4.6.1 Internal Series Resistance
The internal series resistance of a battery determines the maximum discharge current of the battery. Consequently, for applications in which the batteries are required to provide high instantaneous power, the internal series resistance should be low. In addition, the series resistance will affect the battery's efficiency but may change as the battery ages.
Self-discharge refers to the fact that even in the absence of a connected load, the discharge reaction will proceed to a limited extent and the battery will therefore discharge itself over time. The rate of self-discharge depends primarily on the materials involved in the chemical reaction (i.e., the type of battery system) and on the temperature of the battery.
4.6.3 Cold Cranking Current
The maximum amount of current a battery can provide for a short period of time is called the cranking current. This parameter is often specified for transport applications, in which the battery must provide enough current to start a large engine. However, it is typically not an important parameter in PV systems.