As the world electrifies, battery diagnostics has been lagging behind core developments in batteries. Performance transparency must be equal or higher than traditional energy systems that burn fossil fuel. Cadex realizes the importance of battery diagnostics and is developing rapid-test technologies that assess battery capacity, the leading health indicator.

Last month, our Tina Shoa, PhD, presented our Diagnostic Battery Management technologies at the Batterietagung (Battery Event) in Münster, Germany. The conference was organized by the Aachen University, an institution that specializes in battery technology. As anticipated, the participants were highly specialized and demonstrated strong battery knowledge.

Speaker after speaker in the main auditorium talked about the life of a battery that begins with research; then moves to manufacturing, followed by field deployment, and ands in recycling to retrieve valuable materials. While this business model is solid, one vital entry in the life of a battery was missing — the speakers filed to mention battery diagnostic to enable the full use of each battery with call for replacement before failure. Imagine life without a doctor to fix our ailments.

Subsequent speakers filled in by presenting battery diagnostics with a focus on electrochemical impedance spectroscopy (EIS). So prevalent was the topic that entire speaking tracks and poster sessions were devoted to EIS. Most speakers presenting papers were also doing doctoral dissertations on this topic.

What was missing in the presentations, however, was advancing EIS into a test instrument that makes battery performance readable by untrained staff.

Cadex solved this limitation in an instrument that creates a Nyquist plot which is modeled against a matrix to extract battery capacity and other data. Test accuracies rest on the integrity of the matrix composed by taking performance data of aged batteries of same-model. This technology is able to assess battery state-of-health (SoH) of lead acid and lithium-ion systems.

Being first to market to provide battery performance by exploiting EIS data is reminiscent of Thomas Edison who used a glowing filament to commercialize the light bulb. As the Edison light bulb illuminated the world in 1879, scientists predict that the future of battery diagnostics rests in EIS. The full potential of this technology has not yet been fully explored; much rests on the integrity of the matrix. Multi-model EIS, called Spectro™, holds several patents. With close to 10,000 Spectro battery testers in service to date, the devices are non-invasive, compact, cost-effective and easy-to-use. Test-time is roughly 30 seconds, longer with large batteries requiring very low frequencies.

Figure 1: Thomas Edison with the lightbulb in 1879s

Battery Diagnostic Pyramid

With time, several battery test methods have immerged that are captured in Figure 2. A low number in the Battery Diagnostic Pyramid reflects an older and more basic approach while higher numbers include some form of training in use. EIS stands on its own by comparing test results with a matrix serving as lookup table that is analogous to face recognition using AI. Of importance is the ability to assess capacity, the gatekeeper that governs the remaining useful life of a battery.

Figure 2: Diagnostic No universal battery test methods exist that serve all applications. Here is a summary of best uses.

1. Load Test is a proven method to check power, such as cranking an engine but cannot assess capacity. Without knowing the capacity, a starter battery may crank today and fail next week. 
2. Dynamic Response assesses battery SoH by voltage-recovery after applying a load pulse. An analogy is observing the heartbeat when running upstairs that quickly normalizes on a healthy person. With Li-ion, a quick voltage recovery denotes unrestricted ion-flow that manifests good health. 
3. Machine Learning calculates battery capacity by tracking charge and discharge currents in coulombs. (One coulomb is 1A per second.) The System Management Bus (SMBus) developed for portable devices, also serves the EV and Battery Storage Systems. 
4. EIS takes the electrochemical evidence of a battery and compares the results against a matrix. Efforts are made to offer matrices for diverse battery models online.

Strengthening the Weakest Link All battery applications benefit from diagnostics. Service personnel are aware of the weakest link and say: “Half of all breakdowns are caused by the battery.” Many Service centers take special care and only release a device with a checked battery. Think of the passport officer inspecting your credentials when traveling.

Battery testing by EIS also enables monitoring a battery that had been installed and forgotten. Cloud Analytics observes the Minimum Operational Reserve Energy (MORE), a feature EIS offers with capacity assessment. Battery replacement is thus ruled by MORE when the faded battery can no longer provide the operational reserve energy. Think of EIS as the technology that makes batteries transparent.