Charging efficiency LifePO4

[Sunking]

Trying to compare EV with off grid is ridiculous, there is a huge difference between in EV and off grid use. Charging them is completely different in every way. Most EV use li-ion, off grid uses lifepo4. .

Makes no difference what type, size, or application. All lithium batteries behave basically the same, and no different treatment in charging. Both PB and Li use exactly the same Algorythims a CC/CV. If you knew what FLOAT CHARGE meant, you would know it is CC/CV. The only thing different is the Voltage Set Point. For any Lithium, set it less than 100%.

You are spouting nonsense and if you had basic electrical knowledge you would know that because Floating a Battery is exactly the same thing as putting two or more cells in parallel. Soon as you realize that, you will realize how foolish you are. Charge up 69 cells in parallel to 3,45 volts, is no different than 1 cell on a charger set to 3.45 volts. Once the batteries settle on 3.45 volts, no current flows. Essentially an open switch or OFF. Cheese and Rice that is first year apprentice stuff. You do not even understand basic principles of electricity or have any clue what Ohm's Law is. Let me give you a clue: 0 Volts / X Ohms = 0 Amps every day of the week. I can only hope your brain can wrap around such simple fundamentals of ZERO divided by anything is always ZERO.

Wanna know who puts 69 cells in parallel. Tesla does that's who and they FLOAT CHARGE. Tesla and no EV manufacture allows anyone to fully charge or discharge a cell.

No cheap chargers do not use float charge for lithium batteries, expensive 4 and 5 step Smart Chargers do that. You have proved you have not read one link I have posted from multiple sources.from the Industry who says there is nothing wrong with Floating a Lithium at less than 100%. The top dog A123 Recommends FLOATINGE. Every Laptop, cellphone, EV and most Power Tools FLOAT lithium batteries Only thing special about LiFeP04 is they are a lot more tolerant to over charging than the types. EV, Cell Phone, and power tools which use NCO. LFP can take 3.6 to 4.2 volts.

You are right if you are talking about Floating at 3.55 vpc or higher would stress the cells. It would shorten cell life like any Lithium battery. But we are not talking about Floating at 3.55 or higher now are we. Hold at 3.45 to 3.5, and no problem, as the cell is not full and charge current has stopped.. Even if there is 1000 cells in parallel acting like a charger.

[dax]

To the best of my knowledge, lifepo4 is the only lithium chemistry used for off grid in Aus currently, by residential and commercial installers and has been for the last few years and not li-ion. Which in Aus and believe elsewhere is what is used in EV's, although my electric bikes and car all use lifepo4, simply because we import them and it's way cheaper that way.

Yes pack size installs down here are probably small compared to what those in the USA claim, the biggest we've installed is 30000ah x 48v lifepo4 and all in 50amp cells. The majority of installs we do commercially are between 10000ah and 20000ah and off gird homes, 1000ah - 5000ah.

As for charge parameters, the ones we use have been derived from experience and experimentation over more than 7 years of installing lifepo4 systems. If my post had been read properly, it points out why retailers of lithium cells recommended float etc, simply because it is cheaper and more profit orientated to using established lead acid charging, then telling everyone it's cool.

Our tests have shown over 7 years, float your lifepo4 cells, or use any other lead acid parameter and their life drops dramatically. The only fool proof method we've come up with after years of experimenting which keeps cells nicely balanced, bulk charge to 3.5v per cell then stop charging. Set up with a cell voltage censor, which cuts all charge as soon as one cell reaches 3.5v in an off grid 24/7 system, means your cells never get out of balance.

In the commercial retail industry, it's called defining your economies of scale to increase profit growth, through return sales and maintenance regimes. We are constantly getting inquires from those who have installed lifepo4 and are using the recommended charge and discharge parameters given to them by retailers and wholesalers an after a couple of years they are in trouble. In all the lifepo4 installs we've made, the only problems have been one or two bad cells, or when some fool decides to make their own adjustments to the system and stuffs it.

I may not have as much experience with this technology as some here, having only done my first off grid install in 1976, my first full off grid solar install in 1981 and our first lithium install in June of 2007, which was li-ion. Now we do one and two lifepo4 a month, aside along with our earthen home builds, which is all we do now. The demand for earthen and earth covered homes on this continent of extreme climate and bush fires, is growing as they are the only homes that survive a fire ad wind storms of the magnitude we are beginning to see worldwide.

Trying to compare EV with off grid is ridiculous, there is a huge difference between in EV and off grid use. Charging them is completely different in every way. Most EV use li-ion, off grid uses lifepo4. EV packs are charged when not in use so may require a different approach, as they only use energy for short periods of time. Whilst off grid is drawing power constantly 24/7 so requires a very different approach. Things like bottom balancing are stupid for off grid, as energy is needed constantly, so you can never drain your pack or you have no power. Whilst EV can use bottom balancing as they only require energy when in use and never 24/7. EV's like to use as much of the energy as is available, off grid is orientated to 80%, charge parameters are also very different. This thread is not about EV's, so using them as an example is off topic and of no help to those wanting information which has no relationship to EV.

[Sunking]

Never float lifepo4, retailers claim you can so they reduce the life span of the cells and ensure return sales after a few short years.

To bad the battery manufactures and EV manufactures do not agree with you. You are completely misinformed. A123 recommends Float Charging silly boy. Your POV only applies to Floating at 100% SOC. You can Float at less than 100%.

It is the exact same damn thing as putting two cells in parallel. Apparently Silly Boys doing solar where you are do not require such large capacity packs as us EV and US Solar users. You would have to be a fool not to utilize solar power after the battery is charged with good Sun left. Your way stresses the batteries with micro-cycles.

I bet my batteries are bigger than your. Us EV guys tend to use large batteries silly boy.

[SunEagle]

I wouldn't if I was you, he claims many things which are wrong and shows has no experience or knowledge of large capacity lifepo4 packs, listen to those who actually use and have installed them over many years. Never float lifepo4, retailers claim you can so they reduce the life span of the cells and ensure return sales after a few short years. They did the same with lead acid, in the early part of the last century, you could get lead acid batteries to last decades becuas they were desinged and built to do that. After WW2, they changed the configuration of the batteries so they would fail after a dshort time.

Another claim of his is there are no dedicated lifeppo4 chargers available, when we produce them and know of 3 others here on Australia that produce and sell dedicated lifepo4 charge controllers. Everyone with real knowledge and many years of experience with this storage chemistry will tell you, charge your pack to 14, then switch off charge. the pack will settle at 13.8v which is where it should be for long life. It's the same with DOD, never go below 12v in your pack, and you will get a very long life out of them. It's not rocket science using lifepo4, just common sense

Unfortunately most of those batteries and chargers are not easily available to us in the States. And what has been made is pretty much low end which is where Sunking has received most of his hands on experience and knowledge.

I am not saying Lifepo4 batteries are not good because they have made a lot of improvements along with the charging systems and seem to be creating a bigger area in the solar energy storage industry. We just have not seen them here in the US as much as you have in Australia.

So instead of you and Sunking throwing **** at each other why don't you both try to see each others side of the story and contribute to this forum instead of turning it into a trash heap.

[dax]

Hmm. I'm not sure I believe you because I read so much on the internet that says "thou shalt not float lithium", but I'll keep it in mind.

I wouldn't if I was you, he claims many things which are wrong and shows has no experience or knowledge of large capacity lifepo4 packs, listen to those who actually use and have installed them over many years. Never float lifepo4, retailers claim you can so they reduce the life span of the cells and ensure return sales after a few short years. They did the same with lead acid, in the early part of the last century, you could get lead acid batteries to last decades becuas they were desinged and built to do that. After WW2, they changed the configuration of the batteries so they would fail after a dshort time.

Another claim of his is there are no dedicated lifeppo4 chargers available, when we produce them and know of 3 others here on Australia that produce and sell dedicated lifepo4 charge controllers. Everyone with real knowledge and many years of experience with this storage chemistry will tell you, charge your pack to 14, then switch off charge. the pack will settle at 13.8v which is where it should be for long life. It's the same with DOD, never go below 12v in your pack, and you will get a very long life out of them. It's not rocket science using lifepo4, just common sense

[Sunking]

Hmm. I'm not sure I believe you because I read so much on the internet that says "thou shalt not float lithium", but I'll keep it in mind.

Hogwash. You have NOT read any such thing from any reputable authority or source on the subject. Not even A123 Battery manufacture would say that. In fact it is just okie dokie to float Lithium.Read the SPECS.

RECOMMEND FLOAT VOLTAGE = 3.45 volts. Exactly what I have been trying to tell you over 100 times. The qualifier is not to float at 100%, something LESS THAN 100%. How many times do I have to tell you that? I have also provided as of now 6 links to manufactures and Authorities on the subject that confirm what I am telling you. What more does it take?

Lastly Genasun does exactly what I am saying Float at less than 100%.

[createthis]

OK now you are making progress and zeroing in on your number. Looks like 13.6 to 14.0 is your number

OK this is where you are tripping yourself up and splitting hairs.

First Forget Victron and any specific voltage. You want to find your voltage. Understand this, THERE IS NOT SPECIFIC VOLTAGE. It is a range, not a fixed hard number. Even with Pb there is no specific voltage. Every battery owners manual list the voltage as something like 2.25 to 2.5 vpc. Hells Bells on a 12 volt battery that is a range of 13.5 to 15 volts. What is the right voltage? Th eome where the hydrometer says it is fully charged. Right now you have narrowed it down to 13.6 to 14.0 volts. You will find it.

I see how this could be true between different product lines or batches. I hadn't considered it before. I'll keep it in mind.

Then lets clear that up. What stresses a lithium battery is being taken to 100% and/or storing them at 100% which is a big No-No. Your Takeaway is do not go to 14.4 volts. Something less than 100% or less than 14.4 volts.. Ever heard that before? Take a hint from Genasun, they use less than 14.4 or 100%. Read the links I gave you. No problem floating Lithium cells less than 100%. It is the same as 2 or more cells in parallel.

Hmm. I'm not sure I believe you because I read so much on the internet that says "thou shalt not float lithium", but I'll keep it in mind.

[Sunking]

Ok, my 3.4v charge completed. I put in 98.91ah. Currently doing a discharge to see how many ah I get back out at that voltage, but I don't see a high knee on the voltage graph, so I predict I'll get 97% back out ( about 95.94 ah ). The MOST I've ever gotten back out of this cell is 103ah, so let's call that 100% SOC. In that case, using a ratio calculation, 98.91ah is about 96% SOC and 95.94 ah is about 93% SOC, depending on whether you compare discharge ah to charge or discharge ah.

OK now you are making progress and zeroing in on your number. Looks like 13.6 to 14.0 is your number

I guess I'm not sure how this information works in practice though. It seems like I should set my midnite classic 150's bulk and absorb to 13.6v, leaving the float at 13.5v, if I want a 93% to 96% SOC charge. It seems like Victron's 14.2v bulk voltage is too high.

OK this is where you are tripping yourself up and splitting hairs.

First Forget Victron and any specific voltage. You want to find your voltage. Understand this, THERE IS NOT SPECIFIC VOLTAGE. It is a range, not a fixed hard number. Even with Pb there is no specific voltage. Every battery owners manual list the voltage as something like 2.25 to 2.5 vpc. Hells Bells on a 12 volt battery that is a range of 13.5 to 15 volts. What is the right voltage? Th eome where the hydrometer says it is fully charged. Right now you have narrowed it down to 13.6 to 14.0 volts. You will find it.

I guess the only way I could really know for sure would be to use 14.2v bulk/absorb and 13.5v float on the midnite classic 150, let it charge up and float for an hour, then run a discharge test on the same cell using the powerlab 8. I don't think my powerlab 8 has programmable bulk/absorb and float settings. It just uses a single set point. Anyway, I don't really want to do that. I think I'm satisfied with 13.6v bulk/absorb and 13.5v float.

I would not do that, just one voltage, the right one you find.

It's still unclear (no data) if a 13.5v float will trash my battery a lot faster than no float at all, but this plan seems to be the best compromise between automation and longevity.

Then lets clear that up. What stresses a lithium battery is being taken to 100% and/or storing them at 100% which is a big No-No. Your Takeaway is do not go to 14.4 volts. Something less than 100% or less than 14.4 volts.. Ever heard that before? Take a hint from Genasun, they use less than 14.4 or 100%. Read the links I gave you. No problem floating Lithium cells less than 100%. It is the same as 2 or more cells in parallel.

[createthis]

Charging to 3.6v (visible high knee in the graph) gives 108ah, but I only get 103ah ( 95% ) out when discharging. Charging to 3.35v gives 61ah, and I get 59.55ah ( 97% ) out when discharging. I'm currently trying a charge to 3.4v. I expect to get most of the 108ah this time (and hopefully no high knee, or very little)

Ok, my 3.4v charge completed. I put in 98.91ah. Currently doing a discharge to see how many ah I get back out at that voltage, but I don't see a high knee on the voltage graph, so I predict I'll get 97% back out ( about 95.94 ah ). The MOST I've ever gotten back out of this cell is 103ah, so let's call that 100% SOC. In that case, using a ratio calculation, 98.91ah is about 96% SOC and 95.94 ah is about 93% SOC, depending on whether you compare discharge ah to charge or discharge ah.

I guess I'm not sure how this information works in practice though. It seems like I should set my midnite classic 150's bulk and absorb to 13.6v, leaving the float at 13.5v, if I want a 93% to 96% SOC charge. It seems like Victron's 14.2v bulk voltage is too high. I guess the only way I could really know for sure would be to use 14.2v bulk/absorb and 13.5v float on the midnite classic 150, let it charge up and float for an hour, then run a discharge test on the same cell using the powerlab 8. I don't think my powerlab 8 has programmable bulk/absorb and float settings. It just uses a single set point. Anyway, I don't really want to do that. I think I'm satisfied with 13.6v bulk/absorb and 13.5v float.

It's still unclear (no data) if a 13.5v float will trash my battery a lot faster than no float at all, but this plan seems to be the best compromise between automation and longevity.

[Sunking]

I'm sorry. Were you not just making a comparison about how charging LifePO4 is no different than charging any other battery? Is Lead Acid not one of those other batteries?

You charge PB and Lithium the exact same way. Only thing different is VOLTAGE SET POINTS and Termination.

We are talking Float Charging. Makes no diference if we are charging a Lithium or Lead Acid. For lead acid you Float Charge @ 13.2 to 13.8 volts depending on type and temp. For Lithium with respect to only LFP is 13.5 to 14.2 depending on type and temp. Only thing different is the VOLTAGE SET POINT you have to find.

With PB you use your Hydrometer to tell you what the voltage is. With Lithium you need a coulomb counter which you have.

There are a few different ways to charge both PB and Li, but they are the same. Some just Ffaster, some Kinder and Gentler. The Kindest and Gentlest method for both Pb and Li is FLOAT. Only thing that changges between them is the VOLTAGE SET POINT. The trade off is speed on Pb batteries will be slower if FLOAT charged vs 3 Stages of Bulk, Absorb, and finnally Float when charged up.

[Sunking]

Createthis here are some links on Float Charging Lithium cells. It is done everyday.

Electronics Weekly from 2006
Power Stream
Linear Technologies

Avoid charging to 100% capacity. Selecting a lower float voltage can do this. Reducing the float voltage will increase cycle life and service life at the expense of reduced battery capacity.

I can go on and on with Links. But they all say the same thing. You can extend cycle life of Lithium batteries by Float Charging them. Trick is to Float Less than 100% SOC. Find the voltage is the message I have told you now some 50 times. It is going to be in a Range from 13.5 to 14.2. Find it. at 0.0X increments is 7 options

13.5
13.6
13.7
13.8
13.9
14.0
14.1
14.2

See which one fits and buy it.

[createthis]

OK so what? Who is talking about lead acid?

I'm sorry. Were you not just making a comparison about how charging LifePO4 is no different than charging any other battery? Is Lead Acid not one of those other batteries?

[Sunking]

Lead acid can be floated at 100% SOC. That's the contradiction.

OK so what? Who is talking about lead acid? You keep tripping yourself up.

You can FLOAT LFP at 100% if you are willing to sacrifice cycle life. You can Float PB at less than 100% if you are willing to sacrifice cycle life. But for charging them up is no different, they both charge the exact same way with CC/CV. You keep letting Words like Bulk, Absorb, and Float confuse you. They all mean the exact same thing, a voltage set point. Only thing that changes between PB and LFP is the Voltage set points.

[createthis]

Again you are misinterpreting what you are reading and being told. The Genasun Lithium MPPT controllers, all three of them operate exactly the same. The have a set voltage, and only 1 voltage period. You are not understanding what Genasun is telling you. There is nothing to adjust as for Lithium there is no reason to lower the voltage.

Victron is just giving you CYA answer. Can you use 2-stages like Victron suggest? Sure you can, but you are screwing yourself. Both Absorb and FLOAT are the exact same algorithim of CC/CV. In this case Absorb is higher than Float. But what that gets you with Lithium is not desirable. What it does is charges your battery to nearly 100% SOC. Than reduces the voltage to 13.5 volts. So what happens is you end up effectively turning off the solar panels and no go on batteries until they discharge down to 13.5 volts. If there is any sun left at that point will the panels supply any power.

Do you have proof of this, or is it an assumption?

Back to Genasun. There are three models for Lithium

GV5 5 amp controller for a 65 watt panel
GV 10 a 10 amp controller for a 140 watt panel
GV Boost Controller which I will not address as it is made for Golf Carts using 36 and 48 volt battery.

Makes no difference which 2 models we talk about, either 5 or 10 amp. Both work exactly the same way. So here is where you get lost. The 2 Genasun MPPT Controllers come in 3 Flavors

12.5 volts for 3S Lithium Polymer (LiPo) cells
14.2 volts for 4S LiFePo4 or LFP
16.7 volts for 4S LiCo or Lithium Cobalt or NCO

The LFP model does 12.5v. Check this page: http://genasun.com/all-products/sola...ge-controller/

Specifically, this section:

[createthis]

Careful. They might be looking forward to selling you more batteries after you kill the first set.

Yeah. That's always in the back of my mind.