Replacing a battery bank on a cruising sailboat requires a myriad of choices—driven by one overriding goal. What are you hoping to power with your new capability? And what’s the best way to get there?
First, let’s consider the boat. I am just completing a complete rewire on my new boat. That meant I have been reviewing the ABYC regulations and looking at all the updates since I last did a major electrical project.
Here are the basic parameters:
The boat: 32-ft. heavy displacement long keel traditional offshore cruiser.
Sailing: Comprehensive navigation and communications system including radar and inboard autopilot.
Domestic: 1500 W inverter, electric water heater, forced air diesel heater, refrigeration, microwave.
Power required: Estimated at around 150-200 amp hours (ah) day. Maximum draw from inverter is approx 180 A.
Type of sailing: Extended expeditions to remote areas with some offshore passages. The boat will spend much of its time at anchor not in a marina.
Charging sources: 400 W solar panels, 40 A charger, 120 A alternator externally regulated (real world output 90 A).
Currently there is a wider set of options for battery banks on board than there has ever been and this can be confusing. The performance varies widely as does the cost and complexity of the installation. Realistically, we have a choice between flooded lead acid (FLA), sealed lead acid—primarily absorbent glass matt (AGM)—Carbon Foam (Firefly) and lithium iron phosphate (LiFeP04). To be able to make a sensible choice between these we need to think about what we want out of the battery bank and then see how the different options match up. Different boats have different needs, so as well as looking at options for my boat, I will also talk about what may be suitable for different styles of boat and cruising patterns.
What do we want out of the battery bank?
In my case I want good value for money—no bank is cheap so I want it to last several years. The criteria I have set is that the bank should be good for ten years. Having said that, I am not just going to buy on price, it has to do its job reliably. I am also concerned about safety. Battery banks contain a lot of energy and have to potential to cause a fire. They can also contain corrosive chemicals and give of some toxic or explosive fumes. While safety is mostly about correct installation the inherent properties of the batteries also make a difference.
Now let’s look at the main ways we measure performance.
Life span
The lifetime to be expected from batteries is measured by the number of times they can be charged and discharged before their capacity drops to 80 percent of its original level. Eighty percent was chosen as the cutoff point because after that most batteries become more prone to sudden failure. This does get a bit more complex because the number of cycles a battery will give depends on how much it is discharged on each cycle.
In order to get a better idea of a bank’s lifespan, I prefer to think in terms of years of use. If I use the boat every day for six months in the summer that will be about 180 cycles, so if the battery is rated at 1,000 cycles that would be five and a half years. In order to get a ten-year life from the bank, we need to be looking at about 2,000 cycles for a boat with an active cruising season. If I was living aboard, I would want twice that, and if I mainly used the boat on summer weekends, anything over 1,000 would be adequate.
Power output
I want my batteries to supply enough current to run all the things on the boat and some of them draw a lot of amps. I also want to be able to run the boat all day without having to run the engine to recharge the battery bank and still have a safety reserve. How big a safety reserve is sensible depends on the type of cruising you do. For the weekend sailor mostly returning to a dock with shore power each night, 25 percent would be adequate. For most coastal cruisers, I would want that to increase to 50 percent. For an expedition boat like mine, I want enough to be able to run for two to three days. With that size bank there is a good chance I will be able to do most of my charging from solar plus the times I need to run the engine to move the boat.
When thinking about reserve capacity it is worth remembering that the charging system on a boat has several failure points. The alternator can die, you could be short of fuel or it can get contaminated, and a battery can fail. Sod’s law says if it does, it will be at the end of a long night passage and cloudy weather so no solar. You want enough juice left to run the essential systems until you can make repairs or get to the dock. In my case that could be a 500 nm passage!
Charging
I want the bank to be able to take all the power my charging system can provide so that I can recharge it quickly and save engine run times. The fact that a battery may be able to accept a charge rate of 500 A is irrelevant because I don’t have a 500 A charger, I just want it to take what is available.
Lastly the size and weight must be OK for the battery compartment and the boat’s load capacity so that I can fit it!
For my boat, say I need a bank that will supply a minimum of 150 ah plus a reserve of another 150 ah as a safety margin. So 300 ah is the min and 450 ah would be ideal. It must provide my 1500 W inverter with 180 A for 15 minutes continuously and about 45 minutes per day intermittently. That is a minimum, more would be better.
My alternator can provide 90 A so the bank must be able to accept at least 100 A. I also have a 40 A shore charger and the inverter/charger can provide 100 A, so in theory I can charge at 140 A when on the dock.In my case, with a heavy displacement boat weight is not important. My battery box is 24 L x 15 W x 12 H in inches.
What would be the advantages and disadvantages of each option for a replacement?
First a note on what I mean when referring FLA’s. The one I am talking about are true deep cycle 6 V or 4 V batteries from a top manufacturer (I am using Rolls as an example). “Leisure” batteries or any 12 V FLA simply will not give a reasonable service life on a boat.
FLA
I have room for four, 280 A, 6 V batteries giving 560 ah at 12 V. On the plus side, this option has been around for many years so it is available almost anywhere. I can do any work on it myself or any boat yard will have someone who can work on it. I can even get many parts from a local big box store. Since I am sailing to remote areas, this is an advantage.
FLA has the lowest up front cost and does not need any changes to the boat’s electrical system.
However, since the last bank was installed, I have added the inverter and microwave so my max power has increased, as has my daily use. I would now need at least 300 ah capacity to be able to draw 150 ah per day and have an expected life of ten years (2,000 cycles to 50 percent DoD). The max discharge rate is 225 A but that is at the one hour rate, which is hard on the batteries, they would prefer a limit of 90 A (five hour rate) so I would probably want to either fit a bigger bank or run the engine when using a lot of power. I can solve that with a bigger bank and can get taller batteries with the same footprint that would give me 900 ah and a max discharge rate of 145 A at the five hour rate. This would then easily satisfy everything, albeit at a higher cost. So going with FLAs is a practical and simple solution using proven technology
Disadvantages with FLA
They are not sealed so they will occasionally need topping up, especially with fast charging. As long as the batteries are easily accessible this is not a big issue and only needs doing a couple of times a season. What is a concern, however, is that when charging these batteries will “gas” and the fumes are corrosive. This may affect things like the charger and inverter fitted in the same space, so is not ideal. There is also a safety issue. If sea water gets into the batteries they give off highly toxic sulphur dioxide. This is not a big issue for me as my battery compartment is well above the bilges but I would not want these under the floorboards.
The other big issue with FLAs is charging. These batteries have to be charged at 14.8 V to fully charge them and that must be at least every two to three weeks or they will loose capacity and eventually fail. For maximum life, FLAs should never be left partially charged so they also need a maintenance charge whenever the boat is not in use. Charging rates for FLAs drops off steadily once they are up to 85 percent of full charge. With a large bank, this takes at least three hours with a finishing rate of less than 5 percent of the batteries’ ah capacity, some manufacturers recommend as low as 2 percent. No problem on shore power but an issue when cruising. I probably will get enough solar power to give the bank full charges often enough but this does mean I have to keep a careful eye on the bank and have a good battery monitor. For me this is the major disadvantage of FLAs.
AGM
Many boats are not exploring remote coastlines and spending days or weeks away from the dock, instead they are used mainly on weekends and return to the dock most nights. That is about 104 days per year. Adding in a couple of vacations, it is still less than 150 days per year even if you live in an area with no off season. In reality, this boat would probably do less than 100 days per year. Also, and opposite to me, it is rarely going to be more than a few hours from a dock and most nights will be in harbor plugged into shore power. For this cruising pattern a cycle life of 1,000 cycles would mean the bank would be likely to last 10 years.
Cycle life and reserve capacity are now not the concern they are for my boat. Since this boat will rarely undertake a 24 hour passage we can base bank size on 12 hours plus reserve. Based on the consumption for my boat of 150 ah day this boat wants the following bank. 150 ah per day divided by two (for 12 hours), 75 ah. Add a 50 percent reserve capacity equals 112 ah. She still has high peak power demands and this becomes the selection criteria.
A group 31 AGM has enough capacity and using a DoD of 50 percent, an expected life of more than 1,000 cycles. So in theory it would work, however it has a maximum recommended discharge rate of 62 A so not enough to power the inverter. For this boat, meeting the maximum discharge rate becomes the most important criteria. Yes, she could fit a large capacity FLA but most of the time that capacity would be redundant and simply mean extra weight and cost.
A 300 ah AGM bank would last 10 years. That cruising pattern would also rarely involve passages lasting a full 24 hours so you could fit a smaller bank and cycle it down to 50 percent. The bank would also be recharged back up to full charge most nights so for this cruising pattern the advantage of a maintenance-free sealed battery could outweigh the cost of AGMs.
A further advantage of AGM’s for such a boat is that they hold charge better when not in use. All batteries will slowly loose charge if left unused but for AGMs that is at least half the rate that it is for FLAs. If you left an FLA over the winter with no charger attached, it would lose enough charge to damage the battery. An AGM under that same conditions would only be down to about 65 percent DoD so it would be OK.
All this applies even more to a trailer sailor or if the batteries are mounted under the floorboards or in another inaccessible space. Fitting a pair of 12 V 150 ah AGMs would give a peak power output of about 150 A and be well over her minimum capacity requirements including a life, to 50 percent DoD, of 1,250 cycles. If weight and cost was important and there was no problem with running the engine on the occasions when max power was needed, she could reduce this to a pair of 105 ah 12 V batteries, which would still give a peak output of 110 A, enough for the inverter most of the time. It is important to note that these still need to be proper deep cycle batteries. The are plenty of AGMs that will provide a higher maximum current than this but at the expense of cycle life when discharged to 50 percent.
The advantage of AGM’s is exactly this, they will give a much higher discharge rate. In addition, they are sealed and maintenance free so can be fitted almost anywhere. These positives do come at the expense of a shorter cycle life so they would not work for my boat or anyone making extended passages, but we are the exception.
The other issue, again only significant for passage making boats, is that AGMs are limited to 14.4 V when charging compared to FLAs 14.8 V. This does not sound like a big difference but that 0.4 V drop in charge current makes a big difference to the number of amps going in. This is especially true as the battery gets near full charge. Plugged into shore power this does not matter, the boat has all night to charge, but if you primarily want to recharge from the engine alternator it will mean significantly longer engine run times. In practice, I have seen numerous reports from long distance cruisers saying that they could never get there FLAs fully recharged. However, most boats fall into this category of weekend use and for them this would be the ideal setup. It is lighter, cheaper (because you can use a smaller bank) and more convenient than FLAs, which explains why it is the most common battery seen on boats in the marina.
Firefly
were tested and re-tested during our look at the effects
of sulfation on batteries.
These are one of the newer technologies and use carbon foam instead of lead for the plates. This makes them much lighter and also gives them a very different charge and discharge profile. To stay within the 10 year life, I could discharge the battery further than FLAs, or AGMs, down to about 60 percent DoD instead of 50 percent. Like the AGMs, they have a very low self-discharge rate so they don’t need charging if the boat is in winter storage. They also have a very high charge and discharge rate. In order to meet the inverter’s needs I would only need a 250 ah bank. Given that I can discharge the bank further, this would also meet my daily needs and give me an adequate reserve. Because they don’t use lead plates, they also don’t suffer the problem of losing capacity if not regularly fully charged so that solves the issue of long charging times. I could normally run this bank at between 60 and 90 percent DoD. I would probably want to increase the bank’s capacity to give a higher reserve but would still have a smaller and lighter bank.
Cons. As always there are disadvantages. In this case it is cost and availability. There is only one company making these batteries and they are expensive. If anything happened and I needed to replace a battery I would be concerned that I would not be able to get hold of one in a reasonable time. For cruising boats Firefly is definitely a possibility. It has all the advantages of AGMs but without the downsides of shorter life and problems with recharging, but at a significantly higher cost. While this is an interesting development, my view is that it has now been superseded by lithium for most boats.
Lithium
This the newest tech out there. Lithium batteries have been powering mobile phones and cars for some years now, however this is not the technology in deep cycle marine batteries. The battery in your phone has a relatively short life and is a fragile beast. We have all read stories of cars and phones catching fire if the batteries get damaged and this is due to a condition called thermal runaway. Basically, if there is a fault in the battery or it is overcharged it can overheat to the point where the lithium starts to burn and at that point you have a fire that is almost impossible to put out. The only lithium you should fit on a boat is LiFePO4. A combination of different manufacturing and advanced battery management circuits makes fires highly unlikely with LiFePO4.
In many ways lithium is the ideal bank for my boat. A 300 ah bank would give me up to 200 A discharge, can be recharged at up to 150 A, does not need to be regularly fully charged, is completely sealed and even if run flat every day should still give more than 10 years of life. A further significant advantage with lithium is that their voltage stay almost flat and above 12 V until they are around 90 percent discharged. Combined with a very high discharge capacity, this means that if the inverter is running hard the system voltage does not fall off as it does with lead acid. For a lithium system I would simply size the bank according to the reserve I wanted, so again 300 ah is the minimum. What’s the catch?
Considerations
As always there are downsides. Lithium batteries are very expensive both to buy and install. This is a high-tech system and the battery management system (BMS) is a small computer that ensures the battery works safely and reliably. Getting anyone who can work on such a system outside major centers is unlikely and that would be an issue for anyone undertaking long distance voyages or one to remote areas. While in theory its long cycle life may cut the lifetime cost, for most of us having a battery bank that will last 20 or 30 years is not a priority, how many people even keep a boat that long! For a full time live-aboard however that may be a factor.
Careful Charging
Installing a lithium system is also not just a case of swapping the batteries. They require careful charging. While the discharge curve is very flat for about 90 percent of the cycle, it drops very sharply at the bottom end and rises equally sharply at the top. Overcharging lithium rapidly damages the battery and charging cannot be controlled by voltage. To properly charge them you must have a current regulated charger, not the standard voltage sensing system used for lead acid. In addition, lithium will accept such a high charge rate that if you simply hooked the alternator up to it, it would burn out the alternator.
Alternator Setup
What you have to do is attach the alternator to the start battery and then use a battery-to-battery charger to charge the house bank at a regulated rate. Alternatively, there are systems that control the alternator output by monitoring its temperature and throttling back as it overheats. With a good quality marine alternator and plenty of ventilation, preferable a blower directed at the back of the alternator, about 80 percent of its rated output is achievable. For a stock alternator, you would not expect more than 50 percent so a 120 A car alternator would only give you about 60 A. This rather negates the fast charging advantage of lithium, achieving anything above 100 A from an alternator requires a specialist and is expensive!
Another reason for using a battery-to-battery charger rather than a direct feed from the alternator is that part of the BMS’s job is to prevent the battery from being overcharged. The way it does this is that when the battery reaches 100 percent, the BMS shuts off the charging current. If the alternator is directly attached and running this will blow its regulator and diodes so your alternator is now dead!
Lithium is also able to provide massive discharge currents, and in the event of a short, the current can blow the fuse but continue to arc across the gap producing something similar to a lightening strike. We are talking hundreds or even thousands of amps! They have to be installed with specialist class ‘T’ fuses.
Bottom line. I am sure you get the picture—these systems need a higher level of expertise to ensure a safe installation and again that puts the cost up. Despite all these issues, I would consider it the ideal setup for my boat if I could afford it but at more than $2,300 each just for the battery plus the battery-to-battery charger, that is a big if!
Conclusion
Based on cost and simplicity, as well as reliable access to spare parts plus a proven track record, there is still much to be said for flooded lead acid. Provided the bank has a high enough capacity and you fit good quality 6 V cells, it will do the job and last at least 10 years. Bank size needs to be based on the maximum current draw being around the five hour rate.
If I had a lighter weight boat and/or limited space for batteries, especially if that meant fitting them in the bilges, and/or if the boat was only going to be used for 100 days per year or less and mainly moored in marinas for overnight stops, the AGM would work well. I would benefit from a lighter weight system that would still run the services and be less prone to loosing charge when not in use.
If installing the lithium system, I would base the bank size on the 24 hour needs plus a reserve.
Bottom line. If money was not a constraint and I was not worried about fitting very new technology, there is no question that for my boat the solid state lithium would be the way to go. This would probably apply to any boat with high power demands. While it would also work just as well for the boats I just described that spend most of their time in a marina, I think the cost would be hard to justify and I would probably stick with the AGMs.
Bank size
Many of the articles about lithium, and to a lesser extent other advanced chemistries, talk about the ability to use a higher proportion of the battery’s stored energy and thus being able to either fit a smaller bank or run more stuff from the same size bank. This is often quoted as making the system less expensive. If you only need half the bank size for a lithium battery the cost difference seems to be reduced and may even be equal to a lead acid system.
So what size bank do you really need, and more importantly, why?
Think about it this way. If you were planning a passage in a motor boat you would look at the fuel consumption and tank size and make sure you had enough fuel on board to complete the trip, plus a healthy reserve in case of delays or bad weather. Most sailboats rely on the electrical system for navigation, as well as crew comfort, so I would say that adequate electrical power is just as important for a sailboat as adequate fuel is for a motor boat.
The electrical system is also the most common one to develop problems—seawater and electricity don’t sit well together—so it is important to allow for developing problems with the motor or charging system. While solar is a great innovation, it rarely gives sufficient output to run the boat in bad weather. For all these reasons, I suggest that a minimum bank size should be based on you 24 hour power use plus at least a 50 percent reserve to get you back to port or gives you a chance to fix the problem in the event of something going wrong. For any boat heading for remote areas that is expecting to spend multiple nights at anchor or planning on offshore passages, I think it would be better to up that to twice the daily consumption as a minimum.
How far can you discharge a battery?
A lot of people say you must never discharge an FLA below 50 percent of its capacity. This is simply not true. Provided you are able to recharge it within 24 hours, you can discharge FLAs down to 10 percent and it will not harm them. What is true is that if you do this regularly, you will shorten the life of the bank to an unacceptable level. Any lead acid bank will give a much better service life if you base the bank size on using 50 percent of its capacity or less during your normal days sailing. This also gives you a healthy 40 percent (using 10 percent as the minimum safe discharge level) in reserve if you have charging problems.
Charging
All lead acid batteries suffer from a problem called sulfation. As the battery is discharged the lead in the plates undergoes a chemical change. When the battery is recharged this reverses that chemical process. The problem of sulfation arises if the battery is left partly discharged. In that case the changes get locked in and are no longer reversible. If you left the battery flat for a month you would probably destroy it.
Unfortunately, the same is true if the battery is only partially recharged. If a lead acid battery is left at 90 percent full for a month, you will probably lose about 10 percent of its capacity so it is down to 90 percent of its new capacity. If you do the same the next month, you will lose another 10 percent. Once a battery is down to 80 percent of its new capacity, it is considered at the end of its life. So if you only partially recharge any lead acid battery you can easily write it off in a few months.
To maintain their life, these batteries need to be fully charged at least every two weeks. In order to fully charge a lead acid battery, it needs charging with a three-step charger or externally regulated alternator for at least three hours after the current starts to drop, even though it will only be accepting a low current. With a good solar set up this can “finish” the charge rather than having to run the engine or have shore power, but that assumes enough sun!
Lithium advantages. One of the big advantages of lithium is that it does not suffer from this problem to the same extent (they do need a full charge to balance the cells periodically). You can partially charge the bank, and as long as you have enough power for the passage, all is well. The charging issues with lithium are around not burning out the alternator by demanding two much current from it.
Charging capacity calculations. The traditional way in which battery and charging capacity were estimated was to take the typical daily consumption and multiply by three to get the bank size then divide that by five for the alternator size. That is the actual output from the alternator in normal conditions and is generally about 70 percent of its rated output. As an example, assume a daily consumption of 100 ah. That would give a bank size of bank size 300 ah and an alternator output 60 A (rated 85 or 90 A). That is still a good way to estimate system requirements for any lead acid bank.
Battery voltage
The practical limit for alternator is about 130 A in the real-world output. You can get units with much higher claimed output but this tends to be very expensive and they only get near that output level when turning at high speed, so you also need to fit over size engine pulleys. A 130 A alternator will charge a battery bank of about 500 ah without getting into excessive engine run times.
For boats with high loads such as electric cook stoves, air conditioning or just a daily consumption above about 200 ah a day, I would suggest going to a 24 V system with a step down DC converter to run 12 V components. This is more cost effective and also reduces the cable sizes needed. While this is not commonly done in North America, it is becoming standard for larger boats in Europe and some are even going to 48 V. Doubling the voltage halves the current for the same power and means you can use alternators designed for trucks and buses which are more robust and designed to give higher outputs.
Selecting the battery chemistry is just the beginning. You also need to consider the rest of the electrical system that supports it. My approach has been contrary to what is popular…that is, to minimize my electrical needs or KISS (Keep It Simple Stupid). My initial batteries were 2x8D GEL and lasted 15 years including a roundtrip to Hawaii without having to run the diesel for charging…the boat has 560W of solar. When I replaced them in 2019, I considered alternatives but went with my wining experience, Gel again.
Not sure where you are getting your cost comparisons… I just checked Renogy, a 100Ah LiFePO4 battery is $300, and can be discharged to very low capacity. A flooded 200Ah battery at Amazon (since you want to discharge to no less than 50%) is $355. While that’s is a bit more capacity to use (LiFePO4 should not go down to 0), it’s very much in the same range.
Another consideration. Who can guarantee that their bank will never be totally discharged by accident. All it takes is a careless passerby at the dock for your electrical connection to be cut off, resulting in a huge loss of lifetime for the bank. Lithium gives great peace of mind in this respect.
Great article Roland. You provided a nice comparison of the options and things to consider. I have a LA system currently with two 6V Trojan T105 house batteries that are approaching their end of life (they were purchased in 2016). I have been thinking of replacing them with Lithium but this will require many expensive upgrades to my current system. To date, the LA battery system has served me well. Your article has been great in helping me evaluate my alternatives. Cheers
I was hugely disappointed the PS would even publish this without more thoroughly checking the facts presented. Firefly does not exist anymore in any practical sense due to problems with their products and lack of response from the company. The information on lithium is so out of date it does not even make any sense today especially in regards to pricing and skills needed to install. This misleading column might seriously lead someone new to sailing to make totally wrong decisions in setting or improving a battery bank.
Good article and seemingly a through examination of the different chemistries, although I believe that Firefly is currently gone. 5 yrs. ago I got a new (to me) 40′ cat. For the house, I replaced the two automotive FLAs with 4-120AH LifePo4’s. They are charged exclusively by 500W solar. There is a 2500W inverter, with microwave, 42″ flatscreen and 110V refrig (7 cu. ft.) as the main big draws, plus autopilot and chartplotter when moving. Water heating is on-demand propane. All internal and external lights are LED. Occasionally there is some “boat project” requiring a 110V circular saw (15A), jig saw (5A), heat gun (15A), etc. There is also a 1500W pressure washer that I use every couple of months for an hour or so, which pulls the batteries down to 60-70% and they recover by the next day. Cost for the batteries with internal BMS was $400 each (5 yrs. ago) direct from the Chinese factory and that included $100 apiece for air freight. Prices have since come waaaay down since, to where they are advertised for $100-$200 for 100ah. The batteries so far have operated flawlessly, they just sit there and put out, no maintenance. I periodically open the hatch and look to see if they are really there and clean the dust off the tops. We are not liveaboards, mostly day sailors, with a couple of weeks a year at Catalina, but even then, the batteries recover the next day, or day after if it’s particularly cloudy. They never need shore power or engine charging, just solar.
A couple of explanations. Carbon foam batteries are still on sale in Canada but as ‘discontinued’ items with no warrentee. (They were still listed when I wrote the article.) It is an interesting technology but I apologize for being a little out of date on this one
I did make clear in the article that I wanted to compare like with like, so for price comparisons I only including premium North American battery suppliers. Yes you can get cheaper lithium batteries from China which may be a good deal or may not. I suggest you look very carefully at both the type and grade of cells and the BMS on these. I do buy stuff from China and have had some excellent deals but it is very much a ‘buyer beware’ situation and warranties may be useless. I would not consider it a good comparison to put against a manufacturer like Rolls or interstate
I was close to going ahead with a LiFePO4 battery replacement project last week for my three existing Firefly batteries. I pulled the plug definitively on this after double-checking with my insurer. I was advised that the underwriter is no longer issuing or renewing insurance for boats with lithium batteries due to the fire concern. Probably there are other underwriters out there, but my broker thinks it’s only a matter of time until they all pull insurance on Li (this is in Canada; I have no idea whether the US industry will be similar). While I appreciate the distinction of the FePO4 variant of lithium chemistry, it’s not clear the insurance industry will do that. Also, give your head a shake before installing a low-cost, Chinese Li battery in a boat. Fine for your bicycle, maybe even a car, but you risk death if that catches fire on the water, whether cruising or at anchor. The fire cannot be extinguished – the boat will be lost for sure.
Also, the technical challenges of this switch were a little greater than mentioned here. For example, my older inverter-charger would have had to be changed to an updated one to handle the different voltage profile of the Li chemistry, along with a new battery monitor, upgraded cabling, etc. Ka-ching, ka-ching. I’m pretty handy and have rewired my own house without any worries, and no concerns about wiring the 12V system in my boat, but I would be leery of messing something up for a Li installation in a boat due to the fire concern, burning out the alternator, etc. All in with professional installation, quality batteries and all the additional gear required this was going to be a C$7,000 to C$10,000 project for 3 x sched 31 LiFePO4 batteries. Less in US$, I know, but still pricey for what you get.