• Have you tried out dark mode?! Scroll to the bottom of any page to find a sun or moon icon to turn dark mode on or off!

diy solar

diy solar

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

I don't need or want to go to 100% though. ? I did hold absorption for an hour before but it just acted like float, mA going in to the battery so stopped doing that, seems no point keeping the voltage high for more than a few minutes for a few % more soc. More interested in what SOC it might actually get to with those data ? Don't need to know, stopping on the way up the knee is fine, just interested ?Thnx
Ok. Just so you know, going to 100% if you are only using about 3.45V/cell will never harm the cells.

I'm not sure what you will ever get out of the Victron SmartShunt if it never thinks you get to 100% SoC. Periodically resetting to 100% is kind of fundamental to it's using Coulomb counting to give you an estimate of your SoC as you discharge.
 
I'm not sure what you will ever get out of the Victron SmartShunt if it never thinks you get to 100% SoC. Periodically resetting to 100% is kind of fundamental to it's using Coulomb counting to give you an estimate of your SoC as you discharge.
Yep, agree. Just interested what the team think it might be. Think I'll reset it to 90% once in a while as it drifts & go with that rather than bother changing the regulators to get to the top of the knee. Really doesn't have to be bang on accurate. Thnx.
 
update for anyone interested > original question was partly because the data didn't quite make sense and seemed to vary a bit day by day. From logging showing more of a voltage drop under high load turns than there used to be with some investigation one of the connections wasn't great, seems much more logical now. Though I really can't see any benefit of absorption, all it does is keep the voltage high, next to no current goes in to the battery. Here the regs went to float at about 16:47 (then the fridge started) so I altered the regulators to stay at absorption for 1 hour & you can see the current tail off to next to nothing. So couple things learned for me, no point in absorption, also the victron smartsolar regulators don't track the smartshunt moment by moment, they lag behind and seem to sort of average out. I had to cover a panel for 5 minutes after changing settings otherwise they would see a high voltage even though the smartshunt was reading much less even though VE.smart networking was correctly set up. . After a few minutes they seemed to settle down & track much closer
The joy of data ???

1690303708031.png
 
I had to cover a panel for 5 minutes after changing settings otherwise they would see a high voltage even though the smartshunt was reading much less even though VE.smart networking was correctly set up. . After a few minutes they seemed to settle down & track much closer
I’m mostly being sarcastic here, but if you want more ‘instant’ tracking: the cheapo powerMR 60A SCC’s track quickly in variable light; the voltage and watts go wildly hunting and all over the place second by second at higher battery charge states or variable sun. So maybe you just spent too much lol ?

With Victron the “slow” reactions are probably intentional and well thought out in the coding would be my guess.
 
LFP cell cathode material is much more rugged than other Li-Ion battery chemistries. It is due to the iron providing vertical lattice structure support when most of lithium is removed from positive cathode at full state of charge. It is reason why LFP cells have long cycle life. Downside for LFP is lower electrode potential yielding lower energy density.

LFP cycle life is dominantly the degradation of negative graphite anode and electrolyte where most other lithium-ion battery chemistries are life limited by positive cathode material degradation.

For LFP cells, greater cell voltage accelerates electrolyte and negative graphite electrode degradation slightly, but LFP is much more tolerant of being fully charged.

High-rate charge and discharge current is more degrading to LFP when level of current gets into electrode ion starvation region. The thicker the electrode material the lower the current for the onset of electrode ion starvation. Most of the DIY'ers' 'Blue' cells start to have layer ion starvation at about 0.5 C(A) discharge rate.
 
I’m mostly being sarcastic here, but if you want more ‘instant’ tracking: the cheapo powerMR 60A SCC’s track quickly in variable light; the voltage and watts go wildly hunting and all over the place second by second at higher battery charge states or variable sun. So maybe you just spent too much lol ?

With Victron the “slow” reactions are probably intentional and well thought out in the coding would be my guess.
think all I really want is to find out a bit more of what's actually going on in the hope it might be useful ??
And very happy with Victron, wouldn't go anywhere else now. ? Just was a bit surprising the regs didn't actually follow the shunt voltage better, but that was only for a little while after changing settings so who knows. Doesn`t matter really.
So logging helped lots, amazing what a little raspberry pi zero can do. Tried regs set to 13.85v as end of bulk today straight to float. Seems just fine, reliable to stop at the knee, matters little what the actual SOC is, it works, is up not too far from full & is reliable. Boat is a happy boat. Love lithium, what a game changer from lead acid. ????
1690379173553.png
 
LFP cell cathode material is much more rugged than other Li-Ion battery chemistries. It is due to the iron providing vertical lattice structure support when most of lithium is removed from positive cathode at full state of charge. It is reason why LFP cells have long cycle life. Downside for LFP is lower electrode potential yielding lower energy density.

LFP cycle life is dominantly the degradation of negative graphite anode and electrolyte where most other lithium-ion battery chemistries are life limited by positive cathode material degradation.

For LFP cells, greater cell voltage accelerates electrolyte and negative graphite electrode degradation slightly, but LFP is much more tolerant of being fully charged.

High-rate charge and discharge current is more degrading to LFP when level of current gets into electrode ion starvation region. The thicker the electrode material the lower the current for the onset of electrode ion starvation. Most of the DIY'ers' 'Blue' cells start to have layer ion starvation at about 0.5 C(A) discharge rate.
Any links to the research about this would be interesting if you have them. ?
 
I have problem, I just replaced my lead acid batteries with 200ah lifepo4, but cant seem to figure out my mppt settings. My mppt has a lithium battery profile, but its weird, it says that bulk voltage must be less than float voltage and float voltage must be less than absorb voltage, and I cant go around that rule. Yet everywhere online people say that it should be other way around, what am I missing here?
 
Does it have a 'user' profile? That way you can just put your own values. What MPPT charge controller is it?
Nope, only lead acid and lithium, I have "Must 20a" its bought 4 years ago. I can put my own values, but within the rules stated above, so I cant for example put the values recommended here.
 
it says that bulk voltage must be less than float voltage and float voltage must be less than absorb voltage, and I cant go around that rule. Yet everywhere online people say that it should be other way around, what am I missing here?

Yeah, it should be the other way around. Can you adjust the lead-acid values?

I have "Must 20a"

Do you have the exact model name?
 
 
Yeah, it should be the other way around. Can you adjust the lead-acid values?



Do you have the exact model name?
PC1600A 20a.

For lead acid battery the same rules apply (absorb must be highest, then float, then bulk) so yes I can adjust them, but not in the way that I would like to.

Could it be possible that with my mppt bulk, float and absorb mean different things compared to other mppt's?
 
I'm not sure I would trust a thing written on that paper. The first column of the second line says current, but the value is clearly voltage.

Set the solar charge controller according to what your battery vendor specifies.
Yes, but thats the problem, it doesnt allow me to do that.
 
---ORIGINAL TITLE----​

Best charge controller settings to achieve 10%-90% usage on lifepo4 ?​


EDIT-UPDATE and the ANSWER to this question. . . This post is a accumulation of all the great and wonderful information given to me by all the great people on this thread. I consolidated all of this into this post and is the result of many hours of research and consulting with the people of this forum. Again thanks every body!!!!! This would not be possible with out you guys. if you believe i missed something or want to amend something please comment on this thread but please do so in a way that can be consolidated and added to this post , . . this is really not my post per say but an accumulation of the knowledge of the people of this forum and thread. .



BEST SOLAR SETTINGS [SO FAR] FOR MAXIMUM LIFE 5,000-10,000+ cycle life


PREFACE The Best settings possible are actually to run from 14%-90% SOC and this has little to due with voltage [besides staying out of the high and low voltage knee] however this is not possible with out a columb meter,or even better a charge controller that operates off of this principle. . Most charge controllers are designed for lead acid and being that the case we have to enter in voltage numbers numbers, so even tho this is not the ideal way to go about it, its the only way for most of us with cheaper and/or older charge controllers. . Here best voltage numbers possible known by the great contributors of this group to achieve the maximum service life possible and put the batteries under as little stress as possible.

BULK/ADSORB 3.45-3.52 [heavily debated] but universally agreed no higher than 3.52 for max service life [3.52 is what victron recommends for max service life
[lower voltage= slower charge times IE [C rate] which is Good but potentially longer in absorb phase which is Bad]
[Higher voltage=faster charge times which is more stressful on cells, BUT less time in absorb phase which is good ] 3.5v-3.52 seems to be a good compromise fast and slow charge times NOTE: Lower voltages means charge rate will be reduced at high SOC and it will be harder to reach 100%. which is great if your shooting for less than 90% state of charge. !!!IMPORTANT NOTE: While the above mentioned data is recommended for minimum stress on the cells it is important that the voltage you set activates your BMS, to keep your cells balanced, if not your BMS becomes useless and will never actually balance , most BMS activate around 3.4 VERIFY at what voltage your BMS activates at . if you are not sure, it just may be better to higher voltage to ensure that its activated[Will Prowse goes all the way to 3.6v OR another option is to keep an eye on it and make sure the cells stay balanced.

FLOAT 3.35
3.35 volts is a good float voltage for high reserve capacity and minimal cell
degradation [3.35 is not really debated if maximum service life is the goal 3.4 if you want a little bit more reserve. Also 3.4 is recommended by many OEMS, however according to some data at 3.35 the cell is not really in a state of stress while anything higher than this it is. . your choice a little bit more conservative or a little bit more reserve ]

CUT OFF 3.1V [but a more ideal verifying the cut off voltage is is to run down battery pack under average load you will be running and then take note of what cell voltage drops off first, once the first cell drops off in voltage , measure the total pack voltage and set low cut off voltage to that measured total pack voltage.
NOTE: In certain high load situations you may get get voltage drop causing the system to "cut off" and shut down under high load even if its not necessarily towards the end of your desired capacity. . , if this is the cause. you may have to set the cut off lower voltage. . 3.1 is a conservative number 3.0-2.9 is recommended for high load situations, but remember this post is all about having the data to make educated choices if your goal is maximum service life and achieving a balance between functionality and maximum service life

OTHER NOTES:
TEMPERATURE-
"""storage at high State of charge and high temperatures promoted such severe losses that the cells in question were unable to recapture capacity that they had lost reversibly""".DO NOT STORE IN HIGH SOC especially in HIGH HEAT, i dont have all the data yet but it seems operating under 32F or over 100F could/will causes damage[especially under 32] as a good precaution in short if your not comfortable the batteries are not comfortable, [this is a super generic but a safe conservative recommendation] As solutions to this conundrum people will run thermostat controlled heat pads and heat blankets for the winter [search the forum] and use water tanks/pads or ac for high temp operation [search the forum] .

VOLTAGE LOSS Every connector in your system as well as wire length attributes to a certain amount of resistance and which results in voltage loss. in other words If you set the charge controller to 3.5 volts the battery may only see 3.2 due to this voltage loss You have to adjust the controller to compensate for the loss. you may also have different losses for different components in your system depending on where there located for example inverter is on a longer length of cable than where the charge controller is located.

HOW TO RESOLVE use a good quality meter . . .measure the terminals at the battery pack , measure the terminals at the controller or inverter, subtract the difference and add this difference to your charge controller or inverters settings. [when testing for charger controller you want to be under charge, for inverter you would want to be under discharge]. measure and test again to ensure this was sufficient compensation

STORAGE, batteries should be stored at about 40% SOC if going to be in storage for long periods of time. . high SOC storage causes premature cell degradation

DON'T BE AFRAID to use the battery at 100% if needed, calendar aging [definition, loss of capacity due to time alone] [thanks will for this input] also plays a role in long term degradation so if even if you baby these cells to the max, with old age you will still loose capacity. .so these numbers above are to baby the cells, but it is perfectly okay to use full 100% soc when you need it , when taken into consideration that the effect that calendar aging has on the battery. Its is a balance between the battery is loosing capacity on its own due to aging and you babying or not babying the cells , because of calendar aging some say who cares and just use it at 100% at all times , however that defeats the purpose of this post of attempting achieve maximum service life. . but it definitely doesn't hurt to use it when you really need it. .
Balance--(run batteries to a high SOC to trigger a good balance on your BMS 4 months or so, -as a maintenance. think of as a equalization ]

A great read by Joey on taking care of your cells https://diysolarforum.com/resources/how-charging-works-in-the-context-of-lfp-batteries.233/download
END POST


______________________________________________________________________________
ORIGINAL OPENING POST


i have spent about 6 hours reading thru google and and almost every relevant search result this website has as well as youtube. . and and my brain is on information over load. . I have a simple question, but i can only seem to find complicated answers and debates between people. I have several charge controllers and all in one units i will be setting up soon for family members and im looking to find what are the best settings to achieve a usage of between 10%-90% SOC on lifepo4 batteries. . . from everything i read it seems this is the safest for long term reliabilty [10-15 years or more if possible] . . but cant find info how to set the settings to achieve this .. . . . as we all know almost all charge controllers are designed for lead acid, so we are stuck with programming such parameters and have to make do with float and absorption settings. . what im looking for is the approximate voltages settings on a per cell basis for the following

bulk
absorption
float
low voltage cut off


also any other settings you recommended changing for lifepo4. .
should these numbers be different when under load?
any other considerations when using mpp units ?

the most straight forward answer i found was wills on his site, [ https://www.mobile-solarpower.com/diy-lifepo4-solar-battery.html ]
however his recommendations were based on 100% SOC which i prefer not to use since were looking for extra long life with this batteries ,so i prefer to stick to 80% however his post was the most straight forward answer of the 6 hours i have been searching online . . essentially looking for same answer but with 80% in mind. .
Thanks for your compilation of information! Very useful:-)
 

Ampster; He seems completely clueless.​

Quote; "I guess if you want to baby your batteries and let them rot to death in a slow long term torture from shelf life"

Excuse me but this is the most ignorant statement I have ever heard. If you want to pound your batteries every single day and get 1000 cycles then that is your prerogative. personally I think backing off just slightly and getting 3 to 4000 cycles is an much smarter economically sound way to go. Mind you this is WITHOUT a generator so no Gasoline involved. you kind of remind me of a friend I used to have that had one speed only in his vehicle driving like a bat out of hell. "He" was simply clueless as to why his truck was always broke down always whining and crying about it. So finally one day I was tired of hearing him whine abou,t it and I called him a dumb ass to his face and told him he had absolutely so sense what so every and "HE" was the problem of why his truck was broke down all the time. Needless to say we are no longer friends and the dumb ass still has a broke down truck. some people NEVER LEARN.
Quote; "Yes you will be saving the disposable batteries in the long term if life cycling the batteries while doing nothing is your plan"

Another ignorant statement if you ask me. you have no clue as to the type of system he has yet you spout garbage and personal views at everyone. The system's I have designed for a few people do not use a generator maybe once or twice a year and that is just maintenance. they systems were tweaked to back off just slightly and keep the batteries cool during the summer months. they will get 12 years easily out of their systems so go try telling them their doing it wrong and need to pound their batteries getting only 1000 cycles.

Moral of the story; Treat things with some respect and in turn things last longer. Or you can travel your path pounding your batteries every single day then purchase a new set every three years while I laugh at you because I am getting 12 plus years out of my batteries.
I just seen Mr Prowse recent video and it is wise to use the batteries as its intended for .. dont let them overheat , charged them to the max and don't let it die sitting on the shelf .. and nowadays , Temu are selling lithium phosphate 100ah just over 100 dollars using their coupons . https://share.temu.com/UmyEd96IZSA
 
Last edited:
I just seen Mr Prowse recent video and it is wise to use the batteries as its intended for .. dont let them overheat , charged them to the max and don't let it die sitting on the shelf .. and nowadays , Temu are selling lithium phosphate 100ah just over 100 dollars using their coupons . https://share.temu.com/UmyEd96IZSA
Yeah I watched that he keeps saying charge to 100% but he never says what 100% is for a battery. It really easy to toss out a number and many battery manufacturers have different specs so it’s tough to say what 100% actually is.

3.4v/cell? 3.5v/cell?
 
The important part is start of balancing cell voltage. This is typically 3.4v on most LFP BMS's with some +/- 5 to 10 mV tolerance in the 3.4v nominal trigger. Should do absorb at 3.5v per cell to ensure every cell gets some balancing time.

If BMS start of balancing is adjustable, it should not be set lower than 3.4v. Below 3.4v balancing is more likely to further misbalance cells due to mixing with random inverter discharge currents. Restricting balancing to above 3.4v pretty much assures there will only be balancing when there is not inverter discharge current since inverter discharge current will likely load cells so they quickly drops below 3.4vdc.

Self-discharge can range from 0.3% per month to 3.0% per month at near 25 degs C ambient temps. Spread variance gets worse as ambient temp rises. It is not uncommon to have as bad a delta spread of 1% C of capacity leakage between cells in the same series stack in one month of cell self-leakage current.

Depending on your charging bulk rate current, 1% misbalancing of cells will likely result in BMS cell overvoltage charging shutdown trip when attempting a full recharge.

For 280 AH cells with 1% delta spread in leakage rate per month requires 2.8 AH's of balancing. A passive balancer resistor dump BMS with 100 mA bleed will take 2.8 AH's / 0.1 A = 28 hours per month of balancing time.

This is only based on cell self-discharge rates. When you have high discharge or charge current rates, the amount of misbalancing increases on top of cell self-leakage current variance.
 

diy solar

diy solar
Back
Top