The Offshore Voyaging Reference Site

Battery Options, Part 1—Lithium

The summer before last we were stuck close to Base Camp, due to a health issue I was dealing with, and so it seemed like a good time to replace our aging—six years and many hundreds of deep cycles—house battery bank.

Not only was one of the batteries down to 50% of its original capacity, but our house bank was small by modern standards, so we wanted to upgrade to 800 amp hours at 12 volts. (More on how we determined our desired capacity for the new bank.)

Our first task was to decide what type of battery to buy. The options I looked at were:

  • Lithium
  • Lead acid:
    • Carbon foam
    • Liquid filled
    • Gel
    • AGM

A quick aside: Many people use “lead acid” to mean liquid filled but, in fact, all of the commonly available battery types, other than lithium, use lead acid chemistry. The differences are in the physical way the batteries are constructed.

Back to our selection process, what I learned about each battery type, and why we eliminated three of the four to arrive at our final choice (to be revealed in Part 2).

Let’s start with the sexy exciting one…yup, lithium.


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Geir ove

Must say that cost is higher for litium, on your side of the atlantic, then it is on our side.
i have a friend ho has 1000amp Winston batts. and lives in the boat, he does it al electric. cooks +++ and afther 3 years (incl trip to Carib) the batts are at 103% from new, tested on a load test. not bad.
i will go Litium when my 4 years old leads/Trojans start going bad. but they are still doing very well.
over on this side we get 100amps Litium w/BMS and BlueT. for around 7000nkr. (and that is with 25% VAT)
And there are many that runns them and not upgrading there Altenator. just a good heat sensor on it. and have not heard of breakdown yet. there is solar panels, and some motor running when sun is not there.

Philip Wilkie

John,

I hope this series includes a consideration of Ni-Fe Edison batteries. Here are the positives:

1. A guaranteed life of at least 10,000 cycles; properly maintained their life is essentially indefinite.

2. Hit them with an 80% DoD on a daily basis with no loss of cycle life. This is a huge advantage over FLA’s and even Lithiums, both of which suffer if taken below 50% on a daily basis.

3. No complex BMS system needed; you cannot damage them with over or undercharge, storage at PSoC, and they have a remarkably wide operating temperature range. Nor is there any chance of thermal runaway.

4. A high-ish internal resistance means they are electrically safe, a short circuit will result in a self-limited current and excess gassing, without any of the extreme kAmps of fault current that Lithiums and Lead Acids can pump out.

5. They’re considered environmentally benign.

The downsides are:

1. High initial purchase price. A 12volt 500AH battery will cost around U$5000. (But remember no expensive BMS and very simple wiring will offset this, and their total cost per kWhr delivered over their entire life is by far the lowest of any battery. )

2. Their high internal resistance comes at the cost of limiting operating current to about C/5. ie a 500AH battery will work best at less than 100 Amps. This limits their ability to be charged quickly via a genset or engine. It makes them best suited to solar/renewable installs.

3. They are a flooded battery and there is no sealed option. If you routinely fully or over-charge they will out-gas and the electrolyte will need to be topped-up with distilled water every few months. (Although it would seem you can minimise this if you don’t charge past roughly 15% DoD.)

4. Disconnected Ni-Fe’s will self-discharge at about 1% per day. (Some people report a lot less and it’s not an issue for anything with solar charging.)

5. The Charge Efficiency in the top 20% SoC isn’t very good; overall most people allow for an average total ‘rule of thumb’ CE of about 80%. This isn’t as good as Lithiums, but because this figure is very stable of their lifetime, its actually better than most Lead Acids whose CE drops quite quickly with age.

6. Their terminal voltage varies quite a lot depending on SoC. A nominal 12v battery will be about 15.5 volts at 100% SoC and 9 volts a 0%. Not inverters will fully utilise this range. The upside is that SoC is a very simple function of voltage; no fancy Coulomb meters required.

7. In an enclosed space you WILL need to provide venting to deal with hydrogen out-gassing. Fortunately this gas wants to escape upwards so it’s easy to deal with.

8. Their specific energy on a volume and mass basis is similar to lead acid. A 12v 500AH battery will weigh about 260 kg or so. (In my case this is balanced by the similar weight of auxiliary gear I can remove from the same location, but it rules them out for most catamaran installs I’d imagine.)

In my case I have an ancient diesel genset to remove that will free up the perfect space to install Ni-Fe’s. Our true cutter rig balances nicely on both a Fleming wind-vane or an old AutoHelm, and we don’t have a freezer, so with care our total power consumption can likely be balanced with solar/wind/hydro. So I’m fortunate the Ni-Fe stars align for me; it accept won’t for everyone. What really appeals is the robustness of NiFe’s. While I have zero offshore experience, one thing I’m certain of, is that I really don’t want to be messing with complex technical problems on top of all the other usual challenges of good seamanship and fatigue to deal with when I do get there. Ni-Fe’s are generally way more tolerant of mistakes, abuse and idiots than any other available chemistry I know about, and that’s their biggest tick in my box.

(I ruled out the very promising Firefly Carbon Foam batteries simply because you can’t obtain them here in Australia. As you said in your podcast with Andy and Mia, the technology really needs to be licensed to see some real market leverage.)

Philip Wilkie

Correction to above: messed up my currency conversion. The purchase price above should be under U$3500 based on this Australian suppliers prices:

http://www.ironcorebatteries.com.au/page2.php

Ernest

Hi Philip,
your post got me curious and I did some read-up on Ni-Fe batteries when I stumbled across this article:
https://www.rpc.com.au/blogs/news/disadvantages-of-nickel-iron-batteries?_pos=1&_sid=9f239c883&_ss=r
Most if not all issues mentioned here would keep me far away from considering them for a boat installation, offshore or coastal.

Philip Wilkie

Ernest,

I think I covered off all of the issues mentioned in this link in my appraisal above … no question Ni-Fe batteries do come with some specific downsides that must be understood. But addressing each issue mentioned in that link, it’s helpful to be aware of what more could be said:

1. Ni-Fe total new installed cost is somewhere between good AGM’s and Lithiums overall. Certainly not out of the ball park. But when considered on a total cycle cost over a 20+ year lifetime Ni-Fe’s have by far the lowest cost of ANY battery chemistry.

2. Charge Efficiency (CE) overall from empty to fully charged is about 80%. But it’s only the top 20% of the charge where the CE is poor. This suggests two ways to mitigate the issue, one is simply not to fully charge on a daily basis, and the other is to add another 20 % of solar panel.

3. Self discharge is higher than many other chemistries, but insignificant if you have solar/wind available to float charge. It just doesn’t matter.

4. Ventilation is an important issue, but the good new is that hydrogen is an extremely light and diffusive gas. It’s difficult to contain and WANTS to escape. Just about any simple venting scheme will work. Moreover gassing will really only be an issue if you are over-charging. Simply limit the charge voltage to about 1.55 volts/cell and hydrogen production will be minimal.

5. At say 80% DoD a nominal 12v battery will be down close to 9.5 volts. Some inverters may cut out before this, pre-maturely limiting how deeply you can discharge. This means they may not be a drop-in replacement for LA’s on an existing boat, but I do know that Victron and Schneider (any probably others) do have inverters that will operate with this wide input voltage range. Specify correctly and it’s a non-issue.

6. Size and weight are similar to Lead Acid. At 12 v 500 AH battery (that will deliver 400AH of usable capacity on a daily basis for decades) will weigh around 260kg. Sure Lithiums are brilliant by comparison, but it’s not unreasonable either. (In my case they’ll fit right into the space where I’ll be removing about 200kg of auxiliary engine and equipment.)

7. Maintenance is certainly not weekly. You’d have to be heavily overcharging almost continuously to need that much refilling. Most users report that at most they need to check once every few months or so, many much less. All you are doing is looking at an easily seen level through a translucent case and adding some distilled water. Overall maintenance doesn’t seem any more onerous than standard FLA’s and many people live quite happily with them. (And I’m only interested in a 12 volt, 10 cell installation, not 40.)

8. Yes the electrolyte should be replaced at most about every 7 – 10 years. All that is happening is the KaOH slowly reacts with CO2 from the air and forms insoluble carbonates which you can see as a visible deposit on the bottom of the cell. The upside is that now you have a virtually new battery that will last another 10 years or more! Rinse and repeat … hand them onto to your grandchildren.

Here is a video that discusses large fixed Ni-Fe/solar installs in some technical depth. It’s commercial but as a professional engineer who has used Schneider equipment in many projects, I read it as a reliable source. A good comparison table is at the 28 minute mark: https://youtu.be/eGZ9-bp4uZM?t=1687

NiFe batteries are a niche solution. They’re going to best suit offshore mono’s looking to replace an auxilary genset with renewables in a super-robust, long-life dependable system.

To achieve 12v/400 AH of usable storage with Lead Acids will mean installing 1200 AH of battery also weighing close to 300kg. With daily cycling between 80% and 50% DoD you’d be doing well if they lasted 5 years if you treated them well. 3 years with the usual yotti treatment. And they come with a whole bunch of well-known charging and maintenance issues.

And I don’t need to repeat John’s analysis of Lithium’s. Neither of these common solutions is without issues. Nor are Ni-Fe’s fault free. The whole point though is that understanding each type’s strengths and weaknesses, and understanding how these fit with YOUR individual boat and YOUR sailing needs is what this excellent series is about.

Philip

RDE

Technology assessment: Bleeding edge or best fit for the job?

We were building a cost-is-no object 116′ motorsailor for an Owner who loved to create problems and then observe how people solved them. So he comes to me saying “Richard, I’m having a terrible problem deciding what battery arrangement to use. I want you to research the field and produce a recommendation for me the next time I visit. ”

Now I’m smart enough to know that my hydraulic theory of electricity won’t be sufficient for this task (LOL) so I bought beers for several friends who design factory trawlers for the Gulf of Alaska and tourist submarines for Hawaii. They strongly favored 2V conventional deep cycle lead acid submarine batteries in series. (somewhat similar to Steve Dashew’s approach) When I did an analysis of this concept I found that I could package them between the ring frames below the sole and achieve a higher power density than the AGM batteries that were the state of the art for that era, still keep each unit within a manageable weight range and drastically improve the storage utility of the “garage”.

So I walk into the meeting with the Owner and discovered that the other participants were the President of Sparkman & Stephens and a senior electrical engineer from MIT that the Owner had paid $75,000 to produce a study of the state of the art in batteries for our project. Of course you know what happened! I will say that the MIT/Victron design with individual heat sensors and controllers on each battery racked along the hull sides worked just fine for the 4 years before I lost track of it.

Philip Wilkie

An Owner with that much money to burn can afford the risks and costs of a custom install like that; but the next person to own the boat may not be so fortunate. If there is one thing a lifetime of heavy engineering has taught me is that robust and slow to degrade solutions are always the best life-cycle value for most scenarios, most of the time.

Innovation has it’s place (and I’m always a sucker for it), but complex, fragile innovation does not belong offshore.

RDE

Hi Philipe,
“robust and slow to degrade solutions” Kind of the opposite of a runaway Lithium battery!” LOL.

I would note that a power failure on a lee shore in Antarctica with a complex automated yacht is equally serious regardless of whether money is of no object to the Owner—.

Jim Evans

I’m surprised you considered that your whole charging system would have to be changed. Lithium batteries are being quite commonly used in motorbikes these days as a simple replacement for lead acid, apparently without problems other than the need to “wake them up” by switching on lights before cranking the engine.
Could it be you’re overthinking this?

Scott

No, he’s not. I’m a boat yard electrical technician, and I just had my first service experience with lithium batteries. Here’s the story:

A customer brings his nearly new Alieron 40 to us for storage on the hill during hurricane season. The vessel has 48 volt electric propulsion, two large lithium battery banks capable of powering the motor for about one hour ($20,000 worth), a 48V diesel generator, a Victron changer/inverter, and a battery management system.

Whilst the boat is in the hard, we have a power failure that lasts multiple days and the inverter/charger is in the default invert mode, so it inverts until the batteries are deeply discharged. Why the bms didn’t shut the system down when the batteries got low, I don’t know.

With the batteries deeply discharged, the bms won’t allow the inverter/charger to connect to the batteries, so consulting with the guy who designed the system, I charge each individual 12V battery with a specially designed rescue charger that puts out about 280 milliamps in rescue mode. The hitch is that this smart charger will only stay in rescue mode for three hours before needing to be reset.

To make a long story a little shorter, it took me three weeks to get the batteries up to the point where the bms would allow the charger to operate, and it finished the charge cycle in a few hours.

Anywho, to echo John’s point, you don’t want to have such a delicate system on an offshore cruising vessel. Just imagine what could happen if that system went off line during heavy weather. Yow.

That’s my two cents.

RDE

Another tale from the bleeding edge of design engineering—.

I was asked to work with an engineer from a Paul Allen company called Advanced Lithium to design and fabricate the battery containment module for the Fisker EV. (the design that the Muskrat stole and evolved into the Tesla Model S)

Upon viewing the AL operating prototype my immediate reaction was “this is nutz” . Their battery design consisted of thousands of laptop batteries in series, each with its individual controller. So far so good– a copy of Tesla’s early battery except that the AL design had the batteries air gapped instead of liquid cooled, and thus was 100% dependent upon flawless operation of every single controller. Needless to say, Advanced Lithium’s cash burn soon rose to a million $ per day as they learned to never test a battery in anything but a fireproof and explosion proof room. Something that even my hydraulic theory of electricity could predict!

Rob Gill

Hi Scott,
Thanks for the example – although I’m not sure it demonstrates that lithium (phosphate?) batteries are delicate. It suggests the BMS did shut the batteries down but at a minimal level. Or it didn’t shut them down and yet the batteries recovered even after being put in a condition they should NEVER EVER reach. In which case the battery system designer should have a red face and probably a warranty claim by the owner for probable loss of lifetime cycles.
As I understand it (from reading a manual), below 20% charge the lithium phosphate batteries undergo a chemical change that can at best damage them often irreversibly, or at worst make them unstable. To combat this, most battery management systems (integrated in the battery in the case of reputable products) will shut down the battery at the 20% charge level as a factory setting and will not allow re-charge until it is checked by a technician to ensure it is safe to do so.
So as normal practice, the system SHOULD be set-up so each battery separately alarms at around 30% charge remaining, and shuts itself off at about 25% capacity remaining. This will be a setting in the battery management system (for MasterVolt anyway). Then, when the power comes on again the battery(ies) will simply re-charge if any isolating switch (if fitted) is turned back on, because they haven’t reached the minimum threshold.
That the system you encountered locks the user/charger out may demonstrate an entirely sensible precaution – an installer / user inexperienced enough to not have set the cut-out above the minimum 20% (save the ship) level, is probably also inexperienced enough to override the 20% cut-off and endanger the battery and / or their boat.
But it may also illustrate (and go against John’s recommendation for single source) how cobbled together lithium battery systems from multiple suppliers can and possibly did go wrong, and even be dangerous.
Rob

Mark Wilson

Dear John

Please accept my apologies if this suggestion has already been covered:

I think I may have found a lithium battery that would be useful on a boat. At least on a reasonably small boat. It is a 10,000 mAh car jump start battery I bought from Amazon at Christmas for £40. It started the 1.6 litre diesel in my car with ease and with plenty of juice left over. It claims to be able to start a 2 litre diesel and I have no reason to doubt it.

A further use for it is as a power bank for iPads and such like should the electrical systems on board completely crash. It has a USB take off and also doubles as a torch. Higher capacity alternatives may be available.

By the time you come to replace your current batteries maybe lithium battery technology will have advanced far enough to be both safe and economical enough to suit our needs.

Best.

Mark

S/V Tumbler (as of 3 weeks ago)

Chuck B

I too have one of those lithium-based portable jumpstarters; they are indeed handy! However, folks should be aware the instructions for its use require a lead-acid battery in the circuit. I tested – the device by itself was not able to start the engine with the starter battery disconnected. Even with the jumpstarter’s safety mechanism disengaged, it would not crank my 3-cylinder diesel AT ALL. But in conjunction with a very depleted lead-acid starter battery, which on its own could not crank the engine, the jumpstarter worked great. In summary: not very useful as a general or stand-alone battery, put perfect for its stated purpose.

Chuck