Battery Economics and Marketing BS

OK, this post is for all you sailing technology nerds out there. Lithium batteries are the newest and hottest thing that every cool sailor suddenly has to have. They are being promoted by some people who really don’t know what they are talking about, and they are enormously profitable for the sellers. But are they the right choice for you? Probably not, but read on to see…

For literally centuries, the only really useful kind of battery for storage of large amount of power was the lead-acid battery. They are cheap, they are well understood, and they work. There was no practical alternative. Technology has (finally!) marched on, and various Lithium battery types are on the market for cruising boats. In many applications Lithium batteries are clearly and simply the best, but that does not mean they are best everywhere.

They command a HUGE price premium, and promise all kinds of great and amazing benefits. Are they worth it the significant extra investment? For the typical cruising sailor the answer continues to be a resounding NO. Now that might change as the costs and capabilities change but as of the end of 2019, the number of sailboats for whom Lithium batteries make economic sense, or even technical sense, is very small. Let’s have a look at why.

I have taken the liberty of pulling a major seller’s list of reasons why you should buy a Lithium battery, and will comment on them point by point. In almost every case, the argument in favor of Lithium batteries is slanted by selecting the LEAST good lead acid battery as a comparator. When we look at the latest, and best, lead acid batteries, a very different story comes to the front. Most of the benefits that are claimed for the Lithium batteries are accurate, or as close to accurate as you can expect from the marketing department, but the vast majority of them are also irrelevant to the cruising sailor.

  • SAFETY – Inherently safe Lithium Iron Phosphate (LiFePO4) chemistry. Safer than flooded or AGM batteries.

This is a difficult point to find a lot of backup information for. Certainly, lead acid batteries (of the sealed, valve-regulated type) have an excellent safety record when properly installed and maintained. Any large battery bank will store a huge amount of energy in a very compact space, and that is a potentially dangerous thing. When dealing with this much energy there are many types of failures that can cause problems. I’ll call this one a draw. If there was NO possibility of any Lithium battery EVER having ANY kind of issue, modern sealed valve-regulated lead acid batteries are safe enough that the difference is not worth much to me.

I wonder exactly what the writer of this statement meant by “inherently safe.” The phrase “intrinsically safe” has a very specific meaning well understood by engineers. Why did the author choose not to use it? Maybe because “inherently safe” doesn’t really mean anything…

  • MULTIPLE BUILT-IN SAFETY FEATURES – Internal BMS provides full protection from overcharge, high or low voltage, over-temperature, excessive charge or discharge current, etc.

This is a classic salesman’s trick of handwaving a bug into a feature. Lithium batteries require a complex electronic BMS (Battery Management System) because they do not tolerate over or undercharging and temperature extremes. Lead acid batteries do no need these complex electronics to work reliably. I don’t see this as an advantage of the Lithium battery at all, it is just more to go wrong.

  • DROP-IN REPLACEMENT – Available in most standard industry sizes. Some sizes available in 24v and 48v, eliminating need for the undesirable practice of wiring batteries in series to increase voltage.

This is TRUE, kind of. First, most boats use 12V systems and do not require series wiring. For those boats that do use 24 V systems, inexpensive battery balancers completely eleminate any issues with series connections. Claiming this a a magic benefit of Lithium is a misdirection, because balancing charging voltage to the individual cells is actually far MORE important for Lithium batteries, and is one of the reasons they require the complex electronics in the BMS.

  • LIGHTWEIGHT – 50-60% less weight than lead-acid equivalents.

Here is the ONE place where the Lithium batteries win, flat-out, hands down, no argument. If you are sailing a boat where weight is a critical issue for performance, and you have the money, then go for it. Are you listening all you hotshot catamaran sailors? Also, boats where physical space is limited, can get more energy storage out of the same physical space if they use Lithium.

BUT…. On my boat, the weight of the batteries is used to trim the boat and balance the weight of the genset. Removing weight from the battery bank would NOT be a good thing, it would leave my boat with a permanent list to port. Of course I COULD add lead ingots to replace the lost weight and retrim the boat, but I think we all agree that would be rather silly.

  • LONGEST LIFE – Up to 10X longer cycle life than lead-acid equivalents.

Whenever you see a salesman use a term like “up to 10X” you know it is a really bad comparison, based on the worst case possible. Using a high quality lead acid battery like the Firefly there is a forecast cycle life of 3600, while the lithium battery claims 7300 under similar usage profile. So the “Up to 10X” actually becomes 2X–maybe.

My Firefly batteries have a 6 year warranty period while the ReLIon marine Lithium batteries are covered for only five. Why do they not put their money where their mouth is?

There is another issue with battery lifespan that is not often discusssed by the proponents of Lithium batteries. Batteries age and degrade even if they are not cycled. A battery that might last 10 years if cycled twice a day (7300 cycles) might only last 15 years if cycled once a day (5475 cycles). That can have a HUGE impact on per cycle cost. Ask to see the data on this before you assume that your expensive new batteries will last “forever.”

On my boat normal usage has me cycling batteries every other day. So even the 3600 cycle life forcast for Firefly batteries gets me 20 years of life–in theory. Why would I pay more to get a long life than this?

  • MORE USABLE CAPACITY – 25-50% more capacity than lead-acid equivalents.

This is a silly number. I do not care how many “boxes” it takes to store my power, I care about how much it costs, capacity per dollar. Other people might care about capacity per pound. Who really cares how many boxes it takes? And again, the “50%” number is a worst possible case comparison. It is absolutely true that for the same usable energy storage, you need fewer Lithium batteries than lead-acid ones, but with batteries like the Firefly that difference is 25%, NOT 50%.

  • CONSTANT POWER – Full power available throughout discharge. Voltage does not drop like lead-acid. Voltage drops by only 0.3 volts between fully charged and 80% Depth Of Discharge (DOD).

This is sort of true, and completely irrelevant. My battery bank drops from 12.8V at 100% change to about 12.2V at normal discharge levels. Who cares if it only dropped to 12.5V? This is also a gross misuse of the word “power.” Either the person writing this doesn’t understand the word, or they are trying to pull the wool over your eyes. A small drop in the voltage during the normal usage cycle does NOT mean there is less power available!

  • FULL CAPACITY AVAILABLE UNDER HEAVY LOADS – Unlike lead-acid, 100% capacity is available whether a 1 amp or 100 amp load.

Another case of yes, it is true, and completely irrelevant to a cruising sailor. There certainly are applications where this matters, but a typical sailboat almost always draws power at a slow and steady rate, but high amp draws are infrequent and of very short duration and have no real world effect on the battery bank’s capacity.

  • TEMPERATURE TOLERANT – 2.5X more efficient operation at low temperatures than lead-acid. Safely operational up to 150°F (65°C).

Once again, the statement is true, and is also not helpful on a sailboat. My batteries see temperatures MAYBE down to 55F and as high as 95F. Why would I pay more for performance outside this range? There is also a catch that people in cold climates should be aware of. Below 32F, very special charging regimes are required to avoid serious damage to a Li battery. In fact charging needs to be done VERY slowly at temperatures this low. So “temperature tolerant” is not even really a completely true statement. Just like with lead-acid batteries, running a set of Lithium in a high temperature environment (like a poorly vented engine room) will result in greatly shortened lifespan.

  • FAST & SAFE CHARGING – Highly efficient charging. Will absorb maximum charging current available from charger, alternator, etc. until battery is fully charged. Can fully charge in 1-3 hours. Built-in overcharge protection.

Yes, and no. If solar power supplies a significant fraction of your boat’s electrical needs, a high charge acceptance rate is most likely pretty irrelevant to you. If you are charging by alternator is is VERY unlikely that your alternator will be able to supply full rated output for even 1 hour without seriously overheating. Your alternator controller will ramp back the output to keep the alternator from a literal meltdown, so the charge acceptance rate of the battery will be irrelevant. Also, Firefly batteries have charge acceptance rates that are probably higher than you can generate, so, again, the difference is not relevant to the typical sailboat.

If you can generate and feed 0.5C or 1.0C of charge current to your battery bank, then maybe you are a good candidate to spend the extra for Lithium batteries. My genset is close to fully loaded generating 0.3C (170A@24V) into my bank, and my Firefly batteries can take that all the way up to 85% SOC. A higher charge acceptance rate is not helpful to me.

  • PARTIAL STATE OF CHARGE (PSOC) TOLERANT – No damage from partial state of charge operation or storage. Will recover from complete accidental discharge without damage.

This comparison is certainly true of older lead-acid battery types, but the Firefly carbon-foam battery is not limited or damaged by POS operation, so no help here.

  • LONG SHELF LIFE – Low self-discharge rate, so battery stays charged for years if unused.

If you are not using your batteries for long periods of time, then spending the money for the superior lifecycle performance of Lithium batteries is pretty silly…

  • MAINTENANCE-FREE – Plug, play, charge, and use.
  • NON-HAZARDOUS – No watering. No gasses emitted. Inherently safer than lead-acid batteries.
  • INSTALLATION FLEXIBILITY – Can be installed upright or on its side

All of these are features that are supplied by any good AGM or GEL style valve-regulated sealed lead acid battery, and don’t really count as advantages unique to a Lithium battery.

By my calculations, Firefly batteries have a total life cycle cost that is SLIGHTLY higher than a similar bank of Lithium batteries. The Firefly batteries would last about 10 years, (with daily cycling) and the Lithium bank 20 years. Break even would come after AT LEAST year 17. Even longer if the batteries are not cycled every single day. There is no way that anyone can realistically argue that an investment with a 17 year payback makes ANY financial sense. And I can see NO technical reason to use a Lithium battery for the vast majority of cruising sailboats.

If you are considering Lithium batteries for a cruising sailboat, consider very carefully exactly what it is you are spending all that extra money for. Don’t do it just becasue someone else tells you they are the “best.” Remember, that for a lot of people, the most expensive option must always be the best one… They cost a LOT more than even the very best lead-acid batteries, and you need to be SURE that that premium is worth it for the way you use your batteries. They might be a significant improvement over an oldfashioned flooded lead acid battery, but make the comparision to a modern, carbon foam, sealed valve regulated, battery that cost half as much as the Lithium option and you’ll likely make a good choice.

Usable battery capacity desired 200 A-hrs @24V



Firefly minimum SOC 55%
Firefly Capacity/G31 unit 58.5 A-hrs
Firefly Units Needed 8
Firefly Cost per G31 Unit $512.00
Firefly Total Cost $4096.00
Firefly Cycle Life at DoD  3600
Firefly Battery cost per cycle: $1.14



ReLiion Minimum SOC 30%
ReLiion Capacity/G31 Unit 50 A-hrs
ReLiion Units Needed 6
ReLiion Cost per G31 Unit $1270.00
ReLiion Total Cost $7620.00
ReLiion Cycle Life at DoD 7300
ReLiion Battery cost per cycle: $1.04
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Landed!

We’re back in Annapolis, docked at Jabin’s Yacht Yard after a delightful passage south. We made good speed, and had excellent weather.

One of the trip’s highlights came south of Cape Cod, after we got into warmer water: We set out trolling lines as we motored along in a calm patch. We were about 100 miles off New York City on the edge of the continental shelf where the water drops from about 200 feet deep to over 3000.

Out here you have to watch for the floats that the long line fishermen set over their gear. Mostly they are fishing for tuna and swordfish very deep; 1000 feet, or even more. The lines are set at least overnight, and as long as several days, and when they say “long” lines, they mean it! There can be miles of hooks stretched between floats set every mile or so.

Long line float and radar reflector

These floats consist of a large fender, and a pole with a radar reflector attached. They are not lit, so at night the minimally effective radar reflector is the only way to see them–assuming you have your radar on and properly tuned!

Out here, in deep water, far from land, ANYTHING on the surface of the water attracts fish, and very quickly. In Hawaii there are buoys anchored in the deep water off the islands for the sole reason to attract and concentrate fish. They are locally called Fish Attracting Devices (FADs). Anything floating on the surface works as an FAD from a log to a patch of seaweed, and it does not need to be very big.

As our spread of trolling lures came up to the first of these long line floats, the idea of it possibly being an effective FAD was just beginning to form in my head… Zing! FISH ON!

A mahi-mahi who had been hanging out around a long line float.

We trolled past two floats in the next hour, and picked up a mahi-mahi off each of them. None of the fish were really large, but more than big enough to end up in our freezer.

Fresh off success around the long line floats, we made a small detour off of our straight line course to a permanently moored deep water weather buoy.

Anchored in 1600 feet of water, this large research buoy creates its own ecosystem.

We stopped next to the buoy, and I cast a jig up close, and quickly hooked another mahi-mahi. It is typical for the whole school of mahi-mahi to follow the hooked one right up to the boat, and in this case they did not disappoint. About a half dozen of the brilliently colored fish were swarming around their doomed cousin, but even more amazing, down as deep as we could see (in very clear water!) were hundreds and hundreds of large jacks. We could have caught jacks until our arms fell off. Lucky for them we do not consider them great table fare.

Other fun and exciting events on our passage were seeing an unusual “fog bow” in the dense fog off Nantucket.

Not as colorful as the regular rainbow, the “fogbow” is a bit rarer.

We frequently ran into groups of common dolphin who usually broke off whatever they were doing to ride along with Harmonie. On this trip we also saw a group of the much larger Risso dolphin, but they did not closely interact with the boat.

We’ll be in Annapolis at Burt Jabin’s Yacht Yard for several weeks while we do projects, go to boat shows, take some classes, and attend to other business. If you’re in the neighborhood, give a shout and stop by!

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Fast is Fun

21:00 local, 14 Sept 2019
Lat: 42° 13.4’ N
Lon: 67° 16.1’ W
Weather Clear, wind 16knots, SE
Water temperature 63°F/Air temperature 66°F
Course 253M
Distance from St Peters Canal Entrance: 344 NM
Distance from Delaware Bay Entrance: 409 NM

We just crossed the international border, and are back in the waters of the USA, and moved from Atlantic time back to Eastern time.

We are watching a great example proving that cliche of “the grass always being greener” has a lot of truth to it. Lined up fishing within yards of the Canadian side of the line are Canadian flagged fishing boats, while on the USA side, the American flagged boats are doing exactly the same thing. I am sure each captain is certain in his conviction that there are more fish on the other side!

After motoring last night the wind picked up this morning and we have had another beautiful sailing day running pretty steady at over 8 knots. We were visited by large schools of dolphin, and during one calm spell we stopped and in short order caught a cod and a haddock for the freezer.

The weather forecast continues to look great for the rest of our voyage.

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A fast and fun start!

20:00 local, 13 Sept 2019
Lat: 43 34.3’ N
Lon: 64 42.8’ W
Weather Clear, wind 2 knots, NE
Water temperature 60F/Air temperature 63F
Course 253M
Distance from St Peters Canal Entrance: 205 NM
Distance from Delaware Bay Entrance: 547 NM

Upon leaving the canal at St Peters we were treated to a delightful sail as brisk northwest winds pushed us along on a fast broad reach. For all of the afternoon and night, and much of today we blasted along at speeds from 7.5 to 9.5 knots. Of course all good things must come to an end, and the wind has died to a zephyr, but we made over 25% of our ocean passage in a fast 24 hours.

Our destination is Annapolis, via the Delaware Bay and C&D Canal, and our plan is to go straight on through until we get to the Chesapeake Bay. We are carefully watching the path of the depression that is forecast to become hurricane Humberto. Right now, it is forecast to stay well south of our track, but if that should change, we’ll have many places along the coast we can put in until it is out of the way.

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And we’re off!

Power back on, and we squeezed through the lock with three other boats. Once again, we are out in the ocean, and Harmonie gets to stretch her sea legs. We have a beautiful north northwest wind pushing us on a fast reach southeast to warmer climes!

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Hurry up and wait!

We got down to St Peters without problem, got our provisioning run complete, and have the boat set up and ready for offshore sailing. We are all ready to go… Unfortunately power is out in town again, so the lock is not functional, and the queue of southbound boats waiting to get through is starting to build.

We have enough of a weather window that waiting a day or two isn’t a problem, except it is getting COLD at night!

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On the Move Again.

After a hurricane passes over your boat there is one good result: Your boat is CLEAN. It basically gets a freshwater power wash for hours and hours. Yesterday we spent all day undoing all the things we did to prep the boat for the storm. This morning we pulled up our lines and anchors, and in less than an hour we took the boat from as clean as it has been in months to a filthy muddy mess as all the lines, chains and anchors did their best to move as much lake bottom to the topsides of Harmonie as possible.

A muddy mess!

Under sunny, clear, and chilly sky we sailed south on Bras d’Or Lake. On the shores of the lake we see the first hints of fall color showing in the maple trees. That can only mean one thing: It is time to turn further south before winter arrives.

Fall color starting on the hills.

We are anchored at the southern end of the lake, at the town of St Peters. We tried to do a grocery run today, but the storm still had power out in much of the town so the grocery store was closed. Tomorrow, it is supposed to be open for business again so we can stock up for our coming passage south.

Our weather forecasts suggest that we wait a day here before taking passage through the canal back into the Atlantic. Our plan is to reverse the route we took to get up here two months ago: Leaving from Nova Scotia, straight down the coast to the Delaware River, through the Delaware Chesapeake Canal, then down to Annapolis. A total trip time of about seven days.

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