Best LifePo4 charge controller settings known to man for Maximum Service life and Minimum battery stress!!! 5,000-10,000+ cycles?

[Goboatingnow]

For example of for a given terminal post voltage you measure a current of x Amps. Clearly you have an equivalent series resistance of V/X. But that resistance is purely for that precise operating point , temp , Soc , soh etc. you can’t then generalise that resistance

 

[curiouscarbon]

Emphasis on that. Floating at 3.4v / cell (13.6v nominal 12v batt), if given enough time like days, will eventually reach full capacity. That's why I disagree with any recommended float-voltage of 13.6. Only 100mv drop to 13.5 (3.375v) makes a big difference, because chemically, the cell simply can't achieve it.

Worse yet, is that at 3.4v/ cell, some cells react differently. Some will be willing to be recharged to full in days at this voltage, and some won't. A guaranteed way to imbalance the cells. Some get lucky and they all react the same. Some don't at this knife-edge. Don't take the chance at 3.4v for float OR balance triggers.

how do you feel about charge to 3.5~3.55 volt per cell and activating balancing at >=3.415?

---

while charging my 17Ah LFP 4S pack at ~1C, all cells sat at ~3.440 volt per cell near end of charge before reaching "the knee"

 

[justgary]

For example of for a given terminal post voltage you measure a current of x Amps. Clearly you have an equivalent series resistance of V/X. But that resistance is purely for that precise operating point , temp , Soc , soh etc. you can’t then generalise that resistance

But we can generalize when the cells are full and the temperature is fairly constant. We are talking about applied voltage after the cells are full, not during the rest of the charge cycle.

Eve, for example, generalizes when they tell you to stop charging when current falls below 0.05C at 3.650v.

 

[Sojourner1]

With all this advice being given I can't wait to see all these systems with day in day out longterm use with success. The foundation seems to be poured.

 

[toms]

With all this advice being given I can't wait to see all these systems with day in day out longterm use with success. The foundation seems to be poured.

Plenty of systems well over a decade old now (mine included). Pity the lessons learned over that decade seem to have been forgotten.

It’s amusing to me that people ask for the source. I get my information directly from people that design and build LiFePO4 cells. - never thought to ask them for their source when they share the intended operating parameters and reasons why with me.

 

[Horsefly]

It’s amusing to me that people ask for the source. I get my information directly from people that design and build LiFePO4 cells.

But, everyone here is just "someone on the Internet". I've personally heard some questionable things from people, and when asked for any source information they turned out to be just talking. That's even happened here on this forum, you may recall.

 

[robby]

I pay attention to what the Big Tier1 Battery Pack makers have to say. Smaller companies will most likely not even be around in 10 years so they can say anything. I am not saying their batteries are bad but the question is will they really be around to honor that warranty if it's needed.

The big Tier1 companies all seem to be gearing up and expanding for the long term and are experiencing growth that is in the double digits every year.
If your plan is to be even bigger in 10 years then you really want to make sure that your older products don't come back to bite you in the Butt in the future.

Common figures I see thrown out for 48V packs are between 54 and 55V charging voltage.
Discharge to no lower than 20% SOC. Also don't charge past 90% SOC.

Now I am not following the 90% max charge figure but I like to stay at 54.5V - 55V with my charging and i don't go below 20% on the discharge.

Everyone will have their own ideas and some people don't really care if the battery last for 10+ years. I think those are all valid directions to go in.
I just chose going for as close to the maximum time as I can get. It does not matter to me if they have Solid State batteries or some other vastly superior tech has replaced LFP in 8 years.
If my house is still getting a proper cycle from my batteries at night then there is no need to change them.

 

[justgary]

Now I am not following the 90% max charge figure but I like to stay at 54.5V - 55V with my charging and i don't go below 20% on the discharge.

What do you use as a cutoff current? Do you use a float voltage also?

 

[robby]

What do you use as a cutoff current? Do you use a float voltage also?

Cutoff current? I use 55V for the Float.

 

[justgary]

Pity the lessons learned over that decade seem to have been forgotten.

Did you guys forget to post your notes? I get more info reading white papers than I get here because there's a new thread about it every day and the discussion starts over.

 

[justgary]

Cutoff current? I use 55V for the Float.

That's a 3.4375v float. I'll be a bit critical and say that sounds high, but not so critical to suggest you shouldn't do it.

 

[Browneye]

If you’re servicing loads in a mobile application a higher float works better. Battery never stays full on solar anyway.
A ‘power wall’ is a different application.
All systems are a little different.

 

[robby]

That's a 3.4375v float. I'll be a bit critical and say that sounds high, but not so critical to suggest you shouldn't do it.

Yes I agree. I use to use 54.5V but the one EG4LL I have in my system will often have problems fully balancing the cells before it goes into standyby mode.

 

[12VoltInstalls]

Memory effect may occur if the cell is 'short cycled' leading to temporary capacity loss. This is removed by a full charge to 100%

I have not yet read 21 pages of posts. Sorry if this interrupts any active discussion on the tailwind of this thread.
I am here because I know little about having a happy marriage to LiFePo batteries and I’m soon to be putting 280Ah (may add another batter for 420Ah) at nominal 12V. I will eventually read the whole thread a page or so every morning. So by Christmas lol

Having read several pages, though, I have not seen the below idea questioned. Unless i slept through that part of my reading. But the ‘memory effect’ comment is what got me thinking.
So if ‘we’ are suppressing top end max voltage slightly for the purpose of longevity, yet ‘we’ still want to be mindful of providing optimal conditions for the BMS(s) to balance the cells, and use:

Bulk and absorption are the same voltage. I recommend 3.45.

… it begs the question in my mind to be asked, “could we use a modest 14.4V setting in the SCC (Epever 4215AN for example, 12V nominal system) in the FLA ‘equalize’ menu to (say monthly?) stimulate the “full charge” environment while using a lower (14.1V or 14.2V?) for the regular daily charging voltage?”

It’s unclear to me that ‘equalize’ at a level appropriate for LiFePo would be a bad tool to use. Especially considering that @RCinFLA post mentioning suppressed top-end charging as an issue to be mindful of.

 

[Sojourner1]

I have not yet read 21 pages of posts. Sorry if this interrupts any active discussion on the tailwind of this thread.
I am here because I know little about having a happy marriage to LiFePo batteries and I’m soon to be putting 280Ah (may add another batter for 420Ah) at nominal 12V. I will eventually read the whole thread a page or so every morning. So by Christmas lol

Having read several pages, though, I have not seen the below idea questioned. Unless i slept through that part of my reading. But the ‘memory effect’ comment is what got me thinking.
So if ‘we’ are suppressing top end max voltage slightly for the purpose of longevity, yet ‘we’ still want to be mindful of providing optimal conditions for the BMS(s) to balance the cells, and use:

… it begs the question in my mind to be asked, “could we use a modest 14.4V setting in the SCC (Epever 4215AN for example, 12V nominal system) in the FLA ‘equalize’ menu to (say monthly?) stimulate the “full charge” environment while using a lower (14.1V or 14.2V?) for the regular daily charging voltage?”

It’s unclear to me that ‘equalize’ at a level appropriate for LiFePo would be a bad tool to use. Especially considering that @RCinFLA post mentioning suppressed top-end charging as an issue to be mindful of.

This is one of those subjects that the end user of the installed batteries believe their settings are the best from what they have interpreted in forums, white papers, manufacturers suggestions.

There seems to be alot of advice given by some that have their test batteries and no longterm day in day out use.

My personal hands on since 4/2016 of everyday use is absorb at 14.1v (3.52vpc) , float 13.6v (3.4vpc). Seems to be working and I'll have a daily use from batteries of 35-50% DOD depending on what's used and solar conditions. Going into my 7th winter season and just had 18 days of no full charges with the SOC between 40-90% still using high draw items.

Equalization charge should be turned off.

 

[12VoltInstalls]

Equalization charge should be turned off

…typically true because it is a lead acid need.

But did you read the link I included mentioning internal cell balance from insufficient charging over time?

The question was regarding hijacking the ‘equalize’ function and periodically charge at the 3.6V rate to give the bms opportunity to insure cell balance. Not to ‘equalize’ the battery in a lead acid way.

 

[Sojourner1]

…typically true because it is a lead acid need.

But did you read the link I included mentioning internal cell balance from insufficient charging over time?

The question was regarding hijacking the ‘equalize’ function and periodically charge at the 3.6V rate to give the bms opportunity to insure cell balance. Not to ‘equalize’ the battery in a lead acid way.

I forget that there is other chemistries besides LFP.

That OP in that thread is at the mercy of whatever was put in the dropin and that goes for any dropin.

A decent set of matched cells to start with should eliminate the need to drive the cells that high to start with, I'll also guess that dropin need a higher charge voltage to reset the SOC if it has that function.

I'll use my 20 cells as an example. They are a couple that are .04 of each other and been this way since first installed. I don’t break out in a cold sweat, knees start to shake and get heart palpitations because every cell isn't perfectly match like some do. Mine passively balance if the cell gets to 3.55v. Some cells will bleed off a little others don't. It just the way it is.

 

[gelmjw]

Fair enough, i’ll refrain from further comment until i can gather all the information i have and present it in a simple to follow format.

Anyone that is keen to ask further questions feel free to do so via PM like most people do.

Are PMs searchable?

 

[HRTKD]

Are PMs searchable?

No. You have access to your PM's, but not other forum member's PM's. They're Private Messages, not Public Messages.

 

[gelmjw]

No. You have access to your PM's, but not other forum member's PM's. They're Private Messages, not Public Messages.

So then posters that use PMs excessively to discuss topics must have a treasure trove of material they can draw from to copy and paste into public postings, yes?

I personally abhor PMs and if I get one, I will ask permission to reply publicly so all can enjoy.