absorption lifepo4

[shvm]

it's ok to keep the float voltage same as bulk is not causing problem to battery ? In my case charge voltage is 55.2, and I plan to use float at 55.2, because when my inverter reach the float voltage it's stay there, and lowing the amps of charging .

On a per cell basis, you can use any voltage ranging from [3.37 to 3.65] WITH proper current cutoff threshold.
At 3.37Volts/cell, you can let the current drop all the way down to 0. At 3.65V, you must stop charging as current tapers below 0.05C.
For any voltage value inbetween, do simple linear interpolation.

For, float, you're leaving the cells extended with no current going into them, do it at 3.37V/Cell. This will come out to ~53.9V for 16S.

no I have balance at 3.45v

You can balance at any voltage at or above 3.37V AS LONG as there is no current going in/out the battery cells. Current going in/out the cells will affect the voltage representing a cell's charge (V - Current × Internal_R).
Most BMS'es only feature a fixed voltage based criteria for triggering balancing. We can't blame them but it is what it is.

 

[RCinFLA]

The new MB family of cells have a higher Silicon content in the anodes which improves charging & performance while reducing the creation of dendrites.

Where did you hear this information?

LFP cell long cycle life is dominated by graphite anode longevity since LFP cathode is very rugged, and I would not expect silicon doping would be added to anode on LFP cells as it would noticeably degrade overall LFP cycle life.

Silicon is doped in NCA and NMC anodes because the cathode dominates cycle life with over 10x worse cycle life then graphite anode so reducing anode cycle life with a bit with silicon doping is insignificant compared to the cathode which sets the overall battery cycle life.

I heard of several manufacturers, including Tesla, looking at encapsulating silicon in a polymer to contain the silicon fracturing which is the dominate issue with silicon.

You can balance at any voltage at or above 3.37V AS LONG as there is no current going in/out the battery cells.

Not practical.

Many BMS's restrict balancing to only when charging current is detected. This is to prevent random inverter discharging loads from confusing cell voltage readings resulting is misdirected balancing direction. With start of balancing set above 3.40v you are pretty much restricting balancing to charging only periods since with random inverter loads the cell voltage will quickly drop below 3.4v when inverter draws load current.

 

[shvm]

Not practical.

We have engineered ways around it to counter though.
One of my personal proposals is to increase the balance delta in proportion with current. This shrinks the windows for targeting convergent balancing.
So, let's say if no current going into the battery, balancing will occur till 0.003 mV,
Then with 10A of charging/discharging current, the BMS should balance only until, say 0.030 mV.

 

[panos851]

Now, with the settings at 55.2V for bulk absorb (in my case, the inverter shows this setting as the equal voltage) and a flow voltage of 54.4V in the morning, I have 50% battery charge. It goes up to 90% until it reaches 54.4V. After that, the amps lower until they reach 0 amps at 54.4V. This takes about 2 hours, which means it's doing absorb at this voltage and fully charging the battery this way. This follows the lead-acid charging algorithm of my inverter, and I hope it won't stress the cells.

When the battery charge gets low (for example, 10%), it reaches the equal voltage of 55.2V. However, this takes about 25 minutes, going from 15 amps to about 1 amp before stopping the charging. Based on all the information I’ve read on this forum, thanks to everyone, it doesn’t seem to be the best but it's acceptable. The other option I have is to buy another inverter with more battery settings.

 

[panos851]

Now, with the settings at 55.2V for bulk absorb (in my case, the inverter shows this setting as the equal voltage) and a flow voltage of 54.4V in the morning, I have 50% battery charge. It goes up to 90% until it reaches 54.4V. After that, the amps lower until they reach 0 amps at 54.4V. This takes about 2 hours, which means it's doing absorb at this voltage and fully charging the battery this way. This follows the lead-acid charging algorithm of my inverter, and I hope it won't stress the cells.

When the battery charge gets low (for example, 10%), it reaches the equal voltage of 55.2V. However, this takes about 25 minutes, going from 15 amps to about 1 amp before stopping the charging. Based on all the information I’ve read on this forum, thanks to everyone, it doesn’t seem to be the best but it's acceptable. The other option I have is to buy another inverter with more battery settings.

 

[panos851]

this is my setup

 

[Skypower]

Pro Tip (Industry spec), DO NOT FLOAT at the same Voltage as Bulk/Absorb, always step down by at least 0.100. Absorb @ 55.2, Float @ 55.1 !

Are you saying you normally float at 55.1 or is this just about holding the voltage high enough and long enough to balance ?

 

[Steve_S]

Are you saying you normally float at 55.1 or is this just about holding the voltage high enough and long enough to balance ?

By absorbing at 55.2 and waiting for EndAmps/Tailcurrent to be reached the batteries will be "full" but may still be somewhat out of balance internally, then by floating at just a slightly lower level. that allows the internal Active Balancer of the JK to level up the cells. I myself, allow for 0.005mv differential not the default 0.010. A-Typically, by the time all my packs (6x280AH) in my home system, switch to float, it may take as long as 15 more minutes to get them to 0.005 deviation - so really well balanced.

My Home system has 6 packs, some with original LF280's, then LF280N & LF280K-V3. One of these packs of a Frankenstein of LF280 & LF280N.
My installed systems are all consistent packs with identical cells.
Of note though, the LF280K V3 cells (dual hole) actually perform incredibly well (3 packs) and are always in lockstep with each other with the highest deviation between the packs never more than 0.005V. ALL packs have flexible busbars, either the Mesh Type or the Laminated Copper (dual hole). I documented all of this extensively elsewhere in here somewhere to show how it was done but I forget the thread it's in...

As I stated, I am in observer mode now. I only got into this thread to help our Greek Member out of a pickle... Even went to search for the manuals & docs for his inverter but their docs (what I found) do not get into custom settings for the battery profiles etc and to be honest, not into spending hours trying to find that info... I will only respond "if I feel like it" if/when I pop in.

@panos851 looking at your photo's is helpful. It appears the Battery Wires you are using are under sized for the potential amperage delivery.
Also a small point on Power Balance, the wires from the Inverter should be center of the busbars with the battery wires on each side.
Finally I recognize those busbars.... The ever infamous $40 for the pair E-Bay/Amazon specials... they can't even properly handle 100A (forget the label) and that plastic is terribly soft, especially when warm. Please for Gods Sake, get a pair of High Quality Busbars rated for 600A.

Unfortunately, I cannot (will not) suggest anything on Amazon or EBay as I am Canadian and part of the Boycott Everything USA movement.
The busbars I personally use & have deployed are from AMOMD which are Pure RED Copper link to manufacturer. They are on Amazon & Alibaba or look for Victron ones in Europe. https://www.amomdmarine.com/Busbar-pl3583698.html

To readers, if you do not know what Red Copper is, it is true PURE Copper and these bars are Nickle Plated (not tinned or chromed).

 

[Skypower]

My absorption is 55.2 volts and I have no control over tail current or absorption time, it’s dependent upon the inverter’s algorithm which can be 15 to 45 minutes.(unless I intervene with float cheat) The algorithm is usually enough with a JK’s 2amp balancer if it reaches absorption voltage about once a week or so, but weather might have more to say about that. I added an 4amp EnerKey balancer and reduced the JK’s balance current to 1amp and it’s trigger voltage to.015(delta) to let the balancer do the brunt and finish (.005 delta)
The balancer starts at 3.45( same as bulk) which the first runner cell triggers and shuts off when the cells are below 3.44 I’ve been playing with it for a while and noticed when starting balance earlier like 3.415, the balancer actually has to undo SOME of the work a little while later at absorb. Normal float voltage is 54volts. Looks like I can get to 45 non full cycles before an absorb can now finish balance. My end goal is no intervention and no need for anything other then occasional remote monitoring and I might just get there. Of course this works for me but everybody has different use patterns so it might not be for you.

 

[Skypower]

this is my setup

What Steve said about wires and busses
The only choke point are the small short leads of the JK, beyond that everything should be bigger. The inverter manual should have cable recommendations.

 

[DPC]

Unfortunately, I cannot (will not) suggest anything on Amazon or EBay as I am Canadian and part of the Boycott Everything USA movement.

I just ordered a make sky blue MPPT controller without using The Great Satans of e-commerce...
Directly from MSB, coming in via DHL

This will be my first modern build, thanks for the information.
Ill book mark this post and try and use this to set my charge parameters..

 

[panos851]

---

looking at your photo's is helpful. It appears the Battery Wires you are using are under sized for the potential amperage delivery.
Also a small point on Power Balance, the wires from the Inverter should be center of the busbars with the battery wires on each side.
Finally I recognize those busbars.... The ever infamous $40 for the pair E-Bay/Amazon specials... they can't even properly handle 100A (forget the label) and that plastic is terribly soft, especially when warm. Please for Gods Sake, get a pair of High Quality Busbars rated for 600A.

The busbar is rated for 400 amps is 8 mm and the cables is 2awg 35mm2.

 

[shvm]

this is my setup

You're already using Home Assistant and JK-BMS. You can check If your inverter supports comms using PylonTech (or any well documented protocol, they're easy) for lithium batteries.
You can put all this headache behind you.

 

[panos851]

You're already using Home Assistant and JK-BMS. You can check If your inverter supports comms using PylonTech (or any well documented protocol, they're easy) for lithium batteries.
You can put all this headache behind you.

It only supports KSTAR batteries. I have spoken with support — the inverter has two options: LFP (which requires a BMS, no additional settings needed) and lead-acid battery.

 

[Skypower]

---

The busbar is rated for 400 amps is 8 mm and the cables is 2awg 35mm2.

If it’s nickel plated brass, that’s already a strike against it. Brass is a surprisingly poor conductor. Oxygen free copper or 6061 aluminum with the oxide surface cleaned is far superior. If any of the terminal tension includes passing through the plastic, the plastic can flow over time and loosen and catastrophically if warm.
I don’t know if this involves the pictured ones, but it’s some things to look for.
Edit, if the studs are threaded in the buss, then it’s probably ok.

 

[panos851]

If it’s nickel plated brass, that’s already a strike against it. Brass is a surprisingly poor conductor. Oxygen free copper or 6061 aluminum with the oxide surface cleaned is far superior. If any of the terminal tension includes passing through the plastic, the plastic can flow over time and loosen and catastrophically if warm.
I don’t know if this involves the pictured ones, but it’s some things to look for.
Edit, if the studs are threaded in the buss, then it’s probably ok.

Even with 100 amps passing through it, this busbar remains cold to the touch.

 

[Skypower]

Even with 100 amps passing through it, this busbar remains cold to the touch.

How many watts is the inverter? I’m more concerned about 2awg cables.
Edit for a 5000 watt inverter I’d like to see 1/0 copper from buss to inverter. The 2awg is a tad light from buss to batteries. If you look at an ampacity chart, it looks ok, but in this application you really can’t afford voltage drop. A few volts lost under load at half charge could result in the inverter shutting down or going to grid early.

 

[Daddy Tanuki]

My problem is I am not saying you're wrong, or even that your voltage is not the best over all. I am saying you're pretty narrow minded and narcissistic to think other voltages won't work. There is evidence posted in this very thread that says lower voltage can extend battery life.

If you can't deal with other opinions without being so dismissive, the Internet is probably not for you.

I have felt this way about many of this threads.. from the time he was pushing one BMS maker until he swapped out to another. I actually bought one of the units he used to praise to high heaven so I could test it to find out that it was total garbage... I think its more than narcissism.. possibly profit motivated. these of course are my thoughts and impressions alone and may or may not represent the truth.

 

[Daddy Tanuki]

As I stated, I am in observer mode now.

really? you sure do blather on a lot for an observer.

 

[JJJJ]

I have been following Steve_s for a long time. There is no evidence that he has any financial investment in any of the ventures he has mentioned. Regarding vendors, that is out of the control of any of us. Changing products and support issues have plagued a number of companies and will continue to be a challenge to us all for years to come I suspect.

Regarding settings. A ton has been discussed on this. I can say that my settings have mirrored Steve's for some time and I am very happy with the results. My 4, (soon to be 5) 24 v batteries are all working well with each other. I did use the Overkill BMS which many have been happy with, but for my situation, had better results with the JK brand. Again, an individual choice.

In the end, settings, vendors, battery brands, etc are an individual choice. We each have our favorites. In the end however there are a number of brands that have been serving members well for a long time. The bottom line is that we assume all responsibility for our choices, whether we go with a company which does everything, or we go the DIY path.

I have a great deal of respect for the work Steve has contributed to this forum. He has years of experience in a true off grid environment. He has helped many over the years with their projects.

 

[Daddy Tanuki]

I have been following Steve_s for a long time. There is no evidence that he has any financial investment in any of the ventures he has mentioned. Regarding vendors, that is out of the control of any of us. Changing products and support issues have plagued a number of companies and will continue to be a challenge to us all for years to come I suspect.

Regarding settings. A ton has been discussed on this. I can say that my settings have mirrored Steve's for some time and I am very happy with the results. My 4, (soon to be 5) 24 v batteries are all working well with each other. I did use the Overkill BMS which many have been happy with, but for my situation, had better results with the JK brand. Again, an individual choice.

In the end, settings, vendors, battery brands, etc are an individual choice. We each have our favorites. In the end however there are a number of brands that have been serving members well for a long time. The bottom line is that we assume all responsibility for our choices, whether we go with a company which does everything, or we go the DIY path.

I have a great deal of respect for the work Steve has contributed to this forum. He has years of experience in a true off grid environment. He has helped many over the years with their projects.

whatever.... his pro stance on several systems is well documented on his own posts.

 

[JJJJ]

whatever.... his pro stance on several systems is well documented on his own posts.

I think we have all been enthusiastic about certain products at some time. Look at the posts on Victron, Midnite, the list goes on. It is basic human nature. I respect what is being said. However, if you read some of his posts, he tips his hat towards Victron at times as well, even though he is not currently using it.

I think in the end, we all have our personal choices for the products we use. There are countless posts on the merits of each.

At the end of the day however, we each vote with our wallets.

 

[Daddy Tanuki]

I think we have all been enthusiastic about certain products at some time. Look at the posts on Victron, Midnite, the list goes on. It is basic human nature. I respect what is being said. However, if you read some of his posts, he tips his hat towards Victron at times as well, even though he is not currently using it.

I think in the end, we all have our personal choices for the products we use. There are countless posts on the merits of each.

At the end of the day however, we each vote with our wallets.

I am not sure this is accurate. a lot of folks try to use their influence to make sales... pretty sure thats what going on. You might think differently... thats the joy of free speech you think one thing, I think another.

 

[TomC4306]

Hello all. My question is if I use absorption at 3.45 per cell and wait to reach 1A or close to 0A I'm overcharge my battery?

Direct answer is no, you are not overcharging your battery. And there's absolutely no reason in the world to go to 3.65.

 

[JJJJ]

When testing my cells I have been surprised that the bulk of the charge seems to be between 3.3 and 3.4. It was equally surprising that it typically was a small jump from 3.4 to 3.65 if performing a top balance.

On the other hand my top end operating level is less