Battery isothermal calorimeterIt is a high-precision thermal analysis instrument designed to measure the thermal changes of batteries during charging and discharging processes, providing key data support for battery thermal management, safety assessment, and performance optimization. Based on the principle of power compensation isothermal calorimetry, the electric heating element is feedback controlled to maintain a constant temperature of the battery throughout the testing process. Its core component is the isothermal temperature measurement block, consisting of a bottom layer and a measurement layer: the bottom layer maintains a constant temperature through Peltier elements, while the measurement layer records changes in the power of the electric heater, accurately calculating the heat generated or absorbed by the battery. Instruments are usually equipped with reference batteries, which compare the thermal effects of the test battery and the reference battery to eliminate external interference and ensure measurement accuracy.
Battery isothermal calorimeterCoordinated by multiple precision subsystems. The main components are as follows:
1. Constant temperature chamber
Function: Provide a highly stable and uniform constant temperature environment, which is the basis of isothermal calorimetry.
Structure and characteristics:
It is usually made of high thermal conductivity materials such as aluminum or copper to ensure uniform temperature distribution inside the cavity.
The inner wall has undergone special treatment and has good thermal radiation characteristics.
Equipped with efficient insulation layers (such as vacuum interlayers or multi-layer insulation materials) to minimize heat exchange with the external environment.
The chamber door/cover is equipped with an O-ring seal to ensure airtightness and prevent airflow disturbance and moisture from entering.
2. Precision temperature control system
Function: Real time monitoring of chamber temperature, and controlling the temperature within a very small fluctuation range (usually within ± 0.1 ° C) of the set value (such as 25 ° C) through heating or cooling methods.
Key components:
High precision temperature sensor: usually a platinum resistance thermometer (Pt100 or Pt1000), used as a reference probe to monitor the actual temperature of the cavity in real time.
Heating element: such as electric heating wire or heating film, distributed around the cavity, used to compensate for system heat loss.
Refrigeration unit:
External circulating cooler: The most common method is to remove heat by circulating liquid (such as ethylene glycol aqueous solution).
Built in compressor refrigeration: integrated inside the equipment.
Liquid nitrogen refrigeration: used for special models that require extremely low temperatures.
Temperature controller: receives sensor signals and precisely adjusts heating/cooling power through PID algorithm.
3. Thermal flow measurement and calculation system
Function: This is the "brain" of the calorimeter, responsible for calculating the actual heat generation of the battery based on the compensation power of the temperature control system.
Principle:
In steady state, when the battery is not producing heat, the temperature control system only needs to provide a small amount of power to compensate for the small heat leakage from the chamber to the environment.
When the battery starts to generate heat, the temperature control system will automatically reduce the heating power (or increase the cooling power) to maintain the same temperature in the chamber.
Battery heat generation rate=change in compensation power of temperature control system.
Implementation method:
Real time measurement of input power of heating elements through high-precision power meters or current/voltage sensors.
The data acquisition system records power changes and calculates the total heat generation through software integration.
4. Sample stage and electrical connection
Function: Fix the battery to be tested and provide electrical connection with external battery testing equipment (charging and discharging machine).
Structure:
Sample stage: It is usually made of high thermal conductivity materials to ensure rapid temperature balance between the battery and the chamber. Different fixtures may be equipped to accommodate different battery shapes such as cylindrical, square, and soft pack.
High voltage/high current terminal: connects the positive and negative terminals of the battery to an external charging and discharging motor, capable of withstanding high currents during battery testing.
Voltage sampling line: used for precise measurement of battery terminal voltage.
Thermocouple/RTD interface: can be connected to additional temperature sensors to directly monitor the surface temperature of the battery.
5. Gas management system
Function: Manage the atmosphere inside the chamber for safe discharge of gases that may be generated by the battery, or create an inert environment.
Components:
Inert gas inlet: Nitrogen (N ₂) or argon (Ar) can be introduced to eliminate oxygen, prevent battery fire and explosion, and reduce oxidation reaction interference.
Exhaust port: Connect to the laboratory fume hood or exhaust gas treatment system to promptly discharge harmful gases (such as HF, CO, organic vapors).
Flowmeters and valves: control gas flow rate and on/off.
Pressure Balance Tube: Maintain pressure balance inside and outside the chamber to prevent excessive pressure caused by gas generation.
6. Data acquisition and control system
Function: Integrate all signals, run control algorithms, display data, and store results.
form:
Main control computer: runs specialized software.
Data acquisition card: high-speed acquisition of multiple signals such as temperature, power, voltage, current, etc.
Control software:
Set experimental parameters (target temperature, gas flow rate, experimental duration).
Real time display of temperature, heat flux, voltage, current and other curves.
Automatically calculate and output results such as heat generation rate, cumulative heat generation, heat capacity, etc.
Support communication with external battery testing equipment (such as through CAN, USB, or Ethernet) to achieve charge discharge and calorimeter synchronization.
7. Security protection system
Function: Ensure the safety of equipment and personnel, especially in the event of thermal runaway of the battery.
measures
Overtemperature alarm and automatic shutdown: When the temperature exceeds the safe threshold, the heating is cut off and forced cooling is activated.
Pressure sensor: monitors the pressure inside the chamber and alarms or activates emergency exhaust when there is an abnormal increase.
Gas detector (optional): detects the concentration of specific harmful gases (such as H ₂, CO).
Emergency stop button: Manually cut off the power and gas supply immediately.
Explosion proof pressure relief valve: releases pressure under extreme conditions.