BU-925: EIS Direct Drive, non-invasive Capacity Test

Spectro™ departs from load testing by modeling a battery against a matrix to assess capacity, the leading health indicator. Testing large batteries is made possible with EIS Direct Drive by injecting sinewave signals that causes a voltage ripple which is filtered and used to create a Nyquist plot.

BU 925 EIS — *EIS Direct Drive tests large batteries down to 300µΩ*

Typical test time for batteries up to 300Ah is 30 seconds; longer with large batteries that require frequency scan below 4Hz.

After filtering, the data is fed to multiple models for magnitude extraction to secure Minimum Operational Reserve Energy (MORE).

Capacity reads the remaining useful life while resistance validates power. Multi-model EIS also finds hidden battery anomalies to improve safety.

BU 925 Complex EIS — *Complex EIS modeling assesses capacity and CCA through modeling*
U.S. patent 7,072,871, U.S. patent 6,778,913

Cadex provides matrices serving lead acid and lithium-based systems. Matrix development involves scanning same-type batteries at difference state-of-health. Accuracy rests on the Matrix Integrity Level (MIL) that can be improved by scanning batteries with distinct characteristics. Cadex can also develop matrices to test batteries exposed to unique environmental conditions. The matrices are stored in the Matrix Library for downloading into the Spectro™ test device with Cloud Analytics.

EIS Direct Drive also support modern Battery Management Systems (BMS) to assess capacity and detect anomalies, such as dendrite growth that cause electrical shorts, leading to fires. Li-ion fire reaches temperatures of 800ºC (1,500ºF), twice that of burning fossil fuels. Water does not douse a lithium fire but protects the surroundings.

Conclusion

EIS Direct Drive replaced the earlier capacitor-copped Spectro™ model by expanding the upper test limit from 100Ah to 500Ah or 300µΩ. Eliminating the capacitors also shrank the footprint into a compact hand-held device with Bluetooth connection to a host with cloud connection to store share test data. Typical applications are testing starter, deep cycle and stationary batteries.

Scientists envision the future of battery diagnostics in EIS. Cadex was first to offer commercial units assessing battery capacity non-invasively with the patented Multi-model EIS technology. EIS stands for Electrochemical Impedance Spectroscopy.

Last Updated: 22-May-2026

Previous Article Next Article

Batteries In A Portable World

The material on Battery University is based on the indispensable new 4th edition of "Batteries in a Portable World - A Handbook on Rechargeable Batteries for Non-Engineers" which is available for order through Amazon.com.

More Details Buy On Amazon