Balancing LiFePo4 Cells

Al Slitter

Trying to learn something new every day!
I am waiting for the arrival of my 4- 200Ah LiFePo4 Cells they are new grade A cell direct from a manufacture.
I have been working on setting up a back board with all of the connection and testing points on it and am waiting
for the cells to complete the installation.

In preparation I have a few questions regarding the testing and setting up for these cells:

#1 Using a 150Watt Digital Battery Capacity Tester that I purchased of of Ali Express do I need to test the capacity of each cell
or will a test of the battery pack be sufficient?
I am a bit confused by this based on Wills video on the use of this Capacity Tester.

#2 After receiving the cells I believe I should check there voltage and verify that they are at the same state of charge. Then is it best
to configure them in parallel then let them sit for a couple of days to balance out?

#3 After this should I reassemble the cells into a series connection of 12Volts add my BMS and deplete the battery down to 12 volts
and then check the status of each cell. Once this is complete using my DC desktop power supply should I then raise the voltage of
the pack to 13.3 volts?

#4 Based on Wills suggestions he recommends using a upper voltage limit of 13.3 Volts and a Flood Voltage of 13.2 Volts with a disconnect
of 12 volts for solar applications. I have a EPEVER Tracer controller and will set the high and low voltages there. The issue now is do I have to
set a flood voltage level as these batteries do not need I believe a flood level voltage?

Thank you for your time and I will await your replies.
 

Ampster

Renewable Energy Hobbyist
#2 After receiving the cells I believe I should check there voltage and verify that they are at the same state of charge. Then is it best
to configure them in parallel then let them sit for a couple of days to balance out?
Voltage is a poor way to verify SOC unless the voltage is 3.65 immediately at end of charge. Puting them in parallel witll not balance them unless you apply some voltage and current. Doing that until the cells reach 3.65 volts is called parallel top balancing. Another form of top balancing is to charge each cell to 3.65 individually. It will take a little longer to do that because of the time to connect and disconnect each cell. Either way it may take some time depending on the charge current.
 

Gazoo

Dumb Dumb
I am waiting for the arrival of my 4- 200Ah LiFePo4 Cells they are new grade A cell direct from a manufacture.
If you bought the cells Grade-A from a manufacturer you should not need to capacity test each cell. Are the cells capacity matched? Who did you buy from and what cells did you choose? Link?

#1 Using a 150Watt Digital Battery Capacity Tester that I purchased of of Ali Express do I need to test the capacity of each cell
or will a test of the battery pack be sufficient?
I am a bit confused by this based on Wills video on the use of this Capacity Tester.
I didn't capacity test my cells. After parallel top balancing I connected the cells in series and I capacity tested the battery using the BMS and another coulomb counter. I used an inverter to provide the load.
#2 After receiving the cells I believe I should check there voltage and verify that they are at the same state of charge. Then is it best
to configure them in parallel then let them sit for a couple of days to balance out?
As Ampster said, voltage is not a good indication of SOC and the cells should be parallel top balanced. Even if they are capacity matched.
#3 After this should I reassemble the cells into a series connection of 12Volts add my BMS and deplete the battery down to 12 voltsand then check the status of each cell. Once this is complete using my DC desktop power supply should I then raise the voltage of
the pack to 13.3 volts?
Once connected in series I recommend charging and discharging until the HVD and LVD kicks in to make sure the BMS is working. This will give you the opportunity the test the capacity of your battery. Are the HVD and LVD programmable on your BMS? The LVD of the BMS should be 2.50 volts and the HVD should be 3.650 volts.

#4 Based on Wills suggestions he recommends using a upper voltage limit of 13.3 Volts and a Flood Voltage of 13.2 Volts with a disconnect
of 12 volts for solar applications. I have a EPEVER Tracer controller and will set the high and low voltages there. The issue now is do I have to
set a flood voltage level as these batteries do not need I believe a flood level voltage?
I think you mean float voltage? The float voltage of 13.2 and the 12 volt disconnect sound good. Charging to 13.3 volts is leaving quite a bit of capacity on the table. All of this comes down to a personal choice. What some recommend may not apply to what others need. I will attach a graph that may help you.

Using Will's recommendations will keep your cells well within the knees and possibly extend the cells life. I have never figured out what the difference is between using conservative settings to extend the cells life and using the cells full voltage range of 2.50 to 3.65 volts. It could come out to be a wash.

Keep in mind cells are generally rated for 2000 cycles until they reach 80% capacity. If you put the cells through a full cycle every day they would last apx. 5.5 years. Of course this is with ideal temp conditions.
 

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Al Slitter

Trying to learn something new every day!
Thank You for the point by point discussion it is helpful in assisting me to make the right decisions.
 

MisterSandals

Participation Medalist
First thing to do with your cells is to label them. I recommend using letters A, B, C... because when configured in a battery, the cell position is a number.
And, make sure you put some red tape or something on the positive side next to the terminal of every cell. The black is the positive (see yesterdays molten metal thread) and the tan side is negative. VERY easy to forget and make a bad mistake.
 
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