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I am trying to calculate the heat generation by joule heating due the internal resistance of a Sony US18650VTC6 battery cell during its discharge (Pheat = R·I2). We need to calculate the heat generation of a cell to design a cooling system to cool the cell. While we know the discharge current I, we are unsure of the internal resistance of the cell.

According to the cell spec sheet, the cell's impedance is 8-18 mΩ. I understand the impedance is dependent on the internal resistance and reactance.

Could we use 18 mΩ as a worst-case scenario for heat generation of the cell, and design the cooling system to this worst case to cool by forced convection?

I do not have an electrical engineering background so any help or resources to look into would greatly be appreciated.

ocrdu
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Joey
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1 Answers1

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Any reactance should be very small, almost non-existent. It won't generate heat anyway. Using the 18 milliohm resistance and your maximum discharge current is correct. If the temperature changes, do your fan calculations at the higher ambient temperature. Perhaps add 10 to 20% headroom.

As time goes on the batteries internal resistance may increase. Try to find specs on the aging of the battery relating to internal resistance.

RussellH
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