LiFeP04 Batteries for Solar & BMS

[Willy T]

What average SOC do you run your Solar system at?

Simon

He doesn't have LFP batteries in a Solar System, he has a Golf Cart, charged on grid power.

It doesn't mean that his input is invalid though. Some works for me and some doesn't. At some point I'll try bottom balance, until then I'll keep on slogging along.

[karrak]

No that would be DIY EV owners. Well to start the thinking you do not operate a Lithium battery in a Solar system in the lower SOC range is delusional in of itself. With a Lithium system you do not normally size the batteries for 5 day autonomy like you would for Lead Acid. That line of thinking is just plain ole nucking futs. You size Lithium for 2 to 3 day autonomy, and unless you live in Utopia Green Land where the sun shines bright everyday all day, the rest of us in the real world have long cloudy spells and cloudy days. That means you spend a lot of time near the bottom before running the generator. That is just a fact of life. Deal with it.

What average SOC do you run your Solar system at? From my battery monitor my average battery SOC in ah is 103.997703 (71%SOC) for the period from when it was installed in November last year to now.

My battery capacity is around 3 times my daily use as you suggest, and I don't have a generator.

Cells do not stay Balanced if you Top Balance because you have parasitic loads. The Vampire Boards, Temperature and Battery monitors are attached to each cell and powered from each cell. No two draw the exact same amount of power, thus unequal load throwing them out of Balance. In Bottom Balanced system you have no Parasitic Loads. The exact same current flows through each cell every time in Series circuits.

If you just have balancing boards, unless they are balancing they should draw less than 100uA. Now 100uA for a year equates to 0.876Ah per year, for a 100ah cell this is way below the cell leakage, and of course our solar panels are charging the battery every day.

Now if we have fancy battery monitoring that could be powered from the whole pack as I do, we don't have any problem with with unequal load or even if they are powered by the individual cells the unequal load should certainly not be more than 100uA, and more likely less than 10uA so the same applies as with just balancing boards.

Expecting any battery to last 10 years is far fetched.

Yes, maybe with the way you treat LFP batteries it is far fetched. How about Tesla's 10 year warranty with 10 year extension, not sure what the fine print is here. I believe Bosch and Sony are talking about 10 years with their home LFP batteries.

You are taking things out of context and cherry picking. My guess is you have not read all replies and threads on the subject matter. I charge at C/2 constant Current with Commercial power. I or NO ONE EVER SAID you turn off the controller. First thing to know is there are NO SOLAR CHARGE CONTROLLERS made for Lithium batteries on the market with the exception of a Marine and toys with very limited power of 130 or so watts. A Solar Charge Controller made for Lithium would require to interface with a BMS. How do you do that since there are none available? Simple you don't. You have to deal with it and work around it and only if you know exactly what you are doing.

If you top balance most of the programmable Solar Controllers can be used with LFP batteries.

I thought you have been recommending to others that you don't need a BMS to charge an LFP battery, just set the charge controller to stop charging at the weakest cells fully charged voltage.

In a Top Balanced System you would set the voltage to 3.55 to 3.6 vpc or whatever your Vampire Board Trigger voltage is set to. The problem with that analogy is the Vampire boards can only shunt .5 to 1 amps, and there is no way to tell the Controller to limit current to Vampire Board limit. When the first Vampire Board turns on, it can only shunt a small amount of current.

Maybe you should follow your recommendation and reread the post that have been made before. This has already been covered in this thread. You only need to charge to 3.55-3.6 Volts/Cell once in a blue moon to re-balance the battery. The battery will only be slightly out of balance so the 0.5 to 1 amp is ample to balance the individual cells.

In a Bottom Balanced system you set the voltage well below 100% SOC in the range of 3.3 to 3.4 volts. The final voltage is a a bit of trial and error for the first few days. You settle when the weakest cell reaches 3.4 volts. All other cells will be just slightly lower in voltage. So in a 48 volt pack a Bottom Balanced set point voltage is something slightly less than 54.4 volts.

Sounds dangerous to me, lets just hope that that weak cell doesn't drift and we remember to keep an eye on it. Now on my system 3.375 volts/cell can take the cell SOC between 80% and the same SOC as if I charge to 3.45 volts/cell to a current of C/20 depending on the current coming from the solar panels. SK, you give a resting voltage of 100% = 3.450, not far away from your 3.4 volts?

A Top Balanced system would be 57.6 volts.

Wrong, could be exactly the same as the voltage you set your lower balanced system to.

At that point the Controller is Constant Voltage keeping the batteries charged up and supplying power to the load assuming the panels are able to meet the demand.

So you are talking about keeping the weak cell at 3.4 volts for a long period of time, isn't high cell voltage bad for LFP batteries. No wonder you give a lifespan of only 5 years.

Simon

[Sunking]

After further thought I would have to agree that you only have to bottom balance once to cover the issue of cells varying in capacity, but it comes at a cost, in that the voltages of the individual cells will vary when the cells are fully charged and this variation will get worse if the capacity of the cells diverge.

Capacity will drift Simon, but that does not relate to voltage. The only thing that might change is which cell becomes the weakest. Loss of capacity cannot be fixed. Only replacement can fix that. There is no sacrifice.

Does this mean I am going to change to bottom balancing for my solar power system, no for the following reasons.

1. Until someone convinces me otherwise I think that charging cells up to different voltages will put the weakest cells that are charged to a higher voltage under more stress so they will age quicker.

2. I would have to modify my charge controller to take input from my battery monitor to terminate the charging, for people with commercially made charge controllers this may not be an option.

3. One is relying on the BMS to end the charge cycle. If it fails and our battery has cells with differing capacity we could easily overcharge the weakest cells.

4. It is reasonably easy to top balance a 12 or 24 or 48 volt battery pack which are the common voltages used by people with solar power systems. I don't think this would be the case for EVs where the battery packs are more than 100 volts.

Simon

1. Charging Voltage stress does not happen until you get to the top. The weakest cell is only taken to 90 to 95% capacity. So that reason is not valid.

2. Completely false assumption. No need to signal your controller to do anything. You set Bulk = Absorb = Float to make your controller behave as a CC/CV which is the correct algorithm to use on Lithium batteries. The voltage you set is lower than 100% SOC. It is set just high enough to get the weakest cell to 90 to 95% SOC. When the batteries equalize current stops flowing through the batteries and they stop charging. You panels and controllers are still active and supplying power to your load like an Inverter. You don't don't need to have anything turn off, just change your way of thinking. The only other requirement is to set you rInverter LVD to whatever you are comfortable with. You do not even need to do that as default is good enough because it is set and designed for Lead Acid Batteries. Default is 11, 22, and 44 volts respectively. You can even go a bit lower with LFP with no worries of 10, 20, and 40 if you want to go to the edge of 2.5 vpc. Or if you are like me, I were suspenders and a belt and set my LVD to 49.6 volts or 10% SOC 3.1 vpc.

3. So WTF does that have to do with Bottom Balance. There is no BMS or Vampire boards to fail or waste money on. Bottom Balanced systems cells all have the same capacity. So I am clueless what your argument is with this one.

4. Again False. Mine is 48 volts. DIY EV's start at 36 volts up to 144 volts in 12 volt increments.

[Sunking]

Just because you use shunts, doesn't mean you are "top balancing"


I use shunts to keep cell voltage the same when my solar controller is in the process of providing current for loads under a "fully charged" situation.

Beg your pardon. but that is the main reason you use Vampire Boards for. They are the heart and should of every passive Top Balance system there is. They have no other purpose other than more expensive units will also have voltage and temp monitoring. But to get that means now means you need a BMS Programmable Controller. Those are not cheap.

The "fully charged" voltage can be pre-set, and ISN'T at 3.65 or 100%SOC of the cells. It can be at any cell voltage you wish.

The shunts aren't expensive as Sunking has incorrectly stated, they cost me $13.50 AUD each.

No $13 Vampire boards are programmable. 16 cells x $13 adds up real quick on a 48 volt battery. The ones that mount on the battery terminals I know of are pure shunts with indicator light to signal either on or off and completely passive and dumb. More expensive models add Cell Voltage and Temperature with Communications to a Central BMS Controller. To have programmable systems require a Central BMS

If you don't use shunts, and just use a pack level voltage at which your system is designed to have zero net current, the cells will very slowly drift apart. Despite what Sunking says, this WILL result in one cell being lower than the others, and if you take the pack to it's original zero setpoint, one cell will reach the lower voltage knee first. If you are using pack voltage or capacity to reference your 0%SOC, you will run the risk of having no protection for that cell.

Completely false. Capacity fades. That only possible changes what the weakest cell can be. With No Vampire boards or monitors, there is no way to drift from 0% SOC and AH level. That is the basic fundamental of series circuits.

There are commercially available LFP solar controllers, GSL electronics make one that I have used.

Never said there were not. I said a few for Marine applications and Toys. Those are toy sized. I took a look at GSL BMPPT which they say can be used with Lithium. But there is nothing special about it that makes it good or bad for lithium. It has no interface to communicate with a BMS. I can think of 3 other manufactures that can do the same thing.

If you don't ever bottom balance, it doesn't mean you aren't protected against over-discharge. The shunts I use monitor cell voltage, and will disconnect the pack from the load if any individual cell voltage falls below a pre-set value.

I agree with you there but you did not disclose that takes an extra expensive programmable Central BMS control unit on top of those 16 $14 Vampire Boards. If your Inverter cannot interface to the BMS, that program feature is useless. You would have to put some external LVD between the battery and Inverter like your GSL model has to do. Theyy worked around th eproblem which has already been discussed in great detail here.

Bottom Balance no external LVD, no BMS or anything is required. Just set your Inverter Low Voltage Cut Off to whatever you want, or leave it at default will work also at 11, 22, and 44 volts.

Of course this can be done with simple cell monitoring, but the extra cost of the shunts is negligible in the overall system cost. (the contactors required in either case are the most expensive components). The reason I use shunts is that it very quickly sets all cells at the charge controllers operating voltage, and in effect the batteries are inactive the majority of the time (ie. zero current)

Yep about $300 to $600 dollars for a 16 channel PLC, plus 16 x $13 Vampire boards. Should not cost you much more than $550 to $800 to add BMS with control. You still have to solve the interface for LVD and Controller. That cost extra

[karrak]

After further thought I would have to agree that you only have to bottom balance once to cover the issue of cells varying in capacity, but it comes at a cost, in that the voltages of the individual cells will vary when the cells are fully charged and this variation will get worse if the capacity of the cells diverge. Now if someone had put forward a good case that bottom balancing will not drift without trying to bully me into accepting this position I might have come to this position earlier.

I think that the bottom balance may drift if the cell current leakage is different between cells but will have to think further about this.

Does this mean I am going to change to bottom balancing for my solar power system, no for the following reasons.

1. Until someone convinces me otherwise I think that charging cells up to different voltages will put the weakest cells that are charged to a higher voltage under more stress so they will age quicker.

2. I would have to modify my charge controller to take input from my battery monitor to terminate the charging, for people with commercially made charge controllers this may not be an option.

3. One is relying on the BMS to end the charge cycle. If it fails and our battery has cells with differing capacity we could easily overcharge the weakest cells.

4. It is reasonably easy to top balance a 12 or 24 or 48 volt battery pack which are the common voltages used by people with solar power systems. I don't think this would be the case for EVs where the battery packs are more than 100 volts.

Simon

[tom rickard]

Just because you use shunts, doesn't mean you are "top balancing"

I use shunts to keep cell voltage the same when my solar controller is in the process of providing current for loads under a "fully charged" situation.

The "fully charged" voltage can be pre-set, and ISN'T at 3.65 or 100%SOC of the cells. It can be at any cell voltage you wish.

The shunts aren't expensive as Sunking has incorrectly stated, they cost me $13.50 AUD each.

If you don't use shunts, and just use a pack level voltage at which your system is designed to have zero net current, the cells will very slowly drift apart. Despite what Sunking says, this WILL result in one cell being lower than the others, and if you take the pack to it's original zero setpoint, one cell will reach the lower voltage knee first. If you are using pack voltage or capacity to reference your 0%SOC, you will run the risk of having no protection for that cell.

There are commercially available LFP solar controllers, GSL electronics make one that I have used.

If you don't ever bottom balance, it doesn't mean you aren't protected against over-discharge. The shunts I use monitor cell voltage, and will disconnect the pack from the load if any individual cell voltage falls below a pre-set value.

Of course this can be done with simple cell monitoring, but the extra cost of the shunts is negligible in the overall system cost. (the contactors required in either case are the most expensive components). The reason I use shunts is that it very quickly sets all cells at the charge controllers operating voltage, and in effect the batteries are inactive the majority of the time (ie. zero current)

I'm sorry Sunking, I missed the part about how you provide your inverter load from you solar panels while having zero current flow through your battery pack?

[reed cundiff]

Willy - thanks. Son and grandson did the design and fabrication. I was the gopher though I have been told numerous times that my showing up on a job is like having the two best workers quit.

There was an inch of rain last night in the mountains of northern NM. I guess this washed off the dirt and sand that built up while we were "holidaying" in South America. The TriStar monitor showed 1360 W and the Manzanita monitor for the BMS showed 21 amps at 54 V charge rate on the battery suite. Demonstrating once again that keeping panels clean is a good idea.

Since our RV is our only home (AK to Keys, Newfoundland, Baja, Guatemala) and we only boondock or dry camp (kids' backyards) there is no such thing as excess battery or solar.

Reed and Elaine

[Sunking]

The question you should be asking yourselves is this:

If commercial EV Manufactures DO NOT USE TOP BALANCE, then why do you insist Top Balance is the way to go?

The only correct answer be is you do not know any other way, and what the risk are. All you know is what you have been told by BMS manufactures to spend money and take risk. That is all you ever learned and did not ask critical thinking questions. Even the custom EV shops are now offering Bottom Balanced systems and equipment.

EV West is the premiere custom EV builder, and they make Bottom Balanced EV's. Everything known about LFP used in solar comes from EV's.

Look you can use Top Balance. It is expensive, comes with risk, and offers no protection for over discharges the main killer of lithium batteries. It sets the conditions for over discharge. That is why commercial EV manufactures do not use Top Balance. The last two places you ever want your batteries to see is the Top or Bottom while in operation.

If you are a novice, inexperienced, lacking knowledge, or lazy you have no choice but Top Balance. That is the market it is designed for.

[Living Large]

I have a few comments on this thread having been one of the people that has been using LFP cells in a house bank as a stand alone power supply for over 3 years.

Bottom balancing: Great for EV's where you want to take the cells close to zero charge.

It would also be fine for off-grid solar application except that the batteries do not stay balanced for prolonged periods of time. To say that you bottom balance your cells once, then run your system for the next 10 years with no difference in performance from the cells is pretty far fetched.

So... Until you can explain how you manage to make your cells behave in an identical fashion over their lifespan, and also explain how to manage the charge controller so that it matches the load current in a fully charged situation, then I don't think bottom balancing is for me..

There was never any suggestion on this board that one could bottom balance once and be done. If you researched the threads (I think this one) you will see that this topic has been discussed in detail. What has been discussed it that they TEND to stay in balance over months. Not years. The plan was that LFP is NOT FOR EVERYONE, but someone who doesn't mind monitoring their cells regularly would see an imbalance develop slowly, by either using a DVM with sufficient accuracy or a monitoring system. This has all been covered.

The plan as far as I was concerned was to suspend charging at the top, which some charge controllers support, using a BMS monitor at the cell level.

[Sunking]

Curiously enough, our RV system with LFP was designed and fabricated just about two years ago. It has a BMS (designed for EV but works great). It endured one winter that went down to -20 C while we were on holiday in Guatemala and Honduras,and has suffered very little loss in capacity (none that we have been able to measure). We have boondocked in the Olympic Rain Forest for six days, the same amount of time in heavy timber in SE Arizona, four days with 8" of snow on panels. We never went below 40% SOC. We did turn off the inverter at night and did not run the fridge on AC during the day. We still ran the micro-wave to make hot water and watched Mystery Theater DVDs at night.

The 16 Cells are CALB, fabricated by Manzanita for EV world and matched to their EV designed BMS. It is expensive but it does work. I was a senior optical physicist for US Army Research Labs at WSMR and US Army Science Advisor in Iraq. I do know physics and science.

Reed and Elaine

Reed that only means your batteries are way over sized. Nothing wrong with that as long as you can afford it. Most cannot.

[Willy T]

Curiously enough, our RV system with LFP was designed and fabricated just about two years ago. It has a BMS (designed for EV but works great). It endured one winter that went down to -20 C while we were on holiday in Guatemala and Honduras,and has suffered very little loss in capacity (none that we have been able to measure). We have boondocked in the Olympic Rain Forest for six days, the same amount of time in heavy timber in SE Arizona, four days with 8" of snow on panels. We never went below 40% SOC. We did turn off the inverter at night and did not run the fridge on AC during the day. We still ran the micro-wave to make hot water and watched Mystery Theater DVDs at night.

The 16 Cells are CALB, fabricated by Manzanita for EV world and matched to their EV designed BMS. It is expensive but it does work. I was a senior optical physicist for US Army Research Labs at WSMR and US Army Science Advisor in Iraq. I do know physics and science.

Reed and Elaine

Reed, nice to hear that your batteries are performing for you. Your accomplishments are Impressive, it's good to have you here and thank you for your service to the troops.

[reed cundiff]

Six day autonomy with RV based LFP battery suite

Curiously enough, our RV system with LFP was designed and fabricated just about two years ago. It has a BMS (designed for EV but works great). It endured one winter that went down to -20 C while we were on holiday in Guatemala and Honduras,and has suffered very little loss in capacity (none that we have been able to measure). We have boondocked in the Olympic Rain Forest for six days, the same amount of time in heavy timber in SE Arizona, four days with 8" of snow on panels. We never went below 40% SOC. We did turn off the inverter at night and did not run the fridge on AC during the day. We still ran the micro-wave to make hot water and watched Mystery Theater DVDs at night.

The 16 Cells are CALB, fabricated by Manzanita for EV world and matched to their EV designed BMS. It is expensive but it does work. I was a senior optical physicist for US Army Research Labs at WSMR and US Army Science Advisor in Iraq. I do know physics and science.

Reed and Elaine

[Sunking]

This not what the EV / Grid Charging Bottom Balancer's want to hear. They drive their EV, take it home and plug it in and charge it, unplug and it's left until they drive it again. They have no parasitic loads and no floating, they have no standby soc to worry about.

You have a lot of trouble with reading comprehension there Willy. I never said you stop charging with a Solar System. Only Karrak is ignorant enough to say that. As for me I use commercial power to charge at constant C/2 current. I do not FLOAT, but I could just as easily because I do have the luxury of time. . But FLOAT TAKES TOO DAMN LONG.

Another issue is that some here do not know or understand the features of the equipment used for Solar Charging and how it functions.

I agree with that 100%. People like you and Karrak do not have the knowledge or experience to Bottom Balance Lithium batteries. In that case you should use a expensive Top Balance BMS. All you have to do is wait until the Solar Manufactures start making the equipment for it.

As far as it goes for Top or Bottom balancing they argue and fight about it in every thread on the DIY EV forums same as they do here.

That is true. Me, Myself, and I were once ignorant and strongly argued for Top Balance. Go back a few years on this forum here and you will see the transformation. I evolved. That was the Engineer in me pushing Technology as a solution. Top Balance Systems require expensive equipment. something companies are in biz to do. The whole objective to any biz is TO SELL YOU SOMETHING. Bottom Balance takes no special expensive equipment. Just knowledge and common sense.

But if you look back in those DIY EV forums going back to 2007 when the Large Format LFP cells became available to the DIY crowd all of us were Pro Top Balance. It made sense to us coming form the Lead Acid World stuck in that box. Once you hang around there a few years you get to know the members. Some are users, some are in the DIY EV business. As I said all of us started out Pro BMS. It was the only game in town. Then the problems started, very expensive problems of destroyed cells from over discharge. It was discovered the Top Balance boards and Controller LVD were the root cause. A new way of thinking came about. Bottom Balance. Now if you look the crowd is evenly split. Users and some R&D engineers have switched to Bottom Manufactures selling BMS, and engineers designing BMS naturally have no choice but to stand by BMS. It is not hard to understand.

How did it start? Well for one DIY took a look at what commercial EV manufactures were doing. Yes they use a form of BMS, active BMS where they can transfer power from a strong cell to weaker cell. But what we finally realized they had a couple of tricks. Some DIY can duplicate and some we cannot. EV manufactures buy lithium batteries by the 100's of thousands at a time from top quality manufactures made to their specifications. Tolerances are very tight. What the EV manufactures do is test every cell and sort them out to be precision matched to 1% or less. They then BOTTOM BALANCE the cells before assembly. Then assemble them and do not every fully charge or discharge the cells. Chevy Volt for example only charge to 80% and discharge to 20%. That is what is called Middle Balance and what every EV manufacture uses. They are not stupid enough to Top Balance. Bingo!

A DIY cannot fully duplicate what a commercial EV manufacture can do. But we can mimic what they do and steal their ideas at no charge or royalties. We can Bottom Balance and we can limit charge and discharge. That is what you do not understand or even want to understand. So please please stick with your Top Balance. You do not have the knowledge or skills to do Bottom Balance.

[Sunking]

Maybe the rumors of failed cells you have heard of have also come from rival manufacturers?

No that would be DIY EV owners.

Bottom balancing: Great for EV's where you want to take the cells close to zero charge.

It would also be fine for off-grid solar application except that the batteries do not stay balanced for prolonged periods of time. To say that you bottom balance your cells once, then run your system for the next 10 years with no difference in performance from the cells is pretty far fetched.

Well to start the thinking you do not operate a Lithium battery in a Solar system in the lower SOC range is delusional in of itself. With a Lithium system you do not normally size the batteries for 5 day autonomy like you would for Lead Acid. That line of thinking is just plain ole nucking futs. You size Lithium for 2 to 3 day autonomy, and unless you live in Utopia Green Land where the sun shines bright everyday all day, the rest of us in the real world have long cloudy spells and cloudy days. That means you spend a lot of time near the bottom before running the generator. That is just a fact of life. Deal with it.

For EV's it is great. All large format LFP technology and equipment comes from EV's. That includes the BMS and Top Balance being pushed by BMS manufactures. Cells do not stay Balanced if you Top Balance because you have parasitic loads. The Vampire Boards, Temperature and Battery monitors are attached to each cell and powered from each cell. No two draw the exact same amount of power, thus unequal load throwing them out of Balance. In Bottom Balanced system you have no Parasitic Loads. The exact same current flows through each cell every time in Series circuits.

Yes batteries loose capacity as they age. However A Bottom Balanced System is referenced at 0% capacity and SOC which never changes. Zero will always be Zero. What does change is capacity. Full capacity is what you loose, thus the Top changes, but not ZERO. Only thing you might change is the reference cell, not the reference point you are Balanced too. Zero is Zero. Expecting any battery to last 10 years is far fetched.

Also, to charge until one cell hits 3.45 (or whatever) volts, then stop the charge source is impractical in an off-grid application. You need to have the charge controller match the load as best as possible once your cells hit your chosen top voltage. (ie. zero net current from charge controller and loads)

You are taking things out of context and cherry picking. My guess is you have not read all replies and threads on the subject matter. I charge at C/2 constant Current with Commercial power. I or NO ONE EVER SAID you turn off the controller. First thing to know is there are NO SOLAR CHARGE CONTROLLERS made for Lithium batteries on the market with the exception of a Marine and toys with very limited power of 130 or so watts. A Solar Charge Controller made for Lithium would require to interface with a BMS. How do you do that since there are none available? Simple you don't. You have to deal with it and work around it and only if you know exactly what you are doing.

Well what you do, and I have said repeatable many times, is there are a couple of Charge Controllers on the market that allow you to set Bulk = Absorb = Float voltage set points to whatever the user desires. That forces the controller to quit operating as 3-Stage which is useless in any Solar Application, and make it operate CC/CV mode used for Lithium Batteries. In either a Bottom or Top Balanced system you set the voltage according to the requirements. In a Top Balanced System you would set the voltage to 3.55 to 3.6 vpc or whatever your Vampire Board Trigger voltage is set to. The problem with that analogy is the Vampire boards can only shunt .5 to 1 amps, and there is no way to tell the Controller to limit current to Vampire Board limit. When the first Vampire Board turns on, it can only shunt a small amount of current. The remaining still flows through the fully charged cell resulting in a over charged cells. Only thing you can do is turn on enough load to absorb the unknown current value at any given moment in time.

In a Bottom Balanced system you set the voltage well below 100% SOC in the range of 3.3 to 3.4 volts. The final voltage is a a bit of trial and error for the first few days. You settle when the weakest cell reaches 3.4 volts. All other cells will be just slightly lower in voltage. So in a 48 volt pack a Bottom Balanced set point voltage is something slightly less than 54.4 volts. A Top Balanced system would be 57.6 volts.

At that point the Controller is Constant Voltage keeping the batteries charged up and supplying power to the load assuming the panels are able to meet the demand.

So... Until you can explain how you manage to make your cells behave in an identical fashion over their lifespan, and also explain how to manage the charge controller so that it matches the load current in a fully charged situation, then I don't think bottom balancing is for me..

I pretty much covered that above.

[Sunking]

I have read enough posts from the three others in this sample to know that they are not battery manufacturers but real people who have installed real power systems where the LFP batteries are charged from solar panels.

Sure about that? Anything you want to disclose. Only an equipment manufacture would standby and claim to you should use a BMS. Otherwise you are out of biz.