Renesas Introduces Battery Management ICs to Protect High-voltage BMS

November 17, 2021 by Ikimi .O

A new family of multi-cell, battery front-end ICs may speed battery development in a number of high-voltage applications—including energy storage systems, UPS, and mobility.

By 2026, battery management systems (BMS) will reach a value of approximately $13.4 billion, according to a recent report. These systems promise a wide range of battery-specific functional benefits, including efficient current measurement, battery life maximization, and temperature monitoring.

This article outlines key functions of battery management systems, design limitations, and promising solutions, including the latest battery front-end IC family from Renesas.


The Place of Battery Management ICs in BMS

Battery management ICs in BMS can address functions like cell voltage, fuel gauge, and temperature monitoring. The BMS also includes other functional blocks, such as a real-time clock (RTC), state machine, and cutoff FETs. Each block plays a unique role in keeping the system up and running efficiently.


Typical presentation of a battery management system. 

Typical presentation of a battery management system. 

Battery management ICs are essential for monitoring and balancing battery cell voltage. Designers can maximize battery charging by opting for two major battery pack charging techniques. The first involves connecting a current-limiting resistor-based bypass FET across the battery cell. The second requires a charge displacement scheme. 


Common cell-balancing techniques

Bypass cell-balancing FETs (left) and cell balancing with a charge displacement scheme (right). 


Several companies are working on meeting the growing demand for high-performance BMS-based ICs for rapid recharging and battery pack efficiency, including Renesas.

In general, a BMS needs an extra battery IC when the number of series cells exceeds the existing IC-based cell inputs. This daisy chain design ensures that the remaining cells will be adequately incorporated into a separate module. In high-voltage systems, however, conventional battery front-end ICs can still pose several challenges in daisy-chained designs. These may include costly isolation and additional ICs, semiconductor material waste, and cross-talk-intensive firmware requirements. 

Daisy-chained battery configuration renders battery management ICs obsolete, thus, increasing the need for redundant controllers to support each IC. Optocouplers and isolation may also be needed for efficient communication across the battery modules.


Renesas Unveils Family of Battery Front-end ICs

Renesas recently announced the release of its multi-cell full battery front end (BFE) ICs for battery management systems. These latest solutions are designed for large high-voltage battery packs in heavy-duty applications, such as high-voltage power tools and energy storage. Since BMS are critical for battery power packs, they require high-performance ICs for cell balancing.

Cell balancing in battery packs can maximize charging capacity and enable quick recharging and plug tolerance. Renesas says its RAA48920x IC family offers cell balancing up to 200 mA and hot-plug tolerance up to 62 V.

The IC family includes two variations: the RAA489204 and RAA489206.


Block diagram of the RAA489206. 

Block diagram of the RAA489206. 

Some key features of the RAA489206 solution include:

  • 16-cell voltage measurement
  • 10 mA internal cell balancing and 200 mA external cell balancing
  • High hotplug rating of 62 V
  • Real-time charge/load detection
  • Operating voltage range of 12 V to 55 V

Renesas claims its BFE IC solution is well suited for high-voltage applications, including wireless power tools, energy storage systems, electric motorcycles, telecom and server farm powering, and electric scooters. The solution is said to optimize battery life and prevent failure by scanning the battery's status and its operating environment periodically.

Similarly, the RAA489204 is a 14-cell BFE IC variant offering temperature monitoring, cell balancing, and comprehensive system diagnostics for battery management systems.


Leveraging the Battery ICs in Daisy-chained Designs

Renesas says that when used in daisy-chained designs, the RAA489204 BFE IC can meet high voltage battery requirements, eliminate the need for extra ICs, and significantly reduce design costs. The image below shows how designers can achieve a simplified design by incorporating the RAA489204 solution.


RAA489204 in daisy-chained designs

Conventional BFE IC vs. RAA489204 in daisy-chained designs. 


This solution is said to adequately monitor and protect daisy-chained battery configurations for high-voltage applications. 

Some benefits of this RAA489204 configuration include erroneous fault reaction minimization, cost-effective support for hardware reset commands, and daisy-chain data rate of up to 1 Mbps, useful for up to 30 devices stack. Moreover, the configuration is highly adaptable for reading and writing registers as well as asynchronous SPI transfer management with its increased memory buffer.


All images used courtesy of Renesas.