21-07-2020 | | By Robin Mitchell
Infineon announced their latest battery balancer IC, the TLE9012AQU multi-channel battery monitoring and balancing platform, for use in automotive applications. What are battery balancers, why are they important, and what features does the TLE9012AQU boast?
Battery technology has changed immensely in the past few decades, thanks to developments in electric cars and mobile devices. The requirement for high-density batteries has resulted in the wide-spread adoption of technologies utilising lithium due to its reactivity (in general, more reactive compounds provide more potential energy). However, packing more energy per unit volume also means that a failure in the battery will be more devastating. This becomes apparent when damaged batteries used in mobile phones can heat up, expand in size, release gas, and then ignite. Failures in batteries can also occur during overcharging, undercharging, and temperature swings which is why it is essential to monitor these very carefully.
However, the problems of battery monitoring are made even more complicated when considering that most lithium batteries are made up of multiple cells connected. Many applications require voltages far more significant than what a single cell can provide, which is why numerous cells are connected in series. Even then, each battery can only provide so many amp-hours which results in multiple batteries being connected in parallel. The result is many cells in a complex matrix that all need to be charged correctly to avoid overcharging or undercharging. In an ideal world, this would be easily achievable by using identical cells, but the real world is very unforgiving. Minor differences in cell resistances and chemical makeup mean that an array of cells will quickly fail as one cell will charge/discharge faster than the other cells resulting in potential failure.
To solve this problem, a battery balancer is used. These devices fall under two categories: passive and active. Passive battery balancers use resistors and capacitors to discharge extra energy as heat to protect cells. However, passive balancers are inefficient due to heat losses which is why more intelligent solutions use active battery balancers. These use multiple sensor wires with individual charging circuits to ensure that each battery and cell is correctly charged and discharged. Not only does this increase the longevity of the battery system, but also protects from dangerous scenarios.
Battery balancers are an essential part of battery technology, and the use of one should be made a legal requirement. Recognising their importance, Infineon has released a new battery monitoring integrated circuit (IC), the TLE9012AQU.
The TLE9012AQU is a battery monitoring IC designed for use with Li-Ion battery packs with an emphasis in the automotive, industrial, and consumer industries. The IC provides four main battery monitoring functions, including cell voltage monitoring, temperature measurement, cell balancing, and isolated communications with the main battery controller. Connecting up to 12 cells simultaneously, the TLE9012AQU supports communication with up to 20 devices as well as hot-plugging, and the use of a ring topology allows for unbroken communication even if devices fail.
Cell voltage measurements are done using a 16-bit ADC with a high accuracy measurement for the state of charge and state of health calculation. All voltage readings from the cells are compensated for temperature, noise filtering is built-in, and the bit-length of the result of selectable. The TLE9012AQU allows for up to 5 external temperature readings using NTC thermistors, while the internal temperature of the IC is also available. The TLE9012AQU supports up to 150mA balancing current, and the communication method used between the TLE9012AQU and the main battery controller is UART.
Safety is a crucial factor in battery systems, and the TLE9012AQU battery analyser packs a range of safety measures. To start, the IC integrates two independent voltage references if one should become damaged. The IC integrates configurable over-voltage and under-voltage comparators for fine-tuning, and end-to-end CRC secured communication ensures glitch-free messaging. Other safety features integrated include internal open load detection, CRC secure configuration registers, and AEC-Q100 certification.