LifePO4 GBS Amp Hour Testing 2.5v to 3.6v per cell

[Sunking]

407 amps, which exceeds the 3C (300 amp) max charge rate for this battery according to the specs page: http://www.batteryspace.com/lifepo4-...-2vx4-dgr.aspx
Interesting. This means you could damage a LifePO4 battery by attempting to jump a low voltage LifePO4 battery from a fully charged LifePO4 battery, correct?

In theory yes, in practice no. What is throwing you is assume that current is going to be flowing for a significant period of time, when in real world just a fraction of a second. Your battery is also rated for 10 C for 30 seconds, and 3C contnious

Ri limits current on the high knee. Super interesting.

OK try this, Charge your cells to 4.0 volts and let them saturate. Don't be scared you can take LFP to 4.2 volts. Then check the Ri and see how high it goes up. You could not push 1 amp through with a Truck. Your battery Ri will be well above 1 ohm

But if you change that voltage to 13.4v or 3.35vpc, you'll only charge the battery 40-60%. I proved that by measuring the AH in at that voltage using the PL8.

OK like I have said over 100 times you have to find the voltage. Go to 13.5, then 13.6 until you find the voltage that correlates with 90% SOC. FWIW it will be around 3.45/cell.

Those knee bumps are the signal you are looking for. You want to charge until the voltage starts that upward fast turn. That happens at around 3.4 volts. As soon as it starts up you are 90%. SOC STOP!

[Sunking]

Huh. I remember reading batteries weigh more when fully charged, but doing some research now, it appears this is due to oxygen and CO2 venting, not electron movement:

Nonsense, don't be silly. Where would that weight come from or go to?

Now the electrolyte specific gravity changes in a FLA battery as it charges and discharges. Perhaps that is how you or whoever told you that made that silly conclusion. However that does not change the mass. When you discharge a Lead Acid battery a chemical reaction takes place. You remove lead sulfate from the electrolyte and deposit it on the plates of the battery as crystals. That makes the specific gravity go down. So if you weighed the water it would be less weight, but that does not change the weight of the battery. All you have done is shifted it from the water to the plates. Once you charge the batteries reverses the process by dissoving the lead sulfate crystals back into the water.

Now you can electrolise the water out of the battery charging at 2.4 vpc or higher which changes water into Hydrogen and Oxygen. But as soon as you replace the water you are back to specified weight of the battery.

So, as I've been building my V3 portable solar generator, I've been thinking about this heat issue. I guess if you could adequately cool the battery you could charge at a higher rate, right? Prismatic cells are probably poor candidates for water cooling, but I guess this is another area where small cylindrical cells shine.

In theory yes, in practice not so much. But you are making mountains out of molehills. Just where in the world are you going to get a charger that can generate 100 amps or more of current? It can be done, but you will never do it. You are talking 1500 watts of power on a 12 volt battery. Your PL8 is only capable of 55 amps max or C/2 on your batteries. At 12 volts is 700 watts.

Do some math. What is the Ri of your battery? 2.5 milli-ohms ring a bell? So at 55 amps ho wmuch power is being converted to heat?

Current x Current x Resistance = Watts.

55 amps x 55 amp x .0025 = 7.5 watts of heating from 150 watts input. Will the cell get warm? Yes it will, but not hot. It would have to go to 70 degree C or 160 degree F to be a real problem. If th ecell started at room temps, would still be cool to the touch at 7 watts in such a large area of the cell.

Look at the specs of your cell and not recommended charge rate. What does it say? C/2 right? What is max? 1C right? You wil never get close to 1C charge rate. Even if you do is no problem if th ebatteries are at room temp with ventilation. Heat issues are not a concern with solar or stationary applications. That is only a problem with EV's where the batteries are in a insulated box and heat cannot escape easily.

Lastly don't let yourself get confused about Ion in lithium vs Chemical reaction of a lead acid battery. There is no difference you need to know or be concerned with. In a Lithium battery you move ion particles from Cathode to Anode by changing its polarity. In a lead acid you move lead sulfate particles from solution to plates. Physically different, but no difference to you or how to charge up a battery. Both Lead Acid and Lithium use the exact same chargers. Electrons do not know the difference as they are just passing through picking up hitchhikers on the way and dropping them off on the other side.

[karrak]

Huh. I remember reading batteries weigh more when fully charged, but doing some research now, it appears this is due to oxygen and CO2 venting, not electron movement: reddit.com/r/askscience/comments/1hj8k7/do_discharged_batteries_weigh_less_than_fully

If you look closely at that post you will see they are talking about zinc hearing aid batteries. You have to look very carefully at the detail, all batteries are different.

Regarding Lithium Ion based batteries, when they are being charged they will not loose or gain any weight by gaining or loosing atoms or electrons unless they are abused but they will gain weight because of that famous formula E=mC². One of your 100Ah 3.6V cells stores around 327Wh (100*3.27) which is the same as ~ 1,180,000 J (Joules) of energy. m=E/C² so a fully charged cell is ~.000000000013g (.00000000000046oz, 1,180,000/(300,000,000*300,000,000)) heavier than a fully discharged cell.

So, as I've been building my V3 portable solar generator, I've been thinking about this heat issue. I guess if you could adequately cool the battery you could charge at a higher rate, right? Prismatic cells are probably poor candidates for water cooling, but I guess this is another area where small cylindrical cells shine.

I actually agree with Sunking that at the sort of charge and discharge rates that your battery is likely to see you will not have any problems with heat. For long life you should limit the charge and discharge rates to C/2 and keep the charge voltage below 3.5V and float voltage below 3.4V . If you do this I can't see any reason your battery will not last 10+ years.

Simon

[karrak]

When you discharge a Lead Acid battery a chemical reaction takes place. You remove lead sulfate from the electrolyte and deposit it on the plates of the battery as crystals. That makes the specific gravity go down. So if you weighed the water it would be less weight, but that does not change the weight of the battery. All you have done is shifted it from the water to the plates. Once you charge the batteries reverses the process by dissoving the lead sulfate crystals back into the water.

You do not remove lead sulphate from the electrolyte and deposit it on the plates of the battery as crystals, you take sulphate ions from the electrolyte and combine them with lead and lead oxide from the plates to form lead sulphate. Lead sulphate is insoluble, it will not go into solution. If it were soluble a lead acid battery would not work. Want to learn more, try https://www.av8n.com/physics/lead-acid.htm for more information.

Lastly don't let yourself get confused about Ion in lithium vs Chemical reaction of a lead acid battery. There is no difference you need to know or be concerned with. In a Lithium battery you move ion particles from Cathode to Anode by changing its polarity. In a lead acid you move lead sulfate particles from solution to plates.

You do not change the polarity between the anode and cathode to move the lithium ions. The + terminal is always the plus terminal and the - terminal is always the - terminal. See http://www.nova.org.au/technology-fu...-ion-batteries for more information on lithium ion battery charging and discharging.

Physically different, but no difference to you or how to charge up a battery. Both Lead Acid and Lithium use the exact same chargers.

That is very different from your past statements that you need a special Lithium charger to charge Lithium Ion batteries properly.

Electrons do not know the difference as they are just passing through picking up hitchhikers on the way and dropping them off on the other side.

This is one of the biggest loads of rubbish that you have ever stated. Pure fantasy and totally wrong. Electrons flow through the wires, lithium ions and sulphate ions diffuse (travel) through the electrolyte.

Sunking, you are really embarrassing yourself making these totally incorrect statements, they just show that you don't have a basic understanding of how Lead Acid batteries or Lithium batteries work.

Simon

[Sunking]

You do not remove lead sulphate from the electrolyte and deposit it on the plates of the battery as crystals, you take sulphate ions from the electrolyte and combine them with lead and lead oxide from the plates to form lead sulphate. Lead sulphate is insoluble, it will not go into solution. If it were soluble a lead acid battery would not work. Want to learn more, try https://www.av8n.com/physics/lead-acid.htm for more information.

Shove it up you arse Simon. I have forgottemn more about batteries than you wil ever know. Geez you are a salesman of cheap Chi-Com junk. Stick with what you know. You cannot even comprehend what you are reading. I can take blame for not going into technical depth, and would if the audience could comprehend what was being said.

In Laymen terms, when you discharge the lead sulfate moves from the electrolyte and coats the plates in the form of soft crystals. During charge the crystals in Laymen terms are dissolved back into the electrolyte. Simon I know you are not aware of it but electrolyte is is acid, not water. Electrolyte (sulfuric acid) is diluted with water.

The process is the same with both Pb and Li. Both are metals, and both work by moving atomic particles called ions from cathode to anode and back again. Pb is chemical, and Li is electrical.

You do not change the polarity between the anode and cathode to move the lithium ions. The + terminal is always the plus terminal and the - terminal is always the - terminal. See http://www.nova.org.au/technology-fu...-ion-batteries for more information on lithium ion battery charging and discharging.

Learn how to read, you change the ion charge polarity.Again you do not know what you are talking about and cannot comprehend what is being said. I never said the positive terminal changes polarity. Only an idiot like yourself would believe that. Again the lithium ions change polarity by gaining or loosing an electron. When Li ion give up an electron, it becomes charge positively charge and moves to the negative cathode electrode. When it gains an electron negatively charged and moves to the positive anode electrode. Opposites attract, basic chemistry and physics.

Sunking, you are really embarrassing yourself making these totally incorrect statements, they just show that you don't have a basic understanding of how Lead Acid batteries or Lithium batteries work.

Keep on dreaming Simon.

[Sunking]

Jesse here is what I am trying to lead you to discover, but Simon keeps clogging the works up with attacks. Remember that is the only reason Simon is here for. He sells cheap Chi-Com junk batteries and has vested interest. He calls himself an Electronics Importer. That is how he butters his bread. I can give you his web page if you want it.

You charge Pb and Li the exact same way. There is no difference in charging. The difference is how you Equalize the two.

As I stated and you performed the experiments, Li batteries have one unique characteristic no other battery has. In fact it works exactly opposite of all of the other batteries. As a lithum battery charges up, its Ri goes up. As it discharges, its resistance goes down. If you were to look at a graph of Resistance as the Vertical line, and SOC as the Horizontal line would look exactly like the charge graphs you made with your PL8. You would see a sharp knee bend lower at the 0% SOC, and a sharp rise when charged. Everything in the middle is pretty flat. That is very desirable in a battery. No other battery does that.

What the effect is, a Li battery is not capable of passing current when fully charged. Pb, NiCd can all pass current when fully charged because their resistance is at the lowest point. Why would you want to pass current through a fully charged battery?

Answer is simple, so you can pass that current along to undercharged cells to Equalize them and get them charged up. Thus with Lithium if you want to maintain 100% SOC every time you charge requires a VAMPIRE Board aka BMS or Bypass Circuit Board. So when the board senses 3.6 volts, it turn on and bypasses a predetermined amount of current around the cell to pass current onto the other cells still in need of a charge.

Those knees at the ends of a Li battery charge/discharge curve are your signals, red light signals you do not want to go past. Where do the knees occur? Take a look. Around 2.9 and 3.4 volts. Note I said AROUND not EXACTLY 2.9 and 3.4.

[karrak]

Answer is simple, so you can pass that current along to undercharged cells to Equalize them and get them charged up. Thus with Lithium if you want to maintain 100% SOC every time you charge requires a VAMPIRE Board aka BMS or Bypass Circuit Board. So when the board senses 3.6 volts, it turn on and bypasses a predetermined amount of current around the cell to pass current onto the other cells still in need of a charge.

If you charge to 3.45V/cell at an end current of around C/20-C/50 you are going charge to >99%SOC. Under these conditions you do not need any balancing boards if you are prepared to do the balancing manually.I don't have any balance boards. The last time I did a manual balance was in February. Yesterday at the end of charge my highest cell voltage was 3.48V and lowest cell voltage was 3.43. This is on a battery in use 24 hours a day, 365 days of the year.

Simon

[karrak]

I can take blame for not going into technical depth, and would if the audience could comprehend what was being said.

How condescending. Due to the number of things you have got wrong in the past, I don't think so. You are just using this to cover your own ignorance.

In Laymen terms, when you discharge the lead sulfate moves from the electrolyte and coats the plates in the form of soft crystals. During charge the crystals in Laymen terms are dissolved back into the electrolyte. Simon I know you are not aware of it but electrolyte is is acid, not water. Electrolyte (sulfuric acid) is diluted with water.

No Sunking, in Layman's terms when you discharge you take sulphate ions from the electrolyte and combine them with lead and lead oxide from the plates to form lead sulphate. During charge you convert the lead sulphate back to lead and lead oxide and the sulphate ions go back into solution.

The process is the same with both Pb and Li. Both are metals, and both work by moving atomic particles called ions from cathode to anode and back again. Pb is chemical, and Li is electrical.

Not correct. In all lithium ion batteries there should be no lithium metal, there are only positively charged lithium ions which go backward and forward between the anode and cathode. With lead acid batteries we have lead and lead oxide that are converted to lead sulphate in situ. The only thing that moves are sulphate ions, hydrogen ions and water which move from the plates to the electrolyte. Very different processes.

Learn how to read, you change the ion charge polarity.Again you do not know what you are talking about and cannot comprehend what is being said. I never said the positive terminal changes polarity. Only an idiot like yourself would believe that. Again the lithium ions change polarity by gaining or loosing an electron. When Li ion give up an electron, it becomes charge positively charge and moves to the negative cathode electrode. When it gains an electron negatively charged and moves to the positive anode electrode. Opposites attract, basic chemistry and physics.

More rubbish, lithium ions do not change polarity, they are always positive. If they gained an electron they would be converted to lithium metal. During discharge, electrons leave the anode and flow via the external load to the cathode, positive lithium ions travel through the electrolyte from the anode to the cathode to balance the charge of the electrons. During charge the external power supply pushes electrons from the cathode to the anode, positive lithium ions travel through the electrolyte from the cathode to the anode to balance the charge. The link nova.org.au/technology-future/lithium-ion-batteries that I gave in my previous post gives a really good explanation of this with an animation of the current and ion flow.

Simon

[Sunking]

More rubbish, lithium ions do not change polarity, they are always positive. If they gained an electron they would be converted to lithium metal. During discharge, electrons leave the anode and flow via the external load to the cathode, positive lithium ions travel through the electrolyte from the anode to the cathode to balance the charge of the electrons. During charge the external power supply pushes electrons from the cathode to the anode, positive lithium ions travel through the electrolyte from the cathode to the anode to balance the charge. The link nova.org.au/technology-future/lithium-ion-batteries that I gave in my previous post gives a really good explanation of this with an animation of the current and ion flow.

Simon

I am not even going to bother any more with your Blather and nonsense. You are way undereducated to understand what you are copying and pasting.

[Sunking]

If you charge to 3.45V/cell at an end current of around C/20-C/50 you are going charge to >99%SOC. Under these conditions you do not need any balancing boards if you are prepared to do the balancing manually.I don't have any balance boards. The last time I did a manual balance was in February. Yesterday at the end of charge my highest cell voltage was 3.48V and lowest cell voltage was 3.43. This is on a battery in use 24 hours a day, 365 days of the year.

You idiot, you just confirmed what I have been saying all this time. No BMS is required, cells do not become unbalanced, do not fully charge or discharge the batteries. Only difference is you Top Balance and willing to risk over discharging your batteries and relying on a monitor to save your dumb arse. You are such a moron you do not even know you agreed with me.

[createthis]

You idiot, you just confirmed what I have been saying all this time. No BMS is required, cells do not become unbalanced, do not fully charge or discharge the batteries. Only difference is you Top Balance and willing to risk over discharging your batteries and relying on a monitor to save your dumb arse. You are such a moron you do not even know you agreed with me.

Sigh. Ease up with the personal attacks.

[createthis]

I actually agree with Sunking that at the sort of charge and discharge rates that your battery is likely to see you will not have any problems with heat. For long life you should limit the charge and discharge rates to C/2 and keep the charge voltage below 3.5V and float voltage below 3.4V . If you do this I can't see any reason your battery will not last 10+ years.

Simon

I actually intend to discharge at up to 2C or 200 amps. I have a Xantrex SW 2000 inverter, a 250 amp class-t fuse, and a Victron BP-220 for the LVD. I'll be using 4/0 MTW for the cable. This is just a toy system; an experiment, so I don't know how often I'll draw 2C, but it's definitely on the radar. Use cases include running power tools like table saws, planers, drills, and even small window air conditioners.

So yeah, I'm thinking about heat.

[Sunking]

Sigh. Ease up with the personal attacks.

I did not start it or come here to attack anyone. Simon is here for only one reason, to attack me.

Look the moderators and owners know why Simon is here and they approve of the attacks. It is not my problem.

[SunEagle]

Sigh. Ease up with the personal attacks.

It has gotten as bad as the mud slinging political commercials seen on prime time TV. I haven't figured out to turn off the TV and walk away or just stuff cotton in my ears. The same goes for this forum and some of the threads.

[Sunking]

So yeah, I'm thinking about heat.

Why?

You are not even close to pushing thermal limits. Only time to ever be concerned is if the batteries are so hot, you cannot touch them and keep your hand on them. They perform best when at 85 to 100 degrees. You will never see them get that warm in room temps @ 2C operation. Heat does not become an issue until the batteries are in an enclosed box with no ventilation, in 100 degree plus weather, in an EV pulling 10 C accelerating and cruising at extended periods of 1C.

In short your batteries were made to be in an EV. Your mode of operation is not putting any stress on the batteries. So relax.