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LiFePO4 Voltage Chart?

I think JASONHC is correct ...

Charging LiFePO4 is a two step process … FIRST step uses constant current (CC) to reach about 60% State of Charge (SOC); And then STEP 2 kicks in until the charge voltage reaches 3.65V per cell. Turning from constant current (CC) to constant voltage (CV) means that the charge current is limited by what the battery will accept at that voltage, so the charging current tapers down asymptotically.

If you had to time the process – STEP ONE (60% SOC) needs about one hour and the STEP 2 (40% SOC) needs another two hours .. I have seen it that way ever since I started working with LiFePO4

At what C-rate are you charging if you get to only 60% SoC before entering the CV state? With charge rates < 1C my experience is to get almost full cells before switching to CV mode, and with a very quick current taper after that.
 
As in a voltage vs SoC table? Such a table only makes sense if the cells are well rested. During charge, it means nothing.
All tables are for reference.

The forest we are in is battery charging.

The tree we are looking at is a used Lifepo4 tree.

In the forest of battery charging all batteries charge to match the voltage they are presented with, at the amperage they can absorb. The voltage potential (difference in battery and source of voltage) is all that there is.

What ever you decide the top limit to be is the decision to make. There is brand new limit, and of course there is everything else, which is determined by any number of unlimited factors. Only a brand new lifepo4 battery will get to use a brand new factory table, everything else is less.

Most lifepo4 cells come with 3000 cycle 0% to 100% warranties. As soon as you operate those cells in the 20% to 80% range their longevity becomes all but irrelevant, ie nearly infinite cycles are possible. Furthermore, by operating a lifepo4 battery, within the 20%-80% a cycle is never even actually recording as even happening.

I have operated 30 days straight and "cycled" twice a day in the 20%-80% range of the new table, and not even one recorded cycle completed by the bms. The usage AH from the day to day shows a discharge of about 45 to 55 AH @ 48v setup. The bms registers that the SOC goes from 92% to 86%. That's when telling the bms that the battery is 800 AH and 48v setup. The actual physical battery is 260 Ah though.
 
You are fooling yourself. If you want to know the state of charge of a cell without letting it rest for a long time, you need to do Coulomb counting. Trying to gain information from cell voltage while charging and comparing that to a table of resting cell voltages is nonsensical. I'll leave you to your illusions and remain in the real world...
 
20-80% range means you miss 40% of your battery capacity. That's ok, but the purpose of getting these battery was you do not need to half discharge them only like lead. I think a 15-95% range would be more efficient for your dollars.
 
20-80% range means you miss 40% of your battery capacity. That's ok, but the purpose of getting these battery was you do not need to half discharge them only like lead. I think a 15-95% range would be more efficient for your dollars.
Another purpose of buying lithium batteries is to get long life, right?

Anyway, is percentage of battery used determined by your settings in the BMS? Settings of discharge and overcharge voltage? I am new, so forgive me if this is a dumb question.
 
Another purpose of buying lithium batteries is to get long life, right?

Anyway, is percentage of battery used determined by your settings in the BMS? Settings of discharge and overcharge voltage? I am new, so forgive me if this is a dumb question.

So we run our batteries 5% to 95% ... to each his own though ... we got LiFePO4 NOT to have them last 30 years -- but to be able to have a battery that will last 3X as long as heavier Lead Acid ... some folks can get away with running 40% to 80% .. we can't ... our systems are sized to truly take full advantage of the LiFePO4 capability .... and lets face it .. as fast as battery technology is changing -- by the time these LiFePO4's even get to the 2000 cycle mark there will probably be another "soup of the day" out ...
 
You are fooling yourself. If you want to know the state of charge of a cell without letting it rest for a long time, you need to do Coulomb counting. Trying to gain information from cell voltage while charging and comparing that to a table of resting cell voltages is nonsensical. I'll leave you to your illusions and remain in the real world...

Show us your setup.

I don't have batteries to sit and look pretty.

They are used every day, in the real world.
 
How long should it take me to charge a 280ah 12v battery from 20% - 80% with a 45amp smart charger? The charger tops out at 13.6 volts.
Exactly 3.73 hours, or 3 hrs and 44 minutes. Assuming your charger is connected to the battery with very little voltage loss, i.e. heavy gauge and very short cables. At these parameters the entire charge will be in CC mode, so the math is very simple - (280AH * 60%) / 45A

BTW, this thread is so full of nonsense that it should be pinned at the bottom of the forum, not at the top :cry:
 
I have 2 Battle Born 24 vdc for 48 volt system and I agree it takes a long time to get them to 100 percent and have given up on topping them all the way up. My garage is averaging 45 degrees F and I have not found a chart that tells the temp is the reason they don't appear to reach 100 percent. When I usually charged then let them sit they get to 52.8 (52.8/4=13.2).

I am looking for more info on battery temp effecting SOC.
 
Temp isn't effecting your charging. It's your charge source. What are you using as a source, parameters?

I've seen those temps and never had a problem getting full if needed.
 
SOCVCellMy LimitsMy LimitsMy LimitsMy Limits
48V setupSelf imposedSelf imposedSelf imposedSelf imposed
12V Setup24V Setup48V Setup
100.00%58.403.653.29413.226.452.7
99.50%55.203.45
99.00%54.003.38
90.00%53.603.353.27713.126.252.4
80.00%53.203.333.26013.026.152.2
70.00%52.803.303.24213.025.951.9
60.00%52.403.283.22512.925.851.6
50.00%52.203.263.20812.825.751.3
40.00%52.003.253.19112.825.551.1
30.00%51.603.233.17312.725.450.8
20.00%51.203.203.15612.625.250.5
14.00%50.403.15
9.50%48.003.003.15612.625.250.5
5.00%44.802.80
0.50%40.602.54
0.00%40.002.502.95011.823.647.2


View attachment 5359
My self imposed limits are based on what the cells return to after a bulk charge. For the first month, I was bulk charging to 3.55V per cell, they always returned to 3.295V on their own, so why try to force them. Let them be happy at 3.295 and "call it 100%".

These are for USED cells.

New cells are just that. Battleborn expressly states to use them 100 to 0, but charging them to 90 will let the cells last far far longer. It takes 3 times more time to go from 80% to 100% as it does from 0% to 80%. But it takes about 30 minutes to go from 100% to 80%, and 24 hours to go from 80% to 0%.

I set my 0% SOC at the top of the slope down to zero at about 15% SOC actual, I simply don't use that very low end so I can avoid further degradation. LiFePO4 cannot be fixed once degraded, it's a one-way process.
I too have used batteries and I just charge to 13.8 4s pack. I just need to use custom settings on chargers. Too many chargers are fixed at 14.4 and don't allow custom settings.
 
Hi guys, I was looking through the mobile-solarpower.com website, and on this page I found a battery voltage chart for LiFePO4 batteries.

msf4vpdl-1_14.jpg

But I noticed it wasn't showing the exact voltage ranges that my battery data sheet does.
My data sheet shows 100% charge at 14.6V and 0% charge at 10.0V.

Battery Model100Ah 3.2V
Nominal Voltage3.2V
Standard Charging Current0.5C (50A)
Standard Discharging Current0.5C (50A)
Fast Charging1C (100A)
Charging End Voltage3.65V (14.6V)
Discharge End Voltage2.5V (10.0V)
Charge Temperature Range0 - 55°C
Discharge Temperature Range-20 - 55°C
Max Cont. Discharge Current1C (100A)
Max Burst Discharge Current3C (60sec) (300A)
Impedance<045mΩ
Screw TerminalM6
Weight2.2Kg (8.8Kg)

I thought that maybe I could make my own voltage chart more suited to my battery's specifications, shown below.

Capacity %Pack VoltageCell Voltage
100%14.603.65
99%14.453.61
95%13.873.46
90%13.303.32
80%13.253.31
70%13.203.30
60%13.173.29
50%13.133.28
40%13.103.27
30%13.003.25
20%12.903.22
17%12.803.20
14%12.503.12
9%12.003.00
0%10.002.50

I was wondering if someone could cast their eye over it and let me know if anything needs to be changed. I'm a beginner at this so would like to learn how to be accurate when making the voltage chart.
Thanks.
Just simply observing and waiting for the charge to be higher.

Yes, I get it the resistance getting much much higher as the cause. That's why they are so much less expensive as used, and frankly why they are not still being used where they were installed.
I see lots of batteries on this site:
Are there any other site resources to go to? Or is LG Chem only one?
 
With such a huge change (70-30%) over just a 0.2V range you're really not getting a very good idea of the actual SOC by using voltage. IMHO using a shunt/hall sensor is really the best way to tell how much power is left in your pack.
Would you have a recommendation for the type of sensor I could purchase in regards to a shutlnt sensor for checking capacity
 
Would you have a recommendation for the type of sensor I could purchase in regards to a shutlnt sensor for checking capacity

I bought this one which seems to work just fine. You can get a 100A or 350A shunt depending on the power you plan to use.

 
SOC_Voltage compared.PNG
Surfing the web I came across the above chart to the left from Bestgobattery I added the 12v column so a pack voltage could be seen for ease. Full explanation of their test can be seen at the link.
Immediately voltage- right after charge
3rd day- resting for three days
10th day- resting for 10 days

Using the chart that gets posted most the time I added the 10 day resting voltage to the % column that it represented. I was curious how close that chart was with no link to know how they came to the ٪/v. :unsure:https://www.bestgobattery.com/technology/documents/temperature-test.html
 
Whats up with the Battery S.N. column? It implies that you are checking SOC vs voltage on different cells. Or is it just an unrelated column?
 
Links to sources are important to understand how they got results or abbreviations for s n (serial number), yes different cells tested.

Click and read. ;)
 
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