As the equivalent circuit of the lead acid is the parallel combination of the Resistance and capacitor. How much is the variation occurs in the impedance (parallel combination of Resistance and capacitor) at room temperature.
Why are you interested in the capacitance? Lead acid battery technology is quite old, and charge-discharge curves abound. These all express the resistive component of the impedance. The U.S. Navy publishes volumes, because of shipboard uses.
Lead acid batteries are well behaved, resistances always positive, over wide changes in currents. Lithium Ion, on the other hand, exhibits instability due to negative resistance under many conditions.
Sir Presently I am working on the SOC measurement of lead acid battery, thats why I am interested in the dynamic parameters of battery.
Rajeev,
The battery is an electrochemical cell which is composed of two metal electrolyte junctions. The anode junction and the cathode junction. These junctions like the p-n junction has a small signal junction resistance and the junction capacitance. In addition, there is in addition the series resistance originated conducting paths resistance including the electrolyte resistance. Investigations showed that he battery capacitance is very large shunting the electrochemical resistance and thereby masking its small signal behavior at the practical measurement frequencies.
Consequently, the cell shows almost resistive behavior because of the series resistance RS dominated by the electrolyte resistance. Investigations on the Lead Acid batteries show that the resistance of the electrolyte depends on the state of charge of the battery and therefore can be used as an indicator of the charge of state of the battery provided that he temperature of the battery is kept constant. So. the curve of the battery resistance versus the state of charge of the battery is unique and therefore can be used as SOC indicator fro a fixed temperature.
For more information follow the link:http://www.arttec.net/Solar_Mower/4_Electrical/Battery%20Charging.pdf
wish you success
Hi Prof. Abdelhalim Zekry,
Thank you very much for this nice explanation and share this article with me. It helps me a lot.
Regards
RC
Technically, the impedance is unique for every cell. Impedance change in cell is most of the time depend on ageing. the effect of impedance during Charging & Discharging can be explained as below :
Impedance imbalances do not cause differences in fully relaxed OCV,
when any effect from current flow is already dissipated. However, they will cause differences in cell voltage during discharge. For steady-state current flow,
cell voltage can be approximated as V = OCV + I * R, where R is the lowfrequency
portion of cell internal impedance. If the current is negative (discharge), the voltage will be lower for a cell with higher R. If the current is positive (charge), the voltage will be higher for a cell with higher R.
Please refer attachment : it is for Lithium Ion battery, but logic still holds good.
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