Is the internal resistance of 18650 lithium battery pack large or small?

   Resistance indicates the degree of resistance of a circuit element to current transmission. The unit is Ohm. The internal resistance of 18650 lithium battery pack is related to the capacity and type of battery.

  Generally speaking, the larger the capacity, the smaller the internal resistance. For batteries with the same capacity, the internal resistance of magnification type is less than that of capacity type. The internal resistance of a general lithium battery pack is only a few milliohms.

Inside the lithium battery, lithium ions move from one pole to the other. The factors that hinder the movement of ions in the process together constitute the internal resistance of the lithium battery. Its main part includes the physical internal resistance of conductive parts; Inherent impedance of electrochemical substances such as motor material, diaphragm and electrolyte; The resistance to the movement of lithium ions temporarily increased in the presence of current inside the battery; These three parts together constitute the main body of internal resistance.

The internal resistance of 18650 lithium battery pack is the most sensitive to temperature. The internal resistance value can change greatly at different temperatures. One of the important reasons for the decline of battery performance at low temperature is the excessive internal resistance of the battery at low temperature.

18650 lithium battery pack as a power supply, from the outside, the smaller the internal resistance, the better. Especially in the case of power application, small internal resistance is a necessary condition. The larger the capacity, the larger the area, and the smaller the resistance through which the current passes. The internal resistance of lithium battery pack must be as small as possible. The smaller the internal resistance is, the less energy is wasted for the battery, and it is helpful for the heat production and magnification of the battery.

In recent years, new energy vehicles have higher and higher requirements for high rate charge and discharge performance of power batteries, and internal resistance is an important factor affecting battery power performance and discharge efficiency. With the use of 18650 lithium battery pack, battery performance continues to decline, mainly manifested in capacity attenuation, internal resistance increase, power decline, etc. the change of battery internal resistance is affected by temperature Discharge depth and other service conditions.

Internal resistance is an important parameter to measure the power performance and evaluate the battery life of lithium battery. The greater the internal resistance, the worse the rate performance of the battery, and the faster it increases in storage and recycling. The internal resistance is related to the battery structure, battery material characteristics and manufacturing process, and changes with the change of ambient temperature and state of charge. Therefore, the development of low internal resistance battery is the key to improve the power performance of battery.

At the same time, mastering the change law of battery internal resistance has very important practical significance for battery life prediction. 18650 lithium battery pack has high internal resistance and cannot discharge with high current. The lower the theoretical internal resistance, the better. The internal resistance is directly related to the capacity. The general lithium battery assumes that the internal resistance is about 30 to 80 ohm at 1 ampere hour, while a good power lithium battery can be less than 15 ohm. The internal resistance of lithium battery is high. When discharging, the heating of the battery should be higher. In short, the smaller the internal resistance of lithium battery, the better.