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LiFePO4 charging levels

neoflyer

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Oct 23, 2020
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Got LiFePO4 batteries to install and a new inverter charger on its way for my motorhome. Now I hear lithium batteries don’t “like” to be charged to 100%, more like 90%, and certainly shouldn’t be stored above 90% but rather 50%. Is this true? And, if so, can I program a Magnum MS 2012 inverter/charger this way? If they should be stored at 50% how do you get them to that level? Just shut off the charger and wait? Please enlighten me on this subject.
 
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Both of those things will cause a reduction in the life of the battery ..... but you will still get very good life compared to lead batteries.
If you do searcheson the forum , you should find charts showing how much the batterie might be affected..

I don't know that Magnum device, but maybe someone who does will check in.
 
Got LiFePO4 batteries to install and a new inverter charger on its way for my motorhome. Now I hear lithium batteries don’t “like” to be charged to 100%, more like 90%, and certainly shouldn’t be stored above 90% but rather 50%. Is this true? And, if so, can I program a Magnum MS 2012 inverter/charger this way? If they should be stored at 50% how do you get them to that level? Just shut off the charger and wait? Please enlighten me on this subject.
You should have a shunt in your system to measure state of charge.
Just discharge to 50% using a load through your inverter/charger.
Doesn't have to been bang on 50.

Same for charging.
Use your shunt to figure out what charge voltage, charge current and termination logic get you to 90% based on observation in your particular setup.

I'm here when you want to know about low voltage disconnect ;)
Hint... its a similar process.
 
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Simplest answer is just run stuff for a bit before storage. Getting a load measuring shunt is a good teacher, including on both stuff and bit.
 
You should have a shunt in your system to measure state of charge.
Just discharge to 50% using a load through your inverter/charger.
Doesn't have to been bang on 50.

Same for charging.
Use your shunt to figure out what charge voltage, charge current and termination logic get you to 90% based on observation in your particular setup.

I'm here when you want to know about low voltage disconnect ;)
Hint... its a similar process.
When I see "long term storage" at 50% I have to ask,... I've also seen people say Lifo batteries discharge ~5% per month, so how long term are we talking here? I plan to use Lifo bank at vacation home and when I leave, I put my lead acid batteries on float and maybe I'm back in a month, maybe I'm not back for 9 months, so what should I do with my Lifo bank, ...program the inverter charger to keep them hovering around 50% or are people saying just put them on the shelf at 50 and walk away?
 
When I see "long term storage" at 50% I have to ask,... I've also seen people say Lifo batteries discharge ~5% per month, so how long term are we talking here? I plan to use Lifo bank at vacation home and when I leave, I put my lead acid batteries on float and maybe I'm back in a month, maybe I'm not back for 9 months, so what should I do with my Lifo bank, ...program the inverter charger to keep them hovering around 50% or are people saying just put them on the shelf at 50 and walk away?
I'm by no means an expert but here's my perspective. So the cells are generally advertises something like 2,000 cycles 100% discharge and still keep 80% capacity. Running them say 95 to 5% maybe you'll get 3000 cycles and still have 80% capacity. That's a beauty of lipo you can fully cycle them and they have an extremely long life. Let's say you're running only 80/20 maybe you'll get 5,000 cycles before losing 20% of your capacity. If it was me leaving long-term I would disconnect them. I really highly doubt there's any difference between charging them 50% and 70% before leaving them to store they won't drain much being completely disconnected over 9 months.
 
When I see "long term storage" at 50% I have to ask,... I've also seen people say Lifo batteries discharge ~5% per month, so how long term are we talking here?
Not sure if lifo = lifepo4.
For lifepo4 self discharge of ~5% per month seems very high.
If it was me I would check and possibly add some charge to my lifepo4 cells at least twice a year.

I plan to use Lifo bank at vacation home and when I leave, I put my lead acid batteries on float and maybe I'm back in a month, maybe I'm not back for 9 months, so what should I do with my Lifo bank, ...program the inverter charger to keep them hovering around 50% or are people saying just put them on the shelf at 50 and walk away?
I don't know what people other people are saying.
When you say storage I was thinking disconnected but still with a bms.
Leaving them attached to an inverter/charger that floats at 50% is probably ok but you need to think about all the failure modes.
I guess its ok but I would adjust the bms pack voltage and cell voltage cutoff to values that represent ~40% just in case.
I have not had coffee yet so I reserve the right to change my mind.
 
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First things first, download the LFP Voltage chart from the link in my signature (the downloadable PDF is higher rez).

LFP (LiFePO4) nominal Voltage is 3.200, Working Voltage Range / Curve is 2.900-3.450 or more generally 3.000-3.400.
Voltage Maximums are 2.500 = 0% totally empty, and 3.650 is maximum full.
Below 2.900 and Above 3.500 are the cliff edges that represent approximately 5-7% of total capacity and which is normally reserved off for longevity & maximum cycle life.
ALL LFP can be charged all the way to 3.650V and saturated till they take less than 1A charge, stop charging and they will immediately begin to settle and within an hour they will be at 3.550 and in 2 hours settled around 3.500-3.525. This is Perfectly Normal for LFP.

NOTE: We talk about cell Voltage often will be noted as Vpc (Volts per cell). 12V=4S (4 cells), 24V=8S(8 cells), 48V=16S(16 cells). and Battery packs as a whole as multiples.

Self-Discharge info from EVE - Typical of LFP.
Monthly Self-discharge Rate ≤3%/M (25±2)℃, Storage SOC 30%~50%SOC
FYI on TEMPS: LFP likes the same temps as people do, cannot be charged below 32F/0C (pending on chemistry variant)
Charging Working Temperature 0℃~60℃
Working Temperature -30℃~60℃
Storage Temperature Short Term (Within a Month) -20℃~45℃

IMPORTANT SPECIAL NOTE !
LFP has a very flat voltage curve, this requires Millivolt Accuracy across the entire system or things will not work well !
Your system, the equipment like Solar Charge Controller, Inverter/Charger etc ALL have to be Calibrated for accuracy. Failure to do so may result in early or late cutoffs, overrunning the BMS or other equipment, and subsequently risking damage or worse outright failure. (That can be Very Bad ! and not just $ poofed away either).
Please review this link from my Signature:

Some handy Reference Links to answer most questions.
 
Not sure if lifo = lifepo4.
For lifepo4 self discharge of ~5% per month seems very high.
If it was me I would check and possibly add some charge to my lifepo4 cells at least twice a year.


I don't know what people other people are saying.
When you say storage I was thinking disconnected but still with a bms.
Leaving them attached to an inverter/charger that floats at 50% is probably ok but you need to think about all the failure modes.
I guess its ok but I would adjust the bms pack voltage and cell voltage cutoff to values that represent ~40% just in case.
I have not had coffee yet so I reserve the right to change my mind.
My cell phone keeps spell checking to the investment acronym Lifo. My apologies for spelling errors. I intended to say Capital "L" - i, Capital "F" - e, Capital "PO" - 4.... equals LiFePO4 aka "Lithium iron phosphate".
 
My cell phone keeps spell checking to the investment acronym Lifo. My apologies for spelling errors. I intended to say Capital "L" - i, Capital "F" - e, Capital "PO" - 4.... equals LiFePO4 aka "Lithium iron phosphate".
I wasn't sure if you meant lifepo4 or lipo.
Lipo is lithium polymer.
 
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