14-cell Li-ion battery management extends EV driving range

An automotive-grade battery management IC is claimed to provide the industry’s most accurate cell voltage measurements and safety features. The ISL78714 provides cell voltage and temperature monitoring, cell balancing and system diagnostics to protect 14-cell Li-ion battery packs.

It maximises driving time and range for electric vehicles (EVs) and hybrid EVs (HEVs) by monitoring and balancing the cells with ±2mV accuracy. It includes a precision 14-bit analogue to digital converter (ADC) and data acquisition circuitry. It also offers up to six external temperature inputs (two available from GPIOs) and includes fault detection and diagnostics for all key internal functions.

The IC’s safety features allow manufacturers to achieve the ISO 26262 automotive safety integrity level (ASIL D). It also monitors and reads back over-/under-voltage, temperature, open wire conditions, and fault status for 112 cells in less than 10milliseconds, or 70 cells in 6.5 milliseconds.

Multiple ICs can be connected via a proprietary daisy chain that supports systems up to 420 cells (30 ICs) to provide transient and EMC/EMI immunity that exceeds automotive requirements, claims Renesas. The daisy-chain architecture uses low-cost capacitive or transformer isolation, or a combination of both, with twisted pair wiring to stack multiple battery packs together while protecting against hot plug and high voltage transients. A watchdog timer automatically shuts down a daisy-chained IC if communications is lost with the master MCU.

The AEC-Q100 Grade-2 qualified IC operates across the -40 to +105 degrees C temperature range.

A battery management system (BMS) reference design is available, which includes five ISL78714 ICs and a RH850/P1M microcontroller. The reference design kit provides set-up and data logging via CAN and UART. There are also a GUI, Altium layout files and low-level drivers for the RH850 peripherals and ISL78714. Hardware, software, and interface reference manuals are included, along with an EMC report.

Mass production quantities of the ISL78714 Li-ion battery management IC are available now in a 64-lead TQFP package.


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