Lithium Ion Batteries for Boating

Tahina's existing battery bank

Tahina's existing battery bank

Electric power is a very important part of our lives on Tahina. It is what gives us a convenient lifestyle not unlike what we were used to before we began traveling around the world and living on the water. We need power continuously for our refrigerator and freezer which stores our food. For basic food preparation – microwave, blender, etc. We also need it for our electronic toys that enable us to document and share our experiences (computers and cameras), and for our entertainment (computers, TV, e-books). We need it for our lights at night (cabin lights, flashlights). And, we need power for many necessities for running the boat – fresh water maker, electric winches, navigation lights, electric instruments, chart plotter, GPS, etc. We even have AC/heat available if we need it – although they require the use of the generator or shore power.

We have been using a 735 amp hours (12V) battery bank which lets us operate most of our electric needs without requiring the use of our diesel generator for a couple of days at a time. We have solar panels which help add a few amps back into the system every day. When we need to use the more power hungry items (like the microwave, air conditioners) we have to use the generator.

Our current main battery bank (shown above) is showing signs they need to be replaced. When we first went to buy our boat in 2008, I was interested whether new Lithium Ion batteries used for electric cars were available yet for boats. [UPDATE 6PM] The particular version we are looking at are Lithium Yttrium Iron Phosphate which are particularly safe – with almost no risk from fire, or exploding like earlier Lithium-based batteries. These batteries (like the ones in your laptop) have fantastic qualities for our needs. They can be charged much faster, they can be deep cycled (used) to more than twice the amount of typical marine batteries, and they can be cycled many more times than standard batteries (so they will last longer). Not only that, but the batteries take up far less space, and weigh much less than traditional batteries. Weight is a big factor for sailing catamarans. In 2008, the only Lithium Ion batteries on the market were prohibitively expensive for marine applications. At that time, I got quotes for more than 300% the going rate for high-end traditional batteries (AGM).

Lithium Ion bank on s/v Sirius

Lithium Ion bank on s/v Sirius

When we heard about Tahina’s sister boat s/v Sirius in New Zealand, I was excited to learn that her new owner Mike had recently purchased Lithium Ion batteries. He told me that the price of the batteries are much more reasonable now. When we were in Fiji, I actually had a chance to see his installation as shown in this photo. Notice how much less space they take in the same location under our salon couch seats. Now that our current batteries are going bad, I’m in the process of getting a quote from the same New Zealand outfit that delivered the batteries for Sirius.

Here’s a summary of the benefits to the Lithium Ion battery bank of 600 amp hours we are looking to purchase:

  • The new batteries will take up about 1/4th the space of the originals
  • They weigh over 200 pounds less than our current batteries. This benefit is especially beneficial to catamarans which are weight sensitive (effects sailing performance).
  • Although fewer total amp hours than our current bank we will get more useful amp hours. We will get over 400 amp hours of usable power for each cycle (since we can use them down to 30% of remaining charge). With our current battery bank we would only use about 200 amp hours, because those batteries could only go down to about 75% (i.e. only 25% of the power) of their rated amount (without damaging life cycles and our voltage would go down too far – below 12 volts).
  • The lithium batteries hold a higher voltage under load than the regular batteries. They maintain that voltage even as they are discharged. Sirius now sees 13+ volts all the way until it is time to recharge the system. That means your devices are all happy.
  • By using “only” 70% of the power, the new batteries are rated to 7000 to 10,000 cycles. This is more than twice our current batteries. If the batteries actually last that long, we recover far more than our investment.
  • The new batteries can be charged a much higher rate. They can handle up to 300 amps of charging. And, the absorption period for topping off the batteries is correspondingly higher as well. This means the total time for us to re-charge the system is much less resulting in less diesel fuel being used to charge.

The new batteries will be more expensive than our last set. However, only about 25% more expensive. And, the prices are still coming down for the Lithium batteries. In my estimation, we will easily recover the extra expense. First, by saving diesel fuel since the system will recharge faster, and we will have to charge less often (we’ll probably recover the extra cost in the first year alone from that factor). Second, because they are rated to last more than twice as long as our existing bank.

The new bank can operate with our existing charger and charge controllers. However, we will need to buy a new monitoring system since you can’t tell as easily how deep they are discharged based on the voltage. This adds another few hundred dollars to the purchase, but is worth it to help protect the investment.

As with any decision, there are some risks involved. The biggest risk is that this technology hasn’t been used much in boating applications. However, the fact that it has been used for millions of cars and other electronic devices reduces that risk. We won’t know whether the batteries will reach their life cycle estimate because no one has had these new models long enough. We similarly won’t know whether the company the batteries are coming from will honor warranty issues. Hopefully that risk won’t be a factor, but if it is, the fact I am a widely read technology writer might help. And, finally of course, we are spending more than traditional batteries would cost. However, as a technologist, I’m willing to take that risk for what I feel is a superior technology.

This is the next major advancement in battery power for boating. I think it will improve the quality of our life on board, and provide us with a reliable and improved power system. If not, we’ll have something else to write about on the blog. 🙂

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20 Responses to Lithium Ion Batteries for Boating

  1. Ben Campbell says:

    I wish I had thought of this when going to AGMs from my original wet-cell batteries a while back. How will they behave if they get flooded with salt water?

    • Frank Taylor says:

      I haven’t asked about salt water since in our boat it is extremely unlikely to happen. However, I don’t think they would be at any more risk than regular batteries except the casing is metal instead of plastic so they are more likely to be subject to corrosion.

  2. Steve May S/V Endless Summer says:

    Hi Frank,
    Thanks for writing about this. I need to replace my AGMs now too. I have a true charge charging unit. I don’t think it can do any fancy charging. It has three settings. Lead, AGM, and something else. How will you set up your system to charge your new batteries? And what will you use to measure the discharge so that you know when they need a charge?

    We are currently in Palau after sailing OZ to New Guinea over the last few months. Enjoy OZ!!


    • Frank Taylor says:

      Hi Steve, thanks for commenting! Karen and I have been following your blog, so we knew about your travels. We will be using our existing charge controllers (both solar and electric) and monitoring system. The charge controllers should work fine with the right parameters. The trick is the monitoring. Our source has a new monitoring system that will do a more accurate job of monitoring the new batteries, but it’s not yet ready for shipping. We will buy that when it’s available – and they will extend our warranty on the batteries out to 10 years when we get it. Will send you an E-mail with more details.

  3. nanag says:

    This sounds just like what I need for my cell phone…since here in the mountains it is constantly searching for service, the battery runs down in just a few hours!!!! (Of course you realize I am just kidding…just wishful thinking) I love both of you and miss you very much.

  4. Will says:

    Hi Frank,
    I’m on a dutch barge (live-aboard) and our batteries need changing so I’m thinking about LiFePo4 batteries. I was wondering how you’d got on with them so far?
    Could you send me a link to the company you used?
    Did you get a monitor yet? I’d be wary of getting a system which I couldn’t monitor…


  5. I read with much interest your experience with your LI batteries. I recently decommisioned my old perkins diesel engine in favor of electric propulsion on my 20,000 pound Gulfstar sailmaster 39. The key to the success of my electric propulsion is LI technology. The system pushes me at hull speed and in addition to that, it regenerates my batteries while sailing, at up to 540 watts. This eliminates the need for solar or wind generator ( allthough I will be installing a generator for our blue water passages, just in case) and the spinning prop only slows boat speed by about .5 knot, but the BEST part of the system is that it is QUIET, in fact I sometimes dont know the prop is spinning unless I look at my meters. It seems that technology advancement has finally begun to make sailing more “green”, and less dependant on fossil fuels, doing our parts to help save the oceans.

    Cooper Anderson
    S/V Panormos

    • Frank Taylor says:

      @Cooper: great to hear you have the newer battery technology. I’ve heard of others using the newer battery technology for electric propulsion, and I’m sure it is a huge improvement over older battery tech. The nice thing is that you can charge them at a much higher amperage rate to get them topped off quicker, which means less fuel. That, combined with the lighter weight per AH, means you can have a bigger bank for less cost. It makes more sense now than ever before to have electric propulsion. I just hope someone comes up with a well-engineered system and they become popular enough to bring the cost down.

    • Dennis Templeton says:

      I’d be very interested in learning more about your electric propulsion refit. There are a lot of dubious claims but few reports from people who have lived it. Do you have a link or writeup?

      • Hi Dennis,
        Sorry for such a delayed response. I am extremely happy with my electric propulsion units. There have been a couple hiccups, but I am happy to report that the system is running even better than advertised. The two electric motors I have on the boat give me the equal of a 45 HP diesel motor and pushes Panormos about 6.5 – 7 knots at full throttle. I could get more speed with a few modifications, but to be honest, I will never use it. I did install a diesel generator for emergency backup in case I would need to “motor” my way out of any situation that might potentially drain my battery bank entirely. I took her out 175 miles into the pacific, motoring the whole way before needing to top off batteries, so my range is good if your not in a hurry. If I can share anymore information please let me know.
        S/V Panormos

  6. Jon D says:

    Hi Frank
    Just what we (and the cruising fraternity ) needs….better battery technology.
    I was very interested to read about your brave decision to try the Li batteries aboard and I am keen to hear of your results so far. You seem to be a good number cruncher, quoting 25% cost increase for 7000 cycles, and even accepting that a newer battery monitor was required for this newer technology. I am interested to see how the metal case has weathered so far. Why not use a plastic/grp case?? If LI eats it, try aluminium?
    We own a Leopard 45 and intend to follow your tracks someday – our boats have very similar designs to the extent that either Lavranos or Morelli were watchhing each others products! Only they know.
    I do like your bridgedeck clearance though – ours slams like a jackhammer in the carib shortwave chop.
    Many more questions but lets solve the battery issue first!
    Cheers and fairwinds to you and Karen.
    Jon and Tina
    ps. how did LiFePo4 progress with his Dutch barge??

    • Frank Taylor says:

      @Jon D: Thanks for your interest. The batteries are working FANtastic so far! The new solar controller I got over the holidays has exceeded expectations (read here for more details: ). The extra power in the batteries allows me to run more things. I can even run our 30 amp water maker while under sail when I don’t want to hear engine noises. Even at those load levels it stays above 13 volts! I’m definitely using less diesel for power generation and recharging. Plus, I’m using the sun more. The casing on the batteries are not metal, there is just a stainless steel set of bands that go around the casings to make the cells into one large battery unit.

  7. Hi Frank, I am wondering if you can tell me which battery company you went with ? I am going to be combining my house and propulsion banks this spring, so that they are all LI.


  8. Jesse B says:

    We are building a new catamaran as a “smart boat” in France this year, and we are fitting a set of L-I batteries that look identical to the ones in your picture. We are happy with all the figures we’ve seen so far, but I have one question that has been weighing on my mind. Does anyone know what happens to L-I batteries in a lightning strike? I was hit twice on the first boat I lived on (Florida thunderstorms) and the old lead/acid batts were fine. I know in some cases L-I batts have been known to catch fire or explode when overcharged or shorted – Anyone have any experience with this? (email me at

    • Frank Taylor says:

      @Jesse B: I do not have any specific data for lightning. It is an interesting question. However, I do know that the batteries we have were tested for military applications to insure they do not catch fire during explosions or artillery fire. The stabilizing element of Yttrium in these batteries is intended to reduce the risk of fire from the highly volatile Lithium element.

  9. Mark Bradley says:


    I haven’t read any of your posts yet, sorry if you have covered this elsewhere……do you know the more common voltage configurations for dc (reverse induction) motors – I have heard 72 volts for vessels needing 20 – 25 HP propulsion, 144 volts for larger motors (I could squeak by with 25). What are considerations for larger voltage applications (controllers, switching, etc). Our Charger / Inverter (outback) is great but I don’t know if it can charge the newer generation Batteries (hope so – keeping as many options for 12 volt (110) would be ideal). Several factors are floating around – we are rebuilding diesel tanks – I may go with less capacity for fuel and more for batteries – going solar is still the plan (charging from propeller underway is great, but not when you are just hanging out at anchor for weeks).


  10. Minko Sotirov says:

    Hi Frank,

    I came to your blog by chance in a search for Li ion batteries for my boat Arabella. She is a Bavaria 46 Cruiser and I bought her last year second hand. It turns out my batteries need replacement and I am quite in the woods what to do – stay with the old lead-acid type (cheap to buy), go to Gel (rather expensive) or go directly to Li-ion (very, very expensive)? Actually I did not expect that this problem would be so complicated and would need so much effort – both in research and in execution. It turns out it will be a matter of compromise as usuall. But as we say here in my home country Bulgaria – there is no such thing as “full” happiness 🙂 🙂 🙂

    Anyway, my question to you is are you happy with your Li-ion batteries which you have been using for 3-4 years now? How did they behave during your amazing expedition around the globe?

    Finally, I really envy you for the fantastic trip, for the amazing places you’ve been to and for the courage to undertake it. I hope that beginning next year when I retire me and my wife shall experience at least part of that pleasure sailing around the Aegean. 🙂 🙂

    Wish you and family lots of health and nice moments on the Tahina

    Kind regards

    • Frank Taylor says:

      Minko, I wish you the best of luck both in your battery replacement, and your plans to travel the world. After 3.5 years the Lithium Yttrium Iron Phosphate batteries we are using are performing flawlessly. I am very happy with them. Frank

      • Minko Sotirov says:

        Thanks, Frank 🙂
        Just one more question…
        Did you change the battery charger or just attached the new batteries to the original charger of the boat?
        What engine/charger do you have on the boat?
        Mine are Volvo Penta D-2 75 hps engine with 115 A alternator and 45 A charger. Wonder if these would be suitable for a similar type of battery bank that you have.

        Have a pleasant and safe trip on the Tahina! 🙂

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