other added benefit of great insulation that I especially came to appreciate as I spent time on other boats was how quiet LTY was at all times. This was not just a “nice” feature but dramatically reduced the tension onboard when you were out there really taking a licking with high winds and seas which certainly generated enough of their own noise but the ship didn’t add or amplify any of it which was a huge benefit we came to learn over time.
But the big benefit of such extreme insulation was that we didn’t have much heat being added inside the boat when in hot climates like Fiji and the Marshalls so it didn’t take much too cool down. Therefore we will be building Möbius to be an even better thermos bottle with eXtreme amounts of insulation and I think this is perhaps one of the most important aspects of answering your question about having great AirCon on Möbius in hot climates. By keeping as much sun out of the boat as possible with good window glass treatments and awnings, then having an extremely well insulated boat we should be able to use the AirCon to bring the inside temperatures the boat down whenever we want and then turn it off and have the boat stay at that temperature for several hours at least. In such climates we would expect to maybe run the AirCon for a few minutes before we go to bed and then turn it off for the rest of the night with fans continuing to circulate the cool air.
The other key and mitigating factor in this for us is that we are almost always at anchor which means: we always have the temperature mitigation of being surrounded by sea water, we almost always have a breeze blowing and it is always coming from the same direction, over the bow as we swing with the wind at anchor.
You obviously read my previous posts very carefully and we don’t tend to use AirCon very much whether that be in homes, vehicles or boats. In part we have as you noted a higher tolerance than many it seems for heat and humidity but we certainly do appreciate cooler drier air when things do get hot and sticky and we are ensuring we have that option on Möbius. You asked “what is your position on air conditioning in general” and I’d summarise it as something we want to have as an option but not likely use too often. We find for example every time when we head ashore to visit friends and family and are in homes, restaurants, malls and the like that we feel like we end up living in meat lockers! People and business seems to complain about the cost of their electric bills and yet they have their AirCon set on overdrive all the time it seems? And it doesn’t seem to be just us, we look around a restaurant with chattering teeth and see a lot of other guests with sweaters and jackets on! More so we think that too much AirCon has a certain degree of health related problems in that the shock value of going from a cold air conditioned environment out into the natural heat of the day seems to cause greater incidents of colds or at least a good deal of discomfort. So for us we try to find ways of moderating and dealing with the temperatures primarily with good clothing choices and ways of maintaining good air circulation. We make sure our boats have lots of fans for example to ensure that there is always a good flow of air around us, we work on ways of providing shade and reducing being in direct sunlight with good window glass, awnings and overhangs. If we are thus shaded and have good air flow we find it quite comfortable up to about 36-38C / 96-100. We are starting to experience these kinds of temparatures here in Antalya and often had them when living in places like Fiji, Marshall Islands and the Caribbean and for sleeping we simply have well sized and placed fans blowing onto and across the bed and we sleep well.
As a result one of the top priorities we have with the design and now building of Möbius is ventilation and our overall HVAC systems. (Heating Ventilation and Cooling) In many ways Möbius has been designed around the ventilation system. Most of this work has been to devise ways of capturing natural breezes on anchor, which is our most common situation and bringing it onboard and into all the living spaces. We have come up with some very “cool” ways of doing this I think and you will see them highlighted in future posts. Once we had the passive ventilation planned out we then looked at ways to add an active or assisted component to these same ventilation systems by adding fans within the venting system. And lastly we looked at adding AirCon to the equation. I’ve painted the picture of our AirCon and HVAC systems in very broad strokes above and as we work on Möbius you will see these and I will write about them in more detail.
As usual for me I’m afraid, far too many words to answer such a simple and important question so my thanks for bearing with me if you got this far Markus. Let me end by saying that as per my earlier post which you read so well outlining all our priorities and key design criteria, COMFORT is one of the top items and your question would suggest you feel similarly. As I often say “we aren’t camping”, Möbius will be our full time home and where we host our friends and family so being just as comfortable at sea as at anchor was a top priority in our design. While we may not run our AirCon system for as long as others would, it is a key part of our overall planning and design of the HVAC systems on Möbius and thanks for this chance to outline those a bit more here today. If this prompts more questions and you are brave enough to want more answers please ask and I’ll do my best to answer.
Some pretty good and recent videos on the (battery) subject:
Thanks for passing these along Andy. Good to see more people trying LiFePO4 batteries out on their boats. Is not a good choice for our use case but I hope it is for theirs.
IMHO Lithium batteries and their required components will remain a new and unproven system, as are all new technologies, until such time as there are enough installations for enough years to provide the real world data on their use, safety, maintenance and longevity. So I’m delighted to see more people installing this on their boats.
For people like us for whom our boats are our full time home and we do long range ocean crossing passages spending the majority of our time at anchor in very remote locations it is imperative that all our systems are as robust, reliable, safe and low maintenance as possible so we go with tried and true systems and components wherever possible. Hence as we’ve discussed here previously, an eXtremely large house bank of 2v OPvZ gel cells kept fully charged by an eXtremely large set of solar panels and/or large alternators is the choice we feel is just right for us.