Mixed switched mode and linear Lithium Ion battery tester for high power and large bandwidth

Next generations of Li-Ion-Cells for Hybrid and Electric vehicles must be characterized under real operating conditions and with high precision before they start into production. A new cell-tester allows flexible test conditions with arbitrary current waveforms up to 250A and minimum rise time of less than 5μs. It consists of a switched mode current source in the charging direction and an extreme fast linear current sink. Current profiles identical to real inverters and DC-DC-converters as used in future automobiles can be generated. The linear current sink consists of 5 identical voltage to current converters in parallel. They show high bandwidth and high stability as well as low offset and high linearity. The performance precision was reached by several servo loops. A larger number of safety functions are implemented to protect the battery and the circuit.