Lead-acid batteries have a low impedance, therefore the ability to deliver high currents. Hence the large, short circuit current specified on battery datasheets, e.g., 2,500A for 12V 80 Ah battery. Typical impedance for a battery in the standby industry:
The resistance of modern lead acid and lithium-ion batteries stays flat through most of the service life. Better electrolyte additives have reduced internal corrosion issues that affect the resistance. This corrosion is also known as parasitic reactions on the electrolyte and electrodes.
Impedance includes resistance and any added opposition to alternating current flow due to factors such as inductance, capacitance and rectification. In most battery applications impedance = resistance, but higher frequency impedance measurements have some utility in pulsed applications and in battery testing.
As many electrical engineering graduates will recall, a lead acid battery is an analog device that is often represented in electrical circuits by resistors, capacitors and inductors. However, the actual behavior and performance of the battery is more complicated and can be misrepresented by such primitive descriptions.
If the internal resistance increases on one of the battery cells this means the battery will supply less current and will probably heat up more than it should. There is a direct connection between the battery internal resistance and the C-rating of the battery pack. Typically the high C-rating batteries have lower internal resistance values.
Factors affecting a battery’s ability to act as an ideal voltage source include: Age of the battery: Older batteries tend to have higher internal resistance. Temperature: Extreme temperatures can affect the internal chemistry, leading to increased resistance. State of charge: A battery’s internal resistance can vary depending on its charge level.