Interesting reading all the comments on lithium.
I built my own 280Ah 24v ( equivalent to 560Ah at 12v) battery using CATL cells purchased in the USA. I had them shipped to Antigua.
I used a JK 200A BMS with 2A active balance.
The convertion to lithium has been a game changer for us.
The 720w of solar we have used to harvest circa 2kWh per day when connected to our lead domestic bank. That same solar now harvests over 3kWh per day. The simple fact with lithium is that you dont need to get the battery full every day to maximise its life like you do with lead. Infact, keeping the battery below 90% full,  will lengthen the life of lithium. As a result, we can use more battery capacity and keep the lithium battery on bulk charge, rarely floating the battery.
We now do 95% of our cooking on an induction hob. We boil the kettle on the induction hob. We use the immersion heater for hot water and we make water with our 220v watermaker all through a 3000w low frequency inverter.
We added 4x50w flesible panels on a canvas backing that are our roving panels for when anchored. They fold up in to the space of a single 50w panel when not in use. With this additional 200w of solar we are averaging 3.6kWh per day of solar harvest. More than enough to run all our loads electrically.
Our propane consumption is now negligible. We only use the gas cooker at sea, when our portable hob is stowed.
With the increasing number of people moving to lithium there are a few things to note.
24v boats are ideal for lithium. The load limiting factor is the BMS. They are rated in amps. If you are a 24v boat, you half the amp draw off your 24v battery.
Two lithium batteries is the ideal number. This actually needs to match your load but 2 batteries is way better than 4 batteries.
When you install multiple batteries in series, it can be difficult to balance the batteries with each other. This can result in one battery being dominant and taking most of the load. It can cause battery shut down of the highest or lowest charged battery in extreme cases. Parallel is less of a problem but balancing can still be an issue.

I am currently building a second lithium battery of a smaller size. 105Ah. It will use the same JK BMS and it be wired in parallel to the existing 280Ah battery. This will give me resilience should one BMS fail. It will allow me to carry on whilst we replace a BMS, etc.
The additional capacity will allow us to get through a few cloudy days without having to resort to the diesel generator.

Don't under estimate how much rewiring you may need to do to accommodate lithium. There is no such thing as a drop in replacement battery.

Stay clear of cheap lithium batteries.  It is far better to build your own with cells from a known source and a good BMS than buy something in a sealed box that you know nothing about. The cost of building your own battery is about half the cost of a cheap drop in lithium battery.
Building your own battery also allows you to install the battery in a ventilated battery box. If you sail in the tropics, heat is not your friend. Cooling drop in lithium batteries isnt possible. The BMS mosfets make considerable heat when charging and particularly discharging. This heat cannot escape a sealed box. By comparison, a diy battery can easily accommodate forced ventilation.
Lithium and solar were made for each other. Maximise your solar install.
Speak,to your insurance company. Mine were happy for me to install lithium

Thank you very much for this write-up of your recent experience. We had some battery balancing issues which we eventually resolved with a battery balancer and some tweaks to the wiring. Well worth the effort though.

Simon

+x

 

Wild.Bird - 17 Sep 2023

Interesting reading all the comments on lithium.
I built my own 280Ah 24v ( equivalent to 560Ah at 12v) battery using CATL cells purchased in the USA. I had them shipped to Antigua.
I used a JK 200A BMS with 2A active balance.
The convertion to lithium has been a game changer for us.
The 720w of solar we have used to harvest circa 2kWh per day when connected to our lead domestic bank. That same solar now harvests over 3kWh per day. The simple fact with lithium is that you dont need to get the battery full every day to maximise its life like you do with lead. Infact, keeping the battery below 90% full,  will lengthen the life of lithium. As a result, we can use more battery capacity and keep the lithium battery on bulk charge, rarely floating the battery.
We now do 95% of our cooking on an induction hob. We boil the kettle on the induction hob. We use the immersion heater for hot water and we make water with our 220v watermaker all through a 3000w low frequency inverter.
We added 4x50w flesible panels on a canvas backing that are our roving panels for when anchored. They fold up in to the space of a single 50w panel when not in use. With this additional 200w of solar we are averaging 3.6kWh per day of solar harvest. More than enough to run all our loads electrically.
Our propane consumption is now negligible. We only use the gas cooker at sea, when our portable hob is stowed.
With the increasing number of people moving to lithium there are a few things to note.
24v boats are ideal for lithium. The load limiting factor is the BMS. They are rated in amps. If you are a 24v boat, you half the amp draw off your 24v battery.
Two lithium batteries is the ideal number. This actually needs to match your load but 2 batteries is way better than 4 batteries.
When you install multiple batteries in series, it can be difficult to balance the batteries with each other. This can result in one battery being dominant and taking most of the load. It can cause battery shut down of the highest or lowest charged battery in extreme cases. Parallel is less of a problem but balancing can still be an issue.

I am currently building a second lithium battery of a smaller size. 105Ah. It will use the same JK BMS and it be wired in parallel to the existing 280Ah battery. This will give me resilience should one BMS fail. It will allow me to carry on whilst we replace a BMS, etc.
The additional capacity will allow us to get through a few cloudy days without having to resort to the diesel generator.

Don't under estimate how much rewiring you may need to do to accommodate lithium. There is no such thing as a drop in replacement battery.

Stay clear of cheap lithium batteries.  It is far better to build your own with cells from a known source and a good BMS than buy something in a sealed box that you know nothing about. The cost of building your own battery is about half the cost of a cheap drop in lithium battery.
Building your own battery also allows you to install the battery in a ventilated battery box. If you sail in the tropics, heat is not your friend. Cooling drop in lithium batteries isnt possible. The BMS mosfets make considerable heat when charging and particularly discharging. This heat cannot escape a sealed box. By comparison, a diy battery can easily accommodate forced ventilation.
Lithium and solar were made for each other. Maximise your solar install.
Speak,to your insurance company. Mine were happy for me to install lithium

+x

 

Simon Currin - 18 Sep 2023

Thank you very much for this write-up of your recent experience. We had some battery balancing issues which we eventually resolved with a battery balancer and some tweaks to the wiring. Well worth the effort though.

Simon

+x

 

Wild.Bird - 17 Sep 2023

Interesting reading all the comments on lithium.
I built my own 280Ah 24v ( equivalent to 560Ah at 12v) battery using CATL cells purchased in the USA. I had them shipped to Antigua.
I used a JK 200A BMS with 2A active balance.
The convertion to lithium has been a game changer for us.
The 720w of solar we have used to harvest circa 2kWh per day when connected to our lead domestic bank. That same solar now harvests over 3kWh per day. The simple fact with lithium is that you dont need to get the battery full every day to maximise its life like you do with lead. Infact, keeping the battery below 90% full,  will lengthen the life of lithium. As a result, we can use more battery capacity and keep the lithium battery on bulk charge, rarely floating the battery.
We now do 95% of our cooking on an induction hob. We boil the kettle on the induction hob. We use the immersion heater for hot water and we make water with our 220v watermaker all through a 3000w low frequency inverter.
We added 4x50w flesible panels on a canvas backing that are our roving panels for when anchored. They fold up in to the space of a single 50w panel when not in use. With this additional 200w of solar we are averaging 3.6kWh per day of solar harvest. More than enough to run all our loads electrically.
Our propane consumption is now negligible. We only use the gas cooker at sea, when our portable hob is stowed.
With the increasing number of people moving to lithium there are a few things to note.
24v boats are ideal for lithium. The load limiting factor is the BMS. They are rated in amps. If you are a 24v boat, you half the amp draw off your 24v battery.
Two lithium batteries is the ideal number. This actually needs to match your load but 2 batteries is way better than 4 batteries.
When you install multiple batteries in series, it can be difficult to balance the batteries with each other. This can result in one battery being dominant and taking most of the load. It can cause battery shut down of the highest or lowest charged battery in extreme cases. Parallel is less of a problem but balancing can still be an issue.

I am currently building a second lithium battery of a smaller size. 105Ah. It will use the same JK BMS and it be wired in parallel to the existing 280Ah battery. This will give me resilience should one BMS fail. It will allow me to carry on whilst we replace a BMS, etc.
The additional capacity will allow us to get through a few cloudy days without having to resort to the diesel generator.

Don't under estimate how much rewiring you may need to do to accommodate lithium. There is no such thing as a drop in replacement battery.

Stay clear of cheap lithium batteries.  It is far better to build your own with cells from a known source and a good BMS than buy something in a sealed box that you know nothing about. The cost of building your own battery is about half the cost of a cheap drop in lithium battery.
Building your own battery also allows you to install the battery in a ventilated battery box. If you sail in the tropics, heat is not your friend. Cooling drop in lithium batteries isnt possible. The BMS mosfets make considerable heat when charging and particularly discharging. This heat cannot escape a sealed box. By comparison, a diy battery can easily accommodate forced ventilation.
Lithium and solar were made for each other. Maximise your solar install.
Speak,to your insurance company. Mine were happy for me to install lithium

We have been using Victron Battery balancers for several years on our lead batteries. We still use one on the pair of 12v starter batteries that are configured in series to give us 24v. They work really well. We actually ran different sized batteries for several years as we struggled to get new batteries in Panama. The balancer sorted it out

Tim
s/v Wild Bird

+x

 

Wild.Bird - 17 Sep 2023

Interesting reading all the comments on lithium.
I built my own 280Ah 24v ( equivalent to 560Ah at 12v) battery using CATL cells purchased in the USA. I had them shipped to Antigua.
I used a JK 200A BMS with 2A active balance.
The convertion to lithium has been a game changer for us.
The 720w of solar we have used to harvest circa 2kWh per day when connected to our lead domestic bank. That same solar now harvests over 3kWh per day. The simple fact with lithium is that you dont need to get the battery full every day to maximise its life like you do with lead. Infact, keeping the battery below 90% full,  will lengthen the life of lithium. As a result, we can use more battery capacity and keep the lithium battery on bulk charge, rarely floating the battery.
We now do 95% of our cooking on an induction hob. We boil the kettle on the induction hob. We use the immersion heater for hot water and we make water with our 220v watermaker all through a 3000w low frequency inverter.
We added 4x50w flesible panels on a canvas backing that are our roving panels for when anchored. They fold up in to the space of a single 50w panel when not in use. With this additional 200w of solar we are averaging 3.6kWh per day of solar harvest. More than enough to run all our loads electrically.
Our propane consumption is now negligible. We only use the gas cooker at sea, when our portable hob is stowed.
With the increasing number of people moving to lithium there are a few things to note.
24v boats are ideal for lithium. The load limiting factor is the BMS. They are rated in amps. If you are a 24v boat, you half the amp draw off your 24v battery.
Two lithium batteries is the ideal number. This actually needs to match your load but 2 batteries is way better than 4 batteries.
When you install multiple batteries in series, it can be difficult to balance the batteries with each other. This can result in one battery being dominant and taking most of the load. It can cause battery shut down of the highest or lowest charged battery in extreme cases. Parallel is less of a problem but balancing can still be an issue.

I am currently building a second lithium battery of a smaller size. 105Ah. It will use the same JK BMS and it be wired in parallel to the existing 280Ah battery. This will give me resilience should one BMS fail. It will allow me to carry on whilst we replace a BMS, etc.
The additional capacity will allow us to get through a few cloudy days without having to resort to the diesel generator.

Don't under estimate how much rewiring you may need to do to accommodate lithium. There is no such thing as a drop in replacement battery.

Stay clear of cheap lithium batteries.  It is far better to build your own with cells from a known source and a good BMS than buy something in a sealed box that you know nothing about. The cost of building your own battery is about half the cost of a cheap drop in lithium battery.
Building your own battery also allows you to install the battery in a ventilated battery box. If you sail in the tropics, heat is not your friend. Cooling drop in lithium batteries isnt possible. The BMS mosfets make considerable heat when charging and particularly discharging. This heat cannot escape a sealed box. By comparison, a diy battery can easily accommodate forced ventilation.
Lithium and solar were made for each other. Maximise your solar install.
Speak,to your insurance company. Mine were happy for me to install lithium

Interesting comments on your system.  Seems everyone's system ends up different.  We ended up with 540 ahrs LFP and 800 watts of panels for 160 ahrs daily usage.  Works very well here in the tropics of SE Asia.  Good advice at the end, especially of using quality equipment; it does not have to be expensive.  Enjoy your cruising.

+x

 

SoggyPaws - 20 Sep 2023

+x

 

Wild.Bird - 17 Sep 2023

Interesting reading all the comments on lithium.
I built my own 280Ah 24v ( equivalent to 560Ah at 12v) battery using CATL cells purchased in the USA. I had them shipped to Antigua.
I used a JK 200A BMS with 2A active balance.
The convertion to lithium has been a game changer for us.
The 720w of solar we have used to harvest circa 2kWh per day when connected to our lead domestic bank. That same solar now harvests over 3kWh per day. The simple fact with lithium is that you dont need to get the battery full every day to maximise its life like you do with lead. Infact, keeping the battery below 90% full,  will lengthen the life of lithium. As a result, we can use more battery capacity and keep the lithium battery on bulk charge, rarely floating the battery.
We now do 95% of our cooking on an induction hob. We boil the kettle on the induction hob. We use the immersion heater for hot water and we make water with our 220v watermaker all through a 3000w low frequency inverter.
We added 4x50w flesible panels on a canvas backing that are our roving panels for when anchored. They fold up in to the space of a single 50w panel when not in use. With this additional 200w of solar we are averaging 3.6kWh per day of solar harvest. More than enough to run all our loads electrically.
Our propane consumption is now negligible. We only use the gas cooker at sea, when our portable hob is stowed.
With the increasing number of people moving to lithium there are a few things to note.
24v boats are ideal for lithium. The load limiting factor is the BMS. They are rated in amps. If you are a 24v boat, you half the amp draw off your 24v battery.
Two lithium batteries is the ideal number. This actually needs to match your load but 2 batteries is way better than 4 batteries.
When you install multiple batteries in series, it can be difficult to balance the batteries with each other. This can result in one battery being dominant and taking most of the load. It can cause battery shut down of the highest or lowest charged battery in extreme cases. Parallel is less of a problem but balancing can still be an issue.

I am currently building a second lithium battery of a smaller size. 105Ah. It will use the same JK BMS and it be wired in parallel to the existing 280Ah battery. This will give me resilience should one BMS fail. It will allow me to carry on whilst we replace a BMS, etc.
The additional capacity will allow us to get through a few cloudy days without having to resort to the diesel generator.

Don't under estimate how much rewiring you may need to do to accommodate lithium. There is no such thing as a drop in replacement battery.

Stay clear of cheap lithium batteries.  It is far better to build your own with cells from a known source and a good BMS than buy something in a sealed box that you know nothing about. The cost of building your own battery is about half the cost of a cheap drop in lithium battery.
Building your own battery also allows you to install the battery in a ventilated battery box. If you sail in the tropics, heat is not your friend. Cooling drop in lithium batteries isnt possible. The BMS mosfets make considerable heat when charging and particularly discharging. This heat cannot escape a sealed box. By comparison, a diy battery can easily accommodate forced ventilation.
Lithium and solar were made for each other. Maximise your solar install.
Speak,to your insurance company. Mine were happy for me to install lithium

Interesting comments on your system.  Seems everyone's system ends up different.  We ended up with 540 ahrs LFP and 800 watts of panels for 160 ahrs daily usage.  Works very well here in the tropics of SE Asia.  Good advice at the end, especially of using quality equipment; it does not have to be expensive.  Enjoy your cruising.

Our average daily usage here in the Caribbean since I built the battery 4  months ago is 114Ah at 24v, so 228Ah at 12v equivalent.

Hats off for this excellent thread mates!!!

Our 1996 J42  limped home from Newfoundland in 2022 with 4 terminal Gp27 100AH Lifeline AGMs..

So we have also taken on a year-long DIY LFP upgrade voyage in our side yard.  Spent 9 months studying sources mentioned above and designing.  We are going with a Victron Lynx Smart BMS Bus nannying 2 330Ah Victron Smart LFP batteries .  Victron ATC and ATD smart relays.  The 2 LFP's and their proper non-arc fuses fit under the nav seat where 3 AGMs lived. DC DC converter charges the Get Home Starter bank of 2 GP 27 new Gel batteries, Wakespeed 500 alternator regulator under DVCC control of the BMS. New Victron Inverter/shore charger. New Victron MPPT regulators.  The  key is an ElektroMaax 250A remote rectified GenMaax alternator.  The rectifier diodes are in a fan cooled heat sinked aluminum fin case mounted in the oilskin hanging locker of the aft head  It will have a separate T sensor for the Cerbo GX to monitor,  The small frame rotor on our 47 HP turbo Yanmar will be downrated to deliver180A steady state output without needing thermal cutback. 

We have labeled latched out means of cross connecting the LA bank to charging and loads, and reenabling the old Balmar MC616 regulator if the Victron BMS disconnects.

Cheers
Bill Bowers
SV ConverJence

+x

 

Bill.Bowers - 28 Sep 2023

Hats off for this excellent thread mates!!!

Our 1996 J42  limped home from Newfoundland in 2022 with 4 terminal Gp27 100AH Lifeline AGMs..

So we have also taken on a year-long DIY LFP upgrade voyage in our side yard.  Spent 9 months studying sources mentioned above and designing.  We are going with a Victron Lynx Smart BMS Bus nannying 2 330Ah Victron Smart LFP batteries .  Victron ATC and ATD smart relays.  The 2 LFP's and their proper non-arc fuses fit under the nav seat where 3 AGMs lived. DC DC converter charges the Get Home Starter bank of 2 GP 27 new Gel batteries, Wakespeed 500 alternator regulator under DVCC control of the BMS. New Victron Inverter/shore charger. New Victron MPPT regulators.  The  key is an ElektroMaax 250A remote rectified GenMaax alternator.  The rectifier diodes are in a fan cooled heat sinked aluminum fin case mounted in the oilskin hanging locker of the aft head  It will have a separate T sensor for the Cerbo GX to monitor,  The small frame rotor on our 47 HP turbo Yanmar will be downrated to deliver180A steady state output without needing thermal cutback. 

We have labeled latched out means of cross connecting the LA bank to charging and loads, and reenabling the old Balmar MC616 regulator if the Victron BMS disconnects.

Cheers
Bill Bowers
SV ConverJence

Hi Bill.  Good idea to switch to LFP and take your time with the research.  Lots of Victron equipment in your build.  Good stuff!  Big alternator too.  I didn't see any mention of solar, but maybe there's no sun up that far north.  We survive on solar down here in the tropics.  Let us know how it works out for you.

+x

 

Wild.Bird - 17 Sep 2023

Interesting reading all the comments on lithium.
I built my own 280Ah 24v ( equivalent to 560Ah at 12v) battery using CATL cells purchased in the USA. I had them shipped to Antigua.
I used a JK 200A BMS with 2A active balance.
The convertion to lithium has been a game changer for us.
The 720w of solar we have used to harvest circa 2kWh per day when connected to our lead domestic bank. That same solar now harvests over 3kWh per day. The simple fact with lithium is that you dont need to get the battery full every day to maximise its life like you do with lead. Infact, keeping the battery below 90% full,  will lengthen the life of lithium. As a result, we can use more battery capacity and keep the lithium battery on bulk charge, rarely floating the battery.
We now do 95% of our cooking on an induction hob. We boil the kettle on the induction hob. We use the immersion heater for hot water and we make water with our 220v watermaker all through a 3000w low frequency inverter.
We added 4x50w flesible panels on a canvas backing that are our roving panels for when anchored. They fold up in to the space of a single 50w panel when not in use. With this additional 200w of solar we are averaging 3.6kWh per day of solar harvest. More than enough to run all our loads electrically.
Our propane consumption is now negligible. We only use the gas cooker at sea, when our portable hob is stowed.
With the increasing number of people moving to lithium there are a few things to note.
24v boats are ideal for lithium. The load limiting factor is the BMS. They are rated in amps. If you are a 24v boat, you half the amp draw off your 24v battery.
Two lithium batteries is the ideal number. This actually needs to match your load but 2 batteries is way better than 4 batteries.
When you install multiple batteries in series, it can be difficult to balance the batteries with each other. This can result in one battery being dominant and taking most of the load. It can cause battery shut down of the highest or lowest charged battery in extreme cases. Parallel is less of a problem but balancing can still be an issue.

I am currently building a second lithium battery of a smaller size. 105Ah. It will use the same JK BMS and it be wired in parallel to the existing 280Ah battery. This will give me resilience should one BMS fail. It will allow me to carry on whilst we replace a BMS, etc.
The additional capacity will allow us to get through a few cloudy days without having to resort to the diesel generator.

Don't under estimate how much rewiring you may need to do to accommodate lithium. There is no such thing as a drop in replacement battery.

Stay clear of cheap lithium batteries.  It is far better to build your own with cells from a known source and a good BMS than buy something in a sealed box that you know nothing about. The cost of building your own battery is about half the cost of a cheap drop in lithium battery.
Building your own battery also allows you to install the battery in a ventilated battery box. If you sail in the tropics, heat is not your friend. Cooling drop in lithium batteries isnt possible. The BMS mosfets make considerable heat when charging and particularly discharging. This heat cannot escape a sealed box. By comparison, a diy battery can easily accommodate forced ventilation.
Lithium and solar were made for each other. Maximise your solar install.
Speak,to your insurance company. Mine were happy for me to install lithium

Tim,
Thanks for the description of your LFP install.  It seems everyone does it differently.  A couple of things to note. 
Not all BMSs are internal Mosfet relay rated in amps.  A number are external relay BMSs with few of the internal Mosfet BMS disadvantages you mention.  We used a very well regarded ElectroDacus SBMS0 external relay BMS that does require more wiring, including separate relays for the various charging devices and loads that the BMS can control.  These are commonly available up to about 500 amps each.  Using an external relay BMS greatly expands the amps a BMS can control and without any internal heat issues. 
One battery can reasonably be used for most installs requiring only one BMS instead of two or more batteries, each requiring a separate BMS and having the battery balancing problems you mention.  If you are concerned about a rare cell failure just carry a spare.  We do.
Insurance coverage is a big deal and may get more difficult in the future.  Read your insurance policy for its current requirements, but be aware that they may change in the future.  They are all different right now.  However, the future may require compliance with recently developed ABYC or ISO standards so understanding those is important before starting an install.
We live on solar in the tropics, almost never having to resort to our alts or portable generator for charging.  We designed our system for at least 3 days holdover with no charging.  It doesn't get much better than silent auto charging all day.
And finally using electric for cooking is safer, more convenient and produces far less heat than using LPG.  LFP makes that possible.
Dave McCampbell
SV Soggy Paws
 

+x

 

SoggyPaws - 5 Dec 2023

+x

 

Wild.Bird - 17 Sep 2023

Interesting reading all the comments on lithium.
I built my own 280Ah 24v ( equivalent to 560Ah at 12v) battery using CATL cells purchased in the USA. I had them shipped to Antigua.
I used a JK 200A BMS with 2A active balance.
The convertion to lithium has been a game changer for us.
The 720w of solar we have used to harvest circa 2kWh per day when connected to our lead domestic bank. That same solar now harvests over 3kWh per day. The simple fact with lithium is that you dont need to get the battery full every day to maximise its life like you do with lead. Infact, keeping the battery below 90% full,  will lengthen the life of lithium. As a result, we can use more battery capacity and keep the lithium battery on bulk charge, rarely floating the battery.
We now do 95% of our cooking on an induction hob. We boil the kettle on the induction hob. We use the immersion heater for hot water and we make water with our 220v watermaker all through a 3000w low frequency inverter.
We added 4x50w flesible panels on a canvas backing that are our roving panels for when anchored. They fold up in to the space of a single 50w panel when not in use. With this additional 200w of solar we are averaging 3.6kWh per day of solar harvest. More than enough to run all our loads electrically.
Our propane consumption is now negligible. We only use the gas cooker at sea, when our portable hob is stowed.
With the increasing number of people moving to lithium there are a few things to note.
24v boats are ideal for lithium. The load limiting factor is the BMS. They are rated in amps. If you are a 24v boat, you half the amp draw off your 24v battery.
Two lithium batteries is the ideal number. This actually needs to match your load but 2 batteries is way better than 4 batteries.
When you install multiple batteries in series, it can be difficult to balance the batteries with each other. This can result in one battery being dominant and taking most of the load. It can cause battery shut down of the highest or lowest charged battery in extreme cases. Parallel is less of a problem but balancing can still be an issue.

I am currently building a second lithium battery of a smaller size. 105Ah. It will use the same JK BMS and it be wired in parallel to the existing 280Ah battery. This will give me resilience should one BMS fail. It will allow me to carry on whilst we replace a BMS, etc.
The additional capacity will allow us to get through a few cloudy days without having to resort to the diesel generator.

Don't under estimate how much rewiring you may need to do to accommodate lithium. There is no such thing as a drop in replacement battery.

Stay clear of cheap lithium batteries.  It is far better to build your own with cells from a known source and a good BMS than buy something in a sealed box that you know nothing about. The cost of building your own battery is about half the cost of a cheap drop in lithium battery.
Building your own battery also allows you to install the battery in a ventilated battery box. If you sail in the tropics, heat is not your friend. Cooling drop in lithium batteries isnt possible. The BMS mosfets make considerable heat when charging and particularly discharging. This heat cannot escape a sealed box. By comparison, a diy battery can easily accommodate forced ventilation.
Lithium and solar were made for each other. Maximise your solar install.
Speak,to your insurance company. Mine were happy for me to install lithium

Tim,
Thanks for the description of your LFP install.  It seems everyone does it differently.  A couple of things to note. 
Not all BMSs are internal Mosfet relay rated in amps.  A number are external relay BMSs with few of the internal Mosfet BMS disadvantages you mention.  We used a very well regarded ElectroDacus SBMS0 external relay BMS that does require more wiring, including separate relays for the various charging devices and loads that the BMS can control.  These are commonly available up to about 500 amps each.  Using an external relay BMS greatly expands the amps a BMS can control and without any internal heat issues. 
One battery can reasonably be used for most installs requiring only one BMS instead of two or more batteries, each requiring a separate BMS and having the battery balancing problems you mention.  If you are concerned about a rare cell failure just carry a spare.  We do.
Insurance coverage is a big deal and may get more difficult in the future.  Read your insurance policy for its current requirements, but be aware that they may change in the future.  They are all different right now.  However, the future may require compliance with recently developed ABYC or ISO standards so understanding those is important before starting an install.
We live on solar in the tropics, almost never having to resort to our alts or portable generator for charging.  We designed our system for at least 3 days holdover with no charging.  It doesn't get much better than silent auto charging all day.
And finally using electric for cooking is safer, more convenient and produces far less heat than using LPG.  LFP makes that possible.
Dave McCampbell
SV Soggy Paws
 

Yes, well aware of relay based BMS. For us there was no need to go that route with the added complexity. On a 24v boat the FET based BMS is hardly stressed as our amps are so low. Now we have two batteries in parallel with their own BMS we have redundancy of two independent systems. We run the batteries in parallel but either battery can easily run the boat. We never see total loads above 100A but each battery has a 200A BMS with 2A active balancer.
My install is ABYC compliant and my insurance company are happy with lithium.
95% of our cooking is on our induction hob.
We rarely run the diesel genset now. I occasionally do it just to keep it moving but we have so much power that we just run off solar and a wind turbine.

Tim