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Internal Resistance
Capacity
Temperature rise under different discharge currents – Test current justification: 1A will be a typical load for a small pack cell, 3A is high load for a small pack cell (just below peak load for MSXV), 5A is worst case scenario for small pack cell //TODO: Update with new pack conditions (21700 cells)
Cell current testing note: All the current ratings are current per cell, DC = discharge, Cells are discharged based on relative size and associated rough capacity (21700 cells discharge I*5/3.5, where I is the current that a similar test is used on for 18650 cells)
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Charge the cells using either a DC power supply set to 4.2V, 1.0A, and monitor it until the current reaches under 100mA - OR - Use the iCharger 306B on a 1S LiPo setting at 1A. You can connect either of these to the probes on the Gamry Universal Battery Holder for an easier connection.
Use the iCharger 306B to measure internal resistance of the cells – it is one of the preconfigured tests.
Update the result in the spreadsheet
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Starting and Setting Up the Discharge Test
Start the Battery Test program and click on “Discharge Test”.
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Setting | Value |
Discharge Condition | Discharge Current |
Discharge Current | 1, 3, or 5 Amps multiplied by the number of cells in parallel, for 21700 cells, multiply the 1,3, or 5 Amps by (5/3.5) in order to test equivalent C rates. While discharging at high currents, ensure that the force wires (F+, F-) can handle the current flowing through them. |
Stop Condition | Cut-Off Voltage |
Voltage | Look on cell’s datasheet for End Voltage of Cut Off Voltage (Usually 2.5V, Samsung 35Es are 2.65V) |
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The connection between the thermistor and the cells is critical in getting correct, as this will influence the temperature readings the most. If the RTD temperature sensor (thermistor) is loosely attached, it will measure the temperature of the air rather than the temperature of the cell.
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