The internal resistance of the 18650 battery varies depending on the type. The same type of battery has different internal resistance due to different chemical properties inside. The internal resistance inside the battery is very low, and it is usually expressed in ah. Internal resistance is an important technical indicator of battery performance. Under general conditions, the battery with low internal resistance has high large current discharge capacity, while the battery with high internal resistance is lower. From the perspective of the circuit diagram, we can separate the battery from the internal resistance into a completely unobstructed power supply, which is connected to a resistor with a very low resistance value.

If the external load is very light, the lower the pressure it will bear, and if the external load is large, then the pressure it will bear will be greater, and its energy will be consumed. The resistance of a rechargeable battery at the factory is very low, but over time, as the content of electrolytes and chemical composition in the battery gets lower and lower, this resistance will become larger and larger, which will eventually lead to the battery of the battery. The capacity is exhausted. Most of the old batteries will be scrapped because the internal resistance is too high. Therefore, we should pay more attention to the release ability of the battery, not the power of charging.

1. Internal resistance non -constant value

The problem is that in different charge conditions, the internal resistance will be different; under different service life conditions, the changes in the internal resistance of the battery are different. Technically, we usually divide the resistance value of the battery into internal resistance in the state of power and discharge.

1. The internal resistance of the charge state refers to the internal resistance of the capacitor measured when the battery is completely filled.

2. The internal resistance of the discharge state refers to the internal resistance of the measured battery (under the standard disconnection voltage) after the battery is completely discharged.

Under normal circumstances, the internal resistance of the discharge state is unstable, the measured results are much higher than the normal value, and the internal resistance of the charge state is relatively stable. Therefore, the determination of this value has a certain practical value. Therefore, in the measurement of the battery, we all use the internal resistance of the charge state as the benchmark.

Second, internal resistance cannot be determined accurately by conventional methods

Some people may say that in middle school, there is a simple formula+resistor box to calculate the battery resistance value, but the resistance box operation on the physics textbook is too low in its calculation accuracy. The internal resistance of the battery is very low, and we usually define it as Microcy or ah. In conventional testing, the measurement accuracy error of the resistance of the battery needs to be controlled below 5%. Such a low resistance and such accurate requirements require special instruments to complete.