Testing safely in high-voltage environments

Automated testing and evaluation of e-vehicle batteries

When developing new batteries and battery management systems for electric vehicles, extensive tests and validations are the order of the day. This includes life cycle testing and misuse tests. These can be used to determine the load limits of battery cells, battery modules and complete battery packs. Investigations include charging and discharging cycles in climatic chambers as well as crash loads, penetration, compression, bending and vibration tests. These comprehensive tests require a flexible, automated test system, including data evaluation. The measurement technology acquires data safely and without disturbance in a high voltage environment. SK Innovation, one of the world's largest battery manufacturers, relied on the HV measurement technology from imc Test & Measurement and commissioned several measurement racks for battery tests.

Endurance test with the imc test rack

The 19”-test rack captures all measured values on a battery module consisting of several individual battery cells. Cell voltage and temperature are measured and monitored during the test on each bat-tery cell. For this, SK Innovation uses several 19” racks. The test system also acquires the voltage of the battery modules and the entire battery pack. imc STUDIO software also controls and regulates the bidirectional DC source for the charging and dis-charging process and monitors measurement quantities

Schematic structure of the measuring rack
Schematic structure of the measuring rack. The imc CRONOSflex measuring system measures, controls and regulates.

Life cycle and destruction tests

The various battery tests are used to deter-mine the life cycle and reliability of the e-vehi-cle battery in different load situations, such as simulating an accident. Tests with crash, pene-tration, compression, and bending loads serve to provide information about the safety of a battery pack and are stipulated by standards. Lithium-ion batteries require the correct test environment for the tests specified here, as the targeted destruction of the battery system leads to the dreaded “thermal runaway”. The melting of the separator leads to an un-controlled release of the stored energy of the cells. The oxygen content in the environment can lead to a fire or an explosion of the battery cells. The test environment must be designed to be fire-proof and explosion-proof, or pressure waves must be diverted in a tar-geted manner and the pollutants produced may only be filtered into the atmosphere.

Penetration Load Test

When testing penetration load, the imc test system records the battery cell voltage. The temperature is recorded with a thermal imag-ing camera. A film camera documents 5 destruction. All images and measurement data are stored synchronously for evaluation.

Misuse- and crash-Test

A thermal imaging camera and a high-speed camera are used for dedicated mechanical de-formation tests on the battery pack (crash, compression, and bending loads). Here, too, the measurement data and camera images are stored synchronously.

Vibration-test

In the vibration test, the batteries are sub-jected to oscillations that occur during vehicle operation to analyze material loads on the sys-tem. A so-called “shaker” generates strong vi-brations, while the test system monitors the condition of the battery pack during charging and discharging.

Life cycle test in a climatic chamber

The life cycle test of a battery pack includes charging and discharging cycles over several weeks to test the performance of a battery. The battery pack is exposed to various de-grees of humidity and temperature profiles in a climatic chamber

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