Study about lithium battery´s characteristics

To make certain the lithium battery´s terminal limited discharge voltage and internal resistance in different load, four 3.2 V/60Ah lithium batteries are put in series to form battery pack in tests. The lithium battery pack terminal voltage, current and overall internal resistance were recorded with the discharge time. By analyze datas from the tests with MATLAB, the lithium battery pack capacity, energy consumed by the load and internal resistance are figured out, lithium battery pack t-U, t-I, t-ΔU/Δt and t-r₀ graphs are drawn. From the graphs, we can draw that the limited discharge voltage of a single lithium battery is about 2.75 V, the internal resistance of a single lithium battery is about 0.75 mΩ, the lithium battery pack current and the voltage change trends are the same when the load keeps changeless, the higher load the less capacity lithium battery pack can release, the energy comsumed by internal resistance to the energy that lithium battery release is higher as the load increase. All the conclutions can do good to develop battery management system.