Study on the characteristics of lithium batteries with different load

Lead-acid batteries are widely used as backup power source in wireless base stations and as power source in electric vehicles. To determine the lithium battery´s terminal limited discharge voltage and internal resistance with different loads, four 3.2V/60Ah lithium batteries are put in series to form a battery pack in tests. The lithium battery pack terminal voltage, current and overall internal resistance were recorded with the discharge time. By analyzing data from the tests with MATLAB, the lithium battery pack capacity, energy consumed by the load and the internal resistance were determined. The lithium battery pack t-U, t-I, t-ΔU/Δt and t-r₀ graphs are drawn. From the graphs, it is shown that the limited discharge voltage of a single lithium battery is approximately 2.75V, and the internal resistance of a single lithium battery is approximately 0.75mΩ. The lithium battery pack current and the voltage change trends are the same when the load is constant, and the higher the load the less capacity the lithium battery pack can release. The energy consumed by internal resistance to the energy that lithium battery releases is higher as the load increases.