BU-921: Testing Batteries by Multi-Model EIS

Multi-Model EIS assesses a battery against a matrix to extract capacity, CCA, state-of-charge (SoC) and other characteristics to secure Minimum Operational Reserve Energy.

The non-invasive scan tests lead- and lithium-batteries of up to 300Ah with resistance as low as 300µΩ. Test time is 30 seconds; longer when scanning to 0.1Hetzz. Low frequency testing is made possible with EIS Direct Drive; a technology offered in Spectro devices by Cadex.

*Test accuracy is based on Matrix Integrity Level (MIL)*

Research leading to Multi-Model EIS involved studying network functions to assess battery state-of-health (SoH) as outlined in BU-907b. The test pool includes 800 lead acid batteries examining correct predictions mainly on capacity. Best results are achieved using Gaussian Process, Neural Net and Fuzzy Logic.

Spectro™ stands for Multi-Model Electrochemical Impedance Spectroscopy, a technology that secured several Cadex patents. Scientists predict that battery diagnostics will gravitate to Multi-Model EIS with battery specific matrices that are prepared by scanning batteries of same model but different performance levels as described in BU-919. Test accuracy is governed by the Matrix Integrity Level (MIL) outlined in BU-920. To improve classification, matrices can be improved by scanning additional batteries.

Matrices serving Spectro test devices can be downloaded from Cloud Analytics by subscription service to test batteries in machines illustrated below and described in BU-922 and BU-923. Cloud Analytics also stored the test history that can be downloaded by scanning a QR code attached to the battery.

The Spectro CM-24 as illustrated is a compact battery rapid-tester that evaluates capacity, CCA, SoC and anomalies of starter batteries in consumer auto, trucks, buses and machinery. The ability to assess capacity is of special interest to wheeled mobility, such as scissor lifts, people movers and floor cleaners to assure sufficient capacity for field use. There is currently no practical alternative.

Without periodic capacity assessment, batteries are often replaced to soon, but most stay in service too late, waiting for field failures at high costs. When asking operators: “At what capacity do your replace the battery?” eyes roll with no clear answer.

MORE values of batteries are commonly not known, yet assessing runtime is key to get reliable operation of a machine. One alternative method reading capacity by discharging a battery on a load bank, but this involves dismount with 24-hour service.

The capacity of a new battery is slightly overrated to enable fading. A typical MORE threshold for wheeled mobility is 60%. Verification can be made by checking leftover charge at the end of a busy day. Think of the remaining fuel when landing an airplane.

Spectro™ reads SoC in percentage. If tight, request a matrix with a higher pass/fail threshold to give more reserve; however if plenty of reserve is available at the end of day, a lower threshold will keep batteries in service longer.

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

To examine the cause of battery failure, Johnson Control examined 800 AGM starter batteries and discovered that 48% reached end-of-life by capacity fade while 12% failed by low cranking power. A similar test by ADAC (2024) in Germany reveals that 45% of vehicle breakdowns are caused by the battery that is twice the level of other vehicle malfunctions..

When checking SoC before charging, also check matching of the serially connected packs by reading each battery. It’s the weakest battery in a chain that determines runtime as illustrated in BU-923. Replace a weak battery with a pack of similar capacity. SoC checking should be made at room temperature in relaxed state by giving the battery 15-30 minute rest after use.

By knowing capacity, new batteries can reserve for heavy duty use while older packs may be reserved for lower duties. All batteries in service should be checked once a month or before a critical mission.

Hotel Load

When lights and monitors must be kept on with engine off, as in transit buses during long stops, batteries must have a MORE of 50% for a regular bus and 65% for an articulated vehicle. Starting the engine requires a minimal capacity of 30% to deliver power.

Bus1 — *Regular bus needs a MORE of 50%; articulated bus 65%*

Long distance trucks and armored vehicles also depend on a MORE of 50% while private cars gets away with 40% and grace period to next service without fear of getting stranded.

Mechanics check battery CCA to validate power. We ask: “If the vehicle starts, why test the battery again?” Most battery failures occur by capacity fade that goes unnoticed while poor CCA would give sluggish cranking.

Another application in which capacity assessment is beneficial is predicting the remaining useful life is of stationary batteries. The owner must also be aware of the hours of operation when the electrical supply fails. Without ability to measure capacity, stationary batteries are often installed and forgotten. Battery suppliers focus on date stamp but this is not be the economical or reliable as environmental conditions paly a role. Stationary batteries should be checked for capacity and voltage balance every six months.

Last Updated: 12-Apr-2026

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Batteries In A Portable World

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