Still Required?
Ever since we published my thought that lithium batteries had come of age, I have been pondering whether or not they have reached a point of reliability that would make me comfortable installing them on an offshore boat without the lead-acid serial backup we have recommended for years.
After all, we now have systems from Victron and Mastervolt that have, or at least can have if configured properly, redundancy with two or more BMSs. So surely the time has come?
After giving it a lot of thought, I’m not convinced, and would still install a serial lead-acid backup to support critical loads while upgrading to lithium on an offshore boat of mine.
Here’s why:
I would suggest another reason for a lead acid backup—lightning. I would assume that the lithium BMS’s are more susceptible to a lightning strike than their lead acid counterparts. While the other components in charging system are also susceptible, having an analog battery backup may provide the time to jury rig some charging until back to port.
Hi Michael,
Very good point!
Hi John and all,
I am putting together a lithium system, basically with Victron components and using 2 of my grp 31 gel batteries as starter batteries and, possibly, use as an emergency bank . They will be charged by a DC-DC charger off the lithium house bank.
In controlling my system, I do not have the usual off/on/both switch but rather separate on/off switches for house/parallel/starter.
This has been fine for combining similar chemistry battery banks, but I know the parallel switch will become useless and even dangerous as it would put lithium together with gel. But it seems to me, that there may be a possibility of using the parallel switch to bring my 2 gel starter batteries on line to power essential equipment were the lithium bank to have become unusable.
Three things jump out at me:
one would be ensuring that the lithium bank did not “pop” back into action and get into catastrophic mischief with the gels. Possibly accomplished by an isolation switch for the lithium house bank.
The second would be to be able to quickly change the charging algorithm, probably easily done with a Wakespeed regulator.
The third is that I would have to be diligent in monitoring the gel cell single bank with combined duties to ensure the engine would always be able to be started.
I am wondering what other considerations should be jumping out at me? And/or what designs others have put together.
My best, Dick Stevenson, s/v Alchemy
Hi Dick,
I would recommend just implementing a serial backup for mission critical loads. Simple, inexpensive, fool proof, and no manual switching required until you have a moment to think, and then only if the lithium does not come back up. What’s not to like. Here are all the details on how to do that: https://www.morganscloud.com/2022/07/03/building-a-seamanlike-lithium-battery-system/
Think of it as a UPS for your boat (thanks Matt).
I also recommend against using the engine start as a backup
Any backup system that requires you to switch over is, in my view, fundamentally flawed, for example, the crash jibe has already happened when the lithium kicked out.
And yes, you are right, lithium and lead acid should never be paralleled.
If you want to discuss this further, please do so on the linked post since we have already covered most all of this there in great detail, including the points you raise.
Hi John,
No argument from me, but perhaps a different perspective when considering if lithium has reached “that point”.
We have run 3 x 180 AHr Mastervolt lithium batteries since January 2016, with a 100AHr AGM battery as our start battery (small diesel, heavy duty battery).
We average 80 nights aboard per year, not including 6 months full-time cruising the SW Pacific with this system, and in this time have registered zero faults. The few times we have powered the system down, it has re-booted perfectly.
According to the Masterview terminal we are approaching 200 battery cycles – the system is rated around 2500. We haven’t noticed any loss of capacity or performance in this time.
As you are aware MV lithium batteries are internally and individually managed, then monitored externally by the Masterview terminal. We can lose two of the three batteries AND the Masterview terminal, and still maintain all our loads and 24hr power needs without intervention.
Manually isolating our lithium bank and cutting over the house load to our “dual-purpose” engine battery in the event of total failure is not as resilient as your UPS styled solution, but we are very confident in our system and carry emergency Nav LEDs, magnetic compass, tablet navigation, paper charts and more torches than I care to admit.
It could be argued we have other critical systems aboard with less redundancy than our lithium system to focus on first, like the auto-pilot and wheel steering.
But I do feel in our case that adding a lead acid bank would make things more complex to manage and diagnose for us – but that’s very much a layman’s view.
Hi Rob,
I agree, the Mastervolt system is great, and arguably the most robust of the lithium options. I think I would still implement the UPS style backup, since it’s easy and cheap, but that’s certainly a matter with no right or wrong, but rather one each of us must evaluate, at least for the Mastervolt system.
But many people, perhaps most, are not going Mastervolt because they don’t want to spend that much.
The other variable here is I think you had really good people install the system for you but sadly that’s rare and extremely hard to evaluate ahead of time.
And finally, a blackout is the classic high consequence but low frequency failure so that reduces how much we should rely on your good experience.
One thing I do disagree with is that adding the UPS type backup would make it harder to diagnose and manage. Like a UPS the system is serial and so simple that anyone who has ever had a battery should be able to deal with it. Have a look at the diagram in the linked post and you will see what I mean.
Hi John,
Another factor to consider is we installed our batteries, charger, inverter and solar controllers in a dedicated and well ventilated space with two regularly changed “DampRid” packs keeping the space bone dry.
Our original house AGMs were in the front of our engine bay. So the MV lithiums are (to add to Matt’s UPS analogy) in an environment more akin to a server room, than a typical battery locker.
Hello, John
The real test, for me, to switching from Lead based technologies to lithium would be if you can trust a lithium battery specifically allocated for windlass operation. To put it plainly, can I trust my anchoring to a lithium battery?
Hi John,
Probable not without backup, in fact we have a reader who had his new lithium system kick out on him while anchoring giving him and his son a very nasty scare.
With backup, as described in the linked post, sure.
That said, there are a lot of variables here, for example see Rob’s comment.
We had this exact problem, a mastervolt system with two independent banks and BMS failed. Mastervolt could not determine why both banks would shut down with out warning with in seconds of each other. All components were healthy according to thier diagnostics. In the end the owner chose to covert to a lead based system. The other option was to start replacing the master volt components hoping to catch a gremlin that the network diagnostics could not find.
Hi Carl,
Wow, that’s indeed sobering and really reinforces my thinking that a lead acid serial backup is still required and may indeed be for many years to come. In my years of first being a mainframe technician and then running computer support departments I have been down that path of not being able to find a cause for intermittent problems and so being faced with no other option but to start a systematic replacement process in the hope of finding the problem that way—deeply frustrating and very hard to explain to an end user who just wants the damned thing to WORK.
What?? I am building a boat – all mastervolt. that is super scary.
Was that recent equipment? each battery has BMS ?
I’m glad the capacity requirements on our boat still keep AGM batteries on what I perceive as equal footing compared to the benefits of converting to a lithium system. The additional complexity to insure proper operation and longevity of a lithium system is still a bit intimidating to me.
After reading your first post on this topic, and now reinforced by this latest one, it seems best to treat lithium battery systems as just another onboard electronic device, and lead acid batteries as simple chemical devices. One requires redundancy, one does not (as much).
Hi Shane,
I think that’s a very clear eyed way to look at it. Added to that, when we lose a lithium system (without backup) we have lost everything electrically dependant, so perhaps even worse that say losing just one piece of electronics, say the radar or plotter.
Totally agree. I love my 24v LTO battery bank, but I fully took on board all your advice over the years and have two independent lead acid 12v batteries for the engine and essential nav/comms/lighting.
The end result is moderately complex – being an EE I couldn’t resist that entirely – but the whole system looks after itself with manual switches that are only necessary for maintenance isolation.
Essentially my thinking is that if the 24v system fails completely I can still sail safely in basic ‘camping’ mode as would have been the norm 30 or 40 years ago.
Hi Philip,
That sounds very sensible. I would guess that being an EE you have a good appreciation for the intrinsic vulnerabilities of complex lithium systems.
1- Wow. thank you. Thank you.
1a Read through this thread… sub threads… Martha Stewart… hehehe.
1b- how do you sleep at night?
2- Lead Acid / UPS design for the critical loads. Love that.
3- I am slightly relieved that the Mastervolt Systems with individual BMS systems by battery (I will have 5 X MLI Ultra 24/6000) reduces the likelihood, of blackout; but a common mode failure would be a real bummer.
4- that accidental gybe… i may have to rethink some things.
5- I will work on that UPS model… i think i have it in effect with DC-DC Thruster chargers.
6- I’m still dizzy on the alternator/sense wiring but will re-read. I am going Mastervolt (including Alternator) with a zillion sensors. but it is a lot of electronic stuff.
I did sail across the gulf of mexico on my Swan 46, blacked out. We rigged battery powered nav lights, used hand held gps, and, perish the thought stars, wind, waves, steered manually and channeled the guys on the Kon Tiki… if they could do it…
I do keep a phone mounted at the helm running as a backup chartplotter and AIS receive for that bad foggy night. Radar would be nice.
But that gybe while on autopilot, short handed. i will have nightmares now until I fix that. I may have to re-engineer the whole boat. Glad build has not started yet.
Thanks Again
Hi Rob,
I just can’t not comment on the Kon Tiki guys comment. Off topic, definitely, but it was a mostly Norwegian thing, as myself. I actually met the leader Thor Heyerdahl once, in Oslo. Fascinating personality, who has been much misunderstood.
Most people say he wanted to prove how various places were populated. That’s totally wrong. He wanted to prove that the ocean was not a barrier, but rather a facilitator. That prehistoric ancient peoples must have travelled all over the place and mixed much more than was the accepted truth back then. Modern science has proved him right.
I would also say that the Kon Tiki, and other ancient vessel types he crossed oceans with, were not really proof of competence or skill. They managed those voyages in spite of very poor equipment, because it’s usually quite easy to do such trips, unless you’re unlucky…
At the time, those trips were hugely entertaining, with noting much matching the level of adventure inspiring the imagination of all hearing about it. Young, blond muscular guys with significant charme and little clothes added to the allure. 😀
For inspiration I’m far more impressed by Joshua Slocum (Sailing alone around the World), and Bernard Moitessier (The long route). They both proved incredible skill and stamina, with very simple tools.
As for the topic, having a DC to DC charger from the lithiums maintaining a lead acid battery, and putting all essential loads on that battery, absolutely! At best, you will never need it, but if so, you just got a cost and weight penalty really not noticeable. It’s a “no-brainer”, which you already know, of course.
sorry if i bungled the kon tiki reference. I did meet a modern-day Thor Heyerdahl; Hawaiian guy Ooaki Ho. Chartered his J-29 ish boat to support my girlfriend swimming a relay race from Kuai to Maui (crazy).
This guy sail this stripped out boat (zero electronics) from Hawaii to Tahiti with a compass, with his wife and kids. And back. I felt like such an a-hole with all my tech gear, electronic route optimization and yadda yadda.
From Mexico, we were (15 years ago) hung over (from race to Mexico) middle aged less muscular guys but had a few loincloths.
And those were lead acid days – and as my memory fills in, we lost the starter on the old perkins, catastrophically, gears blew up (since repowered with yanmar) which left us no charge capability leaving mexico.
We were only few miles out, could have gone back, but decided to go for it – its only 400 miles.
We flipped on real nav lights when we saw ships at nigh (one ship called us and offered to drop us a small generator, but we figured we’d smash the boat up getting alongside; said thanks and sailed on).
We, of course, came upon a wandering catamaran. My crew thought they might be pirates.
I reminded my crew that we were the unshaven, loinclothed, blood soaked (from some weird in-edible fish we caught and battered to death with a winch handle) pirates. Blood everywhere. but anyway.
So these folks were just smoking cigarettes waiting for wind but needed jumper cables.
In return for promise of rum, we paddled over to fix their boat. Secured the rum; then tried to fix their boat, but they had bigger problems.
We kept the rum and sailed our way back to tampa bay.
The coast guard later interrogated us – apparently those folks were up to something, but didn’t see fit to mess with us. we were probably scarier looking than we thought. CG followed them with a C-130, and let us go.
I am too old for the kind of fun now… just want super reliable systems and a glass of wine.
Hi Rob.
Thanks for the kind words. As to nightmares, I think you will be fine with the system you envision. If it’s any comfort I have never in 50 years of offshore sailing had a blackout with lead acid batteries, which gives a lot of comfort for the lead acid UPS design.
That said, I agree that the sudden autopilot failure is the thing to focus on since its can be such high consequence. Of course we could have an autopilot failure for any number of other reasons, but a blackout is particularly intimidating to me because we simaltaniously lose everything.
I did have a different autopilot near failure in really bad conditions in North Atlantic (Newport to Bermuda Transit).
Getting the crap kicked out of us as we did not wait long enough after Hurricane Sandy passed.
A lifejacket got stuck in the helm wheel spokes/deck. Autopilot (SIMRAD) screamed. boat started swerving.
I was naked showering below (after days of getting hammered) and heard the autopilot alarm. its was blowing 35 plus.
I thought gybe and done for. Rig Down. Screwed.
I could run up and get tossed overboard naked, or hope the crew figured out the problem. They did, just in time.
I think you may know the guy John. Phil, from Halifax. The guy who salvaged that German boat Escape after that tragic accident.
Phil is an incredible sailor/human – I was very lucky to have him on board.
Maybe i should ditch the new boat and find a safer hobby… go back to swimming in shark filled channels or something.
Hi Rob
Sure Phil is a good friend of mine, no one would figure and handle a problem like that faster than Phil.
Anyway, don’t ditch the boat, instead take a deep breath and read this: https://www.morganscloud.com/2018/10/26/11-things-we-do-to-stay-rational-about-safety/