Battery Internal Resistance

Battery internal resistance happens when current passes internal battery and can be classified into AC & DC internal resistance. Since rechargeable battery‘s internal resistance is very low; when testing DC resistance, electrode capacity causes polarize resistance, so it is impossible to test the exact value. As for AC resistance, free of polarize resistance affection enable to get the exact value of internal resistance. AC internal resistance test method, with a battery as active resistance, sending battery a 1000HZ/50mA constant current, internal resistance could be tested through rectification, wave filtering etc. for voltage exactly.

For Lithium ion Battery, battery internal resistance is divided into ohm internal resistance and polarize internal resistance. Ohm internal resistance is combined with electrode material, electrolyte, separator impedance and other component contact impedance. Polarize internal resistance is caused by polarization during electrochemistry reaction, including electrochemistry polarization and concentration difference impedance.

Lithium ion battery exact internal resistance is occurs when current passes internal battery. If internal resistance of battery is high, it will cause lot of joule heat then battery temperature rises, the consequence is to lower battery discharge work voltage, shorten discharge time, and badly affect battery characteristic and cycle life. It’s very complex to calculate battery internal resistance exactly, meanwhile, it will change during using. According to experiment, the higher the capacity of lithium ion battery, the less internal resistance is, vice verse.

P.s. Internal resistance is calculated at level of charged; test device is specific internal resistor other than Multimeter.