An adapter includes: a power input terminal for connecting an AC power supply; a power circuit that performs energy conversion on the inputted AC power to obtain electrical energy capable of powering a power tool; and a tool interface connected to a power interface of the power tool to output electrical energy. The adapter further includes a data transmission module connected to at least the tool interface and capable of outputting first communication data and/or first internal resistance data to the tool interface so that the power tool is capable of identifying the adapter according to the first communication data and/or the first internal resistance data. The first communication data includes at least adapter identification data, and the adapter identification data enables the power tool to identify that a connected device is the adapter between the adapter and a battery pack.

A device includes an AC impedance circuit to apply an AC excitation signal to a set of battery cells of a battery pack. The device includes a controller to determine a battery pack identification (ID) value from a battery pack identification (ID) circuit of the battery pack, calculate an impedance value of the battery pack based on the AC excitation signal, identify a maximum charging rate to charge the battery pack using the battery pack ID value of the battery pack and the impedance value of the battery pack, where the battery pack is one of at least two battery packs having a same battery pack ID value with different maximum charging rates, and set a charging rate to charge the battery pack using the maximum charging rate.

An intelligent rechargeable battery pack having a battery management system for monitoring and controlling the charging and discharging of the battery pack is described. The battery management system includes a memory for storing data related to the operation of the battery, and the battery management system is also configured to communicate the data related to the operation of the battery to other processors for analysis.

An apparatus for controlling a main line switch mounted on an energy storage system is provided. The energy storage system includes a plurality of battery racks and a disconnect switch unit. The apparatus includes: a battery connection unit respectively on each of the battery racks, the battery connection unit being configured to measure a current of a corresponding one of the battery racks by using a built-in current measurement unit and to generate an overcurrent detection signal when the current of the corresponding one of the battery racks exceeds an overcurrent protection level; and a switch controller configured to open the disconnect switch unit to block a main line current flowing to the energy storage system in response to the overcurrent detection signal from a reference number or more of battery connection units.

Systems and methods for implementing a plurality of temperature sensors in power tools. An example power tool includes a first electrical component, a second electrical component, and an indication device. The power tool includes a first temperature sensor configured to sense a temperature of the first electrical component, and a second temperature sensor configured to sense a temperature of the second electrical component. A controller is connected to the first temperature sensor and the second temperature sensor. The controller is configured to determine a temperature difference between a first temperature value associated with the first temperature sensor and a second temperature value associated with the second temperature sensor, compare the temperature difference to a temperature difference threshold, and provide, when the temperature difference satisfies the temperature difference threshold, a notification using the indication device.