Mechanisms that decrease the Lifespan of Lithium-Ion batteries and how to avoid them

[wb9k]

I heartily welcome WB9K, and no matter what happens, I have gotten a LOT from you just lurking over the last few years.

So much so, that I cut open many NEW powersports batteries a few years ago just to work with A123 cells, which got me enough hands-on to brave large prismatics from other companies and compare notes - although there are obviously some differences.

I'm actually amazed that anyone working in the industry even steps foot inside a forum, considering the large target it puts on your back. It isn't much different than the hammering I saw "Optima Jim" (Jim McIlvane) go through when he just really wanted to help people understand and improve their setups, and not try to be a salesman or company shill - just a tech trying to help people out. Unfortunately, you don't find much of him anymore in the forums, and I think I know why - like not wanting to get gray hair prematurely.

So please understand that even when threads get contentious, there is STILL VALUE in what is debated, especially for those of us that can look beyond the drama. Basically THANK YOU from a lurker.

Thanks for the kind words. It's gratifying to know that folks are reading and benefiting from my efforts to share useful information. See you around!

dh

[Sunking]

OK, what if you get distracted when you have your bleed resistor hooked across one of your cells when doing a bottom balance.

I have a tool all Bottom Balancers use a PowerLabs 8 hobby charger. Impossible to over discharge. Even using a resistor would be incredible hard to over discharge.

You connect all 16 100 AH cells in parallel. With a .080 Ohm 100 watt resistor gives you a big wide window of a few hours to remember. With a Powerlabs 8 drawing 30 amps, you walk away, go to bed, and by morning you are balanced perfectly at 2.4 to 2.6 volts per cell. You can go to 2 volts but not recommended.

If by chance I should ever need to re balance which is unlikely because I know around 100 people with EV's that BB and have done so for at least 3 years have never ended to re balance, I would drive my EV until it stopped and would use my PowerLab 8 discharging 8 cells at a time until the reach 2.5 vpc again. No driving my EV until it stops will not hurt the batteries because I designed it so it cannot hurt the batteries. They will still be setting around 2.7 to 2.9 volts per cell if out of balance. Right now if I drive until the EV quits all cells rest at 2.8 volts as designed. If they were Top Balanced and I drove my EV until it quits would likely end with a destroyed cell, the weakest one.

[Sunking]

If Sunking puts forward some credible evidence to support his claims them I might change my mind on his credibility regarding Lithium batteries and particularly Lithium batteries being charged by solar energy.

I have done that many times for you Simon, you just do not want to hear it. Start with this written by my peers.

Topologies[edit]

BMS technology varies in complexity and performance:

• Simple passive regulators achieve balancing across batteries or cells by bypassing charging current when the cell's voltage reaches a certain level. The cell voltage is a poor indicator of the cell's SOC (and for certain Lithium chemistries such as LiFePO4 it is no indicator at all), thus, making cell voltages equal using passive regulators does not balance SOC, which is the goal of a BMS. Therefore, such devices, while certainly beneficial, have severe limitations in their effectiveness.

More facts you cannot deny and is well known.

• Limiting SOC to 80% doubles the calendar and cycle life. Which begs the question is why would you ever go to 100%. That is a Pb left over and mentality period.
• You Inverter and Charge Controller already has the protection you need to protect you from Over Charging and Over Discharging. When you Bottom Balance makes it impossible to Over Discharge a LFP cell
• We are talking only about NiFePO4 cells. NOT ANY OTHER TYPE.
  
• We are only talking about very low Charge and Discharge Rates in a controlled environment of room temps.
• Many battery Manufactures make 12 volt LFP batteries as drop in replacements for Pb and most do not have any type of BMS other than a LVD Relay. That includes the almighty A123 LFP 12 Volt Car Battery. Why would a manufacture do that without a BMS? Because it is NOT NEEDED.

You cannot deny anything I have said as not true and factual. You just do not want to hear it. The other thing you have not heard and do not want to hear is I never said: You Should Not Use BMS on a LFP solar system.

I say: A BMS is not required or necessary Everyone else has heard that except you. You do not even understand the concept of Bottom Balancing. It mimics matching cells accurately. You can use a BMS, I do not care, it is your money you are pissing away, not mine. Go spend it, all of it.

[karrak]

Assumptions made by Sunking

Sunking, one of your main arguments for not doing top balancing or not charging above is it 80% or 90% is that it will cause a huge decrease in the lifespan of an LFP battery, to quote you

It is well know if you charge any of the Lithium batteries near or to 100%, you cut your cycle life in half.

Could you provide me with information to back up this claim.

In this study http://www.researchgate.net/publicat...teLiFePO4_cell which I have mentioned before in this thread on page 298 is the following.

Fig. 2(a) shows that, after 240 days (8 months) of storage, the capacity increased by 1.8%, 1.07%, and 1% for SOC nom 30%, 65%, and 100%, respectively. Meanwhile, Fig. 2(b) and (c) shows that the capacity fade is fairly linear as a function of storage time and at a specified temperature, more capacity fade is experienced at higher storage SOC. At 45◦C, after nearly 214–247 days of storage, the capacity has decreased by 2.1%, 4.9%, and 5.7% for SOC nom 30%, 65%, and 100%, respectively. This decrease becomes much more substantial for the cells stored at 60◦C for which the capacity fade percentages of the cells (∼155–188 days of aging) are about 18.1%, 23.7%, and 26.9% for SOC nom 30%, 65% and 100%, respectively.

The other cornerstone of your argument is that if you if you bottom balance you don't need to have a BMS. I can see this would work if the balance at the bottom and top does not change with time. This is not the case. If the capacity of the individual cells vary relative to each other the top balance will change, if the coulomb efficiency of the cells is not identical the bottom balance will change. All this has already been covered before in this thread http://www.solarpaneltalk.com/showth...-Solar-amp-BMS

Simon

[karrak]

I think that the biggest problem is that the S/N ratio is so high, that NOBODY is getting any value from the debate, be it right or wrong or in total agreement.

I have given up on getting any useful information on the subject of this thread from this forum. The thread has been hijacked and I think it is important to discuss the points that Sunking has bought up.

Simon

[karrak]

Like I said you are a manufacture and only have one point of view. The claim that Top Balance and a BMS must be used is completely false and made up by manufactures with BMS and Top Balance products. It i sleft over thinking from Pb battery industry of keeping batteries topped off at 100%. Pb batteries do not like the PSOC world, where lithium batteries thrive in the PSOC world and cannot be treated lik ePb or any other battery chemistry.

I am not saying that top balancing must be used I am saying that I think it is easier to use with off-grid solar systems and is not detrimental to the longevity of LFP batteries. It is nothing to do with Pb technology, that is your fixation.

There is nothing dangerous with Bottom Balancing, it is safer than Top Balance.

OK, what if you get distracted when you have your bleed resistor hooked across one of your cells when doing a bottom balance

As to responding I would have loved to continue a debate, but you shut the thread down.

The moderator on the Endless Spheres forum temporarily locked the thread to give you time to calm down, it is open again now.

So do not give us that crap I would not answer questions. You do not want questions answered unless it is you are th eone giving answers. You cannot have your way here. Now you come here hoping to shut the debate down here. Simon like like you are manufactures, you have to tow the company line. Simon couldn't win the debate here, so went crying to you looking for help. I expect you and Simon both to say exactly what you are saying. As manufactures if you said anything else is Conflict of Interest. You are here to protect your Invested Interest. I am here to tell floks there is another way and you do not like it.

I am not and never have been part of the battery or BMS industries. If you remember I am retired like you. Now how about you having a conflict of interest being involved with the battery industry for so long?

You say it has to be at the top 100% where you only really know voltage, but AH is unknown. I reference at the Bottom where I Know exactly where 0% and 00 amp hours are located. From there once charged they never see anything below 20% or above 90% which is spot on for maximum lithium battery life. Everything I said has been factual.

This only happens if the battery does not go out of balance at the bottom end. How do you reset your Ah meter to take care of the battery coulomb inefficiency?

Your method is to charge lithium cells to 100% every time, and it is well know that is not good on for lithium batteries and can cut battery cycle life down some 50%. That is good practice from a manufacture POV as it generates more battery replacement sales. Me I never go above 90%, so not something I have to worry about is over charging, I eliminated the possibility, where Top Balance does it every cycle if set to 3.6 volts.

This is not true. I only do a top balance one every year or so and do that at 3.5 volts not 3.6 volts. We have been through this all before. It used to be 80%, now it has changed to 90%.

With Top Balance you also set the batteries up for a over discharge and reversing a battery cell polarity. With Bottom Balance I eliminated the possibility because all cells arrive at 0 at the same time. No adjacent cells have any energy left in them to drive a cell into reversal. Cell Reversal is the most destructive thing you can do to a lithium and you know it.

Only works if cells never go out of balance at the bottom end

Simon

[PNjunction]

I think that the biggest problem is that the S/N ratio is so high, that NOBODY is getting any value from the debate, be it right or wrong or in total agreement.

I guess it really comes down to WHO, other than the original op, will it benefit? Can we keep it short and sweet, perhaps a stickie to point to, and ban the topic altogether and just direct newcomers to it? This might save a lot of server space.

At some point, the S/N ratio is so high, (I have been guilty myself!), that it generates more confusion than clarity, and certainly inspires a lack of confidence for the newcomer.

So, do we keep the newcomer / lurker in mind when responding to the original op, so that they don't get immediately overloaded? Should we? What differentiates us from other more focused boards, or should we be general purpose, or cater only to EE's? What and WHO is our focus?

[karrak]

On internet message boards, you have to keep an open mind and occasionally wade through claims that are questionable. Debate is good. It is obvious to me as an engineer that there are multiple ways to skin the cat.

Absolutely agree with you here.

Personally, I find actual discussion useful, not posting links to arguments held elsewhere or even a conversation that was held elsewhere. Have the discussion here, and in J.P.M.'s words, the readers can take what they want and scrap the rest. A single isolated post of a discussion that was held elsewhere, without associated set-up or discussion, I am really not interested in plowing through, or worse - going to that thread and reading the entire thing to figure out what that issue was and how it may relate to the current discussion. OTOH, if in the middle of a post where the author is making an argument, posting a link can add to the discussion. I prefer the "experts" here I have come to respect bouncing concepts off each other, and lurkers like me can ask a question every so often.

I always thought engineering is based on science. In both science and engineering if you put forward a proposition you must be able to back it up with evidence and data, i.e. it must be verifiable. This is the cornerstone of engineering and scientific research. If you look at the scientific papers that I have linked to in this discussion you always see references in them to other works to back up the proposal that is being made. IMO if you put forward a proposition and don't back it up with credible evidence it is merely an opinion and should not be given much weight.

Unfortunately sometimes you just do have to plough through lots of other information to work out if a proposition that is being put forward is correct or not. This is why it is much harder to disprove an unsubstantiated statement that to make it. If you do this research you may even gain considerable expertise in the topic under discussion rather than just accepting another persons point of view.

The problem with experts is if they are wrong and won't admit it. Now Sunking maybe an expert with LA based batteries as that is a large part of his lifelong professional experience, but that does not necessarily make him an expert on Lithium based batteries. His expertise with LA and other battery technologies may actually be an impediment as he looks at Lithium based batteries trough the lens of his experience. He has been proven wrong on many occasions in this forum but just continues on as though nothing has happened.

If Sunking puts forward some credible evidence to support his claims them I might change my mind on his credibility regarding Lithium batteries and particularly Lithium batteries being charged by solar energy.

I am always very wary of anyone who proclaims themselves as an expert. Whether someone is an expert in a topic they are discussing should be gleaned from the information they put forward and not on their reputation.

Simon

[Sunking]

I may be wrong Dereck, but you were still evolving as of about five months ago, when you were answering questions I was asking about safely using an LFP bank in my off-grid solar system. You had already decided against the bypass BMS for this application, and I believe you changed your thinking or refined it as to balancing based on conversations you had with other LFP users while researching my questions. I am a novice, but everything you said made sense. I'm still lurking, and willing to consider alternate viewpoints - but right now I believe I have a practical plan. I plan to use what I would call a Battery Monitoring System BMS - not a management BMS, for peace of mind and backup disconnects, as you outlined above. Also to provide individual cell monitoring so I don't need to move a meter around constantly to assess cell voltages.

That has not changed has it? You are absolutely correct stating I flipped on By Pass Charging and BMS. But make note I was starting my EV build which started 2 years previous. I started collecting the pieces of the EV two years ago starting with 16 Vampire Boards and batteries. Two years ago I was pro Top Balance. After receiving the batteries a year ago. I started some experiments and researching some more. By the time I started my build when you came along I had abandoned all the Vampire Boards and sold them.

At assembly time I wanted cell level monitoring and had two choices. I could buy another Power Labs 8 which is my Hobby charger for RC planes which can only handle 8 cells, or buy something else. After more research got a few tips on DIY EV Forum and a couple of dealers to make me some great offers. I took one up on the Orion Jr. a 16 cell BMS. But I only use the battery cell voltage monitor and Coulomb Counter. I do not use the Bypass Function of the Orion, just the gas gauge and Cell Voltages which I do not really need.

In a off-grid Solar application it is nice to have a cell monitor, but not necessary or needed. It is a Bell and Whistle. In hind site I could have used my Motor Controller Coulomb Counter because all I really needed was a Gas Gauge. If I had it to do all over again, I would not use a Cell Monitor. Every time I have tested low voltage conditions on the EV, the Motor Controller has done its job. When it hits 48 volts, the Controller goes into Limp Home mode, a reduced power setting and warning. At 42 volts or roughly 5% remaining it shuts down nd requires a two home to recharge. Batteries are in no danger until 32 volt. I cannot go any lower than 40, my Inverter will not allow it to happen.

For charging all I do now is set the rectifier to 53.6 volts and let it float. For Solar you do not Operate at the extreme discharge rates and temps as a EV. A battery in a Off Grid Solar has a really easy life. It never gets stressed from Over charging if you avoid the Top. It never sees those high temps of 40 and 50 Centigrade compounded by 1C+ discharge rates piling onto the ambient temps.

So to answer your question I am still evolving. If you want cell level monitoring for an added layer of protection, then go for it if you can afford it and gives you confidence. All I am saying is I cannot say that really buys you much, but you can still afford not to considering it is overkill via Automation and not really necessary with a good strategy and practice. All automated systems have a huge flaw. Most people rely on them to heavily and become complacent. That can leave you stranded on the Hwy or in the Dark. Not a problem with a cell phone or tablet.

Does that help??

PS

If I had to do over. Use 2 of the PowerLab 8's as part of the system in Monitor Mode. Takes two cover 16 cells. With that you can run either Bottom or Top Balanced with the same tool installed. Gives you a lot of options including charge source from a panel. Anything DC sourced. But for Solar, good strategy coupled into the design using what there is to work with respect to Charge Controllers and Inverters works well with LFP because they have the same nominal voltages as Pb for every 6 volt multiples. All i takes is a few little voltage tweaks like a little lower than Pb charge voltage 13.8 to 14 instead of 14.4. Upping LVD from 10.5 to 11 or 12.

Adding Cell level monitoring is nice, and is icing on the cake. Is it needed?? You gotta decide, and when you do, I will try to help as always.

[Living Large]

WB9K I use to take your professional view of Lithium Batteries Demand a BMS. I pounded my chest saying that. I am a pro even a licensed one, not EC, a PE with around 35 years battery plant experience. I had Must Use BMS drilled into me. It made perfect sense to charge batteries to 100% because "By God that is what we have done for over 100 years and no reason to change now". But we cannot charge Lithium batteries to 100% like we do Pb because they do not pass energy on to the next cell in line when they become fully charged. So By God we need to invent a BMS with By Pass Charging.

I thought that way 5 years ago. Hell even as little as 2 years ago. If you had been around here you would have witnessed that change in POV. Research and experience led me out of the darkness.

I may be wrong Dereck, but you were still evolving as of about five months ago, when you were answering questions I was asking about safely using an LFP bank in my off-grid solar system. You had already decided against the bypass BMS for this application, and I believe you changed your thinking or refined it as to balancing based on conversations you had with other LFP users while researching my questions. I am a novice, but everything you said made sense. I'm still lurking, and willing to consider alternate viewpoints - but right now I believe I have a practical plan. I plan to use what I would call a Battery Monitoring System BMS - not a management BMS, for peace of mind and backup disconnects, as you outlined above. Also to provide individual cell monitoring so I don't need to move a meter around constantly to assess cell voltages.

[Sunking]

WB9KI would have enjoyed having an open discussion with you at Endless Sphere. I was not given the opportunity to answer any of the questions before the Thread was CLOSED. If for anything to at least to Inform You of how I operate a Bottom Balanced System with minimum equipment. It is obvious you and others do not even understand what I am doing, because if you had understood, you would know there is no Danger

Last question you asked me is what I call a BMS???

Real simple any system that uses Bypassing Charge Current around a cell or group of Paralleled cells when a voltage reaches a set level. They are called "Balance Boards" aka Bleeder or Vampire boards. In laymen terms a circuit that discharges battery at a steady current rate. The current rate varies from as little as 10 ma up to 1 or 2 amps maximum in rare case. Typical is 150 to 500 ma a small amount. The boards Turn On at some voltage which is typically 100% SOC like 3.6 volts on a LiFePo4 battery. When it turns on, the circuit draws or Bypasses it rated current of say .5 amps leaving the remainder of the charge current flowing through the cell. So if you have a 20 amp charger, you have .5 amps bypassing the battery and still have 19.5 amps flowing through the battery.

It is the Vampire Boards I take issue with and the concept of Top Balancing. Top Balancing takes you to the Red Zone and is dangerous and foolish strategy IMO. There is no reason to go to the Top with any lithium chemistry as it only shortens cell life and playing with fire. Why do that?

WB9K I use to take your professional view of Lithium Batteries Demand a BMS. I pounded my chest saying that. I am a pro even a licensed one, not EC, a PE with around 35 years battery plant experience. I had Must Use BMS drilled into me. It made perfect sense to charge batteries to 100% because "By God that is what we have done for over 100 years and no reason to change now". But we cannot charge Lithium batteries to 100% like we do Pb because they do not pass energy on to the next cell in line when they become fully charged. So By God we need to invent a BMS with By Pass Charging.

I thought that way 5 years ago. Hell even as little as 2 years ago. If you had been around here you would have witnessed that change in POV. Research and experience led me out of the darkness. At least step up to the door and look around and see what is outside your BOX. If I can, you can. Although we know you will never admit it. You cannot admit it, you are enslaved by your employer.

So if you really want a conversation do it here or on DIV EV where you do not get to make the rules and call the shots. The discussion also have to be very specific to application and battery type. Because that changes everything. I am specific in application of Home Solar Energy Storage using large Format Chi-Com LiFePO4 aka LFP cells like CALB. All charge and discharge rates will be less than C/2 under normal operating conditions. Operating temps are room temps with open air ventilation around the cell. No confined spaces, jammed in a box, left out in the sun to broil.

The discussion does not pertain to EV's (although that is what I use it for), consumer electronics, or any other Lithium chemistry other than LiFePO4. No LiPo you guys use on ES, LiCo or any other lithium battery, just Chi-Com LFP period.

I say there is no need for any external BMS other than what the Inverter and Charge Controller already have built into them. I define a BMS as above and back up my method with the definition WIKI gives to BMS under Topology using Balance Boards aka Bleeders and Vampires. I quote:

BMS technology varies in complexity and performance:

• Simple passive regulators achieve balancing across batteries or cells by bypassing charging current when the cell's voltage reaches a certain level. The cell voltage is a poor indicator of the cell's SOC (and for certain Lithium chemistries such as LiFePO4 it is no indicator at all), thus, making cell voltages equal using passive regulators does not balance SOC, which is the goal of a BMS. Therefore, such devices, while certainly beneficial, have severe limitations in their effectiveness.

To protect the cells from Over Discharge a simple 2-step strategy is employed. Initially when cells are received, connect them all in parallel and discharge to 2.4 to 2.6 volts and allow to rest over night until rested cell voltages maintain between 2.4 and 2.6 volts. This is known as Bottom Balancing establishing 2 known reference points of 0% SOC and 0 Amp Hours. Once balanced, then charged in series, all cells arrive at ZERO at the same time because once charged up, they all the same exact amount of Coulomb-metric Energy measured in Amp Hours. With all cells arriving at 2.5 volts at the same time, no adjacent cell has the energy to drive any other cell into Reverse Polarity causing repairable damaged. Thus minimizing the threat of Over Discharge

The second line of Over Charge Defense is in the Inverter. Even low end Inverters have Low Voltage Disconnect aka LVD. They operate by monitoring battery PACK VOLTAGE and most are default for Pb of 10.5 to 11 volts on a 12 volt battery. Well a 12 volt LFP battery is 4 cells and we have established 2.5 vpc as the 0%. So 4 cells x 2.5 volts is 10 volts. Even the cheapest of Invertrs trip at 10.5 volts giving us room to play with on the side of safety.

Now if you are going to spend the bucks LFP batteries, I bet you buy something better than a B&D $50 Inverter at Wally World. If I were you I am looking for one that offers me the option to change LVD voltage. I want my batteries to last. To make them last I select 20% SOC voltage of 3 volts per cell So I disconnect when the battery voltage reaches 12 VOLTS.

Lastly on Discharge protection manufactures are conservative with voltages. Most LFP manufactures state 2.5 volts is as low as you can go under load. That is safe conservative rating and is understandable. But the real number is 2 VOLTS per cell. On a 12 volt system is 8 volts. So even setting your LVD to 2.5 volts or 10 volts pack level voltage is wearing a belt and suspenders safe. So setting LVD to 11 to 12 volts coupled with Bottom Balance Cells eliminates the risk of Over Discharge and cost you nothing to implement . Strategy and knowldge were put to good use.

On the charge side is even easier. Set the Charge Controller to 80 to 90% of pack voltage. Or 3.3 to 3.5 volts per cell. On a 12 volt system 13.2 to 14 volts. When charging current tapers to 5% C or the end of the day measure cell voltages. You are looking for the highest cell voltage. That cell is the weakest cell in the Pack. You want it to be no higher than 3.38 or call it 3.4 volts which is roughly 90%. If it is a little high, lower charger voltage. If it is low, raise charger voltage. You juust do not want a resting voltage of 100%. You want to be around 80 to 90%

Wanna change your mind down the road. Buy a Vampire Board for each cell and install it. Up charger voltage to 3.60 vpc or 14.4 volts and cook away cycle life. If a board fails, and they do fail usually short circuit, you could wake up with a destroyed cell. On a 24 volt system and higher voltage system, you would not likely even notice it until you seen full charge voltage 3 volts lower than normal. Want even more. Buy a Balance Boards with temp and voltage sensors and a Control Box to talk to. Buy two more large relays to connect between Charge Controller and Battery, and between Battery and Inverter. It is only money.

As for me I like my money and KISS engineering with Passive Fail Safe Protection like using a condom after a Vasectomy. If my wife says the rabbit died, I say DIVORCE and win by default.

So WB9K that is what KF5LJW says. What do you say?

[Sunking]

Bottom line is this. A BMS is NOT required, necessary, or needed to use LiFePo4 aka LFP CChi-Com batteries. The very simple fact anyone can go out and buy a 12, 24, and 48 volt LFP battery for their car, RV, boat, Golf Cart, and Motorsports and replace their Pb batteries is testimony to the FACT. Most of those commercial offering have no BMS or non needed. That is why they call them Drop-In Replacements. You could not add a BMS if you wanted one to monitor cell voltages. In a Solar System or even in a DIY EV you already have all the protection needed equipped inside your Inverter and Charge Controller. You do not need to spend anymore money if you employ what you already have, know what your are doing, and use a good strategy.

Even cheap Inverters have Low Voltage Disconnects (LVD) to prevent and protect batteries from being over discharged. Good models even allow you to be able select the LVD voltage. Say 11 Volts on a 12 volt system. The Do Not Dare GO BELOW for a Chi-Com LFP battery is 2 volts per cell despite the claimed 2.5 volts by the manufacture. A 12 Volt LFP system is 4 cells in series. That means Do Not take the battery below 8 to 10 volts. With a Inverter LVD set to 10.5 to 11 volts eliminates Over Discharge. You have 2.5 to 3 volts of breathing room.

On the Charge side is even easier, set your Charge Controller voltage to less than 100% SOC. Something in the 80 to 90% range for maximum cycle life. On a 12 volt system something like 13.8 to 14.0 volts. At that voltage you are well below 100% SOC voltage. With a BMS you have to jack that voltage up to 14.4 to 14.6 volts and you are playing with fire.

If you go buy a Solar Charge Controller or even a AC charger for a LFP battery, do you know what the difference is between a charger made for LFP and Pb is?. The Pb charger is more complex and expensive. A Pb charger is likely a 3 stage charger with EQ that uses quite of bit of controls to give you 3-stage charging. A charger for LFP is just a simple 1 Stage Float Charger. Top of the line LFP chargers are made by Genasun. Take a look, nothing fancy. No user controls or any interface other than Panel Input and Battery Output.

So what does a Solar System look like using LFP batteries. It looks exactly like solar system with Pb batteries. With LFP you have a choice to use a BMS or Not. With a proper strategy, some knowledge, no BMS required. You start by Balancing the cells at a known reference point of 0% and 0 AH at the bottom for a Bottom Balanced System. Then set your Inverter LVD to 10.5 to 12 volts, and set you Charge Controller to 13.8 to 14.0 volts and relax.

You want BMS with that? OK you will likely want want to add a High Voltage Cut-Off Relay (HVC) installed between your charge controller and battery in the event your Charge Controller goes to the heaven and shorts the panels out to the battery causing them to over charge. You will also want an additional Low Voltage Cut Off Relay between the Inverter and Battery in the Event your Inverter LVD fails. You are going to need it because with Top Balanced it is very possible to discharge just one cells leaving others with energy left to drive a dead cell into reversal.

Lastly you need a Black Box (BMS) to control the two external relays, and communicate with Vampire/Monitor Boards for every cell in your system.

Now ask yourself this question. If you are a salesman, which system are you going to insist upon? Easy answer huh?

I respect WB9K as a manufacture. He has control of Endless Sphere but not DIY EV where he lost this argument because the Forum is not full of Mush Heads who do not know about the technology. Endless Sphere audience is kids with E-Bikes and he gets to set the rules and control what information can be made available. He has no control here or DIY EV Forum and will be challenged. Real simple if you know what you are doing, using LFP batteries, No Top Balancing or BMS required, putting a BMS manufacture out of biz.

Karrak does not know, a salesman that has to go beg and plead to find someone to come to their rescue. Pretty lame.

Now what is funny are the BMS manufactures. If all they make is Top Balanced systems, they will tell you Bottom Balanced will not work. What else can they say? But guess what. What does a manufacture who makes both Top and Bottom Balanced systems say?

[Living Large]

Now you come here hoping to shut the debate down here. Simon like like you are manufactures, you have to tow the company line. Simon couldn't win the debate here, so went crying to you looking for help. I expect you and Simon both to say exactly what you are saying. As manufactures if you said anything else is Conflict of Interest. You are here to protect your Invested Interest. I am here to tell folks there is another way and you do not like it.

On internet message boards, you have to keep an open mind and occasionally wade through claims that are questionable. Debate is good. It is obvious to me as an engineer that there are multiple ways to skin the cat. I have appreciated greatly the considerations you have brought to readers' attention as regards to the use of LFP: balancing, cycle life, and operating a bank safely and most efficiently. There is still a chance I will go solar with an LFP bank, and I will be using what I've learned here from you and others if I do.

Personally, I find actual discussion useful, not posting links to arguments held elsewhere or even a conversation that was held elsewhere. Have the discussion here, and in J.P.M.'s words, the readers can take what they want and scrap the rest. A single isolated post of a discussion that was held elsewhere, without associated set-up or discussion, I am really not interested in plowing through, or worse - going to that thread and reading the entire thing to figure out what that issue was and how it may relate to the current discussion. OTOH, if in the middle of a post where the author is making an argument, posting a link can add to the discussion. I prefer the "experts" here I have come to respect bouncing concepts off each other, and lurkers like me can ask a question every so often.

[PNjunction]

I heartily welcome WB9K, and no matter what happens, I have gotten a LOT from you just lurking over the last few years.

So much so, that I cut open many NEW powersports batteries a few years ago just to work with A123 cells, which got me enough hands-on to brave large prismatics from other companies and compare notes - although there are obviously some differences.

I'm actually amazed that anyone working in the industry even steps foot inside a forum, considering the large target it puts on your back. It isn't much different than the hammering I saw "Optima Jim" (Jim McIlvane) go through when he just really wanted to help people understand and improve their setups, and not try to be a salesman or company shill - just a tech trying to help people out. Unfortunately, you don't find much of him anymore in the forums, and I think I know why - like not wanting to get gray hair prematurely.

So please understand that even when threads get contentious, there is STILL VALUE in what is debated, especially for those of us that can look beyond the drama. Basically THANK YOU from a lurker.

[Sunking]

Like I said you are a manufacture and only have one point of view. The claim that Top Balance and a BMS must be used is completely false and made up by manufactures with BMS and Top Balance products. It i sleft over thinking from Pb battery industry of keeping batteries topped off at 100%. Pb batteries do not like the PSOC world, where lithium batteries thrive in the PSOC world and cannot be treated lik ePb or any other battery chemistry.

There is nothing dangerous with Bottom Balancing, it is safer than Top Balance. As to responding I would have loved to continue a debate, but you shut the thread down. So do not give us that crap I would not answer questions. You do not want questions answered unless it is you are th eone giving answers. You cannot have your way here. Now you come here hoping to shut the debate down here. Simon like like you are manufactures, you have to tow the company line. Simon couldn't win the debate here, so went crying to you looking for help. I expect you and Simon both to say exactly what you are saying. As manufactures if you said anything else is Conflict of Interest. You are here to protect your Invested Interest. I am here to tell floks there is another way and you do not like it.

Fact is EV manufactures do not Top Balance, they all Middle Balance never touching 100% and never getting close to 0%. Exact same thing I do with my NEV. I charge up to 80/90%, and only discharge down to 20/30%. The correct formula for a long happy battery life.

What you guys did on EP is distort what I said. Batteries are not Bottom Balanced every cycle as was implied by yourself and others. They are only Bottom Balanced initially when assembled like any dang battery assemble has to be done. Does not matter if it is Top, Middle, or Bottom because any will work once you pick the end means. . Any lithium battery must be equalized with his mates before assembly. You know that as well as I do. I just do it at the bottom when the cells arrive. Wire then all in Parallel and drain then down to 2.5 vpc resting over night. All it takes is a real simple cheap circuit made from a dollars worth of parts and nichrome wire.

You say it has to be at the top 100% where you only really know voltage, but AH is unknown. I reference at the Bottom where I Know exactly where 0% and 00 amp hours are located. From there once charged they never see anything below 20% or above 90% which is spot on for maximum lithium battery life. Everything I said has been factual.

Your method is to charge lithium cells to 100% every time, and it is well know that is not good on for lithium batteries and can cut battery cycle life down some 50%. That is good practice from a manufacture POV as it generates more battery replacement sales. Me I never go above 90%, so not something I have to worry about is over charging, I eliminated the possibility, where Top Balance does it every cycle if set to 3.6 volts.

With Top Balance you also set the batteries up for a over discharge and reversing a battery cell polarity. With Bottom Balance I eliminated the possibility because all cells arrive at 0 at the same time. No adjacent cells have any energy left in them to drive a cell into reversal. Cell Reversal is the most destructive thing you can do to a lithium and you know it.

Is Bottom Balance for everyone. Nope especially the uniformed public. For them, I send them to you to lighten their pockets with Automation and not a thought in their head. . That is good for both if us.

See the deal is I do not represent any company or technology. I got nothing to sell you or anyone else. Just 35 years as a professional electrical engineer in battery plants and power transmission. Retired and giving something back to the public. Endless Sphere is a commercial site, that was my only mistake. You guys do not want anyone there that does not have a commercial product solution and I understand and respect that.

Where we left our conversation before you had it turned off is, I said is some level of monitoring is required and a Strategy is needed with LFP. You replied calling that BMS. That is when I said you cannot define what a BMS is other than something you sell or recommend as a manufacture. We get it. You sell lithium batteries. As a manufacture you can only warrant your product if a BMS of your approval is used.

Have I missed anything?