VRLA battery capacity estimation using soft computing analysis of the coup de fouet region

Automated battery test system

“…Once the discharge is initiated the discharge voltage of a fully charge VRLA battery will drop abruptly to a trough. A recovery in the voltage occurs, where a plateau voltage is reached, signalling the end of what is known as the coup de fouet [1][2][3][4][5]. Both the negative and positive electrodes contribute to the coup de fouet.…”

“…This is due to the coup de fouet. The abruptness of the coup de fouet is primarily dependent on the discharge rate relative to the size (capacity) of the battery [1][2][3][4]. Therefore the sampling frequency required to acquire the trough voltage is also dependent on the discharge rate as well as the voltage acquisition resolution.…”

“…For the 34901A module, setting the range of the voltage inputs to ±10 V DC (for 2 V cells) and selecting 5 1 2 digit resolution, provides a voltage resolution of 19 lV or 20 bits. The current shunt voltage input range set to ±1 V DC and 5 1 2 digit resolution, provides a voltage resolution of 1.9 lV (again 20 bits) which corresponds to a current resolution of 0.38 mA. For the 34908A module, the voltage range required for the voltage inputs is higher.…”

“…The delay between the scan of each channel is user definable (from 1 ms to 60 s) as well as the delay between each scan (unlimited). The channel scan delay was set to the minimum (1 ms for 5 1 2 digit resolution) and the scan delay was set from 1 s to several minutes depending on the test and the stage of the test.…”

“…Although the VRLA battery is based on well-established technology, there are still many poorly understood mechanisms. An example is the coup de fouet, which occurs at the start of discharge of a fully charged battery [1][2][3][4]. This phenomenon will be described in more detail in a later section.…”