Method for detecting internal resistance of battery pack
Here are some common methods for detecting internal resistance in battery module aging cabinets:
DC discharge method: By performing instantaneous high current discharge on the battery module, measuring the instantaneous voltage drop on the battery, and then calculating the internal resistance of the battery according to Ohm's law. For example, forcing the battery module to pass a relatively large constant DC current (such as 40A-80A) for a short period of time (usually 2-3 seconds), while measuring the voltage at both ends of the battery module, and then calculating the internal resistance. This method is widely used, but can only be performed in a static or offline state, and high current discharge may cause certain damage to the battery.
AC injection method: Inject a constant AC current signal into the battery module, measure the voltage response signal at both ends of the battery, use the phase difference between the two, and determine the internal resistance of the battery through impedance formula. This method does not require discharging the battery and can achieve online detection of battery internal resistance without affecting battery performance. However, this method requires measuring the AC current signal, voltage response signal, and phase difference between voltage and current, with many interference factors and high system complexity, which can affect measurement accuracy.
Internal resistance tester method: Using a specific AC discharge testing method, the voltage and internal resistance at both ends of the battery can be accurately measured to determine the capacity and technical status of the battery. You can choose functions such as internal resistance testing, voltage testing, and capacity estimation for the battery according to your own situation. For example, some professional internal resistance testers can provide high-precision internal resistance measurement results and are relatively easy to operate.
Small DC discharge method: a module based on a single battery and measuring the internal resistance of the battery using the small DC discharge method. It can also simultaneously measure the cell voltage, cell resistance, and cell pole temperature of the single battery, and achieve balanced charging function of the battery. This method is applicable to various types of battery modules and can to some extent reflect the internal resistance of the battery under actual usage conditions.