Due to increasing automatization in todays and future vehicles, the functional safety of the power supply including the lead battery as the main energy storage is getting increased attention. For the safe determination of the state-of-function of the lead battery, the precise knowledge of aging effects and the resulting failure mechanisms in the field is a prerequisite.
In the present study, more than 200 batteries have been collected so far from the field that either caused or were about to cause vehicle failure. As the study is still in progress, more batteries will follow. A questionnaire is filled in for each battery supplying additional information about its usage. During the inventory, the weight, open circuit voltage and internal 1 kHz resistance are measured. The batteries are then subjected to an extensive multi-stage electrical test for characterization where first the performance of the batteries in their initial condition is evaluated. Subsequently, the batteries are subjected to an operational charge and the performance check is repeated at decreasing state-of-charge until failure. For the purpose of the performance check, a so-called „safe-stop maneuver“ is used, which consists of two current pulses of different length and rate representing a base load and a peak load. This procedure is followed by a full EN charge and a two-week storage period in order to detect possible cell short circuits on the basis of the OCV. Finally, teardown analyses of the batteries are performed to confirm and complete the results of the electrical tests.
This poster offers a detailed overview on the test procedure and on the results of the electrical testing and teardown. The results of this study are further the basis of an in-depth investigation of the ageing behavior of lead batteries, its estimation and the influence on the “safe-stop maneuver” which will be presented in a separate poster (part 2).
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