Depth of Discharge Myth?

[evm1024]

Sigh....


PSOC goes back at least to 2002 in the scientific and engineering papers.

SOC and DOD both describe the charge in a battery. However, SOC is a measure of the current state of that charge. Where as DOD expresses the lowest SOC that we see in a system (over some time frame).

Example: I'm charging my bank and am currently at 80% SOC. But last night I reached an 80% DOD.

PSOC may look like it is saying that the battery is not fully charged but that is not what it is. PSOC was coined as a charging strategy where the battery bank is deliberately not charged to 100%SOC. This was originated so that the battery system would be able to recover excess energy when available in automotive and off grid systems.

PSOC has also come to mean (and this is how we use the term) any battery - charging system where the charging system is unable to replace the used charge in a charging/use cycle.

For cruising boats that cycle is 24 hours.

With FLA the system is operating in PSOC if we are not able to bring the SOC up to 100%. (Takes a long time to do so in FLA)

With LiFePO4 the system is in PSOC mode when the charging system is unable to bring the SOC up to the desired set point. In general applying PSOC to LiFePO4 is meaningless.

[evm1024]

I just got back from giving a 2 hour talk at a local yacht club on boat battery and charging systems. We had about 20 boats represented there.

It looked like it had a typical mix for the areas clubs.

About 30% to 40% had FLA with stock (internally regulated) alternators.

Another 40% had a mix of FLA, AGM and Gell Cells with external regulated alternators.

The last few were Firefly and just 1 LiFePO4 with externally regulated alternators.

1 was industrial FLA 2 volt cells (and he got 16 years out of the last set)

There was a smattering of smallish Solar. Smallish in this case means that the Solar was typically 100 Watts or less. But there were 2 boats with 400 watts and 600 watts respectively.


What I found is interesting, every one of the lead acid systems with the exception of the firefly and 2 volt cells were being replaced every 3 years or so. This was a dismal statistic because these boats typically did a 3 or 4 week cruise in the summer and 6 or 8 weekend cruises the rest of the year. They were on shore power most of the time.

The ones who had installed battery monitors report that they were seeing gradually decreasing SOC during their summer cruises and were not really ever reaching 100% SOC.

If we were to discount the weekend cruises and consider that they were returned to 100% SOC back at the dock then it appears that operating in PSOC during their cruises was killing their batteries. Three weeks for 3 years gives us about 63 daily cycles at PSOC. Not too far removed from the numbers that Mainesail has reported in his PS battery test article.

The firefly folks have not had their batteries for very long yet. So no real data there. They do like then and state that they are an improvement over their prior batteries. Basically they said that their prior FLA batteries sucked and were always going bad.

The guy with the 2 volt cells is a respected boat builder. These are forklift batteries and are around 120 pounds each. His bank is 24 volts so he has something like 1400 pounds of batteries in his keel. (nice to build your boat the way you want)

16 years out of a set of batteries. He states that he rarely uses more than 5% of his capacity in any given day cruising. Also, he figures that in terms of cycles he likely uses less than 60 cycles per year.

The LiFePO4 boat says that he would not recommend LiFePO4 to anyone who does not have a technical background and the willingness to learn the technology. From there he goes on to wax poetic about all of the advantages he is seeing in his battery.

Where you have it in a nutshell. Typical boats? Hard to say. It was a sample that was attending a talk on charging and batteries.

The FLA people changed their batteries out every 3 years and were not very happy. Those that changed to firefly or LiFePO4 were much, much happier.

True, they did not have alternates to their engine for charging when off shore power. But I suspect this is much, much more common to weekend cruisers then long term cruisers.

They do not want the expense and windage of solar panels, solar arches and frames and the expense of solar controllers. They do not want to learn to live with solar and the same for wind generation. In other words, no solution there.

[ramblinrod]

Originally Posted by newhaul

first just about everyone that has Fla banks on their boats will not admit they killed them due to constant PSOC issues.

Some who kill FLA batteries prematurely either don't know or don't care.

For those who do care, human nature dictates that most people will not own up to their mistakes.

This includes LFP early adopters who have spent a ton of time and money, and trashed $1000s in batteries, or realized little to no real benefit.

I suppose a relatively high percentage of LFP early adopters are likely to kill LFP batteries because they don't know any better.

I believe I heard MaineSail is not consulting individuals on LFP anymore because of the poor results they were realizing, that was attributed to their inability to operate them properly.

This doesn't sound like a mainstream product to me.

Second your statement of 400 watts solar for each 100ah Fla. For 400ah that is 1.6kw of solar. Imo on the average 35 ft cruising sailboat in not a practical solution.

First, most 35 ft +/- cruising sailboats do not have 400 A-hr daily consumption. More like 100 A-hr.

Second, I recommend 400W of solar and/or wind for every 300 A-hrs of bank for every 100 A-hrs of daily consumption.

200 A-hrs per day is a lot of juice.

A typical boat that would require this amount of energy daily at anchor, would include 2 BD-35 refrigerant compressors, one for fridge and another for separate freezer. A significant 12 Vdc watermaker. All the TV one can watch, all the circulation fans one can run 24/7, all the phones and laptops one can charge, all the LED lighting one can light. All the BT speakers one can listen to, leaving the VHF on standby 24/7, radar running 24/7, and so on an so on.

Even at that, with a 600 A-hr house bank (2S3P x GC2s for example), a 160 A alternator, a 400 W wind generator, and a 400W solar array, life is good.

This is the typical amount of wind and solar power generation easily installed on a typical 35' +/- cruising sailboat.

However 400 watts solar is just fine for a 400ah Lfp bank due to not having issues with PSOC .

If you are still referring to 400 A-hr average daily consumption, a 400 a-hr LFP bank and 400W solar for charging, this is untenable.

A 400W solar charging system will typically deliver 100 to 120 A-hrs per sunny day. Less if any panel shading or with any cloud.

The system you prescribe would not come anywhere near close to replenishing the energy consumed.

That is a at least a 280 A-hr shortfall on a perfect day.

Increase load above average, or decrease solar charging from ideal, and it is even worse.

LFP does not generate power, it just stores it.

Third you obviously don't look at the news concerning ev systems. Just about every auto manufacturer is making either a thread or a fully electric vehicle.

Incorrect.

I do follow the news on EV, and have for a long time. My next door neighbour has a "Volt".

To date EV (excluding hybrid) is suitable for the family grocery getter.

Limited range.

Considerable charge time when depleted.

A similar propulsion system on a boat may be used to get from a dock out to open water, back in from open water after a day sail, and back to the dock for charging overnight.

For a cruising boat, that may motor for a full day, one mother of an ICE generator (10kW) is required to continuously replenish the energy consumed.

That is about the same size diesel engine that the electric drive replaces.

And while motoring, the diesel engine on the non electric vessel is driving and alternator, which is recharging the batteries for normal house loads.

Not so on the electric boat, else an even bigger generator is required.

Now in your responses please be specific

I am quite sure most would agree that my responses are generally quite specific. ;-)

(I have only responded to your first 3 or 4 statements as that is all the time I can afford on this particular post, and I believe I covered the most important issues adequately.)

[newhaul]

Originally Posted by ramblinrod

Some who kill FLA batteries prematurely either don't know or don't care.

For those who do care, human nature dictates that most people will not own up to their mistakes.

This includes LFP early adopters who have spent a ton of time and money, and trashed $1000s in batteries, or realized little to no real benefit.

I suppose a relatively high percentage of LFP early adopters are likely to kill LFP batteries because they don't know any better.

I believe I heard MaineSail is not consulting individuals on LFP anymore because of the poor results they were realizing, that was attributed to their inability to operate them properly.

This doesn't sound like a mainstream product to me.



First, most 35 ft +/- cruising sailboats do not have 400 A-hr daily consumption. More like 100 A-hr.

Second, I recommend 400W of solar and/or wind for every 300 A-hrs of bank for every 100 A-hrs of daily consumption.

200 A-hrs per day is a lot of juice.

A typical boat that would require this amount of energy daily at anchor, would include 2 BD-35 refrigerant compressors, one for fridge and another for separate freezer. A significant 12 Vdc watermaker. All the TV one can watch, all the circulation fans one can run 24/7, all the phones and laptops one can charge, all the LED lighting one can light. All the BT speakers one can listen to, leaving the VHF on standby 24/7, radar running 24/7, and so on an so on.

Even at that, with a 600 A-hr house bank (2S3P x GC2s for example), a 160 A alternator, a 400 W wind generator, and a 400W solar array, life is good.

This is the typical amount of wind and solar power generation easily installed on a typical 35' +/- cruising sailboat.



If you are still referring to 400 A-hr average daily consumption, a 400 a-hr LFP bank and 400W solar for charging, this is untenable.

A 400W solar charging system will typically deliver 100 to 120 A-hrs per sunny day. Less if any panel shading or with any cloud.

The system you prescribe would not come anywhere near close to replenishing the energy consumed.

That is a at least a 280 A-hr shortfall on a perfect day.

Increase load above average, or decrease solar charging from ideal, and it is even worse.

LFP does not generate power, it just stores it.



Incorrect.

I do follow the news on EV, and have for a long time. My next door neighbour has a "Volt".

To date EV (excluding hybrid) is suitable for the family grocery getter.

Limited range.

Considerable charge time when depleted.

A similar propulsion system on a boat may be used to get from a dock out to open water, back in from open water after a day sail, and back to the dock for charging overnight.

For a cruising boat, that may motor for a full day, one mother of an ICE generator (10kW) is required to continuously replenish the energy consumed.

That is about the same size diesel engine that the electric drive replaces.

And while motoring, the diesel engine on the non electric vessel is driving and alternator, which is recharging the batteries for normal house loads.

Not so on the electric boat, else an even bigger generator is required.



I am quite sure most would agree that my responses are generally quite specific. ;-)

(I have only responded to your first 3 or 4 statements as that is all the time I can afford on this particular post, and I believe I covered the most important issues adequately.)

True you can not cover 100 ah of usage with 100 watts solar but that's not what you keep saying .

This is what you said in the post I quoted. ( its also in many of your other posts )

quote:
I. For 100 A-hrs of battery capacity it only takes 400 W of solar and/or wind.
End quote
That statement means that with just 2 gc2 batteries ( making 1 12 volt bank of 220 ah nominal) require by your own statements 800 watts of solar.

[ramblinrod]

[QUOTE=evm1024;2716297]

SOC and DOD both describe the charge in a battery.

Like I posted.

However, SOC is a measure of the current state of that charge. Where as DOD expresses the lowest SOC that we see in a system (over some time frame).

Incorrect.

Both terms alone are for instantaneous values.

SOC is the current charge level as a percentage of capacity remaining.

e.g. If the battery has 100 A-hr capacity and it is currently storing 80 A-hrs, the SOC is 80%.

DOD is the current charge level as a percentage of capacity consumed.

e.g. If the battery has 100 A-hr capacity and it is currently storing 80 A-hrs, the DOD is 20%.

PSOC may look like it is saying that the battery is not fully charged but that is not what it is.

Incorrect.

That is exactly what PSOC is.

A PSOC on a FLA battery is not a problem. My batteries are in a PSOC state from sunset to about the next sunset, while swinging on anchor. Lowest PSOC in the morning around sunrise.

The issue you are referring to is "Sustained PSOC".

When an FLA battery is sustained at a PSOC (ie no chemical action going on to charge or discharge) a phenomenon happens.

When the FLA battery discharges, Amphoruos (easily activated) Lead Sulphate crystals form on the lead plates.

The deeper the discharge, the greater the crystals.

If the battery is fully recharged immediately, there is no issue.

If the battery is left in this PSOC state, the Lead Sulfate crystals "harden".

They become less porous and more difficult to re-activate and remove from the plates during the normal recharging process.

This results in less active plate surface area, thus a reduction in capacity.

The longer, deeper, and more often this sustained PSOC condition, the more "hardened" and the greater the capacity loss.

With FLA the system is operating in PSOC if we are not able to bring the SOC up to 100%. (Takes a long time to do so in FLA).

Agreed. Operating in PSOC means not at 100% charge. This can be troublesome the deeper and longer and more frequently sustained.

The solution?

300 A-hrs of FLA battery capacity, 80 A of alternator, and 400W of solar and/or wind, for every 100 A-hrs of average daily energy consumption.

Most times the batteries will be at a high SOC, minimal DOD and not left in a deep, long, frequent, PSOC condition. The FLA batteries will last a long, long time.

With LiFePO4 the system is in PSOC mode when the charging system is unable to bring the SOC up to the desired set point. In general applying PSOC to LiFePO4 is meaningless.

Incorrect, PSOC means the same thing regardless of battery technology.

For LFP, sustained PSOC can harm the batteries.

Leave them at 0 - 10% SOC (90-100% DOD) for any length of time and they are hurt. The longer and more frequently this PSOC is sustained the more certainly they will be killed dead.

Also LFP batteries can be hurt with a sustained 90-99% SOC (1-10% DOD).

In fact they can be killed very quickly if over-charged, meaning the charge voltage is applied when batteries are at 100% SOC (0% DOD), whereas FLA batteries love this condition.

This is why most chargers, charge controllers, and alternator regulators must be replaced when LFP batteries are installed. Even if equipped with a "Li" mode dip switch, when the charge algorithm is rebooted, and the charger goes into absorption, it can hold the charge voltage on a fully charged LFP for hours, killing it dead. A fully charged FLA battery is much more tolerant of this condition. A VRLA is unaffected other than warming up a bit, and a regular cheap FLA may lose a tiny fraction of water.

[Delfin]

Originally Posted by ramblinrod

I believe I heard MaineSail is not consulting individuals on LFP anymore because of the poor results they were realizing, that was attributed to their inability to operate them properly.

No, according to him, he doesn't do REMOTE consulting because people tend not to listen to the recommendations that will maximize their investment in Lithium. Poor results from a properly installed and managed Li bank has nothing to do with it.

Originally Posted by ramblinrod

Incorrect.

I do follow the news on EV, and have for a long time. My next door neighbour has a "Volt".

To date EV (excluding hybrid) is suitable for the family grocery getter.

Limited range.

Just a suggestion, but perhaps you might try to stay up on the topics you make such emphatic statements about. It will make other blanket statements you make seem more, um, plausible. The Chevy Bolt has a 238 mile range and recharges fully to deliver that range overnight. So, I guess your statement would be correct if you lived in Chicago, but like to shop for groceries in Cleveland.

[Dockhead]

Originally Posted by evm1024

I just got back from giving a 2 hour talk at a local yacht club on boat battery and charging systems. We had about 20 boats represented there.

It looked like it had a typical mix for the areas clubs.

About 30% to 40% had FLA with stock (internally regulated) alternators.

Another 40% had a mix of FLA, AGM and Gell Cells with external regulated alternators.

The last few were Firefly and just 1 LiFePO4 with externally regulated alternators.

1 was industrial FLA 2 volt cells (and he got 16 years out of the last set)

There was a smattering of smallish Solar. Smallish in this case means that the Solar was typically 100 Watts or less. But there were 2 boats with 400 watts and 600 watts respectively.


What I found is interesting, every one of the lead acid systems with the exception of the firefly and 2 volt cells were being replaced every 3 years or so. This was a dismal statistic because these boats typically did a 3 or 4 week cruise in the summer and 6 or 8 weekend cruises the rest of the year. They were on shore power most of the time.

The ones who had installed battery monitors report that they were seeing gradually decreasing SOC during their summer cruises and were not really ever reaching 100% SOC.

If we were to discount the weekend cruises and consider that they were returned to 100% SOC back at the dock then it appears that operating in PSOC during their cruises was killing their batteries. Three weeks for 3 years gives us about 63 daily cycles at PSOC. Not too far removed from the numbers that Mainesail has reported in his PS battery test article.

The firefly folks have not had their batteries for very long yet. So no real data there. They do like then and state that they are an improvement over their prior batteries. Basically they said that their prior FLA batteries sucked and were always going bad.

The guy with the 2 volt cells is a respected boat builder. These are forklift batteries and are around 120 pounds each. His bank is 24 volts so he has something like 1400 pounds of batteries in his keel. (nice to build your boat the way you want)

16 years out of a set of batteries. He states that he rarely uses more than 5% of his capacity in any given day cruising. Also, he figures that in terms of cycles he likely uses less than 60 cycles per year.

The LiFePO4 boat says that he would not recommend LiFePO4 to anyone who does not have a technical background and the willingness to learn the technology. From there he goes on to wax poetic about all of the advantages he is seeing in his battery.

Where you have it in a nutshell. Typical boats? Hard to say. It was a sample that was attending a talk on charging and batteries.

The FLA people changed their batteries out every 3 years and were not very happy. Those that changed to firefly or LiFePO4 were much, much happier.

True, they did not have alternates to their engine for charging when off shore power. But I suspect this is much, much more common to weekend cruisers then long term cruisers.

They do not want the expense and windage of solar panels, solar arches and frames and the expense of solar controllers. They do not want to learn to live with solar and the same for wind generation. In other words, no solution there.

Absolutely consistent with the cruisers I know.


In Florida where we cruised in the '90's and early 2000's, maybe 50% of boats had solar systems, and we had a big one which we were delighted with. But there's hardly any wind there and little sailing, and certainly no one sails upwind much.



In UK waters above 50N and much stronger wind, I guess less than 10% of boats have any solar at all.



Some might think that there's no sun in the UK, so why bother with solar. But solar actually performs about the same in the UK, as it does in Florida -- first of all, solar cells output is much higher at lower temperatures, and second, the days are much longer in the summer. But no one wants the windage (or ugliness) of big solar installations -- sailboats here are meant for SAILING.





So the folks I know are the same as your sample -- 3 or 4 years out of a set of lead batteries, and most people I know are not satisfied.

[ramblinrod]

Originally Posted by newhaul

True you can not cover 100 ah of usage with 100 watts solar but that's not what you keep saying .

My statements have been 100% accurate all along.

You are the one who stated that one could recharge a 400 A-hr daily consumption to a 400 A-hr LFP bank, with 400 W of solar.

Here is the exact quote from your post # 750.

Second your statement of 400 watts solar for each 100ah Fla. For 400ah that is 1.6kw of solar. …However 400 watts solar is just fine for a 400ah Lfp bank due to not having issues with PSOC .

(… irrelevent personal opinion removed.)

Your statement is completely, unequivocally, undeniably, incorrect.

This is what you said in the post I quoted. ( its also in many of your other posts )

quote:
I. For 100 A-hrs of battery capacity it only takes 400 W of solar and/or wind.
End quote
That statement means that with just 2 gc2 batteries ( making 1 12 volt bank of 220 ah nominal) require by your own statements 800 watts of solar.

No it doesn't.

Read it again.

400 W of solar and or wind for each 100 A-hr of consumption means exactly what it states.

For your example of 200 A-hr daily consumption, using my ratios, the energy consumed could be replaced by 800 W of solar and/or wind, which could be any combination:

Example A: 800W solar

Example B: 400 W solar and 400 W wind

Example C: 800 W wind

For the average 35 ft +/- sailboat, cruising an area suited to both generating technologies I would recommend option B.

If the owner objected to solar (usually unreasonable IMHO) then obviously I would propose option C.

If the owner objected to wind (usually unreasonable IMHO) then obviously I would propose option A.

If the owner was opposed to either wind or solar (usually completely unreasonable for the target cruising sailboat) I would propose options including the correct size FLA bank and ICE charging, and the correct sized LFP bank and ICE charging.

The PROPER conversion from FLA to LFP is very costly, and to date those I have consulted who refuse to have wind or solar on board (for only god knows why) have opted for correct sized FLA bank and ICE charging.

This is the only reason I have not installed an LFP solution for a customer.

Provided the true facts, none could warrant the high expense for the limited benefit and limited replacement parts availability (which is very important to most Great Lakes, Caribbean, and world cruiser clients I deal with.)

[newhaul]

Originally Posted by ramblinrod

My statements have been 100% accurate all along.

You are the one who stated that one could recharge a 400 A-hr daily consumption to a 400 A-hr LFP bank, with 400 W of solar.

Here is the exact quote from your post # 750.



(… irrelevent personal opinion removed.)

Your statement is completely, unequivocally, undeniably, incorrect.



No it doesn't.

Read it again.

400 W of solar and or wind for each 100 A-hr of consumption means exactly what it states.

For your example of 200 A-hr daily consumption, using my ratios, the energy consumed could be replaced by 800 W of solar and/or wind, which could be any combination:

Example A: 800W solar

Example B: 400 W solar and 400 W wind

Example C: 800 W wind

For the average 35 ft +/- sailboat, cruising an area suited to both generating technologies I would recommend option B.

If the owner objected to solar (usually unreasonable IMHO) then obviously I would propose option C.

If the owner objected to wind (usually unreasonable IMHO) then obviously I would propose option A.

If the owner was opposed to either wind or solar (usually completely unreasonable for the target cruising sailboat) I would propose options including the correct size FLA bank and ICE charging, and the correct sized LFP bank and ICE charging.

The PROPER conversion from FLA to LFP is very costly, and to date those I have consulted who refuse to have wind or solar on board (for only god knows why) have opted for correct sized FLA bank and ICE charging.

This is the only reason I have not installed an LFP solution for a customer.

Provided the true facts, none could warrant the high expense for the limited benefit and limited replacement parts availability (which is very important to most Great Lakes, Caribbean, and world cruiser clients I deal with.)

nowhere have I ever stated anything concerning usage you keep moving the point .I stated a 400ah Lfp bank not 400ah usage . You also said 100 ah bank needs 400 watts solar. Sunroof it was pointed out you then changed to 100ah usage. So which is it persists of bank or per usage ( which by the way is ever changing. )


I'm sure you will say I have way more than I need with ( 200ah Lfp and 400 watts solar) an expected usage of 35 ah per day.

[ramblinrod]

Originally Posted by Delfin

No, according to him, he doesn't do REMOTE consulting because people tend not to listen to the recommendations that will maximize their investment in Lithium. Poor results from a properly installed and managed Li bank has nothing to do with it.


Just a suggestion, but perhaps you might try to stay up on the topics you make such emphatic statements about. It will make other blanket statements you make seem more, um, plausible. The Chevy Bolt has a 238 mile range and recharges fully to deliver that range overnight. So, I guess your statement would be correct if you lived in Chicago, but like to shop for groceries in Cleveland.

Yeah, that's the marketing spec.

We all know how much we can trust those.

Try that at night with lights, windshield wipers, and heat on trying to keep ice off the windshield and the brass monkey.

It is common to go shopping 125 km away from our homes. They will not take the electric car for fear of running out of juice on the way home.

If they did, and pulled over somewhere to recharge (if they could find a suitable charging station) they would have to stay in a nearby hotel or motel overnight.

Yup, suitable for a grocery getter and not much else.

I wonder how many own an EV as their primary vehicle and commute 250 km / day to work?

I know lots of ICE vehicle owners who do.

[newhaul]

Originally Posted by ramblinrod

Yeah, that's the marketing spec.

We all know how much we can trust those.

Try that at night with lights, windshield wipers, and heat on trying to keep ice off the windshield and the brass monkey.

It is common to go shopping 125 km away from our homes. They will not take the electric car for fear of running out of juice on the way home.

If they did, and pulled over somewhere to recharge (if they could find a suitable charging station) they would have to stay in a nearby hotel or motel overnight.

Yup, suitable for a grocery getter and not much else.

I wonder how many own an EV as their primary vehicle and commute 250 km / day to work?

I know lots of ICE vehicle owners who do.

you do realise that a range of 238 miles is a range of 383km right?

[newhaul]

Originally Posted by ramblinrod

Yeah, that's the marketing spec.

We all know how much we can trust those.

Try that at night with lights, windshield wipers, and heat on trying to keep ice off the windshield and the brass monkey.

It is common to go shopping 125 km away from our homes. They will not take the electric car for fear of running out of juice on the way home.

If they did, and pulled over somewhere to recharge (if they could find a suitable charging station) they would have to stay in a nearby hotel or motel overnight.

Yup, suitable for a grocery getter and not much else.

I wonder how many own an EV as their primary vehicle and commute 250 km / day to work?

I know lots of ICE vehicle owners who do.

what does a brass monkey have to do with anything from the last century?

[newhaul]

Originally Posted by ramblinrod

Yeah, that's the marketing spec.

We all know how much we can trust those.

Try that at night with lights, windshield wipers, and heat on trying to keep ice off the windshield and the brass monkey.

It is common to go shopping 125 km away from our homes. They will not take the electric car for fear of running out of juice on the way home.

If they did, and pulled over somewhere to recharge (if they could find a suitable charging station) they would have to stay in a nearby hotel or motel overnight.

Yup, suitable for a grocery getter and not much else.

I wonder how many own an EV as their primary vehicle and commute 250 km / day to work?

I know lots of ICE vehicle owners who do.

how many people commute 155 miles well not many .
Most people live within 50 miles of work .

Then there is me I move my house to the job. ( 75% of the time)
otherwise its usually take the train)

[rgleason]

Ramblinrod wrote:

First, most 35 ft +/- cruising sailboats do not have 400 A-hr daily consumption. More like 100 A-hr.

Second, I recommend 400W of solar and/or wind for every 300 A-hrs of bank for every 100 A-hrs of daily consumption.

200 A-hrs per day is a lot of juice.

A typical boat that would require this amount of energy daily at anchor, would include 2 BD-35 refrigerant compressors, one for fridge and another for separate freezer. A significant 12 Vdc watermaker. All the TV one can watch, all the circulation fans one can run 24/7, all the phones and laptops one can charge, all the LED lighting one can light. All the BT speakers one can listen to, leaving the VHF on standby 24/7, radar running 24/7, and so on an so on.

Even at that, with a 600 A-hr house bank (2S3P x GC2s for example), a 160 A alternator, a 400 W wind generator, and a 400W solar array, life is good.

This is the typical amount of wind and solar power generation easily installed on a typical 35' +/- cruising sailboat.

If you are still referring to 400 A-hr average daily consumption, a 400 a-hr LFP bank and 400W solar for charging, this is untenable.

A 400W solar charging system will typically deliver 100 to 120 A-hrs per sunny day. Less if any panel shading or with any cloud.

The system you prescribe would not come anywhere near close to replenishing the energy consumed.

That is a at least a 280 A-hr shortfall on a perfect day.

Increase load above average, or decrease solar charging from ideal, and it is even worse.

LFP does not generate power, it just stores it.

I found this to be a reasonable example and it is not too difficult to extrapolate from it for other uses. Thank you.

[Stu Jackson]

Originally Posted by ramblinrod

>>>>>>>>>>>>>>>>>>>>>
>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>


If the owner was opposed to either wind or solar (usually completely unreasonable for the target cruising sailboat) I would propose options including the correct size FLA bank and ICE charging, and the correct sized LFP bank and ICE charging.

The PROPER conversion from FLA to LFP is very costly, and to date those I have consulted who refuse to have wind or solar on board (for only god knows why) have opted for correct sized FLA bank and ICE charging.

This is the only reason I have not installed an LFP solution for a customer.

>>>>>>>>>>>>>>>>>>>>>>>
>>>>>>>>>>>>>>>>>>>>>>>>>

for only god knows why


That's priceless.


As a consultant in my business for the past 50 years, I agree with you, Rod, that it is critical to provide the client with the OPTIONS available to them.


Then you said:

If the owner was opposed to either wind or solar (usually completely unreasonable for the target cruising sailboat) I would propose options including the correct size FLA bank and ICE charging, and the correct sized LFP bank and ICE charging.

It seems to me, after keeping up with this enlightening thread since it started, that LFP actually IS one of your options.


Perhaps I have been misunderstanding your repeated posts, but it sure sounded to me that you kept saying that LFP is the wrong answer, when indeed it was one choice, which others have been saying all along.



God should have nothing to do with it.


I'm pretty savvy on boat electrical systems. I believe always that the choices in this regard are management issues of equipment choices.


Thanks for the clarification.