Battery Technical Info

8 important things need to pay attention to when assemble lithium iron phosphate battery pack

lithium battery cell pack

When assemble lithium battery pack, how to select the right battery for assemble? Here are 8 important things need to pay high attention:

1. Capacity consistency

1C constant current charge to 3.65 V, turn to 3.65 V constant voltage charge, current drop to 0.03Cs then stop. Discharge with 1C current until discharge termination voltage 2.0 V, discharge should not be less than 95% of rated capacity.

Lithium battery cell pack 1

2. Charging constant current ratio principle

Discharge to 2.0 V at 1C constant current, charge to 3.65 V at 1C current constant current, charge to 3.65 V constant voltage, stop when current drops to 0.03 C, the ratio of constant current charge to total charge, charge constant current ratio is not less than 93% .

3. Lithium Battery Pack discharge platform requirements

When battery is fully charged, discharge at a constant current of 1C to 2.0 V and record a time of voltage to 3.1 V. Discharge platform not less than 48 minutes.

4. Self-discharge requirements for lithium iron phosphate batteries

①Storage at 55 °C 士 2 °C for 7 days

②stored at 25 ± 5 °C for 28 days.

③uncharged 45 °C ± 2 °C for 10 days, the voltage is measured.

④ Uncharged 25 °C ± 5 °C for 30 days, the voltage is measured.

Charge retention is not less than 95% . Open circuit voltage not less than 2.80V.

5. Internal resistance requirement: the difference between internal resistance of cells is less than 5mΩ

6. The voltage between difference cells is less than 5 mV

7. The higher consistency between the cells, the better performance 

8. Battery cycle life

① The same batch of materials, the same technology, the same equipment, the same type of battery produced at the same time can be assembled into the same battery pack.

②After 200 cycles of charge and discharge at 1C at 45 ± 2 °C, the capacity should be not less than 95% of the initial capacity.

③Quality department spot check 5 samples per batch of batteries for testing, as a basis for matching.

Lithium battery Pack assemble recommended principle is:

Apply the same level of battery cell for assembly, when a certain batch of this class cells are not enough, should consider use of adjacent batches of cell with the same voltage and the same capacity to fill the gap. It is strictly forbidden to use different voltage and internal resistance level cells for assembling the same battery pack.

SmartPropel Original Writer: Nancy