BU-921: Testing Batteries by Multi-Model EIS

Electrification in batteries is advancing at a breathtaking speed, but Diagnostic Battery Management (DBM) is not keeping pace. Every year, over one million good batteries are discarded while the battery remains the weakest link in the chain. Statistics reveal that batteries cause half of equipment failures by ignoring Minimum Operational Reserve Energy (MORE).

Embedding battery diagnostics into chargers calls for service as the capacity falls below the Target Selector capacity, the performance gate keeper. This feature fully uses each battery and calls for service or replacement before failure. Knowing MORE boosts battery reliability, lowers total cost of ownership, and protects the environment.

This document focuses on Spectro™, a non-invasive technology that models batteries against a matrix to assess capacity and other characteristics. Spectro is based on Multi-Model Electrochemical Impedance Spectroscopy (EIS), a technology scientists predict will lead to futuristic battery diagnostics. Typical Spectro applications are illustrated below.

Multi-Model EIS is available in the Spectro CM-24, a battery rapid-tester that is being tested in wheeled mobility. Operators of scissor lifts have no easy way to test batteries beforeand a mission and the battery remains the most failure prone part. Without capacity assessment, batteries are often replaced to soon but are mostly kept too long. On the question: “At what capacity do your replace a battery?” eyes roll with no clear answer other than to replace batteries when the machine breaks down.

Batteries are slightly oversized in capacity when new to allow for fading. A typical MORE threshold for heeled mobility is 60%. Verification of correct setting can be made by checking leftover charge at the end of a busy day with charge reserves that should be 10–20%. If tight, matrices with a higher pass/fail setting are available. With plenty of reserve, a lower capacity threshold can be used to keep batteries in service longer.

If the machine has no state-of-charge (SoC) gauge, leftover charge can be checked by measuring the battery voltage before charge with a voltage reference table on hand to extract SoC. The battery must be in relaxed state with no load applied and dwelling at room temperature.

Knowing battery capacity, operators can reserve high-performing pack for heavy duty while keeping older packs in machies doing moderate work. Batteries in wheeled mobility should be checked once a month or before critial missions.

The recommended MORE for a transit bus is 50%. This enables keeping the lights and monitors on for 15 minutes while the engine is turned off. Energy reserves on an articulated bus increases to 65%. Engine start requires a minimal capacity of 30%.

Bu921 8 — *Johnson Control tested 800 AGM starter batteries (2016)*

Armored vehicles and long distance trucks also draw hotel lod with engine off. A tpical MORE is 50% while consumer auto gets away with 40%. These threshold have worked well since battery testers with capacity assessment have become available. A MORE of 40% fully utilizes each battery with assurance to next service without fear of getting stranded.

Deep cycle batteries on wheeled mobility are capacity based while starter batteries must also deliver a currents of up to 300A to crank the engine. Car mechanics rely on the CCA (Cold Cranking Amp) of a starter battery but statistics reveal that 48% of failures are caused by insufficient capaicty while low cranking power only accounts to 12% of breakdowns. Slow cranking with poor CCA gives early warnings while capacity fades goes unnoticed until getting strandated..

Bu921 9 — *Remaining useful life of stationary batteries rest on capacity*

Another applications in which capacity assessment predicts the remaining uselful life is in stationary batteries. MORE reflects the hours of operation when the electrical supply fails. Typical capacity settings are 50–70%.

Without ability to measure capacity, stationary batteries are often installed and forgotten. Battery suppliers focus on date stamp but this is not be the most economical or reliable method. Stationary batteries should be checked for capacity and voltage balance every six month.

The Spectro CM24 comes with a matrix of choice. Additional matrices are available from Cadex or the Matrix Library for downloading. Spectro™ thus turns into an open battery test platform to test virtually any battery with ability to store test results in the CadexCloud to enable predicitive capacity analysis.

Last Updated: 3-Dec-2025

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