LiFeP04 Batteries for Solar & BMS

[Willy T]

No plastic film electrolyte in Large Prismatic cells, they are not Polymer batteries. It is a gel inside those pouches. Here is what happens when you shoot one with a nail gun. At about 2:15 into the video you will see the electrolyte pouring out. But you can see it still frame below. The gel is translucent purple in the factory when added. Come out scorched blue.

You'd have to ask the poster, of course the story will change now that the actual inside of one has been shown.

[karrak]

There is only 1 algorithm used to charge Lithium called CC/CV which is nothing more than fixed bench DC power supply with current limit.

Do you actually charge your LFP battery from a solar panel via a charge controller?

In a Solar System you are fighting one HUGE BATTLE every day. Time, you don't have enough of it to mess around with any SATURATION. You DO NOT NEED and Saturation as it destroy CYCLE LIFE. Why would any fool want to do that? Lithium batteries are extremely easy to charge. To get to 90% SOC all they require is a Constant Current applied until the cell voltage reaches reaches 3.45 volts. So back to TIME and SOLAR. You do not have TIME on your side. The fastest way to 90% SOC is CONSTANT CURRENT, as much power as your panels can generate.

What is so damn hard you cannot understand Willy. Even a child can understand that. EV manufactures understand that. Most of the DIY EV understands that. Why can't you?. Yes you are stuck in a Pb World because you still use the 4-stage Pb mentality. Lithium Charge is clearly defined, has been for 10 years and you still do not know it. I will tell you what it is, CC/CV. It is that simple. If you only want to go to 90% to maximize battery life, Constant Current to 3.4 to 3.5 volts per cell and you are DONE. Saturate them like you are doing and you cut cycle life 30 to 50%. I am not going to allow you to tell people to destroy their batteries because of your ignorance and incompetence.

What you don't seem to understand SK is that solar panels are not a constant current source, the current varies with passing clouds and with increases and decreases in temperature. Sure you can charge to a constant SOC by going to a set voltage and terminating the charge if you have a constant current source. You cannot do it with solar panels.

Winston is LFP aka LiFeP04. When you use a Solar Panel with a conventional off the shelf charge controller, the charge controller never terminates the charge until darkness. Even if you set BULK, ABSORB, and FLOAT to 14.3 volts as you claim you are saturating the batteries to 3.575 volts which is above 100% SOC.

This is not true of all the programmable charge controllers I have come across. Charge controllers will stop charging an LFP battery after the battery reaches the Bulk Termination voltage, has gone through the Absorb phase at the Absorb voltage for a fixed or programmable time period or on some controllers until the charge current has dropped to a programmable level and then drops down to the Float voltage and the Float voltage is set low enough.

There are two ways to charge a Lithium Ion Battery:

1. Is a 2-stage Constant Current / Constant Voltage method which is basically what you are forced to do with Solar Charge Controllers on the Market.

You are saying there is only one way to charge an LFP battery with Solar Controllers on the market. I can think of three

1. As you have said Set the Bulk, Absorb and Float voltages to be the same (I think a lot of controllers on the market will not let you do this). The charge controller will charge the battery at whatever variable current the panels will supply until the controller voltage equals the set voltage at which point the current will start tapering off till it reaches zero.

2. Set the Bulk voltage to the charge voltage you want, set the Absorb time to zero if possible and set the Float voltage to less that the rest voltage of the battery at the SOC that you have charged it to. If the output from the solar panels is constant you will get the fast charge method you outlined in your method 2.

3. Set the Bulk voltage to the charge voltage you want, set the Absorb time to 30 minutes or so and the Absorb end current to whatever current you want to terminate the charge at, say C/20

Simon

[Sunking]

I don't know of any that use loose electrolyte. Some spiral roll the cells up and they look like a coke can. The cells are vented to the atmosphere that I know of ,GBS, CALB, Winston, Hipower , but the pouches I don't know . I sure someone will find some kind of battery that is different.

They are all the same basic battery design from the failed Thundersky Chi-Com manufacture. Same chit different colored box to identify the manufacture. Winston is on the brink of bankruptcy since Fiskers EV went belly up.

Polyymer lithium batteries are not real useful because they have very high internal resistance limiting charge and discharge rates to less than 1C. They last forever, but poor performance. Chi-Com Thundersky design is a 2 to 4C rate battery burst up to 10C. Only a Gel, Paste, or liquid electrolyte can do that. Polymer plastic sheets just don't cut it and can get the surface contact area close enough to have low resistance. Polymer ar great for low power applications, but not capable of high power.

[Sunking]

What you don't seem to understand SK is that solar panels are not a constant current source

You just lost all credibility here. Even a first year electrical student knows SOLAR PANELS ARE CURRENT SOURCES, not Voltage Sources like a battery or utility. Look it up. Hint: Isc/Imp and Bulk mode charge phase.

[Sunking]

This is not true of all the programmable charge controllers I have come across. Charge controllers will stop charging an LFP battery after the battery reaches the Bulk Termination voltage, has gone through the Absorb phase at the Absorb voltage for a fixed or programmable time period or on some controllers until the charge current has dropped to a programmable level and then drops down to the Float voltage and the Float voltage is set low enough.

Simon you have proven again you do not understand Charge Controller or Lithium batteries. Charge controller never stop supplying power with sun light striking the panels. Absorb. Float, and EQ are all Constant Voltage Modes. Bulk is Constant Current. Look it up. You do not understand what they mean or do.

To charge a LFP battery as fast as possible with a off the shelf Charge Controller you set Bulk = Absorb = Float = Target SOC%. This forces the controller to operate in CC/CV mode. The CC will pump as much current into the batteries as the panels can generate. This is the Constant Current phase to charge as fast as possible. When the voltage reaches Set Point the CC then switches to Constant Voltage and the current will Taper Off to Zero Amps when battery voltage = charger controller voltage Lithium is the only battery that will stop charging when its battery voltage = supply voltage. All others have self discharge and thus never stop charging.

Once equalized as long as there is no load applied current will stop flowing, but the charge controller is still active siting in a FLOAT or Constant Voltage mode. If a load demands current, the panels will supply that power via Charge Controller assuming the load demand does not exceed what the panels can deliver. Works like any Float Service. The charge controller never shuts off until the sunset period end of story. The only question is did your batteries get fully charged up before sunsets

Sorry but you just clearly demonstrated you do not know what you are talking about. You do not know the basic principles of voltage sources, current sources, or even basic fundamentals electrical principles. You are not fooling anyone except yourself.

[Willy T]

You just lost all credibility here. SOLAR PANELS ARE CURRENT SOURCES, not Voltage Sources like a battery or utility. Look it up. Hint: Isc and Imp

Don't get all excited and wet your pants, he said they weren't Constant current sources.

[Sunking]

Don't get all excited and wet your pants, he said they weren't Constant current sources.

Solar panels are Constant Current Sources operating between Vmp and Isc meaning Constant Current at any operating point on the IV curve. Solar Panels are Voltage Sources operating between Vmp and Voc.

[Willy T]

Solar panels are Constant Current Sources operating between Vmp and Isc meaning Constant Current at any operating point on the IV curve. Solar Panels are Voltage Sources operating between Vmp and Voc.

That wasn't the context, he was answering you about Constant Current battery charging from solar panels.

[Sunking]

That wasn't the context, he was answering you about Constant Current battery charging from solar panels.

Willy every charge controller made uses Constant Current Charging. That is the BULK mode. It is Constant, not fixed like a voltage source can supply.

Off the shelf controllers are not designed to charge Lithium Batteries. Some of them can be set up to work with them if you can set Bulk, Absorb, and Float to any value yyou want and set the to all be equal. That forces them to behave like a Float Charger with Current Limit. Set the voltage to something less than 100% SOC and the controller will be in a Constant Current Mode until the Controller Voltage and Battery Voltage are equal and all current stops flowing assuming there is no load. The Controller will sit there in Float mode acting as a Voltage Source so if a load demands current the power comes from the panels rather than the battery.

To take a Lithium battery to 100% SOC safely, there are two methods.

1. The charger and battery must be matched perfectly. You set the voltage to 3.64 vpc and current limit to as low as C/10 and as high as the manufacture sets limit to like 1C. So for a 12 volt battery like you have would be 3.65 volts x 4 = 14.6 volts. You apply that charge and initially the current is going to be whatever limit is set either from the panel wattage or regulator in the conventional charger say 50 amps on a 100 AH battery. 50 amps will until the battery voltage reaches say 14.5 volts and begin to taper off. You terminate when the current reaches .03C or C/33

2. The second method is a bit easier but much slower. Using a simple CC/CV Float Charger power supply. You set it up to 3.6 volts per cell. Any charge rate can be used within manufactures spec. So for you that would be 14.4 volts. Apply charge until current stops and terminate. Terminate means turn the dang charge off. If you let it float you will damage the batteries. There is the point you can work with using a Solar Charger. You set all the voltage to one setting below 100% like 3.4 volts per cell or 13.6 volts. When the batteries reach 13.6 volts charge current stops, but the Controller is now floating and will supply power to the load when the sun is shinning. Batteries will not supply power to load until the load demands exceeds panels capabilities or after sunset. Exactly what you want to happen. It is not that hard to understand if you know basic electrical fundamentals. If you do not understand you are hopelessly lost and only fooling yourself.

Now get out of my thread or I will nuke it.

[karrak]

You just lost all credibility here. Even a first year electrical student knows SOLAR PANELS ARE CURRENT SOURCES, not Voltage Sources like a battery or utility. Look it up. Hint: Isc/Imp and Bulk mode charge phase.

Well you should know then that the current output from a solar panel is proportional to the number of photons hitting it with the correct energy to push the electrons across the PN junctions in the solar cells. I am saying that the current from the panel will be dependent on the amount of sunlight hitting it which is not constant.

Solar panels are Constant Current Sources operating between Vmp and Isc meaning Constant Current at any operating point on the IV curve. Solar Panels are Voltage Sources operating between Vmp and Voc.

You got it wrong again, solar panels are current sources operating between 0 volts and Voc (Open Circuit voltage) with a maximum current at 0 volts of Isc (short circuit current) reducing slowly and nearly linearly to near Vmp (maximum power Voltage) then tapering off rapidly to 0 amps at Voc.

Simon

[karrak]

Simon you have proven again you do not understand Charge Controller or Lithium batteries. Charge controller never stop supplying power with sun light striking the panels. Absorb. Float, and EQ are all Constant Voltage Modes. Bulk is Constant Current. Look it up. You do not understand what they mean or do.

You are right that Absorb, Float and EQ are Constant Voltage modes. If the battery voltage is greater than the voltages set for the same charging phase the controller will supply no current to the battery, no current means no power, i.e it will stop supplying power to the battery. Bulk charge is not Constant Current, it is maximum charge that the panels will supply.

To charge a LFP battery as fast as possible with a off the shelf Charge Controller you set Bulk = Absorb = Float = Target SOC%. This forces the controller to operate in CC/CV mode. The CC will pump as much current into the batteries as the panels can generate. This is the Constant Current phase to charge as fast as possible. When the voltage reaches Set Point the CC then switches to Constant Voltage and the current will Taper Off to Zero Amps when battery voltage = charger controller voltage Lithium is the only battery that will stop charging when its battery voltage = supply voltage. All others have self discharge and thus never stop charging.

Once equalized as long as there is no load applied current will stop flowing, but the charge controller is still active siting in a FLOAT or Constant Voltage mode. If a load demands current, the panels will supply that power via Charge Controller assuming the load demand does not exceed what the panels can deliver. Works like any Float Service. The charge controller never shuts off until the sunset period end of story. The only question is did your batteries get fully charged up before sunsets

Sorry but you just clearly demonstrated you do not know what you are talking about. You do not know the basic principles of voltage sources, current sources, or even basic fundamentals electrical principles. You are not fooling anyone except yourself.

You have just contradicted yourself, I thought you said earlier that Charge Controllers never stop supplying power. I say again, yet again, Bulk charge is not Constant Current. I don't understand what you mean by the term "All others have self discharge and thus never stop charging."

Simon

[Sunking]

You are right that Absorb, Float and EQ are Constant Voltage modes. If the battery voltage is greater than the voltages set for the same charging phase the controller will supply no current to the battery, no current means no power, i.e it will stop supplying power to the battery.

In context that is incorrect. The charger has not stopped providing power, it is still on and active like a wall socket in your home. The battery would be in higher energy state which only happens when you switch from Absorb to a lower Float voltage. That only happens with Pb batteries, what Charge Controller are designed to work with. As soon as the surface charge is absorbed or the load demands power the controller is then providing current. At no point does it ever turn off power except at night. Duh!

Bulk charge is not Constant Current, it is maximum charge that the panels will supply.

You need to look up the definition of Bulk Charge, it is a Constant Current mode.

You have just contradicted yourself, I thought you said earlier that Charge Controllers never stop supplying power.

No contradiction just your lack of understanding electronic and electrical principles. Lithium batteries are the only batteries with such a low self discharge that charge current can stop when both supply and battery voltage are equal. It takes a difference of potential for current to flow. First day electrical student knows this will when he/she learns Ohm's Law. In your analogy a battery does not supply power either, the power is there, you just have to use apply a load to make the current flow. If you have an inverter connected and turned on, current is flowing and some if not all of it is coming the panels assuming sun shine.

Go educate yourself and read up on 3-stage Pb Battery Charging using this link. All commercial off the shelf Charge Controllers except for maybe GenSun, are made for Pb batteries. It starts real clearly describing the 3-Stages every Charge Controller goes through and what each stage does.

Lead acid batteries should be charged in three stages, which are [1] constant-current charge, [2] topping charge and [3] float charge. The constant-current charge applies the bulk of the charge and takes up roughly half of the required charge time; the topping charge continues at a lower charge current and provides saturation, and the float charge compensates for the loss caused by self-discharge.

Don't like that link, try this one. It is from Midnite Solar Classic 150 Owners Manual. Do you think the manufactures do not know what they are talking about and you are the only one who knows better? Go to page 31 bottom of the page CHARGE STAGES AN MEANINGS, MPPT BULK it reads and I directly quote:

Bulk MPPT: This stage of the Classic means; that the Classic will be putting out as much current as it can trying to charge the batteries to the absorb voltage set point. This is also known as constant current mode.

Still not happy, well try this link another Tutorial.

The BULK stage involves about 80% of the recharge, wherein the charger current is held constant (in a constant current charger).

[catharsis]

Some graphs for the bottom/top balance debat

What is the difference?

Here the red cell is 95 Ah, the green cell 100 Ah and the blue cell 105 Ah. For a pre-balanced pack the charge you can use is always depending on the weakest cell.

LiFePo Top Balanced web.png

LiFePo Bottom Balanced web.png

LiFePo Not Balanced web.png

Just don't start without pre-balancing.

[karrak]

Winston is LFP aka LiFeP04.
When you use a Solar Panel with a conventional off the shelf charge controller, the charge controller never terminates the charge until darkness.

How did we get from the above statement 22 posts ago to the following statement with its clever play on words without you addressing the subject. The subject being that with many commercially available charge controllers you can program them to stop charging an LFP battery after the charging voltage has reached a programmed value and not put any more charge into the battery until the next day or until the battery voltage drops to a another programmable value. You are not a politician by any off-chance.

In context that is incorrect. The charger has not stopped providing power, it is still on and active like a wall socket in your home. The battery would be in higher energy state which only happens when you switch from Absorb to a lower Float voltage. That only happens with Pb batteries, what Charge Controller are designed to work with. As soon as the surface charge is absorbed or the load demands power the controller is then providing current. At no point does it ever turn off power except at night. Duh!

All commercial off the shelf Charge Controllers except for maybe GenSun, are made for Pb batteries.

There are a growing number of solar controllers on the market that can be programmed to charge either Pb batteries or LFP batteries.

Here is my explanation for how the terminology "Constant Current" has been adopted by some of the solar controller manufacturers to describe how their products charge a battery.

Before the advent of solar power most batteries were charged by current limited chargers connected to a generator, the power grid or whatever. This current limit was constant and so we get the term Constant Current Charging, this had been going on for over 50 years before solar controllers came along and everyone, both engineers and lay people got used to the term and it correctly described what was happening.

The solar controller manufacturers adopted the same terminology that had been used in the past that everyone understood, so they adopted the term Constant Current Charge even though from an engineering point of view it is not true, as the current from solar panels is not necessarily constant. For Lead batteries it probably doesn't matter whether or not the current is a fixed constant as any variation in the SOC achieved by the battery because of the differing charge current is balanced out by the Absorb phase of the charging. The term "Constant Current Charging" has stuck even though it is not strictly true.

Lead acid batteries should be charged in three stages, which are [1] constant-current charge, [2] topping charge and [3] float charge. The constant-current charge applies the bulk of the charge and takes up roughly half of the required charge time; the topping charge continues at a lower charge current and provides saturation, and the float charge compensates for the loss caused by self-discharge.

The above statement from Battery University has no reference to Solar Charging, I would think the context here is standard current limited chargers which are constant current.

The BULK stage involves about 80% of the recharge, wherein the charger current is held constant (in a constant current charger).

I interpret this as saying that the charge current is constant, but only with a constant current charger.

Bulk MPPT: This stage of the Classic means; that the Classic will be putting out as much current as it can trying to charge the batteries to the absorb voltage set point. This is also known as constant current mode

I do not see that this statement from the Classic 150 Owners Manual says the charge current is constant. To me this part of the sentence "the Classic will be putting out as much current as it can" is saying that the Classic will be putting out as much current as the solar panels will provide, it does not say that it is constant. The statement "This is also known as constant current mode" Is saying that it may generally be known by the target audience as the term "constant current mode". It is not saying that the controller is charging the battery with a constant current.

Simon

[russ]

Repeat over and over - I smart fella, I fella smart