LFP Balancing

[sailorboy1]

I am only in my 2nd month of having my drop in LFP and things have been just fine. But I keep reading about "balancing" LFPs and the when/how/how often etc.

It seemed to me confusing reading all the "stuff" and verbal battles here on CF about it and it often seemed to be a "but" part of threads. I mean just how much can a pack of 4 small batteries wired into series to make 1 12V battery get out of "balance"? Aren't lead acid batteries just the same, but with 6 2V cells instead? We never talk about balancing lead acid and just assume if the "battery" got charged the cells "balanced".

Why shouldn't we just assume the same holds for LFP??My LFP manual says nothing about balancing other than to connect all the batteries in parallel prior to installation to balance each other together.

So I read up on it. From that I got is that if 1 cell in a pack was lower it would shutdown that battery a little early, losing a little capacity. Same for having 1 cell higher would shutdown charging earlier, assuming voltage got to that cells shutoff.

But so what! I agree in the above you lose some capacity of the battery. But batteries aren't perfect and we have always lived in a +/- world far as cells go and didn't worry about it.

I don't know what the +/- specs of manufacturing for the LFP cells are, but lets assume 5% (that would be terrible SPC quality controls in the modern world) So if a -5% cell and a +5% cell got used in the same assembly the battery has lost 5% usable discharge capacity and 5% of charging capacity and the battery is 90% rated.

But that only applies if the -5% cell shuts down that battery 5% sooner and the +5% cell stops charging the battery 5% early. Are people really thinking "I will discharge my LFP to 0% and then getting surprised that it shutdown at 5% instead? And if you only got 95% charged instead of 100% because of the +5% cell isn't one of the advantages to LFP that it doesn't need the 100% charge?

So a 30-100% usable 100ah battery that you normally use 70% of rated capacity, which is 70ah, is now a 90ah battery. Now you get to use 63ah of it in what you think is the same range. Is this really a problem other than on paper? My boat has never operated in real life like the "on paper" suggests.

And what happens if you have a couple batteries in the same bank. What if 1 is all -5% tolerances batteries and another is +5%? The batteries are each balanced, but the bank isn't

I don't know and wonder if I should even care. If you made it this far have at it.

[s/v Jedi]

Originally Posted by sailorboy1

I am only in my 2nd month of having my drop in LFP and things have been just fine. But I keep reading about "balancing" LFPs and the when/how/how often etc.

It seemed to me confusing reading all the "stuff" and verbal battles here on CF about it and it often seemed to be a "but" part of threads. I mean just how much can a pack of 4 small batteries wired into series to make 1 12V battery get out of "balance"? Aren't lead acid batteries just the same, but with 6 2V cells instead? We never talk about balancing lead acid and just assume if the "battery" got charged the cells "balanced".

Why shouldn't we just assume the same holds for LFP??My LFP manual says nothing about balancing other than to connect all the batteries in parallel prior to installation to balance each other together.

So I read up on it. From that I got is that if 1 cell in a pack was lower it would shutdown that battery a little early, losing a little capacity. Same for having 1 cell higher would shutdown charging earlier, assuming voltage got to that cells shutoff.

But so what! I agree in the above you lose some capacity of the battery. But batteries aren't perfect and we have always lived in a +/- world far as cells go and didn't worry about it.

I don't know what the +/- specs of manufacturing for the LFP cells are, but lets assume 5% (that would be terrible SPC quality controls in the modern world) So if a -5% cell and a +5% cell got used in the same assembly the battery has lost 5% usable discharge capacity and 5% of charging capacity and the battery is 90% rated.

But that only applies if the -5% cell shuts down that battery 5% sooner and the +5% cell stops charging the battery 5% early. Are people really thinking "I will discharge my LFP to 0% and then getting surprised that it shutdown at 5% instead? And if you only got 95% charged instead of 100% because of the +5% cell isn't one of the advantages to LFP that it doesn't need the 100% charge?

So a 30-100% usable 100ah battery that you normally use 70% of rated capacity, which is 70ah, is now a 90ah battery. Now you get to use 63ah of it in what you think is the same range. Is this really a problem other than on paper? My boat has never operated in real life like the "on paper" suggests.

And what happens if you have a couple batteries in the same bank. What if 1 is all -5% tolerances batteries and another is +5%? The batteries are each balanced, but the bank isn't

I don't know and wonder if I should even care. If you made it this far have at it.

How can you start with asking questions, then without knowing the answers formulate conclusions?

LA batteries balance their cells during the absorption charge phase. You don’t do that with LFP, so you have to top balance first, then run with it until they require rebalancing. Perfectly matched cells may never need it, other cells may need it every charge cycle.

[Baronkrak]

Originally Posted by s/v Jedi

...
LA batteries balance their cells...

LA batteries equalize their cells

“Equalizing is an overcharge performed on flooded lead acid batteries after they have been fully charged. It reverses the buildup of negative chemical effects like stratification, a condition where acid concentration is greater at the bottom of the battery than at the top.”

[sailorboy1]

Originally Posted by s/v Jedi

How can you start with asking questions, then without knowing the answers formulate conclusions?

Because I know you are there and waiting of course

[s/v Jedi]

Originally Posted by Baronkrak

LA batteries equalize their cells

“Equalizing is an overcharge performed on flooded lead acid batteries after they have been fully charged. It reverses the buildup of negative chemical effects like stratification, a condition where acid concentration is greater at the bottom of the battery than at the top.”

Yes, but we weren’t talking about this. The topic here is the difference in charge/voltage of each individual 2V cell in a LA battery. Every charge cycle they go into an absorption phase, in which full cells start bubbling their electrolyte to deal with excess energy, while lower cells are catching up.

Equalization is a periodic task, which requires the battery to be fully charged already.

[s/v Jedi]

Originally Posted by sailorboy1

Because I know you are there and waiting of course

Yes that makes sense

[Scubaseas]

My understanding is that you need to hire a marine professional with an electrical engineer on staff.

Why worry about what you can't change? The individual cells will be balanced in each drop in battery by their BMS. A better question might be what happens to a bank of 4 drop ins when one battery shuts off?

[sailorboy1]

Originally Posted by s/v Jedi

Yes, but we weren’t talking about this. The topic here is the difference in charge/voltage of each individual 2V cell in a LA battery. Every charge cycle they go into an absorption phase, in which full cells start bubbling their electrolyte to deal with excess energy, while lower cells are catching up.

Equalization is a periodic task, which requires the battery to be fully charged already.

NOT the topic at all!

[sailorboy1]

Originally Posted by Scubaseas

Why worry about what you can't change? in case we are suppose to be doing something about since so many seem to be concernedThe individual cells will be balanced in each drop in battery by their BMS. A better question might be what happens to a bank of 4 drop ins when one battery shuts off?probably nothing and it will come back on and you will never know

just what I currently think

[wholybee]

This is a topic with a lot of contradicting opinions. You have drop in LFP batteries. They have a BMS with a balancer built it. More than likely, it will begin to balance at above 3.45Vpc, or 13.8V. As long as you charge to that level often enough, they will balance themselves. The only time I am aware of people having had balancing issues was when they never charged to more than 90% SOC because they were told it was better to keep the battery between 20% and 80%, or, if they had defective cells to begin with.
Same with an active balancer that some people insist is necessary. Active balancers are only necessary if you have defective cells or are trying to fix a problem created by never charging to high enough SOC.

[sailorboy1]

First I have seen of someone saying balancing at 13.8. But I get into the 14s fairly often so far.

So if 13.8 is enough to "balance" I feel all the stuff that gets thrown around here is just smoke and all you need to do it get the batteries fully charged once in a while.

[s/v Jedi]

Originally Posted by sailorboy1

NOT the topic at all!

You wrote the OP where you claim LA has the same cell balancing issue.

[sailorboy1]

if that is what you wish to believe, it matters little to me

[s/v Jedi]

Originally Posted by sailorboy1

I am only in my 2nd month of having my drop in LFP and things have been just fine. But I keep reading about "balancing" LFPs and the when/how/how often etc.

It seemed to me confusing reading all the "stuff" and verbal battles here on CF about it and it often seemed to be a "but" part of threads. I mean just how much can a pack of 4 small batteries wired into series to make 1 12V battery get out of "balance"? Aren't lead acid batteries just the same, but with 6 2V cells instead? We never talk about balancing lead acid and just assume if the "battery" got charged the cells "balanced".

Why shouldn't we just assume the same holds for LFP??My LFP manual says nothing about balancing other than to connect all the batteries in parallel prior to installation to balance each other together.

So I read up on it. From that I got is that if 1 cell in a pack was lower it would shutdown that battery a little early, losing a little capacity. Same for having 1 cell higher would shutdown charging earlier, assuming voltage got to that cells shutoff.

But so what! I agree in the above you lose some capacity of the battery. But batteries aren't perfect and we have always lived in a +/- world far as cells go and didn't worry about it.

I don't know what the +/- specs of manufacturing for the LFP cells are, but lets assume 5% (that would be terrible SPC quality controls in the modern world) So if a -5% cell and a +5% cell got used in the same assembly the battery has lost 5% usable discharge capacity and 5% of charging capacity and the battery is 90% rated.

But that only applies if the -5% cell shuts down that battery 5% sooner and the +5% cell stops charging the battery 5% early. Are people really thinking "I will discharge my LFP to 0% and then getting surprised that it shutdown at 5% instead? And if you only got 95% charged instead of 100% because of the +5% cell isn't one of the advantages to LFP that it doesn't need the 100% charge?

So a 30-100% usable 100ah battery that you normally use 70% of rated capacity, which is 70ah, is now a 90ah battery. Now you get to use 63ah of it in what you think is the same range. Is this really a problem other than on paper? My boat has never operated in real life like the "on paper" suggests.

And what happens if you have a couple batteries in the same bank. What if 1 is all -5% tolerances batteries and another is +5%? The batteries are each balanced, but the bank isn't

I don't know and wonder if I should even care. If you made it this far have at it.

Originally Posted by sailorboy1

if that is what you wish to believe, it matters little to me

Facts. Matter. First three paragraphs you wrote in this thread you claim LFP and LA react the same to a charge cycle to stay balanced, or at least you assume so.

Edit: ah you’re probably trolling me, that’s cool, hope you enjoyed it ;-)

[Baronkrak]

Originally Posted by sailorboy1

First I have seen of someone saying balancing at 13.8. But I get into the 14s fairly often so far.

So if 13.8 is enough to "balance" I feel all the stuff that gets thrown around here is just smoke and all you need to do it get the batteries fully charged once in a while.

And how do you know that the cells will end up balanced?