Battery Cycling and Endurance Testing.
Most testing of cells and batteries takes place at low currents relative to the capacity of the battery (the ‘C’ rate), and consists of simple full charges followed by a full discharge. Whilst that may be ok for aging the battery / cell, it tells little about how it will perform in actual operation, be that grid connected or in an electric or hybrid electric vehicle. At the University of Sheffield we use our extensive test facilities to subject cells, modules and batteries to test batteries on cycles taken from actual vehicles and grid support operations to assess performance in real-world situations.
A number of battery currents have been acquired from actual vehicles and applications, and these can be scaled to the capacity of the cell / module / battery under test. As can be seen in the figures, the actual battery current and voltage can then be recorded on test, either as single cycles, or on continuous runs to perform endurance testing. Cells / batteries are housed in thermally controlled chambers whilst the tests run to characterise the devices under known conditions. Information on state of charge (SoC), internal impedance and battery health can be obtained from the devices under test.
Test are usually cell chemistry agnostic, with tests being carried out to date on Lithium, Nickel and Lead based chemistries, simulating tests of single driving cycles, to 100,000 mile endurance testing on battery packs.