Quantifying Transient Resistance Measurement Errors Driven by Data Acquisition Delay
Data acquisition delay inflates cell transient resistance measurements by capturing double-layer charging decay rather than pure ohmic voltage drops.
Simultaneous Sampling
Meaning
A measurement technique captures multiple voltage and current channels at the exact same instant in time. To calculate cell impedance accurately, simultaneous sampling is used to measure current and voltage without any timing offset between the two readings. This synchronized acquisition is essential for precise diagnostic calculations in modern battery management systems.
Dynamic Slew
Cell voltage and current fluctuate rapidly during vehicle acceleration and regenerative braking. If the system does not use simultaneous sampling, a timing offset of even a millisecond can cause incorrect impedance calculations. This mismatch leads to errors in the state of power estimation, which can result in the battery pack being pushed beyond its safe limits.
Algorithm Benefit
Real-time diagnostics rely on matched voltage and current data to compute cell resistance. When simultaneous sampling is employed, the resulting datasets provide a true snapshot of the cell state during load transients. This allows the state of health algorithm to operate with high confidence.
Hardware Implementation
Achieving this level of synchronization requires dedicated sample-and-hold circuits for each measurement channel. While a multiplexed system is cheaper, a simultaneous sampling architecture avoids the need for complex software interpolation routines. Sourcing units with this capability increases the design cost but ensures superior performance and simpler firmware development, especially for large battery packs with hundreds of series-connected cells where sequential measurement skew would otherwise accumulate to unacceptable levels.