The Offshore Voyaging Reference Site

Lithium Ion Batteries Explained

There’s a good chance that you are currently sharing the room with a half-dozen or more lithium ion batteries. The computer in front of you has one, your camera has one, your phone has one, the R/C car your kid is racing around your ankles has one. Lithium battery technology is almost everywhere. And, soon, it’ll be coming to a boat near you.

Before we start, let’s (temporarily) forget everything we know from the lead-acid world: charge profiles, cycle life, equalization, voltage setpoints, monitoring, and so on. Lithium is a completely different animal.

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More Articles From Online Book: Electrical Systems For Cruising Boats:

  1. Why Most New-To-Us Boat Electrical Systems Must Be Rebuilt
  2. One Simple Law That Makes Electrical Systems Easy to Understand
  3. How Batteries Charge (Multiple Charging Sources Too)
  4. 5 Safety Tips For Working on Boat DC Electrical Systems
  5. 7 Checks To Stop Our DC Electrical System From Burning Our Boat
  6. Cruising Boat Electrical System Design, Part 1—Loads and Conservation
  7. Cruising Boat Electrical System Design, Part 2—Thinking About Systems
  8. Cruising Boat Electrical System Design, Part 3—Specifying Optimal Battery Bank Size
  9. Balancing Battery Bank and Solar Array Size
  10. The Danger of Voltage Drops From High Current (Amp) Loads
  11. Should Your Boat’s DC Electrical System Be 12 or 24 Volt?—Part 1
  12. Should Your Boat’s DC Electrical System Be 12 or 24 Volt?—Part 2
  13. Battery Bank Separation and Cross-Charging Best Practices
  14. Choosing & Installing Battery Switches
  15. Cross-Bank Battery Charging—Splitters and Relays
  16. Cross-Bank Battery Charging—DC/DC Chargers
  17. 10 Tips To Install An Alternator
  18. Stupid Alternator Regulators Get Smarter…Finally
  19. WakeSpeed WS500—Best Alternator Regulator for Lead Acid¹ and Lithium Batteries
  20. Smart Chargers Are Not That Smart
  21. Replacing Diesel-Generated Electricity With Renewables, Part 1—Loads and Options
  22. Replacing Diesel-Generated Electricity With Renewables, Part 2—Case Studies
  23. Efficient Generator-Based Electrical Systems For Yachts
  24. Battery Bank Size and Generator Run Time, A Case Study
  25. A Simple Way to Decide Between Lithium or Lead-Acid Batteries for a Cruising Boat
  26. Eight Steps to Get Ready For Lithium Batteries
  27. Why Lithium Battery Load Dumps Matter
  28. 8 Tips To Prevent Lithium Battery Black Outs
  29. Building a Seamanlike Lithium Battery System
  30. Lithium Batteries Buyer’s Guide—BMS Requirements
  31. Lithium Batteries Buyer’s Guide—Balancing and Monitoring
  32. Lithium Batteries Buyer’s Guide—Current (Amps) Requirements and Optimal Voltage
  33. Lithium Battery Buyer’s Guide—Fusing
  34. Lithium Buyer’s Guide—Budget: High End System
  35. Lithium Buyer’s Guide—Budget: Economy Options
  36. 11 Steps To Better Lead Acid Battery Life
  37. How Hard Can We Charge Our Lead-Acid Batteries?
  38. How Lead Acid Batteries Get Wrecked and What To Do About It
  39. Equalizing Batteries, The Reality
  40. Renewable Power
  41. Wind Generators
  42. Solar Power
  43. Watt & Sea Hydrogenerator Buyer’s Guide—Cost Performance
  44. Battery Monitors, Part 1—Which Type Is Right For You?
  45. Battery Monitors, Part 2—Recommended Unit
  46. Battery Monitors, Part 3—Calibration and Use
  47. Battery Containment—Part 1
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Interesting post. I have been “noodling” on this same concept for a few months. On thought that you didn’t address is the charge “profile” vs lead/acid. With the more aggressive charging capability I wonder about the need for a separate gen set vs charging off the main engine.

It would seem that a main engine high-capacity alternator could charge lithium ion batteries much quicker. Thus, eliminating the need (advantage) of a slower charging low horsepower gen set.

I’ve just started to play with the math. See this link for some good info on charging acceptance rates ( But, it the math pencils out then the cost savings of eliminating the gen set could more than make up for the additional battery costs.

I’m interested to hear others thoughts on this. I think it could really be one of bigger “game changers” in the yacht industry since roller-furling.

Douglas Pohl

Matt – Deep depth of discharing lead-acid batteries will shorten their life – to extend the lead-acid battery life keep the depth of discharge (DoD) limited to a max of 50% , even less is better.

Lead-acid battery DoD vs Cycles: (lifetime)
DoD Number of cycles
=== ============
80% 100-200
50% 400-600
30% 1000+

LiFePO4 and Ni-Fe cells can both be deeply discharged (80% DoD) with a problem.

LiFePO4 (DoD 80%) 2500-3000 cycles lifetime
Ni-Fe (DoD 80%) 2500-3000 cycles per electrolyte change. 50+ year lifetime

(Check with your battery manufacturer for specific DoD vs Cycle graphs)


Thanks for the reply Matt. Many of the comments below are very valid regarding the dangers, but nothing will change that faster than the entire automotive industry putting big $$$ into these systems. Eventually, the math always wins.


Currently sailing around New Caledonia in the South West Pacific I had to change my dead service batteries recently. I had thought to LFP batteries but eventually decided to stay with Lead batteries (12V-150AH-C10 Gel batteries) for several reasons :
– they are locally available for shore solar grid power supplies ;
– LFP batteries are still not available in the area and all the small islands around ;
– most lithium batteries are classified as dangerous goods and their transportation by airplane is strictly prohibited ;
– transported by ship, as it takes a long time to get them they may arrive dead here (this happened to me with a Torqeedo battery which took six months without any maintenance to arrive from Europe) ;
Maybe the situation will be better in 5 years or more next time I must change my batteries.
Jean-Claude – S/V Bauhinia


This maybe a sweeping statement, but in my experience, only a very small percentage of boaters care about their batteries and charging equipment to the extent that it is all working at 100%. So often do we see bad connections, undersized cabling, non industrial, non robust alternators, output undersized alternators running with special regulators that reduce the amps produced.
LIFEPO4 batteries will stress these systems beyond the limit.
LIFEPO4 batteries, to optimise their fast charging capabilities, require alternators to be at least twice the capacity or maybe even 3 times the capacity currently.
Currently LIFEPO4 systems need you to love batteries nearly more than anything else in the world.
Unless you are one of the few…I would suggest waiting 5 years.


1)- I don’t think that you can make any kind of saving using main engine at full load for lithium-ion batteries charging if you still use classic main diesel + mechanical inverter instead of an adapted genset. To do that you would need an alternator large enough to accept main engine’s full load, which means about 2500 amp. at 12V. for a 40 hp (#30kw…) engine. Cost of this alternator should be substantially more than the cost of an additional 4kw small dedicated diesel + #340 amp. 12V alternator (plus : this dedicated engine could use tax-free diesel…)

2) – This question is very different if you use diesel-electric transmission instead of a classic main diesel + mechanical inverter.
Diesel-electric transmissions without any kind of battery in the way, provide a continuously variable transmission between engine & propeller, and allow to connect efficiently and easily multiple engine to one propeller shaft. Those points are good or very good for motor-sailing because:
– you can install two 20hp engines + alternators instead of one 40hp engine and run on one engine only at a correct load-ratio when motor-sailing instead of using the 40hp engine at much too low load-ratio.
– you can precisely adapt transmission ratio to your motor-sailing needs, including dynamic fine-tuning according to the current wind & sea conditions.
– you can reduce engine size. Engine size is generally decided considering low-speed high-load needs (“bollard pull” requirements…) and high-speed low-load needs (motoring-only required speed in normal wind & sea conditions…). With a continuously variable transmission, those needs can be satisfied with a smaller engine size than when using a classic fixed ratio mechanical transmission, because in this case the transmission ratio will be a very poor compromise between very different needs.

3)- If you have a diesel-electric transmission, you can obtain additional advantages using batteries in the circuit. Those advantages are mainly :
– the capability to use some shore energy (“pluggin capable”…) or green energy (photovoltaic, windmill, sea-energy….) instead of using only diesel.
– the capability to motor quietly (electric-only) in some circumstances (maneuver, low-speed…).
– the capability to be more efficient with diesel-oil & save diesel engine life expectancy, running it part time at full load instead of longer time at limited loads.

I think that diesel-electric transmissions for sailboat aux. propulsion is very promising and is mature enough for educated DIYer (a significant issue is maintenance in current boatyards, so diesel-electric yachts transmissions early-users still need to have serious capabilities to maintain those systems by themselves….).

Introducing batteries and other energy sources in the circuit (shore-energy, green-energy etc….) is not a big issue per itself, but, might be easy or not depending the amount of energy you want to store. If you want only limited quantities (enough to enter or leave harbors..) lead-acid batteries are a reasonable and very mature choice, although heavy and not very efficient.
If you want more energy storage ( several hours at motor-cruising level engine power), you need better technologies than lead-acid. It looks like things are moving rapidly in that field, mainly due to electric cars. Technically correct solution should be available either today or in a very near future. Commercially available packaged solutions for sailing yachts might have to wait a little longer, but I think that those things are not that much complex, and that educated DIYer don’t need to wait for those packaged solutions if they accept to be early-adopters and if they can make most of their maintenance themselves.

Considering fire/explosion risks with non lead-acid batteries, I understand that :
– Apple and Boeing had some recent well-publicized problems with very high-specs batteries
– Tesla seems to have developed volume production without big well-publicized problems, but there is still a slight doubt about 2 recent fire-accidents concerning their cars,
– And that Bollore, in France and Canada, has developed a different (less ambitious ?…) technology (“lithium metal polymer”) with volume production for some time and without any battery-related fire-incident to-date. Those batteries are commercially available.

—> So I am convinced that educated DIYer can install reasonable diesel-electric plugin-capable transmission today, perhaps using Bollore batteries, and that other yachts users will be able to do the same as soon as boat-industrialists, maintenance yards etc. will allow them to do so, which might take “some” time….

John Harries

Hi All,

I really don’t want to go down the long winding path of debating the benefits and drawbacks of diesel electric drive for voyaging sailboats yet again on this post. We have already done that subject to death…several times.

I will move any further posts on diesel electric to the appropriate post on that subject.


John Harries

Hi Matt,

Great post that answers many of the questions I had. I had really hoped that lithium batteries were ready for yacht use since their energy density would solve the problem that we have on “Morgan’s Cloud”, and many other voyagers are struggling with too: our electricity needs have outgrown the space we have for batteries.

Your post makes it clear that we will have to continue as we are by carefully managing lead acid batteries for some years to come since there is absolutely no way that we would install any technology with the inherent dangers, that even Boeing has had trouble managing properly, on our boat.

Bottom line, it’s one thing to experience a “exothermic excursion”—you engineering types have such great euphemisms for things like “you are going to get fried”—in a car, where you simply pull to the side of the road and stop, and quite another to experience the same mid-Atlantic, or even 10 miles off the coast.

Simon Wirth

Hei Matt
This sounds a bit like an emergency eject system would be needed to make them save. Something along the line of the batterie beeing mounted in a colum, say before tha mast built massivle into the boat. If you now make a ventiolation of some kind on top of it, and some form of fast release hatch on the bottom, you could, if done right, “just” pull the handle and the entire thing would dropp out of the boat and away.
Regards Simon

Douglas Pohl

In a nut shell… a LiFePO4 battery bank does not make economic sense in 2014 for my yacht:
1) The Battery Management System (BMS) is expensive ($1500 for a 1000Ah bank) and ‘custom’ electronics are not easily serviceable from a cruising yacht. The reason the BMS is expensive is the current switching relays must be properly sized to handle the large current as a benefit of using LiFePO4 cells;
2) Charging. Several options;
a) Solar with enough wattage for a particular cruising lifestyle with the comforts of refrigeration, freezer, air conditioning etc or
b) Diesel genset; a 100A battery charger would take over 8 hours consuming $5/gal diesel – not economical charging or you should consider two or more 100A chargers in parallel for 200A of charging current but still will require over 4 hours of diesel fuel consumption – still not desireible economics.
c) Underway high-amp alternator(s) as a benefit of motoring. Not a good long term effective charging program with many days spent at anchor. Must look further than just buying expensive batteries when adding new technology – charging is a major fine-tuning how to benefit from using this technology consideration. Solar becomes a good major consideration and expense for a “balanced” electrical system.
3) Alternative to LiFePO4? K.I.S.S.; Wet cell lead-acid still provides the best bang for the buck. Off the shelf lead-acid batteries are available throughout the world with an automotive battery charger to get you back up and charging in a pinch if you have shore-power or a genset. AGM lead-acid batteries are just to expensive in my opinion for the convenience for a label saying “maintenance free”. Many manufacturers say not to equalize AGMs.

For a fraction of the 1000Ah LiFePO4 battery system (80% DoD = 800Ah useable) expense I can totally outfit with like amp-hour usable (@50% DoD) lead-acid batteries (2000Ah bank), including chargers, switches, battery boxes etc AND add solar panels with a MPPT charger. Been there and done it. Love it.

If I was to build a new boat I would strongly consider the bullet proof NiFe (Nickel Iron) Edison Cells because of there 50+ year lifetime with the same or better LiFePO4 80% DoD performance and robustness only requiring the potassium hydroxide (KOH) electrolyte to be changed about every 7-10 years for a like new battery. Sure they are big and bulky but why add lead or steel punchings ballast to trim a new yacht building when you could add beneficial electrical storage capacity with primary solar charging backed up with genset or shore-power which does not need a BMS.

Imagine never having to carry out old batteries nor lug in new batteries – just devise an electrolyte drain and fill system which is like changing the main engine oil. A simple REVERSO like plumbed for your NiFe battery bank – Winner!

Douglas Pohl

Matt et al,
Remember to not discount what was previously stated – displacement boats can benefit from using heavy Ni-Fe cells rather than buying lead or metal punchings for trimming/ballasting a boat with the additional benefit of near bullet proof energy storage from Ni-Fe cells. They do not require a BMS either. If you check further you will see that you cannot hurt Ni-Fe cells by leaving your boat unattended (shame on you) for the winter months. Just re-charge and discharge cycle (80% DoD recommended) a few times and they will be back up and running to normal. Remember you only need to change the KOH electrolyte every 7-10 years to fully restore full storage capacity – the Ni-Fe plates do not wear-out (chemical corrode) like lead-acid plates, it is the electrolyte that looses its ability to store energy over time. Ni-Fe cells are likewise one of the few cells that should it become necessary to replace a cell in a bank you can do it without risking the imbalance preventing traditional cell/battery replacements in a bank. Like you mentioned, when considering life-cycle why not also consider the boat’s systems such that a steel boat has a life of over 50+ years, a solar array for energy production 25+ years and with Ni-Fe batteries 50+ years. That said, Ni-Fe cells moves to the top of the list when life-cycle is factored in to the overall decision making process – there are no negatives except size and weight which can be turned into a benefit as mentioned above – but will John make the decision to use Ni-Fe cells for the Adventure 40? Wait and see…


1) I understand that Boeing had serious overheating problems on lithium batteries while Bolloré had none. Then you may appreciate that it is a difficult stuff because “even Boeing” had problem or that it is an easy stuff because low-brow Bolloré in its very provincial Brittany never experienced such kind of problems. Personally I think that Boeing had many different engineering problems lately, apart from those related to their lithium batteries, and I don’t think that the fact that Boeing did have significant problems with : wing-stringers, brakes, fuel leaks, engine-icing, toilets etc…. proves much more than the fact that Boeing current engineering expertise level is probably lower than it used to be.

2) Personally, I think that lithium batteries in yachts are probably an overkill today, if used only for auxiliaries. This might change in the next 5 to 10 years.
They make much more sense if used also for propulsion, and their appearance and recent development make diesel electric transmission for sailing yacht much more interesting than 10 years ago.


Obviously one does not want to let any battery short. It is, however, a serious issue with these batteries as they can reach injurious (to humans), if not flammable temperatures very rapidly. I have personal experience with two folks who shoved a lithium powered handheld VHF in their pocket. One radio shorted on the change in the sailor’s pocket. The other shorted on a multitool. One received third and the second third degree burns. The one with change had her high-tech fabric melt to her skin and required reconstructive surgery.

Tape over at least one charging contact, if not both.

Eric Klem

Hi Matt,

Thank you for the article, I think that your conclusions make a lot of practical sense. For the time being, I think that the best way to save space in batteries is probably to improve the insulation on the fridge and change to LED lights.

One of the most incredible fires that I have ever witnessed was an early lithium ion powered electric car at Tour de Sol having a thermal runaway caused by someone dropping a wrench when connecting a battery cable. I was asleep several hundred feet away and boy did I wake up quickly. I suspect that we will see safe installations of new battery technologies in boats in the not too distant future but they will either need to be non user serviceable or have a much higher level of protection. Dipping everything but the very end of the wrenches in liquid electrical tape is only the tip of the iceberg when it comes to safety with these systems.


richard e. stanard (s/v lakota)

fascinating (really) although i seriously doubt i will need much more knowledge than this post re such cutting edge technology…still this will keep me at least conversant with it

totally off the subject, but in keeping with your brit background i am wondering if you are catching any of the downton abbey series on pbs ? i think the butler character, carson, completely steals the show although the dowager character played by maggie smith is a close second…i find the segments quite engrossing in spite of not being all that big on spending time with the tube…cheers from tampa bay


Hi Matt
Do you know why NiCd batteries are not used as house batteries on boats? They seem to be rugged, save and have a comparably high energy density (at least compared to lead acid).

Jean-Claude GUILLOT

In the 1960 to 1980 years I was an helicopter pilot in the French Naval Aviation and we had big 24V Ni-Cad batteries on our flying machines to start our around 1000HP turboplants, which took around 1000A during 30s to 1mn to light on and run.
I remember that every few months the Ni-Cad batteries were sent to a workshop in the Naval station where they followed a very precise procedure of unloading and loading in order to last for years.
I think we are unable to apply such procedures aboard our sailboats nor find a boatyard anywhere in the world with the necessary tools to maintain Ni-Cad batteries.
JC Guillot – S/V Bauhinia

Marc Dacey

Well, Matt, when I read “an unstoppable, self-sustaining thermal runaway that culminates in a ball of 600-plus degree hellfire”, I thought: there’s an engineer with a knack for descriptive writing.

While I can see limited applications in light boats, race boats, boats with limited space, or boats that have unusual power demands, I see lithium batteries in the typical “house bank” formats as solutions seeking problems. I’m not a Luddite; I can certainly see the very low self-discharge rate of AGMs, for instance, as making sense for start and windlass batteries. But sad old flooded lead batteries, heavy and sensitive to discharges below 50%, still make sense for the typical boat owner, particularly if you can keep them secured on the centerline and have access to regularly service and maintain them. They are “worse” in the sense that a car with a manual transmission is worse than an automatic or CVT transmission…but I like manual transmissions because I can start them if the battery’s flat and I’m at the top of a hill. The limitations of flooded batteries are well understood, and I find it easier in certain respects to create a variety of charging sources (alternator, solar, wind, portable genset) while keeping a realistic energy budget.

The idea of the BPS being critical to the otherwise dangerous/damaging states of over/undercharging of lithium seems like an extra bit of complexity to me. At the same time, I appreciate the advantages of lithium’s energy density in handheld devices and phones. Just as clearly, they make outboards like the Torqueedo possible. But those are items I can chuck in the drink if they “go hellfire”. Even with a suitcase-sized housebank, I suspect I can’t dispose of that safely if it goes bad.

By contrast, it’s both harder to blow up one’s flooded batteries, the monitoring of their state of charge (and the soundness of connections/crimping) and the “fallout” is easier to contain.

Like others, maybe one day, but not yet. A cruising boat doesn’t necessarily require the advantages of large-capacity lithium batteries that a Tesla does. I have a brother-in-law who owns a Tesla S here in Ontario. I should ask him how it’s doing in the bitter cold winter we’re having.

John Kettlewell

My bottom line is that when something goes wrong, and it always does eventually, you need to be able to fix or jury rig something no matter where you are in the world. I can always count on there being some type of regular old lead-acid battery available anywhere there are people in the world. Also, I know from experience that even if all else fails in the electrical system I can bypass almost everything and still get usable power from the old ones, and recharge them even without monitors, smart this and that, and BPS’s or other acronyms. I lived aboard a cat for 12 years and I totally abused my batteries with no monitors, no charge regulation, nothing but some wind and solar, an outboard with a 10-amp charger, and an analog volt meter. I connected and disconnected various charge sources as needed. Cheapest electrical system I ever had and I got great use out of it.

Mark Morwood

I agree with the assertion that Lithium Ion batteries do not yet make sense on the average cruising boat on a cost/benefit basis. However, on boats which are more sensitive to weight (most catamarans) the significant weight reduction can make them much more attractive. Though I would definitely agree they are still in early adopter territory, and if you are not comfortable with the details of the system, it will be hard to find skilled assistance outside of some large yachting centers.

From what I am hearing from a number of catamaran owners who have relatively recently installed LiFePO4 based systems replacing Lead Acid batteries, you can achieve quite significant weight savings and improved performance. One of their findings has been that they need less than 1/2 the stated AH to get equivalent or better performance in practice. This is because of the high acceptance rates of Li batteries up to 100% as opposed to the tapered acceptance rates of lead acid batteries above about 75%. In effect they found for their lead acid batteries they were in practice only using them between 50% and 80% of state capacity because of the time to recharge lead acids to 100%, whereas the Li batteries were usable from 20% to 100% of stated capacity. The net result for one boat was they replaced 1000Ah of AGM lead acid batteries (650lbs) with 400Ah Li batteries (110lbs) and saw an almost doubling in usable AH.

Geir Ove

Was also looking at al the new types of Batts when we did some adjustments to our Cat.
But i don’t like the Fire hazard, so we went for the heavy Trojan, but found some caps to put on the top , that hopefully will condensate the water, and make it go back in the batts, We will se how it works as our sailing seasons starts.
there are some pictures on our Blogg.
But i guess next time, we hope that there is some new once with out the fire hazard. i don’t like that in a boat.

Douglas Pohl

Please advise battery condenser cap manufacturer and/or website.
Looks interesting but cannot read details with used picture resolution.


Hi Guys,
very interesting stuff indeed. The thread is a little older but stumbled over an interesting test article from a motor boater, who assembled a LiFePO4 housebank and tested it thoroughly. Apparently the guy knows what he is doing. Here the link:
The cost comparison he gives for a DIY bank is interesting as well.

Jim Kevern

Lot’s been happening since this thread started. Perhaps time for Matt to give an update given the postings of Rod Collins (Main Sail), Stan Honey, and S/V Entropy. I’ll be replacing my four 8D’s with LiFePO4 this summer.

John Harries

Hi Jim,

Nothing has happened with Lithium batteries that changes the fundamentals in Matt’s article. The bottom line is that while Lithium has great potential it’s still a technology for well informed and qualified early innovators (like the ones you mention), who are willing to start from scratch to install special safety and charging systems.

I’m looking at new batteries for MC as I write, but after a good look at Lithium I have concluded that the benefits, at least for me, did not warrant the expense, potential dangers, and complication.

My thinking on such things is summed up in this article:


Hi Matt and John,

I found a quite interesting and obviously profoundly based article on LiFePO4 here: . As has already been mentioned above the author insists that Li batteries are never to be just dropped in but it needs to be treated as a complete system.
Regarding a Battery Management System, most LFP batteries have their BMS already built in – e.g. the products Relion offers (no, I don’t have any affiliation with them, did just some internet research besides Mastervolt 😉 ).

That said I still believe that LFP batteries can offer substantial savings once the complete system has been scaled correctly. Take the above example of usable 800Ah, with above mentioned Relion this could be achied with e.g. 5x200Ah with a total cost of 11,987.80 – oops, that’s a lot. What you get is a usable lifespan of approx. 2200 full cycles, lets make this about 7 years (assumed 300 cycles/year), which amounts 1,712.54 per year.
Now build the same with Lead Acid blocks, 2000 Ah to have them not discharged below 50%. We might need e.g. 10 Reliant J185-AGM for this task, as I couldn’t find a conveniently sized flooded model. This sums up to 4,639,70, roughly 39%, or a bit more than a third, of the cost of LFP. Assuming 300 cycles/year as above this battery bank will not live for two years, as usually 4-500 DoD cycles are assumed max for AGM. Lets be fair and assume 2 years lifespan, then the yearly cost of battery is 2,319.85.

A difference of 607,31 per year. Or 4,251.17 for the seven years you might run your first LFP installation. Quite a lot of beer that can be kept cool.

Lets again assume you pour in 2,000.- for the first time to build a good, reliable LFP system, you will still end up saving 2+k for the first LFP set. Not to talk about other interesting benefits, such as having a Peukert constant of almost 1.0 which means the capacity doesn’t degrade with growing loads. Or the fact that you can happily forget about battery equalizing or reconditioning. Or the additional space you get by having only 5 batteries instead of 10.

Jim Kevern

It appears to me from my research that the LiFePO4 (lithium iron phosphate) variant has become more or less the defacto standard for marine house battery bank purposes. One can get expensive turnkey products from the likes of Victron, or can DIY for significantly less. Pointing out issues with other chemistries like the Boeing batteries is irrelevant, because it’s not at all the same technology. There are several Youtube videos of people abusing LiFePO4 and it can be done, but you have to try really really hard. And contrary to the assertion that they are only available in small cells, prismatic cells can be obtained up to at least 700 aHr, and I believe even higher.
One post mentions expensive BMS (what Matt calls BPS) costs upwards of $1500, yet the implementations of MainSail, Stan Honey, and S/V Entropy all use the HousePower BMS that runs around $70. No, it doesn’t record voltage readings – there’s another $30 device many folks use from China that will do that. In my case, I’m in incurable do-it-yourselfer so I will use a $13 Arduino with some resistors for voltage dividers (Arduino can only measure voltages up to 5V. I might add a Raspberry Pi or Udoo for data recording, but I’ll do that because I want to, not because I have to.
I will do this because I have a new boat with cheap Chinese 8D’s that will need to be replaced sometime and I’d rather not have that happen in the middle of the season when I’m down island. The LiFePO4 has too many advantages for me to pass up as they more closely match the kind of use on my boat. Thrive on (rather than killed by) partial state of charge, efficiently use my 4kW DC genset (or my two 120 amp alternators while motoring), life cycles in the thousands rather than hundreds. That I’ll also save weight and maybe some space is secondary. I know I run the risk of something going wrong, but for me the benefits outweigh the risks. Hope I’ll be man enough to post to let you know if that happens:-)
All that said, Rod Collins (MainSail) is right, there is no such thing as a drop in replacement. In my case not only do I have to have relays to cut field voltage to the alternator before a High Voltage Cutoff occurs, but I need to stop the genset in the unlikely event I leave it running too long. And I need to shut off the diesel heater (cabin+hot water) by it’s switch so it goes through it’s normal cool down sequence. (Yes, the boat is tricked out but at our age we no longer are interested in camping.) I fear it will be some time before the run of the mill marine electricians can be assumed to get it right, but that’s an industry problem, not a LiFePO4 issue.

John Harries

Hi Jim,

I guess I can’t really see the logic of claiming that “LiFePO4 (lithium iron phosphate) variant has become more or less the defacto standard for marine house battery bank purposes” when only a tiny percentage of boats use them and further many of those users are very smart technicians and engineers that have designed and built their own systems from scratch.

No one here, not Matt, or me, is saying that Lithium batteries don’t have many advantages, we know they do. Heck Matt has built Lithium battery systems from scratch, he knows of what he speaks.

The larger question is whether this technology is ready for the general non-tech user at a price that makes sense. This is a question that each of us must answer for ourselves.

Jim Kevern

Sorry John, I meant that it seems for those who choose to go lithium for house banks (or DIY electric vehicles) LiFePO4 is the chemistry of choice. I haven’t seen anyone advocating lithium cobalt, yet that’s the first thing people bring up.
I agree with the conclusions, it still is for early adopters so by definition doesn’t meet your 20 year criterion. I probably have lots of other stuff on my boat that fails that test.

John Harries

Hi Jim,

Yes, each to their own and there is no question that LiFePO4 is a compelling technology. My guess is that most everyone will be using something like it within 10 years. I even looked at it for our new battery bank, but decided that the cost and complexity trade offs did not work for me.

Prem Lee Barbosa

It’s been almost ten years, and I don’t see many LFP batteries in house banks. I see tons of AGM though,
I work on yachts in a shipyard in South Florida.


Thank you John and Matt for this interesting topic. I was very interested in replacing my large 10 HD8 battereies with the Revision type units. Started reading your comments and learned about Nickel- Iron cells and kind of decided on these units, but am not sure if the can be used for starting main engines, now powered by 2 HD8 in series to provide the 24V. I usually always have all the batteries tied together when cruising. Do you advise to get the same amps as the present situation?
Many thanks,

John Harries

Hi Rene,

I don’t know anything about Nickel/Iron batteries, but, if it were me, I would not venture off into battery types that don’t have a track record on boats. That said, if you want to experiment with something other than conventional lead/acid (liquid, gell or AGM) have a look at Carbon Foam batteries. That said, do make sure that you design your system so it’s fault tolerant:


Thank you John, much appreciated.

Jan Tore Berg

In recent years Norway has become one of the main markets for electric cars . Like any other cars they have their accidents , and with Norwegian costs and salaries it doesn’t take much to declare them a total write-off . Apparantly , the battery pack is more solid than the car in these situations . In Grimstad there is an enterprising guy who is reusing these cells to build 24V batteries which suits me just fine . Since he is doing this in-house you may specify the capacity you want and to a certain extent outside dimension and form . Last summer I bought a LiFePO4 of 200Ah/24V . This now sits in a battery box that was previously occupied by two lead 110Ah/12V batteries . The weight is also similar – 52kg .The cost ? Including BMS less than the eight 110Ah/12V AGMs it replaced . A little less capacity , but close . Anyway , there is now lots of space for additional LiFePO4 batteries .
I already had a high-end Victron charger so charging by shore-power is OK . Now I have to change the MPPT controller for the solar panels . Guess I will also have to replace the alternator on the engine as well .
As I said , I bought this battery last summer so not much experience with it so far . The only thing I can say is that it is certainly charging fast – if shore-power is up to it .

John Harries

Hi Jan Tore,

Thanks for the report on that. While I’m still not a big fan of Lithium on a boat, I’m certainly interested in how this works out, so it will be good to hear from you again when you have used them for a while.

By the way, if your alternator has an external regulator you should be able to keep it and just replace the regulator.

Jan Tore Berg

Hi John
Thanks for taking an interest as this is my first posting on this forum . Haveing known about it ever since you and your wife replaced John A with the Norwegian Cruising Guide , I finally joined . Unfortunately my alternator has an internal regulator . By the way , the engine is a Perkins 4236 produced in 1978 rated 62HK at 2200 rpm . Swings a fixed propeller thru a Velvet Drive . Just to say that I like your engine update .
As for the battery – recycling batteries is rather “green” wouldn’t you say ? And I really enjoy your society and forum .

Philippe Meloni

I just found this information, sorry, just in french!
But maybe it worth it.
a new lithium battery with an internal BMS (Battery Management System)
No need to change anything, half the weight, you can use it from 100% to 0 without voltage fluctuation. Can charge fast, empty fast. 4000 Cycles
made for marine used.
Not free, but if this battery act as promised, I may worst it 🙂

Have a great day!

John Harries

Hi Philippe,

That’s interesting. That said, it looks to me as if the unit is built from a bunch of small cells and I can’t see any evidence of fire containment, so I’m not sure this changes much.

Also, a built in BMS does not solve all the issuers since there are still things like what happens to the alternator diodes when the BMS decides it’s had enough. In fact, as far as I can see, a built in BMS really does not make a difference to the complication issues. All that changes is that the BMS is inside the case instead of outside. To build a truly fail safe system you will still need the added relays etc.

Thomas Nygaard

Makspower in Norway has sold hundreds of these batteries to boats, mobile homes etc, the last couple of years with no issue with alt diodes burnt as far as I know. I think what happens when the batteries have had enough charge is that the built in BMS bleeds off a small current load anyway, doesn’t go to zero. Regarding fire containment this might be a valid point, however Victron, Mastervolt and my Genasuns seem to come in plastic housings as well, or at best aluminium? Anyway, why you still think relays are needed is a mystery to me, I have first hand experience with two boats with these batteries, definitely no external relays. There are solid state relays (FETs) in each battery.

John Harries

Hi Thomas,

I think I have pretty good reasons for the relays and other external fail safe circuitry, and so do both Victron and Mastervolt. That said, I really don’t want to get into a long and detailed debate with you on this.

As I said in the post, if others wish to use Lithium at this point, I’m just fine with that, but I’m not going to use them and I’m not going to recommend them for the non-technical. I have stated my reasons in the above post, and, to date, have heard nothing that changes my thinking.

You disagree, and that’s just fine.

Perhaps we could leave it at that.

Thomas Nygaard


Ok, fine. I just think it’s a pity your otherwise excellent survey of available battery types don’t include a mentioning of this new breed of lithium ones. They offer all the user benefits of those from Victron, MV etc. at half the cost per kWh, and offer a drop-in installation, so for these appealing reasons is rapidly becoming the type of choice for a large number of boat owners in Europe (including “non-techie” ones) who are replacing worn out lead acid types. This is a fact. I’ve heard of no instances of fires or burnt alternator diodes, the only issue is that just as with other batteries with a high charge acceptance rate, they can fry a standard automobile style alternator because it easily gets overheated.

John Harries

Hi Thomas,

That’s where we differ, I don’t see these units as drop in replacements for an offshore cruising boat and certainly not for the non-technical. As I said, moving the BMS into the battery case is just packaging, it changes nothing that I have said in the above post.

I guess we will need to agree to disagree.

John Harries

Hi Matt,

Thanks for tidying this up.

Philip Wilkie


An old thread, but I have a useful update. As mentioned above I could never quite bring myself to spend a bunch of money on battery tech that I really didn’t have much enthusiasm for. FLA nope, LiFeOP nope, NiFE …sort of but ultimately still too heavy … really leaving the Firefly Carbon Foam AGMs as the only contender standing. Until now.

Being in Australia obtaining the Firefly’s was pretty much impossible, so I kept on looking. The game changer is a relatively recent chemistry called Lithium Titanate. (Actually it’s been around since the 80’s but worthwhile products are quite recent.)

The positive features are:

1. Extreme thermal stability; no realistic chance of fire or runaway, significantly better than LiFePO4 even
2. Insanely high charge acceptance and discharge rates up to 10C!
3. 100% DOD for 10,000 or more cycles; a 30 year life span is highly realistic
4. Wide termperature operating range; no restriction on charge temperatures
5. Exceedingly low internal resistance, usually under a milliohm
6. Exceptional charge efficiency
7. Much less vulnerable to over and undercharge damage, although a BMS is still required
8. Very low maintenance, just keep the terminals clean

All this looks a lot more robust than LiFePO4. People report that they’ve accidentally discharged them to zero volts and overvolt to 3.6v and the cell has recovered. Not good practice of course, but this factor alone dramatically lowers this risk profile using them in blue water marine applications.

The only drawback is the chemistry yields 2.3v instead of the typical 3.2v of LiFePO4. Given they weigh much the same per Ah this means their energy density in kWh/kg is somewhat worse. But for a boat this is still way better than Lead Acids and well within the acceptable range. Typically a 12v 400AH bank (that has the same effective capacity of 1200 AH of Lead Acid) will weigh around 75kg. To achieve this I need around 60 off these:

Importing this bank into Australia, including freight and customs will cost something in the order of A$4k, leaving me the task to integrate the cells into a battery bank and add a BMS. The arrangement will be 5P6S in two banks of 12v 200AH, each with an independent BMS and Battery Monitor, for a total of around A$5k.

Given this bank could easily sustain currents up to 4000A for almost 10 minutes, and short circuit fault currents way higher than this, rock solid wiring and fuse design (Class T’s) will be mandatory.

LTO doesn’t pass the ‘must be in common use for 20 years’ sniff test, but given my technical background and the degree of confidence I have in this chemistry, I’m willing to write a cheque on it. Haven’t placed the order yet, but I’ll update if and when I find out more.



John Harries

Hi Philip,

That sounds interesting. If you go that way, please tell us how it works out.

Note to others: In my opinion this kind of DIY is only for people who have a high degree of understanding of electricity and relevant experience. The very benefits that Philip explains so well, like very low internal resistance, makes just the process of connecting 60 of these cells a potentially dangerous process—don’t try this at home unless you really know what you are doing.

See this article for more:

Philip Wilkie


Just a quick update. After many delays and distractions I’ve finally gotten the 6P11S LTO 24v 240AH bank I described above built and being charged as I type.

It looks good and I’m very pleased with the equalising and protection design that I finally arrived at.

If you like I can email some pics and details when I’ve put it all through full testing.


John Harries

Hi Philip,

Yes, I will be interested in seeing what you have put together, so by all means send it along. That said I probably won’t write about it because, as I say above, this kind of DIY is not something I want to encourage people without deep electrical training to get involved in. And those that have the training and understanding can do this stuff without my help.

Galen Krokum


I am very interested in the LTO battery technology and your project. Would you be willing to email me detailed plans of your project, where you sourced your parts from and how you put together the battery packs?

My email is

Galen Krokum

Prem Lee Barbosa

Howdy Philip from 2024! how’s this going?