Information to having one package it might take a while for each one to become familiar with every nuance here but if it does it does---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] .
Why temperature of lithium cells is important
Temperature is an important parameter that influences the aging of a lithium battery. At 35°C a lithium cell ages twice as fast as it does at 15°C. So if the battery’s useful life is 15 years at 15°C, it will be 7.5 years at 35°C. I summarize...diysolarforum.com
The Degradation Behavior of LiFePO4/C Batteries during Long-Term Calendar Aging
Abstract: With widespread applications for lithium-ion batteries in energy storage systems, the performance degradation of the battery attracts more and more attention. Understanding the battery’s long-term aging characteristics is essential for...
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. .
Best LifePo4 charge controller settings known to man for Maximum Service life and Minimum battery stress!!! 5,000-10,000+ cycles?
- Thread starter Go2Guy
- Start date
I tend to believe....if my battery bank is 400AH and my peak charging is hardly 40A.---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] .
Why temperature of lithium cells is important
Temperature is an important parameter that influences the aging of a lithium battery. At 35°C a lithium cell ages twice as fast as it does at 15°C. So if the battery’s useful life is 15 years at 15°C, it will be 7.5 years at 35°C. I summarize...The Degradation Behavior of LiFePO4/C Batteries during Long-Term Calendar Aging
Abstract: With widespread applications for lithium-ion batteries in energy storage systems, the performance degradation of the battery attracts more and more attention. Understanding the battery’s long-term aging characteristics is essential for...
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. .
Stress to the battery should be almost zero and I should always recharge it to 100% whever possible
What price precision?
All these voltage numbers are sweet. When dealing with LFP, where 100mv (0.1v) differences are trigger levels for the various extended-life strategies are discussed, what are you using to measure / confirm them with?
The front panel of your cheap inverter?
My CBA-IV which has a forward voltage drop of 300mv (typical for a diode). Oh NO! Instead of cycle testing down to 2.5v, in reality *at the terminals* it is 2.8V !!
Has Andy done likewise with his custom charger/discharger and made for that small discrepency? And if so, with what?
If you get to this level, you better have only *ONE* house standard for measuring voltages that hinge on repeatable super-accuracy, and apply compensations for those devices that don't line up to it.
Which means you are going to pony up for a high-end multimeter, like a Fluke, (or other reliable brand) and not one from the hardware store. But people are reluctant to do that, and all these magic potions that rely on this thread's precision mean SQUAT if you don't.
All these voltage numbers are sweet. When dealing with LFP, where 100mv (0.1v) differences are trigger levels for the various extended-life strategies are discussed, what are you using to measure / confirm them with?
The front panel of your cheap inverter?
My CBA-IV which has a forward voltage drop of 300mv (typical for a diode). Oh NO! Instead of cycle testing down to 2.5v, in reality *at the terminals* it is 2.8V !!
Has Andy done likewise with his custom charger/discharger and made for that small discrepency? And if so, with what?
If you get to this level, you better have only *ONE* house standard for measuring voltages that hinge on repeatable super-accuracy, and apply compensations for those devices that don't line up to it.
Which means you are going to pony up for a high-end multimeter, like a Fluke, (or other reliable brand) and not one from the hardware store. But people are reluctant to do that, and all these magic potions that rely on this thread's precision mean SQUAT if you don't.
John Frum
Tell me your problems
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- Nov 30, 2019
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I thought it had voltage sense leads.
But of course those should be validated/calibrated to a reference.
I've heard him say the words "point of truth" so I suspect he is familiar with the concept.
He may be familiar with the concept, but has he vetted it at least once to a *singular* house-standard to make sure he doesn't have a bad sample, and is relying solely on the fact that it has sense leads and not tested it? We don't know, or at least I haven't seen him prove it - maybe I've missed it. I'm sure he has, but things happen.
But this isn't about him - just a warning that when we get to this minute level of detail concerning voltages and lab-like long-term strategies, then you need a single house standard to make sure all else lines up to it. Otherwise, it's all paper-talk.
A common trap at this level of precision is tolerance creep. Say you have 3 voltage measuring devices daisy chained along the way. You verified that the first device agrees with your Fluke at 13.6v. Great. The other two devices don't need to be checked because they also agree with the first one, but you didn't put the Fluke on it. They all read 13.6, so I'm good to go. Maybe not due to tolerance creep!
One day you put the Fluke at the end of this chain, and find that you are in actuality at 13.4v! That might be a go/no go deal for your plan. Tolerance creep was the culprit.
Most diy'ers aren't going to go to such details, which puts all the talk into the non-practical realm.
But this isn't about him - just a warning that when we get to this minute level of detail concerning voltages and lab-like long-term strategies, then you need a single house standard to make sure all else lines up to it. Otherwise, it's all paper-talk.
A common trap at this level of precision is tolerance creep. Say you have 3 voltage measuring devices daisy chained along the way. You verified that the first device agrees with your Fluke at 13.6v. Great. The other two devices don't need to be checked because they also agree with the first one, but you didn't put the Fluke on it. They all read 13.6, so I'm good to go. Maybe not due to tolerance creep!
One day you put the Fluke at the end of this chain, and find that you are in actuality at 13.4v! That might be a go/no go deal for your plan. Tolerance creep was the culprit.
Most diy'ers aren't going to go to such details, which puts all the talk into the non-practical realm.
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John Frum
Tell me your problems
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Having struggled with OCD, I designated my Mastech MS8268 as my reference.
I don't think about it too much lest I disappear up my own arse.
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That's great. No voltmeter snobbery here. (Well, there is a limit).
Just make it your singular house-standard in your battery installs to have the final say and keep daisy-chained tolerance creep from less accurate displays and so forth from fooling you.
The gist of it is that if one is going to talk about .1v differences on paper and in threads for life-extending techniques, then you have to followup with nearly as much precision with the real-world hardware, which often lies to you - hence the need for a house-standard.
OR, shoot for a more general practical approach, and the need for this thread disappears.
Just make it your singular house-standard in your battery installs to have the final say and keep daisy-chained tolerance creep from less accurate displays and so forth from fooling you.
The gist of it is that if one is going to talk about .1v differences on paper and in threads for life-extending techniques, then you have to followup with nearly as much precision with the real-world hardware, which often lies to you - hence the need for a house-standard.
OR, shoot for a more general practical approach, and the need for this thread disappears.
Last edited:
Pete@SolarBatteryBarn
New Member
Please help me understand...
When my Li battery is in float, the charge current is 0. How will this damage the cells?
I set my float below my charge voltage to allow for the "rest period"
When my Li battery is in float, the charge current is 0. How will this damage the cells?
I set my float below my charge voltage to allow for the "rest period"
Horsefly
Solar Wizard
If you float voltage is below you full RESTING voltage, it will NOT damage the cells.
John Frum
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Its depends on the voltage.
The lower the voltage the less effect on the cells.
Holding the cells at or above full resting voltage is where the concern lies.
Horsefly
Solar Wizard
That's what I meant to say. Full resting voltage. I'll edit my post. Thanks Frum.
Pete@SolarBatteryBarn
New Member
It appears that most of us with practical experience agree that float is necessary and ok when set below rest voltage.
What sucks is all of the charge controllers I have tried disable float if you select a Li profile.
What sucks is all of the charge controllers I have tried disable float if you select a Li profile.
Goboatingnow
Solar Enthusiast
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Again for maximum life time do not float Li
Any impressed terminal voltage cause ion migration and sei layer growth and li plating effects
Hence after charging is finished a Li charger shoujd stop
Cheap 4-life
My body is 2.63 trillion volts, .07v per cell
How is that accomplished with a SCC?
John Frum
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Many charge controllers have a user profile which allows more control of the charge parameters.
Most controllers have more or less sophisticated charge termination logic.
This document will give a birds eye view of how charging works for LFP.
One of the assumptions in the document is a base load.
That means as soon as charging is terminated the base load will immediately start drawing down the battery.
You can also set your float lower if you want the battery to discharge a bit more before floating.
Cheap 4-life
My body is 2.63 trillion volts, .07v per cell
Right but what about when the charge controller begins to float the battery. Then solar is fully covering the load. voltage is still being impressed on the batteries terminals.. “after charge is finished the charger should stop” is what @Goboatingnow said..
The battery needs to go into float to allow solar to cover the load
John Frum
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When the charge source goes into float its no different than having 2 batteries in parallel.
Are you ok with having 2 batteries in parallel?
Ampster
Renewable Energy Hobbyist
Or when in series there is also voltage on the terminals. I wonder if it is current that @Goboatingnow may have meant when he used the phrase "any impressed voltage on the terminals"?
Choose an SCC that allows it. Even a Morningstar TS-45 PWM controller will do it.
It doesn’t.
Cheap 4-life
My body is 2.63 trillion volts, .07v per cell
What exactly does your controller allow? Mine floats my battery. That is what @Goboatingnow is saying not to do.. my controller always impresses voltage on the battery terminals and always allows solar to cover the load and keep the battery topped off and that can’t hapoen unless there’s voltage at the batteries terminals..
Cheap 4-life
My body is 2.63 trillion volts, .07v per cell
I am of course ok with that. I’m not saying to not float our batteries. I see no way not to float them if they are being used for excess solar storage
I guess the real question is what float voltage to use. Theoretically you can use 3.37 volts per cell indefinitely, so 53.92 volts in a 16S battery. I'm OK with setting that down a bit and not insisting on getting the cells stuffed completely full. Above that voltage, you probably want the SCC to stop charging at some current limit.
Since I am not present at my installation all the time, I don't want the cells to stay charged too long. I plan to set the float voltage just above the "rebulk" voltage on my Outback Flex 80 controller. Something around 3.325 volts per cell (53.2v for 16S), with rebulk set at 3.320 volts per cell (53.12v for 16S). That should leave me no worse than about 70% SOC, so even if I show up in the evening I should be able to run the A/C all night.
The plan would then be to set the "equalize" voltage to something a bit higher, e.g. 3.425 volts per cell (54.8 volts for 16S), then turn it on manually when I am there all day. I can monitor the current and stop the charge when it gets down to 0.01C. For my cells, that is 230Ah * 0.01 * 2 parallel = 4.6 Amps. Once or twice a year doing that should allow the BMS to reset the SOC calculation and balance the cells for a while.
Cheap 4-life
My body is 2.63 trillion volts, .07v per cell
Yes, that’s what most do if using their batteries for solar storage, they float their batteries at 3.37 and under which constantly impresses a voltage from charge controller on the batteries terminals. which as far as I understand is unavoidable..
I’m not understanding why you are wanting to use equalize. Couldn’t you set absorb set point higher than float and let the current tapper off on its own while absorbing and allow the bms to balance when needed?
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I don't see the need to overcharge the cells every day while I am not there, so absorb will be just under 3.37 volts per cell and float will be well below that.
It is far easier to just start an equalize cycle when I want to than try to diddle the absorb settings. The cells should not need balancing on a frequent basis.
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