New "Super" House Batteries Möbius Update 9 Sept. 2023
The newest update to Möbius is that our all new House Bank batteries are now fully installed and up and running!
As you may recall from THIS post almost a year ago, our original FireFly Carbon Foam batteries had sadly lost most o f their “fire” aka capacity and repeated efforts using the FireFly prescribed “Restoration Charge” was not able to bring the capacity back. Fortunately the combination of having a total capacity of 1800Ah @ 24V and our large solar capacity from 14 320W solar panels allowed us to go for almost a year of full time live aboard cruising running all systems other than extended AC use, without needing to ever plug into Shore Power. So we did pretty well I think!? But about a month ago while docked here in Norfolk, one of the four FF banks started to overheat and so their time was up.
With our new situation (details if interested here) I had hoped that the FF batteries would last until we find the new owners and they take over so they could chose the new replacement batteries that were just right for them But the “fire” had sadly gone out on the FireFly batteries and so I needed to make that call and have all new House batteries installed.
For those interested, this post will give you an overview of how that progressed.
CHOOSING the GOLDILOCKS NEW BATTERIES
The quick summary of my requirements and priorities to determine the just right Goldilocks batteries for Möbius’ and our use case is as follows: (in no particular order)
- WEIGHT: Somewhat unique to us perhaps, weight is not a factor for choosing the batteries. In fact we actually want/need as much weight as possible as we had designed the boat around the batteries to some extent and treated the 1022Kg/2250 lbs of FF batteries as part of the lead ballast of the boat.
- SIZE: Battery size is also not a factor as we had to some extent designed the hull around the battery compartments which ended up being three large watertight and positively vented compartments which spanned and were centered on the 1″ thick x 18″ keel bar that runs from the transom all the way up to the top of the bow. See the GA drawing below to see this layout.
- WIDE TEMPERATURE RANGE: Working well and safely within in as wide a range of operating temperatures as as possible. Our intended use case for Möbius was to go everywhere from the Arctic/Antarctic and high latitude cccccccold climates to scorching hot locations. (which seems to be more and more locations in our world these days!)
- FAULT TOLERANT: In addition to temperature it was also important that the new House batteries were as robust as possible in that they would be able to deal with the typical “accidents” that happen over the years with the battery systems on boats. Things like full discharges when the boat has been left for long periods of time and the charging system fails for some reason.
- SAFETY: Always a top priority of course but in the end I had no concerns with safety of either Lithium or AGM as I’m of the opinion that battery safety is all a matter of good design and installation of the electrical system and battery management, as well as sticking to top quality manufacturers. So I did not consider any of the “off brand” batteries and companies.
- VALUE: Cost is an ever present factor for most of us but I think in terms of overall value rather than price alone. I will gladly pay for quality and other features listed above to get the best match of batteries and our use case criteria. I think this is well evidenced by all the equipment we have installed on Möbius. So I did not consider any batteries or companies that were not IMO offering high quality batteries.
- EXTENDED 100% SOC + FLOAT TIMES: This is a relatively new factor I have come to appreciate and which I believe may have contributed to the early demise of the Carbon Foam FF batteries. Most of us have experienced how leaving things like laptops and phones plugged into their chargers and kept at 100% fully charged for most of the time leads to them loosing more and more of their capacity and shortening their lifespan. I don’t have the expertise to prove this but my first hand experience over the years and my research into that of others has led me to suspect that there is a similar situation with LiFePO4 and Carbon Foam batteries.
Due to our large almost 5KW solar power the batteries on Möbius sit at 100% fully charged state almost all the time. With the large overall available capacity we typically only take the House batteries down to about 85% SoC or less between the end and start of each solar day and most days the solar charging brings them back to 100% fully charged by 10 to noon depending on solar conditions, time of year, geo location, etc. You would think that this would be ideal for battery health. However, I am finding increased evidence and examples that not only do LiiFePO4 and Carbon Foam type batteries deal very well with being in PSoC or Partial State of Charge for extended periods of time, they actually PREFER to be in a PSoC condition the majority of time. Being kept in Float mode at 100% SoC can lesson their capacity over time. It is possible to deal with this by carefully customizing the charging profiles of all the charging sources on the boat and our WS500 regulators for the alternators, MPPT controllers for the solar panels, and MultiPlus chargers all have this ability. However based on my experience to date I think that AGM type batteries actually prefer to be kept at 100% fully charged SoC which is the situation as I’ve outlined above on Möbius. I’m sure this factored to some degree in my final decision.
I should add that the rest of the equipment that forms the overall House Battery system would work well with any of the LiFePO4 or AGM batteries I considered. Things such as the twin 250A 24V Electrodyne alternators with external rectifiers, WakeSpeed 500 Smart Regulators and Victron BMV712 battery monitors, would all work for any of the batteries I was looking at be they Lithium or AGM so this was a non factor in my decision making. Lithium batteries would of course require equally high quality BMS either internal or external so I only considered LiFePO4 batteries with dedicated BMS from their manufacturer.
Click to enlarge and see the location of the three battery compartments on Möbius
BATTERY CHOICES:
I’ve written about this topic of batteries for Mobius multiple postings here on the blog and I spent a LOT of hours discussing this with experts and other boat owners and researching the latest offerings of high quality batteries. This lead me to narrow it down to a choice between Lithium (LiFePO4) and AGM batteries from the likes of Victron, Battleborn/DragonFly, Lithionics, etc. all of whom had some very high quality options.
For example, this new form factor of “12V 270Ah GameChanger 3.0” LiFePO4 batteries from DragonFly had some very attractive features.
I also went back to the original batteries that I had considered for Möbius during the initial design phase which were these type of OPZv Gel type “traction batteries” and they were in the running again in this most recent search.
I paid close attention to how “bullet proof” the batteries were in terms of being able to deal with such factors as the likelihood of a few times in their long lifespan where they would end up being completely discharged for some reason or another. Never planned of course but always possible and when we start talking about lifespans of 10+ years the probability of such “accidents” becomes quite high.
These intriguing 24V 275Ah LiFePO4 “modules” with external BMS from Lithionics ticked off a lot of boxes were also recommended by OPE though came with a deservedly high price as well.
There were several other batteries and companies which I researched and made it onto my short list but the ones above cover the top contenders.
and the WINNER IS …………..
I’m well aware that many of you would make a different choice for YOUR boat, but I do my best with all equipment decisions to find the “Goldilocks” just right choice that best matches with Möbius’ use case.
In the end, this is what I chose; (drum roll please …………………….)
………….. After a LOT of deliberation I decided to go with Victron and chose their “Super Cycle” AGM batteries. 
We chose Victron equipment for the entire electrical system on Möbius including their Isolation Transformer, MultiPlus Inverter/Chargers, MPPT controllers, Octo and Cerbo GX monitoring, etc. so they are a company that we have come to know well and not doubt have a bias for and I’m sure this did influence my final choice and Victron offered multiple batteries in both LiFePO4 and AGM to chose from.
These Victron SC AGM battery model are 12V @ 230Ah C20 and one of their more interesting qualities that caught my attention was their stated ability to withstand 300 complete 100% discharges without any damage to them although it certainly would shorten their lifespan if you were to do that. Having gone with Victron for almost all of the equipment that makes up the overall electrical system on Möbius, I have come to trust and respect them as a company but I still wanted to verify these claims and was fortunate to find that Bruce Schwab at Ocean Planet Energy OPE, was able to personally verify Victron’s claims of these Super Cycle batteries based on OPE’s direct testing and he wrote:
Being a Victron distributor, we have tested the Victron Super Cycle AGM 125Ah (G31 size) in our PSOC regime. Nearly all Pb batteries suffer permanent capacity loss when run through this 30-cycle PSOC test. We’re happy to say that the Super Cycle AGM passed with flying colors, with no discernable loss of capacity.
I was therefore delighted to be able to work directly with Bruce and his tech Kevin at Ocean Planet Energy and can not recommend them more highly. Bruce was incredibly responsive throughout the whole process, answering all my barrage of questions leading up to the choice of these Victron batteries and then getting the new batteries along with some additional Victron equipment ordered and delivered to the marina here in Norfolk VA.
Bruce and Kevin worked with me very closely during the entire installation and configuration of the whole new electrical system to get it dialed in “just right”. It is all too rare in my experience that you find such high degree of expertise along with truly exemplary service and so my hat off to Bruce and Kevin, can’t thank you both enough. If any of you have any electrical needs for your boat I’m sure you will thank me later for contacting Bruce and his staff at OPE and similarly benefiting from their expertise and incredible customer service.
* NOTE: Just to be clear and transparent, I am not sponsored by OPE or Victron or any other manufacturer, just a very satisfied customer wanting to share my first hand experiences with these high quality companies and people.
OUT WITH THE OLD;
Here is the schematic showing how the original House Bank of 24 FireFly L15+ Carbon Foam batteries was setup.
(click to enlarge this or any other photo)
This is one of the three sealed battery compartments that are built into the hull with the batteries stradling the 1″ thick center keel bar so that all their weight acts as nicely centered “lead ballast”. As per the schematic above, each of the four banks of FireFly batteries were wired directly to the positive and negative main bus bars inside the Grey DC Distribution box you see here. All cables are of equal gauge and length, hence the looped Red & Black cables, Positive cables from each bank have their own Off/On Battery Switch (Grey switches top left corner) and the negative cables each connect to the Neg bus bar through their own shunt for the Victron BMV712 battery monitors. Fortunately I was able to reuse all these cables and battery monitors for the new batteries.
This is the forwardmost battery compartment with the lid removed to start disconnecting all the batteries.
With all the interconnecting battery cables and copper bars removed these 8 batteries are ready to leave the building.
Each FireFly battery weighs 43Kg/94lbs but fortunately they had very good handles on both sides so lifting them up and out went well. This is the first eight of 24 batteries out on the dock beside the boat.
OUT OUT OUT with the OLD!
A bit of a sad end to what should have been a much happier relationship with these FireFly batteries, but it is what it is.
Enlisting the generously offered assistance of the marina staff and their golf cart to make the looooooooong trek along the maze of docks to get from the boat to the shore, we were able to transfer the batteries from boat to shore to pickup truck to take them to the battery salvage yard.
A forklift sure makes life easier once I got the batteries to the salvage yard!
At least I was able to offset the cost of the new batteries with the money for the 2317 lbs of lead contained within the 24 FF batteries. (less weight of case, gel, etc.)
Bye bye FireFly; Hello Victron!
IN with the NEW
The new batteries were delivered a few days later and with some help from the marina staff and their golf cart, we were able to bring the new batteries out to the dock beside Möbius.
.With the old FF batteries removed I could take out the fiberglass pans and modify them to fit the new batteries. Not actually required by ABYC for these sealed batteries but a smart “belt & suspender” safety feature I think. 
Each of the three pans needed to be extended in length so I just cut them in half with my circular saw ……….
and then glassed in the space between with new cloth and resin.
Just visible on the far left end of this pan you can see the new SS tie down D rings I installed for the ratchet webbing used to secure the batteries in place.
Now all that was needed was to lift each of the 125lb new batteries from the dock down into the Basement and then lower them into their new home inside each battery compartment.
IN WITH THE NEW:
This schematic illustration will show you how the new House Bank is wired up. Over the many years of boat ownership I have come to appreciate how important it is to keep ALL batteries very well balanced as they are being charged and discharged.
NOTE: this is a schematic diagram only, cable sizes and lengths not shown to scale
This boils down to ensuring that each battery has the exact same resistance as their electrons flow in and out which is mostly determined by having the exact same size and length of cable connecting them to each other in the parallel and series arrangement required for such a multi battery bank setup. It is similarly important that each individual battery bank also has the exact same cable gauge and length for their connections to the main positive and negative bus bars.
Also worth noting that all battery cables are oversized to 120mm2 (two sizes larger than AWG 4/0) to have less than 1% voltage drop.
I have also come to appreciate how much it helps to go the “extra mile” with the interconnecting cables to make all the series and parallel connections between each of the four batteries that make up each bank. I first learned this method many years ago from Nigel Calder’s invaluable “Boatowners Mechanical & Electrical Manual” which you can see in Fig 1.21 page 22 if interested.
This is the wiring I used for each of the four batteries in each battery bank.
You can see this in the schematic above and here in the actual cables installed on the new Victron SC AGM batteries.
Small gauge wires you see here are for the various temperature and voltage sensors for monitoring these batteries with both Victron and Maretron.
Christine’s son Tim flew up for a visit during all of this and being a very good certified electrician he generously worked with me for the whole installation process. Here seen crimping the lugs onto the new interconnecting cables that needed to be made up.
Tim does very high quality work which I certainly value highly and is also great to see in this new generation of electricians and workforce. Good example here of affixing the SS ratchets and straps to this battery bank.
Tim also took on the finicky mounting and then wiring of the three Victron Battery Balancers that we added to the installation.
Thanks Tim, couldn’t have done it without you!!
For those interested, these battery balancers work as follows:
The Battery Balancer equalizes the state of charge of two series connected 12V batteries, or of several parallel strings of series connected batteries. When the charge voltage of a 24V battery system increases to more than 27V, the Battery Balancer will turn on and compare the voltage over the two series connected batteries. The Battery Balancer will draw a current of up to 1A from the battery (or parallel connected batteries) with the highest voltage. The resulting charge current differential will ensure that all batteries will converge to the same state of charge.
With the kind of $$ we boat owners invest in our battery banks, every bit that we can extend their lifespan helps and is well worth doing in my experience.
Not quite finished, still need to tidy up the cables and small wire sensor cables with zip ties but here is what House Bank #1 looks like.
And this is the aft most Bank #3 just about ready to have the lid bolted on to finish this installation.
It took a few days working with Bruce and Kevin at OPE to get all the settings setup just right in the MPPT controllers, WakeSpeed regulators, MultiPlus chargers and BMV sensors and they went the extra mile and then some to help configure and finish up the installation. We have been running the new Victron House Battery setup for about three weeks now and it is performing flawlessly. I’ve tested it both with and without shore power and the each battery and each battery bank has stayed perfectly balanced and performing just as hoped.
A very good feeling after nursing the original House Battery along for the past year but we now have a great setup that should continue to meet all the significant electrical demands aboard Möbius. This is very much a “battery based” boat with all DC and AC power coming from these batteries so this really adds to the SWAN or Sleep Well At Night factor on our beloved Möbius.
Congratulations if you’ve made it this far in this all too typical “brevity challenged” update. With any luck there won’t be any more big jobs like this to report on but I will post updates from time to time as things evolve aboard and soon hopefully off of the Good Ship Möbius.
-Wayne
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