Battery Internal Temperature Sensor with a simple electrical test predicts Catastrophic Failures in Lithium-Ion Batteries. Abnormally high internal cell temperature may cause catastrophic failures in batteries. Scientists at the Johns Hopkins University Applied Physics Laboratory (APL), have developed an inexpensive sensor that can warn of impending catastrophic failure in lithium-ion batteries. The sensor is based on the researchers’ discovery of an intrinsic relationship between the internal temperature of lithium-ion cells and an easily measured electrical parameter of the cell.

Battery Safety Concerns

Due to their high energy density, lithium-ion batteries power millions of consumer electronic devices and are the most common type of battery used in hybrid and electric vehicles. They are also growing in popularity for power grid, military and aerospace applications.

But safety concerns remain a challenge to the industry. Battery malfunction and fires in electric vehicles, mobile phones and laptop computers have been reported in the media. Such failures typically result from thermal runaway, a self-perpetuating condition that occurs once a cell reaches a critical temperature.

Working Principle of Battery Internal Temperature Sensor (BITS)

The Battery Internal Temperature Sensor (BITS), developed by the Johns Hopkins University Applied Physics Laboratory, is a miniature instrument with demonstrated capability to measure and report the internal temperature of individual cells in a multi-cell Li-ion battery pack at the rate of 200-ms/cell. It is designed to operate using power from the battery it is testing. With multiplexing circuitry, a single sensor can monitor multiple cells in a battery pack.

Unlike surface-mounted thermocouples, Battery Internal Temperature Sensor provides a direct measure of the internal temperature of Li-ion cells through a simple electrical connection at the positive and negative terminals of the cell. Battery Internal Temperature Sensor works by perturbing the cell terminals with a low-amplitude AC current and measuring the phase shift of the resulting voltage output. This phase shift is independent of the battery state-of-charge and relates directly to the temperature of the anode and the cathode. It measures the internal temperature online, i.e. when the cell is under charge, discharge, or rest conditions.

Battery Internal Temperature Sensor (BITS) Features and Applications

Battery Internal Temperature Sensor (BITS) uses a technique that is non-intrusive; nothing is inserted into the cell. A four-probe electrical technique that enables real-time temperature monitoring of the carbon anode in a lithium-ion rechargeable cell during charging and discharging. This technique uses only electrical contacts to the positive and negative terminals of the cell, eliminating the need to insert temperature sensors inside the cell.

Battery Internal Temperature Sensor (BITS) is the most accurate and immediate method available for measuring the true temperature of a Li-ion cell. And it is the only method for measuring a battery cell temperature where it counts: inside the cell where temperature changes originate. BITS enables battery management systems to more closely manage battery performance and, more importantly, to detect unsafe thermal conditions at the critical moment when they occur before they have propagated to the surface of the cell.

By integrating BITS into their products, manufacturers of batteries, battery management systems, and battery solution providers can increase both the safety and performance of their products. BITS works with standard off-the shelf Li-ion batteries.