The RS4TC8900QCE is an automotive-grade, ultra-low-power RTC with temperature compensation. Its package outline and pin configuration are shown below.

Core Advantages:
High Precision
Integrated 32.768kHz crystal oscillator with digital temperature compensation
Timekeeping accuracy:
±3ppm (Ta = -40°C to +85°C)
±5ppm (Ta = -40°C to +105°C)
Ensures reliable timing even in extreme temperatures (see diagram below).

1.Automotive-Grade Reliability
Compliant with AEC-Q100 standard
High resistance to vibration and EMC interference
Built for harsh automotive environments
2.Ultra-Low Power Consumption
Standby current as low as 0.5μA (typ.)
Extends battery life in power-sensitive applications
3.Backup Battery Switch Support
Seamless power failover for enhanced system reliability
4.Compact Form Factor
3.2×2.5×1.0mm package
Enables miniaturized and high-density PCB designs
5.Flexible Interface & Integrated Functions
I²C interface (400kHz)
Built-in alarm and countdown timer
Simplifies BMS architecture

The RTC module keeps accurate time when the engine is off and the BMS is in sleep mode. It acts as a wake-up source for self-checks and provides timestamps for logs and fault records.
Low-power operation: Runs on backup battery with minimal consumption.
Scheduled wake-up: Sends interrupt signals to trigger BMS self-checks.
Data logging: Provides time references for monitoring, diagnostics, and optimization.
The Raystar RS4TC8900QCE delivers precise and reliable timing for BMS master control units, enabling critical system algorithms. Below is its application diagram in BMS:

Conclusion