A simple but long LA-Lifepo4 transformation story

[SOLAR SUPPORT]

Before I switched from LA battery to drop-in type Lifepo4 battery that I lived on my Bavaria 35M boat, I read very long discussion contents under the discussion titles of Li-LFP batteries, which included the topics I was curious about. It is not possible to follow them for about a year and read them without getting bored and not be surprised by the multitude of topics. There is a lot of scattered and different information that makes it difficult for boat owners to decide on this issue.

Although the proposed solution options are expensive, it is another problem that they do not eliminate all risks of accidents and malfunctions arising from batteries, auxiliary devices and installations. There are systems with advanced central control systems to minimize these risks, but for small boat owners, there are quite high costs for installing these systems on the boat.

Also, when you look at the general policy of insurance companies regarding boats using Li-LFP batteries, there is a 50% indemnity payment deduction, depending on serious conditions, even for boats with advanced Li battery installation.

Among the options put forward as a solution, there is no standard, economical option that everyone can apply on their own boat. The existing engine-alternator-battery setup has to be changed and this is costly. Therefore, everyone researches this issue more and naturally tends to look for established, reliable and economical transit routes.

Winter of 2022. The 2X200Ah AGM batteries in my boat had lost performance since I used them for 6 years. My next battery choice was the Lifepo4, which I had researched for a long time. I focused on the recently developed waterproof type, closed box, prismatic cell, drop-in Lifepo4 batteries. The 200Ah battery from China, sold in the Turkish market, cost about $1000. This expenditure was reasonable as it was quite close to the cost of a 400Ah equivalent capacity AGM battery.

The simplest solution that came to my mind would be to completely disconnect the alternator from the Lifepo4 batteries, as there is enough solar power system to charge the batteries on my boat. If you have a solar energy system with a power generation capacity slightly above your daily energy needs, this is a very economical and safe way. The only thing left to do is to disconnect the cable from the alternator to the service batteries. You will be saved from spending as much as you spent on new batteries.

If you think that solar power fails or sometimes you will be without power on long cloudy days, it is possible to activate a small dc-dc charger on such rare occasions. Using a simple disconnect switch, you can use the alternator charge and increase the charge of the service batteries above the critical level. I did not implement such a solution, but if it had occurred to me at the beginning, I would definitely follow this path.

Before I decided to switch to Drop-in Lifepo4 battery technology, I had to research for a long time on an important issue that I was curious about. As a non-electrician, it has never been easy for me to research and find ways to safely turn off the charging current of an alternator that is operating under load. I learned that this is only possible by cutting the excitation current of the rotor rotating in the stator of the alternator.

There are two reasons for me to modify the existing alternator for safe charging of Lifepo4 batteries. The first is to continue using my alternator, which has quite enough capacity, instead of replacing it. The second is the elimination of the necessity of purchasing a very expensive new alternator and external regulator or a dc-dc charger with a capacity of 50-60A.

Before connecting the new Lifepo4 batteries to the existing installation, I removed the Mitsubishi 115A alternator from the engine. After meeting with an experienced auto electrician and getting his opinion, there was a complete consensus between us that it is possible to safely cut off the charge going from the alternator to the batteries by cutting off the rotor warning.

It gave me the necessary courage to learn that in the past, my electrician friend had successfully applied the method of turning the alternator charge on and off with a simple on-off switch at the request of an off-road racer who wanted to use maximum engine power on a hill. We set to work in his workshop, disassembled the parts of the alternator.

We disconnected one of the brushes that energized the alternator rotor and the existing internal regulator. The cut place was isolated and two heat-resistant thin wires were soldered to the cut circuit ends and extended from the back of the alternator. Rotor, regulator, stator reassembled. We completed the on-off test of the alternator in the workshop without any problems by touching the two ends of the cables extended outwards.

A 90 C° NC thermostat, which turns the rotor warning on and off, and a 70 C° NO second thermostat, which turns the alternator cooling fans on and off, are mounted on the front of the alternator which is the hottest spot. With the voltage regulated relay integrated circuit assembly, it was possible to turn off the warning energy of the alternator rotor, which does not exceed eight amperes, as soon as the battery voltage reaches the limit voltage value.

Rotor warning connection cables taken out of the alternator were connected to the 20A capacity VSR circuit and 90C°NC thermostat. You can make the control voltage settings of the VSR circuit with 0.1 volt sensitivity yourself. It is enough to make these settings once. Thermostat and VSR are connected in such a way that they can cut off the rotor warning independently of each other at limit control values. In order to stop the alternator charging, it is sufficient that the temperature of the alternator rises above 90°C or the voltage of the Lifepo4 batteries rises above 13.7V.

The VSR measures the system voltage from the alternator's battery voltage sensing line and when it reaches the recorded voltage, the relay activates. It is also very useful to have the option to completely turn off the alternator with a simple on/off switch. This system was sufficient for alternator charging when the batteries were not fully charged.

However, while the alternator was running when the batteries reached near-full voltage, the VSR went into a continuous on-off cycle. In order to prevent this, I delayed the opening and closing by five minutes by using a small electronic timer relay with a capacity of 30A after the VSR circuit. During alternator charging, the system is set to stop the alternator charging immediately by cutting off the VSR rotor warning if the battery rises above 13.7V. Since the time relay is activated simultaneously with the VSR, the alternator continues to run idle for five minutes.

In order to completely stop the charging of the alternator, it is sufficient to turn the on-off button on the same line to the off position. VSR checks the voltage of the Lifepo4 batteries every five minutes unless the alternator charge is turned off completely manually. If the battery voltage is below 13.7V, the alternator starts charging again. VSR will not turn on the rotor warning of the alternator as long as the battery voltage remains above 13.7V.

Load, voltage and temperature measurements taken while the alternator is running:

When you start the engine for the first time, the charging current remains at 45A at 900 rpm. The alternator overheats as the internal fan of the alternator cannot provide sufficient cooling at low speeds. Therefore, it is necessary to increase the engine speed to normal operating speed, approximately 2000 rpm.

When the speed rises a little, the alternator produces 115A current at full capacity and charges the Lifepo4 batteries. It takes approximately three minutes for the alternator to reach 90C° at full load. As the alternator warms up, the charging current drops to 90A. Then the NC thermal switch opens and the alternator charge is cut off. As soon as the alternator cools down and its temperature drops below 80°C, the thermal switch closes and alternator charging continues.

In the meantime, the cooling fans try to cool the engine room and alternator by blowing air continuously. The internal fan of the alternator already works continuously, but it is not sufficient at these loads. Cooling fans help the alternator to prolong the charging time of the batteries. With the engine running, it takes approximately two minutes for the alternator to cool under these conditions. Afterwards, charging continues at full capacity for about three minutes, until the alternator temperature rises above 90°C again.

When the times when the alternator is turned off and on, I observed that the alternator produces about 60% of energy, slightly above half of its full capacity.

Since the installed solar energy on my boat is sufficient, I usually leave the manual on-off button of the alternator in the off position. I rarely use alternator charging as it is not necessary. The system was used continuously throughout this summer season, and I did not encounter any problems.

There is only one problem experienced, and that is sometimes the charge warning sound from the control panel of the engine. Therefore, it is necessary to press the "Alarm Reset" button on the control panel to silence the alarm a few times. When the alternator charge is turned off, there is no alarm warning.

Cooling fans, ready-made integrated relay circuits, thermostats, alternator need to be removed and modified, and precise and complex settings of integrated circuits need to be found in order for them to work the way you want. You may think that this application for the LA-Lifepo4 battery conversion that I have described is economical but not easy. So I go back to the beginning and suggest you follow my first advice again.

There is not enough solar energy available and if there is an opportunity to increase it, it would be the right decision for you to spend your money on it. Good luck sailors..

[PaulCrawhorn]

Did you mention which regulator you chose for your alt?

With a better one, or using a DCDC, the goal should be for your alt to supply a steady current rate, keeping a steady temperature well below harm for as long as needed to recharge.

That may need to be a lower rate when ambient temps are higher.

Slower charging will get you longer lifespan, so long as your engine is running anyway.

If you are running the engine just to recharge, then it's worth going past a 0.4C rate, but hopefully that is only very occasionally.

[SOLAR SUPPORT]

Originally Posted by PaulCrawhorn

Did you mention which regulator you chose for the bottom?

The alternator's own regulator works just fine. I also mentioned that I have used the original altarnator with its original builtin regulator all togeather.

Better yet, or using a DCDC, your goal should be for your sub to maintain a steady current rate and keep a constant temperature well below the detriment for as long as it needs charging.

Battery or alt temp won't be the problem since a small dc-dc charger will be used temporarily. Captain shall think about the very low ambient temperature which is below the safe charging conditions before turing on the dc-dc charge.

This may need to be a lower rate when ambient temperatures are higher.

There will be no problem as the small capacity dc-dc charger will be activated in a controlled manner only in the cases I have mentioned and in case of energy shortage. Main purpose of alt charge is to charge Lifepo4 battery as much as you need. Ambient temperature is not an important issue unless you top up the batteries which is not the case.

A slower charge gives you longer life as long as your engine is still running.

I agree with that. Lifepo4 BMS charge capacity may be high for direct full alternator charging but even if it is not it won't be a problem for rare usage. With solar charging, which is the primary energy source, the life of the batteries will be extended.

If you're running the engine just to charge it's worth going over the 0.4C rating, but hopefully that happens very rarely.

Yes, if you have sufficient solar energy source, alternator charging is very rarely needed. Larger solar panels and higher battery capacity realy matters. I should reiterate that I do not use the DC-DC charger in my own boat.

.......

[goboatingnow]

Originally Posted by SOLAR SUPPORT

Before I switched from LA battery to drop-in type Lifepo4 battery that I lived on my Bavaria 35M boat, I read very long discussion contents under the discussion titles of Li-LFP batteries, which included the topics I was curious about. It is not possible to follow them for about a year and read them without getting bored and not be surprised by the multitude of topics. There is a lot of scattered and different information that makes it difficult for boat owners to decide on this issue.

Although the proposed solution options are expensive, it is another problem that they do not eliminate all risks of accidents and malfunctions arising from batteries, auxiliary devices and installations. There are systems with advanced central control systems to minimize these risks, but for small boat owners, there are quite high costs for installing these systems on the boat.

Also, when you look at the general policy of insurance companies regarding boats using Li-LFP batteries, there is a 50% indemnity payment deduction, depending on serious conditions, even for boats with advanced Li battery installation.

Among the options put forward as a solution, there is no standard, economical option that everyone can apply on their own boat. The existing engine-alternator-battery setup has to be changed and this is costly. Therefore, everyone researches this issue more and naturally tends to look for established, reliable and economical transit routes.

Winter of 2022. The 2X200Ah AGM batteries in my boat had lost performance since I used them for 6 years. My next battery choice was the Lifepo4, which I had researched for a long time. I focused on the recently developed waterproof type, closed box, prismatic cell, drop-in Lifepo4 batteries. The 200Ah battery from China, sold in the Turkish market, cost about $1000. This expenditure was reasonable as it was quite close to the cost of a 400Ah equivalent capacity AGM battery.

The simplest solution that came to my mind would be to completely disconnect the alternator from the Lifepo4 batteries, as there is enough solar power system to charge the batteries on my boat. If you have a solar energy system with a power generation capacity slightly above your daily energy needs, this is a very economical and safe way. The only thing left to do is to disconnect the cable from the alternator to the service batteries. You will be saved from spending as much as you spent on new batteries.

If you think that solar power fails or sometimes you will be without power on long cloudy days, it is possible to activate a small dc-dc charger on such rare occasions. Using a simple disconnect switch, you can use the alternator charge and increase the charge of the service batteries above the critical level. I did not implement such a solution, but if it had occurred to me at the beginning, I would definitely follow this path.

Before I decided to switch to Drop-in Lifepo4 battery technology, I had to research for a long time on an important issue that I was curious about. As a non-electrician, it has never been easy for me to research and find ways to safely turn off the charging current of an alternator that is operating under load. I learned that this is only possible by cutting the excitation current of the rotor rotating in the stator of the alternator.

There are two reasons for me to modify the existing alternator for safe charging of Lifepo4 batteries. The first is to continue using my alternator, which has quite enough capacity, instead of replacing it. The second is the elimination of the necessity of purchasing a very expensive new alternator and external regulator or a dc-dc charger with a capacity of 50-60A.

Before connecting the new Lifepo4 batteries to the existing installation, I removed the Mitsubishi 115A alternator from the engine. After meeting with an experienced auto electrician and getting his opinion, there was a complete consensus between us that it is possible to safely cut off the charge going from the alternator to the batteries by cutting off the rotor warning.

It gave me the necessary courage to learn that in the past, my electrician friend had successfully applied the method of turning the alternator charge on and off with a simple on-off switch at the request of an off-road racer who wanted to use maximum engine power on a hill. We set to work in his workshop, disassembled the parts of the alternator.

We disconnected one of the brushes that energized the alternator rotor and the existing internal regulator. The cut place was isolated and two heat-resistant thin wires were soldered to the cut circuit ends and extended from the back of the alternator. Rotor, regulator, stator reassembled. We completed the on-off test of the alternator in the workshop without any problems by touching the two ends of the cables extended outwards.

A 90 C° NC thermostat, which turns the rotor warning on and off, and a 70 C° NO second thermostat, which turns the alternator cooling fans on and off, are mounted on the front of the alternator which is the hottest spot. With the voltage regulated relay integrated circuit assembly, it was possible to turn off the warning energy of the alternator rotor, which does not exceed eight amperes, as soon as the battery voltage reaches the limit voltage value.

Rotor warning connection cables taken out of the alternator were connected to the 20A capacity VSR circuit and 90C°NC thermostat. You can make the control voltage settings of the VSR circuit with 0.1 volt sensitivity yourself. It is enough to make these settings once. Thermostat and VSR are connected in such a way that they can cut off the rotor warning independently of each other at limit control values. In order to stop the alternator charging, it is sufficient that the temperature of the alternator rises above 90°C or the voltage of the Lifepo4 batteries rises above 13.7V.

The VSR measures the system voltage from the alternator's battery voltage sensing line and when it reaches the recorded voltage, the relay activates. It is also very useful to have the option to completely turn off the alternator with a simple on/off switch. This system was sufficient for alternator charging when the batteries were not fully charged.

However, while the alternator was running when the batteries reached near-full voltage, the VSR went into a continuous on-off cycle. In order to prevent this, I delayed the opening and closing by five minutes by using a small electronic timer relay with a capacity of 30A after the VSR circuit. During alternator charging, the system is set to stop the alternator charging immediately by cutting off the VSR rotor warning if the battery rises above 13.7V. Since the time relay is activated simultaneously with the VSR, the alternator continues to run idle for five minutes.

In order to completely stop the charging of the alternator, it is sufficient to turn the on-off button on the same line to the off position. VSR checks the voltage of the Lifepo4 batteries every five minutes unless the alternator charge is turned off completely manually. If the battery voltage is below 13.7V, the alternator starts charging again. VSR will not turn on the rotor warning of the alternator as long as the battery voltage remains above 13.7V.

Load, voltage and temperature measurements taken while the alternator is running:

When you start the engine for the first time, the charging current remains at 45A at 900 rpm. The alternator overheats as the internal fan of the alternator cannot provide sufficient cooling at low speeds. Therefore, it is necessary to increase the engine speed to normal operating speed, approximately 2000 rpm.

When the speed rises a little, the alternator produces 115A current at full capacity and charges the Lifepo4 batteries. It takes approximately three minutes for the alternator to reach 90C° at full load. As the alternator warms up, the charging current drops to 90A. Then the NC thermal switch opens and the alternator charge is cut off. As soon as the alternator cools down and its temperature drops below 80°C, the thermal switch closes and alternator charging continues.

In the meantime, the cooling fans try to cool the engine room and alternator by blowing air continuously. The internal fan of the alternator already works continuously, but it is not sufficient at these loads. Cooling fans help the alternator to prolong the charging time of the batteries. With the engine running, it takes approximately two minutes for the alternator to cool under these conditions. Afterwards, charging continues at full capacity for about three minutes, until the alternator temperature rises above 90°C again.

When the times when the alternator is turned off and on, I observed that the alternator produces about 60% of energy, slightly above half of its full capacity.

Since the installed solar energy on my boat is sufficient, I usually leave the manual on-off button of the alternator in the off position. I rarely use alternator charging as it is not necessary. The system was used continuously throughout this summer season, and I did not encounter any problems.

There is only one problem experienced, and that is sometimes the charge warning sound from the control panel of the engine. Therefore, it is necessary to press the "Alarm Reset" button on the control panel to silence the alarm a few times. When the alternator charge is turned off, there is no alarm warning.

Cooling fans, ready-made integrated relay circuits, thermostats, alternator need to be removed and modified, and precise and complex settings of integrated circuits need to be found in order for them to work the way you want. You may think that this application for the LA-Lifepo4 battery conversion that I have described is economical but not easy. So I go back to the beginning and suggest you follow my first advice again.

There is not enough solar energy available and if there is an opportunity to increase it, it would be the right decision for you to spend your money on it. Good luck sailors..

Excellent simple solution to the alternator issue

[davil]

..........................................

Winter of 2022. The 2X200Ah AGM batteries in my boat had lost performance since I used them for 6 years. My next battery choice was the Lifepo4, which I had researched for a long time. I focused on the recently developed waterproof type, closed box, prismatic cell, drop-in Lifepo4 batteries. The 200Ah battery from China, sold in the Turkish market, cost about $1000. This expenditure was reasonable as it was quite close to the cost of a 400Ah equivalent capacity AGM battery.

....................

thank you very much for a very comprehensive review.

Question

You refer to "Lifepo4"

are these as listed in Amazon?

12V 140AH Lithium Battery,5000+ Deep Cycle LiFePO4 Battery with Built-in 100A BMS fit for Home Storage,Trolling Motor,RV,Off-Grid System,Solar Power System,Marine
----------------------------------------------------------------
The price differential with the "marine vendors sites" and different brands is significantly higher,like 2 up to 3 times!
----------------------------------------------------------------

I am getting to the time of replacing my AGM batteries.

Thanks

[SOLAR SUPPORT]

I purchased the batteries from an importer company representative. I preferred a waterproof type case like SLA batteries have. Although I knew that this would prevent me from checking the bms and battery cells, for me the waterproofing of the battery box was the primary important feature. I preferred cells with a prismatic structure. Their performance is quite good and their promised life is quite long. I needed to buy two of them since their internal bms's continous load and charge current capacity was limited to 100A. They were connected in paralel to guarantee to meet the high loads arround 150A when needed.

[davil]

[QUOTE=SOLAR SUPPORT;3692097]I purchased the batteries from an importer company representative. I preferred a waterproof type case like SLA batteries
---------------------------------------------------------
thank you very much for taking the time.

my question was prompted by cost.

have read as much as possible, including Rod article in Marine How to.

Perhaps my ignorance precludes understanding how it is possible that Amazon can offer Lifepo4 batteries for a fraction of the cost from marine vendors and the brands Rod refers in his article now withstanding the old "you get what you pay for"

Or perhaps these offered from Amazon are not what I understand a LiFePO4 battery is?


12V Lithium Battery-140ah Lithium Iron Phosphate LiFePO4 Deep Cycle Battery,100A BMS,4000+ Cycles,Perfect for RV,Home Storage,Solar Power System,Outdoor Camping and Trolling Motor

Price $ 396.

[SOLAR SUPPORT]

[QUOTE=davil;3692103]

Originally Posted by SOLAR SUPPORT

I purchased the batteries from an importer company representative. I preferred a waterproof type case like SLA batteries
---------------------------------------------------------
thank you very much for taking the time.

my question was prompted by cost.

have read as much as possible, including Rod article in Marine How to.

Perhaps my ignorance precludes understanding how it is possible that Amazon can offer Lifepo4 batteries for a fraction of the cost from marine vendors and the brands Rod refers in his article now withstanding the old "you get what you pay for"

Or perhaps these offered from Amazon are not what I understand a LiFePO4 battery is?


12V Lithium Battery-140ah Lithium Iron Phosphate LiFePO4 Deep Cycle Battery,100A BMS,4000+ Cycles,Perfect for RV,Home Storage,Solar Power System,Outdoor Camping and Trolling Motor

Price $ 396.

With its low cost and low sales prices due to its high production capacity, China does not recognize any competitors worldwide, especially in the battery industry. Not every country applies the same customs tariff for imported batteries. In my country, 50% customs are applied to such batteries. I think this is necessary for the companies that produce in the same sector in the country to survive.

If the prices of Lifepo4 batteries sold in the US are very high, I guess it is because different quality products are sold in this market. Features such as Bluetooth-enabled BMS, external communication terminal, battery heating device increase the battery price. Since the battery I bought does not have these features, the price may be lower than the Lifepo4 batteries sold in the US.

[davil]

Originally Posted by SOLAR SUPPORT

With its low cost and low sales prices due to its high production capacity, China does not recognize any competitors worldwide, especially in the Li battery industry. Not every country applies the same customs tariff for imported batteries. In my country, 50% customs are applied to such batteries. I think this is necessary for the companies that produce in the same sector in the country to survive. If the prices of Lifepo4 batteries sold in the US are very high, I guess it is because different quality products are sold in this market. Features such as Bluetooth-enabled BMS, external communication terminal, battery heating device increase the battery price. Since the battery I bought does not have these features, the price may be lower than the Lifepo4 batteries sold in the US.

================================
actually, what puzzles me is the opposite.

Ampere Time LiFePO4 Deep Cycle Battery 12V 100Ah with Built-in 100A BMS
for $ 379.
this price is almost similar to a AMG battery???

[davil]

perhaps your comment

"If the prices of Lifepo4 batteries sold in the US are very high, I guess it is because different quality products are sold in this market. Features such as Bluetooth-enabled BMS, external communication terminal, battery heating device increase the battery price. Since the battery I bought does not have these features, the price may be lower than the Lifepo4 batteries sold in the US."

is the answer,do not believe these offered for $ 370 have those features.

[goboatingnow]

[QUOTE=SOLAR SUPPORT;3692106]

Originally Posted by davil

With its low cost and low sales prices due to its high production capacity, China does not recognize any competitors worldwide, especially in the battery industry. Not every country applies the same customs tariff for imported batteries. In my country, 50% customs are applied to such batteries. I think this is necessary for the companies that produce in the same sector in the country to survive.



If the prices of Lifepo4 batteries sold in the US are very high, I guess it is because different quality products are sold in this market. Features such as Bluetooth-enabled BMS, external communication terminal, battery heating device increase the battery price. Since the battery I bought does not have these features, the price may be lower than the Lifepo4 batteries sold in the US.

The EU does apply tariffs to China batteries and pv. It did a few years ago but dropped it. This led to price decrease in the Eu

[goboatingnow]

[QUOTE=goboatingnow;3692124]

Originally Posted by SOLAR SUPPORT

The EU does apply tariffs to China batteries and pv. It did a few years ago but dropped it. This led to price decrease in the Eu

Sorry typo “ does not “

[SOLAR SUPPORT]

The charge and discharge of Lifepo4 drop-in batteries and the monitoring of the constantly changing SOC% is very vital for the healthy operation of batteries and chargers. It is possible to monitor this using a device known as an energy meter or columb meter with an Ah counter.

The charging voltage of the solar mppt charge controller in the boat is adjustable. I increase the charge voltage level to 14.2 volts for best performance. This setting is valid when the battery SOC is below 90% and when the consumption is high. When the SOC was 90-95%, I turned off the solar energy completely and turned the solar energy back on after discharging the batteries until the SOC was 50%.

During the summer months with the freezer running on my boat all the time, I would reduce the charge voltage of the solar charge controller to 13.8 volts before leaving the boat. When I came back to the boat about a week later, the SOC of the Lifepo4 batteries would be around 60-80%. Since the summer season is over, I emptied and closed the deep freezer. Thus, there is no device left on the boat that consumes electrical energy. I set the solar charging voltage to 13.8 volts and left.

When I went to the boat two weeks later, the charge controller was not working. The batteries appeared to be fully charged according to the energy meter. This is normal as there is no device on the boat that consumes electricity. The solar CR led display is in a completely off state and is unresponsive. I will take it to the service, it will be seen if it works again.

I think that when the solar charge is on and the batteries reach the full level, the BMS and CR enter a continuous on-off cycle, just as I observed while charging the batteries with the alternator. Solar CR or BMS malfunctions become inevitable as a result of the on-off cycle between the battery BMS and chargers at full charge of drop-in batteries.

I don't know if there is a solar charge controller that can bring the charge voltage of the Lifepo4 batteries to the required level by sensing the SOC% of the batteries and turn off the charge of the batteries that are not exposed to the load before the HVCutoff action of the BMS.

In order to avoid such malfunctions, if there is no consumption in the boat, I think it is best to turn off the solar energy system or leave the CR charging voltage around 13.4 volts.

[goboatingnow]

Originally Posted by SOLAR SUPPORT

The charge and discharge of Lifepo4 drop-in batteries and the monitoring of the constantly changing SOC% is very vital for the healthy operation of batteries and chargers. It is possible to monitor this using a device known as an energy meter or columb meter with an Ah counter.



The charging voltage of the solar mppt charge controller in the boat is adjustable. I increase the charge voltage level to 14.2 volts for best performance. This setting is valid when the battery SOC is below 90% and when the consumption is high. When the SOC was 90-95%, I turned off the solar energy completely and turned the solar energy back on after discharging the batteries until the SOC was 50%.



During the summer months with the freezer running on my boat all the time, I would reduce the charge voltage of the solar charge controller to 13.8 volts before leaving the boat. When I came back to the boat about a week later, the SOC of the Lifepo4 batteries would be around 60-80%. Since the summer season is over, I emptied and closed the deep freezer. Thus, there is no device left on the boat that consumes electrical energy. I set the solar charging voltage to 13.8 volts and left.



When I went to the boat two weeks later, the charge controller was not working. The batteries appeared to be fully charged according to the energy meter. This is normal as there is no device on the boat that consumes electricity. The solar CR led display is in a completely off state and is unresponsive. I will take it to the service, it will be seen if it works again.



I think that when the solar charge is on and the batteries reach the full level, the BMS and CR enter a continuous on-off cycle, just as I observed while charging the batteries with the alternator. Solar CR or BMS malfunctions become inevitable as a result of the on-off cycle between the battery BMS and chargers at full charge of drop-in batteries.



I don't know if there is a solar charge controller that can bring the charge voltage of the Lifepo4 batteries to the required level by sensing the SOC% of the batteries and turn off the charge of the batteries that are not exposed to the load before the HVCutoff action of the BMS.



In order to avoid such malfunctions, if there is no consumption in the boat, I think it is best to turn off the solar energy system or leave the CR charging voltage around 13.4 volts.

Good advice , mind you got long term storage just charge to 60% disconnect the chargers and remove loads

One of the reasons I’m doing a new BMS is to do what you say ie to select different charge profiles . Really Lithium Charge control needs to be removed from charge sources and done by the BMS.

[SOLAR SUPPORT]

Originally Posted by goboatingnow

One of the reasons I’m doing a new BMS is to do what you say ie to select different charge profiles . Really Lithium Charge control needs to be removed from charge sources and done by the BMS.

Right, you have a battery capacity that you can use fully and being full all the time is not healthy for this type of battery. This is exactly where they diverge from LA batteries. Lifepo4 battery SOC% has to be managed in changing conditional manner and it is not possible for this kind of an application can be managed with exising charge regulators. The topic is about dropin Lifepo4 batteries.