This week, Renesas announced the ISL78714, a 14-cell battery management IC for vehicular lithium-ion batteries, sometimes called Li-ion batteries or LiBs. It is designed to maximize the useful life of battery cells and to extend the driving time and range of EVs and hybrids.
The ISL78714 14-cell battery management chip. Image from Renesas
Of vital interest to designers, the chip’s safety features enable manufacturers to achieve ASIL D (automotive safety integrity level). This is the most stringent level specified within ISO26262 of the ISO (International Standards Organization).
The IC can supervise up to the 14 series-connected cells typical in automotive battery packs and provides critical cell temperature and voltage management, cell balancing and complete system diagnostics.
“The ISL78714 battery management IC enables battery management systems with a best-in-class combination of battery pack monitoring accuracy, fast data acquisition, and fault checking features,” said Niall Lyne, Senior Director of Product Marketing and Applications, Automotive Mixed-Signal/Power and Video, Renesas Electronics Corporation. “Our Formula E technology partnership with Mahindra Racing is already helping them win on the race track. Together, we designed and integrated a low-voltage Li-ion battery management system featuring ISL78714 ICs and RH850 microcontrollers in Mahindra Racing electric race cars.”
Indeed, the RH850 MCU pairs well with the ISL7814. The RH850 was just adopted by Nissan for its Propilot2 driver assistance system.
Specifications and Application Details
The ISL78714 IC provides cell voltage monitoring for up to 14 series-connected cells at ±2mV accuracy across its operating temperature range. It also performs vital cell balancing, provides system diagnostics and also provides cell temperature monitoring.
Up to 29 more ISL78714’s can be accommodated via a proprietary, two-wire daisy chain. In this manner, a total of 30 ICs can support up to 420 (30 times 14) cells. This flexible daisy-chain arrangement can be established with capacitor or transformer isolation, or via a combination of both. Along with twisted pair wiring, protection against hot plug and high voltage transients is established.
A master ISL78714 communicates to its host MCU (Microcontroller Unit) through an SPI (Serial Peripheral Interface.) Communications at rates up to 1 Mbps are possible. A daisy-chained IC is automatically shut down if it loses communications with the MCU.
The ISL78714 is AEC-Q100 Grade-2 qualified for operation over a temperature range of -40ºC to +105ºC. The IC is packaged in a 64 pin TQFP.
Renesas also offers other products that help designers control and monitor complex power systems based on Li-ion batteries.
Reference Design Available
Renesas offers the ISL78714BMS5XBEKIT1Z reference design kit. With it, designers can explore the combination of the Renesas RH850 MCU with the ISL7814 as the nexus of a battery management system (BMS) solution.
The ISL78714BMS5XBEKIT1Z. Image from Renesas
Around the Industry
For EVs, hybrids, and everything in between, Li-ion batteries are the central but most difficult and contentious part of the new automotive universe. Not surprisingly, Renesas is not alone in providing various types of management chips for these powerful but quirky electrical storage devices.
Texas Instruments offers the BQ79606A-Q1, which can monitor up to six battery cells and is stackable for up to 64 cells. Communication is via a UART interface. Since safety is the prime concern in any application related to Li-ion batteries, it should be mentioned that the device is AEQ-Q100-2 qualified for device temperatures of –40°C to +105°C.
Maxim Integrated’s MAX17843 is a 12-cell voltage measurement IC that focuses on 48-volt vehicle battery modules. It allows designers to meet ASIL D requirements. The company also offers an educational video describing its take on automotive battery management.
Have you worked with battery management systems in the automotive space? Share your insights in the comments below.