The capacity of a battery is the product of the current that may be drawn from it and the time for it to be exhausted. For example, a 60A.hr car battery may deliver a current of 5A for 12 hours, or 120A for 30 minutes. The purpose of this laboratory exercise to measure the specific maximum power of a variety of different batteries and to determine their energy densities. Consider a series circuit consisting on a battery of electromotive force E and internal resistance r connected to a meter of resistance R m and a resistor R as shown below. If a value of the internal resistance of the ammeter R m is known, a value of the internal resistance of the battery r may be determined.
Procedure Measure the dimensions and weight of each battery and make up a table of data.
Look up values of the energy of your batteries , or values of E, I, and t to become exhausted, and determine their energy densities. Typical values of energy are 500J in a general purpose AA battery, 75kJ in an alkaline D battery, and 4MJ in a car battery. To read about the new nickel-metal hydride and lithium batteries, go here , and batteries for electric cars go here .