What’s the best battery type for your boat? AGM, Lithium or FLA?

I often get asked “what type of battery should I be using on my boat”. The answer, as always, is “It depends”. In this video I look at the most common types of batteries and why you may want to have one over the others. Specifically I discuss Flooded Lead/Acid, AGM and Lithium batteries and the Pros and Cons of each along with other related topics.
I’m thirsty after all that talking, buy me a beer?…. www.paypal.me/...
If you have enjoyed this video and/or learned something you can now buy me a beer using the link above to make a donation to the channel. If I end up with more beer tokens than I need then I will put your donations towards a better camera, better mic’s and lighting so it ultimately benefits you the viewer. I don’t do Patreon, I don’t sell T shirts but you can help support this growing channel. Thank you
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About Me
I run a small business called The Solent Boat Butler Ltd and spend my days repairing, maintaining and refitting sailing boats (often Contessa 32’s due to my long experience with them). I'm mostly in the central Solent area of the UK. Being a cruising and racing sailor with many thousands of inshore and offshore sea miles logged I like to think that I bring a great deal of real-world experience to my work and help many new (and not so new) boat owners to improve and maintain their boats. When I'm not fixing boats I also provide some own-boat sail training, help owners with deliveries, provide pre-purchase inspections and deliver consultancy services to those that are refitting their own boats for cruising or racing.
Facebook - thesolentboatbutler
Instagram - george_the_boat_butler
Website - www.solentboatbutler.co.uk
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Disclaimer
I hope that viewers both enjoy and learn something from my videos but please remember to take the appropriate precautions for any DIY refit works you undertake with appropriate PPE and the correct tools for the job. If you are in any way unsure as to how to go about a project or are unsure if something on your boat is safe please consult a professional.
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[@wonderingworld119]

Just to add a slight correction. The cycles on lithium cells are measured in 100% cycles ( ie two 50% cycles = 1 cycle, five 20% cycles = 1 cycle ) or at least on every cell data sheet I have ever read. I seem to remember some company once changing it, and basically everyone complained so they released a new data sheet with the correct 100% cycles on them. Some data sheets do vary in how much usable energy is stored after their spec. The new EVE MB31 cells for instance (314Ah) have greater than 70% after 8000 cycles on their datasheet... which is still 220Ah which is still perfectly usable. If anyone is still reading this... we have now reached the point where the depth of discharge is now irrelevant, as age itself is a bigger factor in degrading cells on a solar system. And for anyone wondering, 8000 cycles is about 1 cycle every day for 21 years.

[@kiang8269]

Hahaha just as I was thinking 'Maybe my old school battery monitor is ok'...is when you said 'these are rubbish' and my exact one came up!

[@RefitandSail]

😂 sorry… but I stand by what I said. 😬

[@kiang8269]

@@RefitandSail 🤣🤣 good to know!

[@superformOG]

i have a 300ah lithium and i love it, was on the boat with no charging source for 1 week in winter with the heater running and it was at 40% at the end, having power for autopilots where you dont need to worry about running out of power on multi day ocean passages is the best part.

[@flyingmedic]

Excellent information. I use AGM and happy with them . But I did like the idea of Li.

[@Dulce-Phil]

Thanks George, the best battery video I have seen. Enjoy your beer.😀⛵

[@RefitandSail]

Thanks 🍻

[@allanjames9672]

Excellent explanation of the dark art of batteries! Thank you, George.

[@redsnappersadler34]

Thanks for posting-just about to renew the batteries on my boat so your timing is perfect. Don’t worry about checking your notes-your not reading the news on the BBC😅

[@RefitandSail]

Thanks…. And now it’s time for the sports news….

[@danknox9986]

I’m on my third set of AGM batteries. Each set costs about $1000 and last about 10 years. I am a weekend sailor that averages sailing twice a week with maybe 8 three day weekend trips and one week long trip a year. I’m happy with my setup.

[@MP-qn1jw]

...and they all stink. Lol! THANKS!! You got me at the opening joke. Great video. Making my first attempt re-rigging dual batteries on a 30yr old 26' walk around. Want to add inverter, solar, and/or small genie. Bookmarked this video because you hit all the points I could think of, and then some. Thanks for the knowledge. Cheers!!

[@cmcsailor497]

Fantastic video, makes sense finally a easy video to understand about different batteries, without making it all to much great job thank you 🙏

[@RefitandSail]

Thanks 😊

[@andreadoniselli8724]

I think that it should be added the optima patented battery as it is to me the best choice especially using a bow thruster or anchor winch, they last a lot longer and solved the battery issues on my Southerly after many attemts with oter types. Thanks for all from Andrea and from Italy!

[@normanboyes4983]

George it’s a good round up.👍

[@119066kdl]

Excellent job at explaining this topic that has been so confusing to some of us. Cheers

[@James-cv5tx]

Ooooo, im the second viewer and the first commenter...... #exciting It's always good to see these films arrive, as they're always a weath on knowledge 😀

[@RefitandSail]

Haha, yes I just hit the “go” button to make it live after an 18 hr marathon of filming and editing yesterday.

[@janliljeberg3769]

I saw in a boat video, one battery, not sex, with the capacity of 7000w, if i remember right. Seemed the best at the time.

[@bendaves77]

You're a wealth of knowledge and information which has come from experience rather than someone who has just read about it or taken someone's crappy advice. I'm also curious as to why no one has come up with the idea of using a water turbine to generate power while sailing through the water? They make portable one for camping which are either wind generators or using the flowing water of a small creek to generate power

[@RefitandSail]

Towed generators for boats have been around for some time. Older models like the Aquagen are still available new but also can be bought on eBay for a good price. New hydrogenerators from companies like WattandSea are very good indeed, originally developed for offshore race boats (imoca’s, class 40’s, etc) they are now being seen on cruising boats but they are pretty expensive. I’d certainly consider one as the price drops though competition in the market.

[@gregg6282]

I was thinking about this subject the other day so it’s just what I want

[@RefitandSail]

Excellent

[@hedleyjackson5131]

Great info as usual George, I can see you went to a great deal of effort to produce this thank you.

[@RefitandSail]

Thanks. I think the video took approx 24hrs of my time if I add it all up. Sometimes I wonder if the effort is worth it but the positive comments definitely help.

[@davidkeffen]

Very helpful. Thank you George.

[@superformOG]

one thing you forgot to mention is the discharge rates of lithium, which is dependent on the bms. If you need higher discharge rates you need to carefully plan your battery or parallel banks.

[@MagicMoose14587]

Loved the video, it's always great to hear a deep dive from a knowledgeable and experienced person. I didn't mind you reading your notes, there were a lot of facts to get right!

[@svlamancha9877]

Lots of great info there. Thanks. I’ve got to the stage where I just buy a cheap leisure battery pretty much each year. Boat is on a mooring so I rely on a small wind generator to keep the single battery topped up. How about a DC to DC charger to keep a separate house bank charged is that something you will cover in your next video. 👍

[@RefitandSail]

Dc-dc charger can be a good option and I will probably include them as one of the options for part two. Pleased you enjoyed the video and thanks for the comment

[@kbbarton1]

Excellent video as always; very informative, relevant, and practical. I'd really be interested to see videos like this that talk about renewables like solar and wind (I want to install both on my CO32) and since most CO32s nowadays have Beta 20/25 engines, some videos on maintenance tasks would be very welcome.

[@RefitandSail]

Great suggestion, thanks.

[@Troggination]

Bit late to the party, but what are your thoughts on a battery for a sailboat that basically only needs to power a small hydraulic pump for the autopilot, power a chartplotter, and basically nothing else? the thing I'm concerned about is what happens to the boat if it goes on its side-- when racing a boat this happens from time to time as I'm sure you're aware. is this catastrophic for a flooded battery? is there a brand or kind of battery that is better at this kind of intermittent orientation change?

[@rolandstockham1905]

Would be interested to know what AGMs your are takling about. All theone available in North America for people like Rolls and Interstate only claim half thhe cycle life for their AGMs compared to the 6v FLAs. Possibly this is true for small 12v FLAs but not for the likes of L16s

[@1962gms]

Really interesting video, I am just going through a rewire and potential re battery and have to say that with our 'use case' of sailing and dropping the hook, Lithium is looking like a good option. I could see that we could survive on FLA or AGM, but we only have room for a 2+1 battery layout and if we are away for several weeks it looks like we will be too reliant on the engine and solar to top up a depleted storage. As we are doing the full replacement, I am now minded to go down the Lithium route for House and the current FLA for Engine. Thanks for the info and helping me think through how I want to use the yacht over the next 5 years.

[@RefitandSail]

Thanks for the comment, I’m pleased you found it a useful vid.

[@sailingaphrodite4189]

Thanks George, informative as ever. If you have not already filmed part two it might be worth looking at the amperage/voltage question when a battery is in use. Given the amount of confusion about the voltage 'at rest' and the percentage charged that might open a can of worms. I converted to AGMs and have been impressed with their performance. Added a Victron charging/monitoring system last year and looking at the data that has been interesting, the 0.07 amp (1.6Ah per day or 11.76 Ah per week) just to monitor the system was a surprise!

[@RefitandSail]

Thanks, pleased you enjoyed the video. Yes any monitor will have a power overhead bit it’s fairly minimal, if leaving the boat for a long period the monitor could be switched off, after all it’s not really giving any value to the owner if he or she is away for 6 months unless they dial in remotely to check on the boat but if you are going that then you probably have shore power or solar to keep the batteries ticking over.

[@richardcourtenay8114]

My last AGMs lasted 10 years with good care. Price for quality AGMs beat lithium hands down for price and maintenance provided they are kept at float when not in use. Just check connections are clean, tight and sealing grease.

[@RefitandSail]

We don’t really know how long lithium’s will last yet, but i doubt even the very best agm’s around can compete with overall £/discharge cycle given that agms should not be taken down to more than 50%, if you do the same with lithium bats some are projecting 10,000 cycles and still have 80% of its original capacity. But as I said in the video, they are not for everyone but are a good option if you are a heavy battery user (full time cruiser or light-weight race boat), fir everyone else AGM’s are probably the best option.

[@Wauquiez48Pilot]

Brilliant thanks mate 👏👏

[@jackwright9016]

Great channel.

[@RefitandSail]

Thank you!

[@etherboy3540]

I haven't heard of Unicorn tear batteries. I have heard of Unicorn Fart batteries though via Mighty Car Mods though, those are the best.

[@RefitandSail]

I do watch those guys on MCM, great channel, maybe I was subconsciously influenced by them with my unicorn tear battery.

[@smallprojectscompleted]

Great video

[@mikehogan1827]

Very helpful - thanks!

[@bobthesnobscotland2821]

Cheers

[@Bigfishfun333]

Awesome!

[@hatatfatcat]

It's perhaps worth mentioning recycling of old dead batteries, since old lead batteries can be weighed in at the scrapyard for a few quid whereas honestly I wouldn't know what to do with a dead Lithium battery? I don't think our local amenity site takes them.

[@RefitandSail]

Yes I agree, I think I said in the video it’s easy to recycle a lead based battery but I grew a lithium battery would need some investigation as to where to recycle.

[@usspaul9422]

Really informative. Tyvvvvvvvvvm !!!!❤

[@RefitandSail]

Glad it was helpful! G

[@johnburns3039]

Very helpful.

[@johnburns3039]

What batteries do you have on your yacht?

[@johnburns3039]

I heard your answer, lithium 300 ah.

[@abent74]

great info, thanks

[@sailingdevonscoast]

Awesome video! Love good information like this.

[@RefitandSail]

Pleased you enjoyed it.

[@nigelcrunden]

great video, really easy to follow, looking forward to part 2. You are producing great content/videos, thanks a lot !

[@RefitandSail]

Thanks Nigel.

[@rickpyne]

Your vids are of great interest to me, I am doing total refit on a M&W32 sloop. Looking forward to your bat charging vid. Keep them coming,, and good luck for the future. I wish to ask one question- that is regarding the use of LED lighting and its effect on VHF comms. Both used as cabin lighting also as Anchor light and VHF aerial. Do you have any info??. We all learn by listening to experience, so your input is appreciated. Thanks

[@RefitandSail]

Pleased you re enjoying the videos and good luck with the refit. You need to be careful with led’s a some of the cheaper ones can cause interference to your VHF and other radio equipment, I have certainly experienced that a few years ago on one bulb replacement, it’s more common on relatively cheap leds. The only way to check is to try them and dispose of any that do cause interference. If bought from a reputable shop you should be able to return any that cause interference to your radio but if bought cheap online then it’s pot-luck. When it comes to led nav lights I only buy tested type-approved lights from Aquasignal or similar and not had any issues at all.

[@arlisscott3455]

From what I"ve heard is that insurance on your boat will be effected by which battery you have in your boat. Just another thought

[@RefitandSail]

I have only heard that as speculation and rumour from a couple of boat owners online but not from any insurance company. I have to renew my boat insurance shortly so I will ask them.

[@bendaves77]

Why aren't Optima batteries used more often in boats? They're used here in America on things such as drag racing applications and other things where a alternator might not be used and they can handle being drained and then charged up fully. They're also a sealed 6 cell battery so they can be tipped upside down or rolled over and they're safe they make them for all kinds of applications

[@RefitandSail]

You can buy Optima batteries in the uk and I do see them occasionally on boats, they are an AGM like others on the market but so seem to have a very good reputation, much like Rolls do also. I believe Optima make a few slightly different versions of their batteries for different applications.

[@RefitandSail]

I think one of the key selling points for optima is that they are built to withstand a tough life, particularly vibration which you may get in a race car or jet boat. Less call for that level of ruggedness on a sailing boat.

[@bendaves77]

They do make several variations of their batteries for different applications. I bought one for my Harley and bought 4 for my semi truck when I still owned one. They're awesome because they can be mounted on their side and they are very rugged and reliable.

[@NixToDo]

I missed a litte bit the function description of the BMS in LiFePo4 batteries. I have heared from a lot of users that they assume that the BMS is a charge / discharge controller. It's only a safety device that disconnects the batterie if the conditions are "wrong".

[@RefitandSail]

The BMS is and is not a charge controller. It’s primary function is to protect the battery from damage and to balance the cells. It will switch the battery off if it thinks it’s going to be over charged and the same if it thinks the battery is very discharged, all right protect the cells. So it is a sort-of charge controller BUT it does not control the charge voltage from outside sources so when charging you need to ensure you are the appropriate setup on your shorepower charger, any solar or wind and especially on engine charging. Hope that makes sense.

[@guy.h]

@@RefitandSail there are clever BMS available (even including ones that you can build yourself) that will communicate with the charging systems and regulate the charge going into the bank(s) These can also reduce the charge current right down (1A or so) to enable proper balancing if required.

[@CraigOverend]

Calico Skies wore their Delos hand-me-down Lithium Battleborns out because they were starting their AC motor and diesel engine with them briefly pulling high currents the batteries weren't rated for. I think they were only 3 years old. Never exceed Internal_Resistance/0.9V with LiFePO4, doing so immobilises lithium ions in the anode. This is why the continuous discharge rating is more important than discharge depth with all chemistries if you care about cycle life. The problem with lead acid is the Hour rating. A 100Ah Deep Cycle AGM may only be 20-Hour rated to achieve their rated cycle life. That's 100/20 = 5 A discharge rate. That's only 12V*5A= 60W! Modern electrical systems far exceed this and need many in parallel to get the life cycle the batteries are rated to.

[@RefitandSail]

Hi, thanks for the comment, I don’t follow their channels but it sounds like the damaged the batteries though miss-use rather than wearing them out though normal use. Yes I agree about the C rating, most folk don’t know what it is and why it’s important. There is lots of additional info like this I could have included but the video was long enough and I did not want to get deep and technical beyond what most owners need to get a reasonable grasp of the options. Sounds like you know what you are talking about though.

[@erbster200]

Useful info here - thanks! A question: in what way is the Victron battery monitor better than the Nasa one? I have a Bluetooth Nasa one and it works for me, but I wonder if I am missing a trick?

[@RefitandSail]

The nasa BM1/2 is an ok basic unit but it’s functionality is a bit limited compared to the victron alternative. The victron, for example, can be tuned to accurately monitor different battery types (AGM, lithium, etc) which have a slightly different charge/discharge profiles to FLA batts which is what the nasa unit is set up for. Things like resetting the monitor to “fully charged” has to be done manually on the nasa while it can be automated on the victron + lots of other advanced features. My biggest annoyance with the nasa battery monitor is the cheap and nasty fuse holder they use on the positive lead, it doesn’t create a very good connection so the battery monitor can get a false (low) voltage reading. It would cost little more for them to fit a decent fuse holder but it’s a unit made down to a price (like all nasa stuff) so not what I would fit on my own boat.

[@erbster200]

Thanks for that detailed answer, George. I didn't even think of Victron when I installed the NASA one on my boat. You're right about the "down to a price" quality - I'll know next time. (we're fellow POG members btw). Enjoying your channel.

[@ballottra]

Thank you its the first time batteries were made so clear!

[@RefitandSail]

Great. Thanks for the comment and compliment

[@cristianradu9513]

Thanks a lot. I'm just planning out my battery install, so good timing. Any chance you can talk about or show how to build a proper battery box? Does it need to be vented? Is this a thing that people do or worry about? Since you mentioned smart shunts, do you have any power usage figures you can share for common things on your boat? Like an autopilot running 24/7 on a long passage for example. I realize these can vary a lot but just to get some idea of what capacity I need.

[@RefitandSail]

At some point I will need to build a battery storage box/arrangement on Lottie so that may give you some ideas. If using arms then they don’t vent in normal operation so no specific vents needed into the battery box but some ventilation is not a bad thing into that compartment. On the early co32’s the yard installed a vent pipe between the battery box and the starboard winch handle pocket but later boats didn’t have this (probably because it was a source of water ingress). Power usage with the pilot is very hard to give as it really depends on point of sail, sea state and the settings on the pilot. Other items are easy to get from product manuals to by using a battery monitor and switching things on and off. It doesn’t take too long to get a spreadsheet with all equipment, how much power each items uses and then how many hours a day it’s on for.

[@joesmith1142]

Know this is an older video, but yes, love it but this could easily have been a several pert series. Its hard to get a comprehensive understanding of all of what you described in 30 minutes.

[@RefitandSail]

Thanks, I’m sure I’ll do more videos on this subject in due course.

[@Ajojets]

Another first class video, you always put things in a way that we all understand. Out of interest, I have to replace the outlet valve on my head, it’s an 1 1/2 bsp, it has a ball valve on at the moment that looks to be stainless, I have a brass bodied ball valve would this be suitable?

[@RefitandSail]

Thanks. Unusual to have a stainless bodied ball valve, are you sure it’s not chromed or similar. If replacing it needs to be a good quality DZR or CR ball valve designed for use on boats below the water, using a plain brass ball valve is not recommended as it could de-zink rapidly.

[@Ajojets]

@@RefitandSail yes it is stainless, it is sized solid, I will have to buy a bronze replacement, I had an incline that brass was no good in salty water. Thanks Andy.

[@RefitandSail]

@@Ajojets CR (corrosion resistant) brass is ok but bronze is better. Or go composite like trudesign.

[@kenmcdonald7793]

Are your "leisure" batteries equivalant to " deep cycle marine/RV"?

[@RefitandSail]

I’m not sure exactly what term is used in the US for what we call leisure batteries. But it’s the readily available FLA batteries that most chandleries seem to stock and a lot of people use me abuse. If it’s about £130/160usd for around 100ah then it’s likely of this type, calling them “deep cycle” is a bit of a joke because of you do regularly deep cycle them to 50% you kill them pretty quickly.

[@johan8724]

I have a small solar panel for the start and electric system like radio etc. What i would like to do maybe is install a fridge/freezer for longer trips in the future. What panels would i need for that?

[@KurreB]

👨‍🎓👍

[@SOLDOZER]

No reason to buy anything except Lithium for your house bank anymore.