lithium batteries, bulk float absorb time? end or return amps?

[Sunking]

What if the charge current continued for quite some time and your lowest capacity cell never quite reached the 3.55v trigger point? Is it not possible to overcharge a cell when the current flowing in is lower, but for a long duration?

Look this is the last time I am going to repeat myself for the 3rd time. You need to get your head wrapped around LFP is very low internal resistance. Back again to a single 100 AH cell has an Ri= .0009 Ohms

Pick any charge rate you want from no current to 33 amps or C/3.

Lets start with 1 amp. 1 amp x .0009 ohms = .0009 volts. We stop charging at some voltage like 3.5 (95% SOC) At that point the actual cell terminal voltage is 3.4991 volts. Close enough to 95% in my book.

Now let's go up to 30 amps x .0009 volt = .027 volts. We stop at 3.5 volts gives a cell terminal voltage of 3.473 volts or roughly 93% SOC

Can I make it any more clear to you?

There is only one safe way to charge a LFP to 100% SOC. That is with a CV continuous voltage of 3.65 volt until the charge current tapers off to .05 C. That would be 5 amps on a 100 AH cell. There is no possible way to over charge a LFP cell when charging at less than 1C if you terminate below 3.65 vpc. That is it, I am done. The rest is on your own.

[Sunking]

The one thing I find many forget and do myself, is off grid /RV is very different to EV usage and that's where many fall back to LA understanding.

What is different?

On the commercial side they use Top Balance BMS. That comes from engineers and companies trying to sell you something. On the DIY EV side not many use a BMS in the traditional since because they have discovered it is the BMS that destroys the batteries taking all cells to 100%. It is the Vampire Boards used in a BMS that do all the damage and way over charges the cells. When the Vampire Boards Fail they most likely fail shorted and bleed your cell to death. Get rid of the Vampire Boards as they are the root of evil.

Today Bottom Balance is the way to go. Only has to be done once and only once when initially installed. Only thing it takes is a cell battery monitor with two control outputs. One output to send a signal to the charger to turn off when the first cell (weakest cell) reaches 80 to 95% SOC of your choice. And another output to a LVD if any cell reaches 2.5 volts for 15 seconds or longer. Do that and you increase your cycle life 50%.

Size your LFP for 3.5 day minimum and you will never have to worry about over discharging assuming you have a genny. Only three things you have to guard against:

1. Over charge. Never go above 95% on any cell
2. Over Discharge. Never go below 2.5 volts for more than 15 seconds on any cell.
3. Keep them warm and cool which means above 32 F and below 110 F, and never charge a cold Lithium. They charge best at 55 F and discharge best at 90 F.

Oh one last thing. LFP is NOT LEAD ACID so don't treat them like Lead Acid.

[tasman]

What is different?

Oh one last thing. LFP is NOT LEAD ACID so don't treat them like Lead Acid.

You make the claim, “lifepo4 is not lead acid and not to treat them the same”. Pretty hypocritical statement, considering you are telling me there is no difference is use or charging

What is different, Ev's don't charge and use at the same time, if they do it is only for monitoring purposes. Ev's only use energy when they are in use, Rv and off grid are in use 24/7.

EV's are normally charged from close to top to bottom, with very little safety margin. Off grid and RV to 80-90%, most I know it's 80%. EV's use huge amperages at a time, off gird and Rv, use much much smaller amperages, which tend to be a constant draw with short small spikes, rather than fluctuating high energy use, then nothing as with EV.

May not know a lot about lifepo4 or electrical physics, but have been using off grid solar since 1981 and have a dam good idea of sensible off grid system requirements. Compared to what urban mind set people demand.

You may not like the fact I have a 12v off grid system that works fine, compared to your declared higher voltages. I couldn't care less, it was much cheaper for me to just switch from AGM/gel to lifepo4, without spending huge amounts on higher voltage equipment and improve capabilities for providing the energy we need.

It's the same with a BMS, every successful lifepo4 system I've seen over the last 5 years, uses a good BMS, most have been made by the user, or in collaboration with other interested off grid users. The ones I use were originally made for EV, but were re-engineered and programmed for off grid use. They get by better than every commercial one I've come across, but are far from what is needed.

As for float charging lifepo4, just a waste of time and energy. The solar chargers I've been using, don't do the job at all and one of the reason I came to this forum, to see if anyone has charge controllers that charge to the upper parameter then shut off, rather than reduce charge currents.

As I said, the person or company that builds a charge controller/BMS that addresses individual cell voltages, rather than pack voltages, will make a fortune and it will remove just about all lifepo4 charge problems.

Can't understand those here and else where, who claim all this knowledge and yet haven't designed and built a system that works. Maybe it's just school knowledge they have, rather than hands on long term experience with off grid systems. Rather elitist to claim you have the answers, but can't provide the operating physical evidence that would work for lifepo4 charging. So will continue with my unworkable system of more than 4 decades, as well as look for parts that will allow me to control and monitor individual cell voltage charging, rather than the pack.

[Sunking]

You make the claim, “lifepo4 is not lead acid and not to treat them the same”. Pretty hypocritical statement, considering you are telling me there is no difference is use or charging

You are joking right. Have you not read anything? Living Large, PN Junction and I have gone into great detail on the differences between Lead Acid and LFP. Pull your head out of the sand.

What is different, Ev's don't charge and use at the same time, if they do it is only for monitoring purposes. Ev's only use energy when they are in use, Rv and off grid are in use 24/7.

BS there is no difference technically. They both get charged and discharged. EV's do not use all their energy every day or charge everyday. In fact EV owners charge as infrequently as they possible can to extend battery life. They only charge when needed. Off-Grid recharge every day putting another nail in the cycle count coffin with that Lead Acid Mentality. My EV only gets charged as needed and sometimes that can be once a week or more, and sometimes every other day. My batteries will outlast yours by years because I know WTF I am doing.

May not know a lot about lifepo4 or electrical physics, but have been using off grid solar since 1981 and have a dam good idea of sensible off grid system requirements. Compared to what urban mind set people demand.

You may not like the fact I have a 12v off grid system that works fine, compared to your declared higher voltages. I couldn't care less, it was much cheaper for me to just switch from AGM/gel to lifepo4, without spending huge amounts on higher voltage equipment and improve capabilities for providing the energy we need.

I could care less what voltage you operate on. But you are stuck on antiquated 1981 technology when the only thing was 12 volt systems, using antiquated expensive battery panels and primitive charge controllers. Your stuck in the 80's and have not learned a thing since then. You failed to keep up and afraid to admit you have no idea how electricity works or what you are doing.

It's the same with a BMS, every successful lifepo4 system I've seen over the last 5 years, uses a good BMS, most have been made by the user, or in collaboration with other interested off grid users. The ones I use were originally made for EV, but were re-engineered and programmed for off grid use. They get by better than every commercial one I've come across, but are far from what is needed.

Again you have not read one word of my discussions. You do not even know what a BMS is or how they operate. All commercial BMS for sale are TOP BALANCE. I have been discussing Bottom Balance. You do not understand the difference or the technology.

As for float charging lifepo4, just a waste of time and energy. The solar chargers I've been using, don't do the job at all and one of the reason I came to this forum, to see if anyone has charge controllers that charge to the upper parameter then shut off, rather than reduce charge currents.

Again you have your head stuck in the sand and have not comprehended anything discussed because no one at any time has discussed using a Lead Acid Battery Float Charge algorithm to charge LFP batteries.

As I said, the person or company that builds a charge controller/BMS that addresses individual cell voltages, rather than pack voltages, will make a fortune and it will remove just about all lifepo4 charge problems.

Can't understand those here and else where, who claim all this knowledge and yet haven't designed and built a system that works.

This proves you are completely out of touch with the world. Every BMS and charger made, and every discussion I have been involved with clearly point out it is done at the Cell Level. All equipment made for LFP batteries is a BMS Top Balance and geared to the EV industry. There is no Charge Controller made today that is designed to integrate with a BMS controller. If you had paid attention and could comprehend all my discussions you woul dknow for fact Living Large, PN Junction, and myself have been discussing how to use Solar Charger Controllers and off the shelf BMS equipment to work with LFP batteries using a Bottom Balance method. The reason there is no Solar Charge Controller made for LFP is there is no demand because right now the economics are not there, thus no market to sell it to. The only exception is a company called Genasun that has a low power 12/24 volt controller for the Marine Market and RV TOY markets where they can justify the expense to off load 2/3 the weight of lead acid batteries. Weight is not an issue for off-grid stationary systems.

Pull your head out of the sand or go away.

[Sunking]

I will have a read over the info you have provided.

Sorry things got so far off track. Hope you are still reading along.

Ok since you do not have a BMS or cell monitor your best bet that will work out for you is to do this. Involves a bit of work initially, but once you have done it are set with only periodic monitoring.

1. Disconnect the panels, then the batteries from the Charge Controller. We want to stop any charging. Then start turning stuff on and discharge your batteries. Monitor cell voltages and find the one with the lowest voltage and monitor it. Keep discharging until you see the lowest cell hit 2.5 to 2.6 volts, then turn everythind off. DO NOT GO BELOW 2.3 VOLTS.

2. Remove all the batteries and wire them all in parallel and let them set a couple of hours.

3. Measure the voltage. They should be above 2.5 volts. You are going to need a Load Device to discharge the batteries. There are a few ways to go about it. If you got a old Blow dryer laying around take it apart and cut the heating coil out. Use a pair of wires with alligator clips and connect it to the battery. Or for 5 bucks on Ebay buy a 1-Ohm 20 watt resistor and connect to the batteries. Discharge then until they get to 2.5 volts and let them rest. Repeat until the batteries rest if 2.4 to 2.5 volts.

4. You have now Bottom Balanced your batteries and will not ever have to do that again. What you have done is referenced all cells to 0% capacity or 0 AH.

6. Reconnect batteries charge controller, panels, and inverter.

7. Go into your controller and set:

In your inverter set the LVD = 44 to 46 volts. Anything higher than 42 will work and protect the batteries.

Float = 55.2 volts (3.45 vpc)
Absorb = 55.2 volts or slightly lower if your controller will not allow to set same as Float. Time as little or as much or as little as you want. Makes no difference
Bulk = 55.2 volts or slightly lower if your controller will not let you set same as Absorb.

Here is how it operates. Since you do not have a BMS or battery Cell monitor to control the charger we BOTTOM BALANCE ALL YOUR CELLS to 0% SOC or 0 AH capacity at 2.5 volts per cell which will be a pack voltage of 40 volts. During Charge since we are not monitoring all cells we are only going to charge you battery pack to roughly 85 to 90% by limiting the voltage to no more than 55.2 volts or roughly average 3.45 volts per cell. Rather than to 100% at 58.4 volts. You do not have a BMS to limit individual cell voltage to 3.65 volts. If fact you are intentionally undercharging the batteries which is a good thing with LFP batteries That will give you roughly 50% more cycle life.

What you have to watch out for the first couple of days is watching the cell voltages to make sure none go over 3.6 volts. If you Bottom Balanced correctly that should not be a problem. If you see a cell getting close to 3.6 volts, lower the voltage on the controller .25 volts and monitor for a couple of days until you find the sweat spot. Since you bottom Balanced the weakest cell will have the highest voltage. Find that cell and watch it. DO NOT LET IT GET GREATER THAN 3.6 VOLTS. Aim for 3.5 to 3.55 volts at the end of a charge cycle. At 3.55 volts while under charge is 95% SOC and you battery pack is only as strong as your weakest cell.

All the stronger cells will have a slightly lower voltage than the weakest cell. The magic is when you Bottom Balance is all the cells have the exact same AH Capacity regardless of SOC voltage. Th eonly time and place the voltages will be equal is when all cells are fully discharged to 2.5 volrs which they will never see if you set your inverter LVD to 41 volts or higher. I suggest 44 volts to give you some breathing room.

[northerner]

Look this is the last time I am going to repeat myself for the 3rd time. You need to get your head wrapped around LFP is very low internal resistance. Back again to a single 100 AH cell has an Ri= .0009 Ohms

Pick any charge rate you want from no current to 33 amps or C/3.

Lets start with 1 amp. 1 amp x .0009 ohms = .0009 volts. We stop charging at some voltage like 3.5 (95% SOC) At that point the actual cell terminal voltage is 3.4991 volts. Close enough to 95% in my book.

Now let's go up to 30 amps x .0009 volt = .027 volts. We stop at 3.5 volts gives a cell terminal voltage of 3.473 volts or roughly 93% SOC

Can I make it any more clear to you?

There is only one safe way to charge a LFP to 100% SOC. That is with a CV continuous voltage of 3.65 volt until the charge current tapers off to .05 C. That would be 5 amps on a 100 AH cell. There is no possible way to over charge a LFP cell when charging at less than 1C if you terminate below 3.65 vpc. That is it, I am done. The rest is on your own.

I don't believe that's correct sir. When charging at a constant current sub c rate, at about 3.4 volts, the voltage begins to climb quite rapidly. That means that the Ri of the battery at that stage is increasing and will no longer be .0009 ohms. Therefore you will have a greater differential in voltage for different currents. From what LiFePo4 users are saying, there is really no point in going over 3.4 volts per cell, and doing so increases the risk of cell degradation, even if not overcharged.

If I go the LFP route, that's what I will do. I will top balance and not go beyond about 3.4 volts per cell. There's very little energy beyond that point anyway, and there would be a lower risk in progressively degrading your cells.

[Sunking]

I don't believe that's correct sir. When charging at a constant current sub c rate, at about 3.4 volts, the voltage begins to climb quite rapidly. That means that the Ri of the battery at that stage is increasing and will no longer be .0009 ohms. Therefore you will have a greater differential in voltage for different currents. From what LiFePo4 users are saying, there is really no point in going over 3.4 volts per cell, and doing so increases the risk of cell degradation, even if not overcharged.

If I go the LFP route, that's what I will do. I will top balance and not go beyond about 3.4 volts per cell. There's very little energy beyond that point anyway, and there would be a lower risk in progressively degrading your cells.

You still don't get it. Just how do you intend to only stay at 3.4 volts on a cell while charging?

You have to use Vampire Boards that shunt .5 to 1 amps depending on model around the cell. That is called a By Pass Shunt and how Top Balancing is done. You keep charging until every Vampire Board turns on when they reach 3.5 to 3.6 volts, then terminate the charge. But there is a HUGE FLAW in that analogy and operation. How are you going to control the charger to throttle back to .5 to 1 amp when that first Vampire Board turns on?

To Top Balance you must reduce the charge current to the value of the Vampire Board bypass current which ranges from .2 to 1 amp when the first cell triggers. Care to guess how long it will be before all the other cells reach 3.4 cells on .2 to 1 amps charge current on solar. Chances are there are not enough hours in a day. Not to mention no Charge Controller capable of doing that.
Do you see a problem yet?

Allow me to point it out for you. With Solar charging LFP you want to do it all while in Bulk or Constant Current mode so you can actually get fully recharged in a day as fast as you can before the sunsets. So there you are charging away at say 50 amps. Your first Vampire Board turns on and goes into bypass shunting .5 amps around the cell leaving 49.5 amps flowing through your fully charged cell cooking it. Second Vampire board turns on and now you are cooking 2 cells. This process continues until the last vampire Board turns on and then shuts down the charger. So now you have one properly fully charged cell, and all the others way over charged.

Good luck with that. .

[Sunking]

I don't believe that's correct sir. When charging at a constant current sub c rate, at about 3.4 volts, the voltage begins to climb quite rapidly. That means that the Ri of the battery at that stage is increasing and will no longer be .0009 ohms. Therefore you will have a greater differential in voltage for different currents. From what LiFePo4 users are saying, there is really no point in going over 3.4 volts per cell, and doing so increases the risk of cell degradation, even if not overcharged.

If I go the LFP route, that's what I will do. I will top balance and not go beyond about 3.4 volts per cell. There's very little energy beyond that point anyway, and there would be a lower risk in progressively degrading your cells.

You still don't get it. Just how do you intend to only stay at 3.4 volts?

You have to use Vampire Boards that shunt .5 to 1 amps depending on model around the cell. That is called a By Pass Shunt. You keep charging until every Vampire Board turns on, then terminate the charge. That is how Top Balance works. But there is a HUGE FLAW in that analogy and operation. How are you going to control the charger to throttle back to .5 to 1 amp when that first Vampire Board turns on?

Do you see a problem yet?

Allow me to point it out for you. With Solar charging LFP you want to do it all while in Bulk or Constant Current mode so you can actually get fully recharged in aa fast as you can in a day before the sunsets. So there you are charging away at say 50 amps. Your first Vampire Board turns and bypasses .5 amps leaving 49.5 amps flowing through your fully charged cell cooking it. Second Vampire board turns on and now you are cooking 2 cells. This process continues until the last Vampire Board turns on and then shuts down the charger. So now you have one fully properly charged cell, and all the others way over charged and smoking.

To Top Balance properly you have to limit the charge current to the value of the bypass current of the Vampire Board when the very first cell triggers on. Care to guess how long it will take to get all the other cells up to 3.4 volts until the last cell reaches trigger point? Not to mention there is not one single charge controller capable of doing that.

Good luck with that. .

[northerner]

You still don't get it. Just how do you intend to only stay at 3.4 volts on a cell while charging?

I will size the bank, so that the charge rate will be relatively low, somewhere around 0.1 c, so the cell voltages will not rise as fast as they would charging at rates many in the EV or boat world do. I may go to 3.45 volts per cell occasionally, perhaps in anticipation of bad weather.

You have to use Vampire Boards that shunt .5 to 1 amps depending on model around the cell. That is called a By Pass Shunt and how Top Balancing is done.

I didn't mention anything about using "Vampire Boards" to do the top balancing. I would balance the cells manually initially, and only if needed beyond that, which should be very rarely. But I would only do it manually, and using a power supply. They really should stay in balance beyond that point for a very long time, providing you don't take them above full charge.

I think I mentioned this before, but the reason I would top balance is that I find I am taking the bank up to near full on a fairly regular basis overall. Of course it will not stay there, and so the pack will partial discharge regularly as well. It is rare that I ever go down much below 50% state of charge currently with Pb, let alone to a 20% state of charge. And even if I took an LFP bank down to 20%, there is still a good safety margin from the bottom. But the majority of the time the pack will vary somewhere between about 40% and 80% state of charge, and my charging currents are usually heavier, and heavier for a more sustained duration than the loads, which are overall relatively light, spread out over a longer period of time, and the not so heavy loads are of very short duration. Make sense now?

[Willy T]

My batteries will outlast yours by years because I know WTF I am doing.

It doesn't get any funnier than this, take heed.

[Sunking]

I will size the bank, so that the charge rate will be relatively low, somewhere around 0.1 c, so the cell voltages will not rise as fast as they would charging at rates many in the EV or boat world do. I may go to 3.45 volts per cell occasionally, perhaps in anticipation of bad weather.

What makes you think EV's charge faster than C/10 which is the same as .1C. A 120 volt AC circuit can only operate at a continuous power of 1440 watts and on a 144 bolt 200 AH battery is C/20 or .05C much slower than a solar system. Now there are some that use 240 VAC 30 amp circuits and can charge as high as C/4, but that is the exception to the rule. even on a commercial EV it is rare for most to use anything more than Level 1 charger at C/20. To go to Level 2 and 3 gets expensive. you find that more with folks who own Tesla Roadster where money is no object

I didn't mention anything about using "Vampire Boards" to do the top balancing.

Then you are not Top Balancing and would be foolish to operate that way. You would be much better served to BOTTOM BALANCE one time only initially, and then set your controller Bulk = Absorb = Float = 3.45 x S where S = the number of series cells. So for example a 16S pack would be 55.2 volts.

What is not getting through to you is any form of Top Balance puts you at very High Risk of over charging a cell and cell reverse polarity which destroys the cell immediately. Bottom Balance with monitor eliminates those risk and extends battery cycle life.

[northerner]

Then you are not Top Balancing and would be foolish to operate that way. You would be much better served to BOTTOM BALANCE one time only initially, and then set your controller Bulk = Absorb = Float = 3.45 x S where S = the number of series cells. So for example a 16S pack would be 55.2 volts.

What is not getting through to you is any form of Top Balance puts you at very High Risk of over charging a cell and cell reverse polarity which destroys the cell immediately. Bottom Balance with monitor eliminates those risk and extends battery cycle life.

Not according to this fellow who has an excellent write up on LiFePo4 operation. Check out the link below, and in fact he mentions that "top balancing" for systems that are using variable sources of power and for home off grid use, is often the preferred choice!

http://www.pbase.com/mainecruising/lifepo4_on_boats&page=1

There's very little risk of going too low, if you very rarely go to 20% DOD (more like 40 or 50% normally), plus you have built in protection from the BMS in the event that something does go wrong. Plus a 20% margin at the bottom, which is good to leave, gives you a wider margin, than a less than 10% at the top, particularly if not balanced at the top. If your constantly charging to near full, day after day, then there's more of an issue with cell degradation in going high, IMO.

But it really is a personal choice, and by all means bottom balance if that's what suites you!

[Sunking]

I read that article a year ago. I even know him he is a member of a EV forum, and has done a 180 like me. If you bothered to read the whole 3 pages in detail with an open mind he points out the dangers of TOP BALANCE. He now understands the risk involved with top balance, because he destroyed two of his cells. I DO NOT CARE IF YOU DESTROY YOUR BATTERIES. You have been told. Now it is time you learned with your your money. You will be the one hurting, not me, and I like it that way. Failure and loosing money is a great teacher.

The EV custom build shops that are dropping TOP BALANCE like hot potatoes because it is costing them big bucks replacing batteries under warranty. Bottom Balance is very easy and inexpensive to implement. It is Faster, Better, Cheaper, and less risky than TOP Balance, not to mention increases cycle life. I have no idea whey you cannot get your head wrapped around that. You have to get out of the Pb box you are trapped in. I know what I am talking about, I am a EE and was once trapped in that box. Again I do not care about you and your money. If you want to fly in th eclouds without instruments, please do it over the ocean so when you crash you only kill yourself.

Now if you want to learn how to Bottom Balance and use nothing but off the shelf Solar Charge Controllers and a simple RC hobby charger or resistor, I can teach you how to do it. You will never risk cell reversal or over charge. Do it your way and you run a much higher risk of over over charging or cell reversal. It is that simple. Your way high risk, Bottom Balance lower risk and longer cycle life with less equipment cost. What part do you not understand? .

[tasman]

You are joking right. Have you not read anything? Living Large, PN Junction and I have gone into great detail on the differences between Lead Acid and LFP. Pull your head out of the sand.



BS there is no difference technically. They both get charged and discharged. EV's do not use all their energy every day or charge everyday. In fact EV owners charge as infrequently as they possible can to extend battery life. They only charge when needed. Off-Grid recharge every day putting another nail in the cycle count coffin with that Lead Acid Mentality. My EV only gets charged as needed and sometimes that can be once a week or more, and sometimes every other day. My batteries will outlast yours by years because I know WTF I am doing.



I could care less what voltage you operate on. But you are stuck on antiquated 1981 technology when the only thing was 12 volt systems, using antiquated expensive battery panels and primitive charge controllers. Your stuck in the 80's and have not learned a thing since then. You failed to keep up and afraid to admit you have no idea how electricity works or what you are doing.

Again you have not read one word of my discussions. You do not even know what a BMS is or how they operate. All commercial BMS for sale are TOP BALANCE. I have been discussing Bottom Balance. You do not understand the difference or the technology.



Again you have your head stuck in the sand and have not comprehended anything discussed because no one at any time has discussed using a Lead Acid Battery Float Charge algorithm to charge LFP batteries.



This proves you are completely out of touch with the world. Every BMS and charger made, and every discussion I have been involved with clearly point out it is done at the Cell Level. All equipment made for LFP batteries is a BMS Top Balance and geared to the EV industry. There is no Charge Controller made today that is designed to integrate with a BMS controller. If you had paid attention and could comprehend all my discussions you woul dknow for fact Living Large, PN Junction, and myself have been discussing how to use Solar Charger Controllers and off the shelf BMS equipment to work with LFP batteries using a Bottom Balance method. The reason there is no Solar Charge Controller made for LFP is there is no demand because right now the economics are not there, thus no market to sell it to. The only exception is a company called Genasun that has a low power 12/24 volt controller for the Marine Market and RV TOY markets where they can justify the expense to off load 2/3 the weight of lead acid batteries. Weight is not an issue for off-grid stationary systems.

Pull your head out of the sand or go away.

What pathetically infantile reply and so funny. Just so you understand, got no lead acid batteries, every energy storage we have is lifepo4, including start batteries, which made up myself. That's not 1981 technology, nor is the open source computer system that runs and controls our house energy and lighting usage, rather than the norm of turn everything on at once and leave it. It also gives us state of the art 21st century personal, safe and free computing systems, including phones and tablets. Unlike those trapped in past century useless Redmond bloatware and locked into destructive and expensive 19th century fossil fuels.

Don't have an EV, but have electric mountain bikes, chainsaws and outboard motors, all using lifepo4. Increased the range of the bikes to 80klms and experimenting with regenerating brake systems for the bikes, but that's probably to 1980's for you.

You also have a habit of claiming what others have posted as your own, then attacking them for what they posted. Seems you want no one else's opinion or experiences other than your own in this forum, which explains a lot.

You also seem to be the only one I've run into who demands bottom balancing is the only thing that works, when that is not the case in my experience and others I talk to about this. Good lifepo4 cells should arrive with 3.2v in them balanced, why discharge them so you can balance. It's much easier to set the right parameters, charge them up and top balance them out. That's if your packs cells are all at 3.2v. From there, in my experience, that's it. A BMS with active cell balancing, is a safe guard, with a real dedicated Cell charging BMS, all you'd have to do is watch it function.

You constantly avoid the fact my lifepo4 system has been in operation for close to 2 years and never reached the upper and lower voltage parameters I've set. To me and everyone else I come across, that's a good reliable system which will last an extremely long time. Most others I know have the same experience, it never gets beyond 80% charge or 80% discharge. To someone like you, that doesn't count, only your opinion counts.

Only an egocentric fool would race out and spend a lot of money on new equipment to satisfy some nutters demand that 12v systems don't work in off grid situations. When mine and millions of others have been operationing successfully for decades, why update a system that works. If it fails, then we will consider some changes. You don't seem to have any knowledge or long term experience with off grid systems and it shows.

Economically, all I had to do was change over the storage from deep cycle LA to lifepo4 and organise control of it. The difference in going from 1000ah consisting of 2v x 500ah LA cells, to 700ah of lifepo4 was amazing.

As for a satisfactory BMS, got one that's been operating for close to 2 years. It switches off when one cell reaches its upper limits, which has never happened and will do the job until a real BMS is manufactured.

Sadly it's you who have your head in the sand and by everything you say, no real hands on experience outside your EV and urban lifestyle. Like many others we travel all the time and come across loads of people using lifepo4 and their experiences are the opposite to your claims.

Witnessed some incredible systems in India and Asia and some very dangerous ones, all running on 12v and last year, saw many with lifepo4 packs. They certainly make your claims about 12v look pathetically stupid, but do understand the physics involved and agree with them technically. So don't know what you're crapping on about, other than your ego seems hurt.

In practise, like most things, theory is one thing, real life practise is another. Most people I come across that are off grid, are not super rich, but struggler's trying to keep their head above the never ending price spirals of electrical energy. What of grid and Rv system do you have and built yourself?

As for telling me to go away, fully understandable with the psychological age you exhibit here. How do you destroy a lifepo4 pack that never reaches its upper or lower conservative voltage limits, or is it just you that can make lifepo4 work, grow up fool. By the way, this thread is about bulk float absorb times, not bottom balancing. Which revovles around upper voltaghe limits, so maybe you should stick to the thread, pull your head in, or go away.

[Sunking]

Economically, all I had to do was change over the storage from deep cycle LA to lifepo4 and organise control of it. The difference in going from 1000ah consisting of 2v x 500ah LA cells, to 700ah of lifepo4 was amazing.

12 volts at 700 AH huh? That is some funny stuff, I don't care who you are. I bet you use a few PWM controllers and 12 volt battery panels on that system huh?

FWIW I design, build commission, and help companies and people maintain off grid power systems professionally for the last 15 years for commercial operations. Been a professional EE for 35 years of my 60 years on earth. I have forgotten more than you know about power. Retired happily in Panama tax free and never have to worry about paying any bills, traveling anywhere I want, any time I want. Life is good and comfortable for me at 60 years of age. I started out dirt poor in a military family.