Build an electronic battery simulator: Page 4 of 4

May 18, 2015 //By Jon Munson
Build an electronic battery simulator
Jon Munson considers how to build an electronic battery simulator.
coarse and fine adjust (master adjustment signal MCTL can be connected to several converter sections). For the values shown, the output voltage group coarse is about ±0.9V, the group fine is about ±0.15V, and the cell verniers are about ±0.1V, so collectively the maximum desired range is achieved (in order to provide vernier controls, ability to cross-control cells to the full limits was sacrificed). All the control circuitry is powered by 3.3V derived from the 12V bulk supply. For computerized voltage control, the op amp signals can be replaced with DACs such as the 16-channel LTC2668.

Figure 4. Complete Cell Simulator Schematic

Q101 and T100 are the main flyback elements, with Q102 being the synchronous rectifier. For fast and isolated control of Q102, the gate is driven by T101 via current buffers Q103 and Q104. Feedback is scaled from an auxiliary winding in T100. A 10mΩ series resistor is included at the output so that current sense measurements are possible by taking Kelvin connections to a voltmeter (by use of signals I+ and I-). The total output impedance of the circuit is about 25mΩ and provides a solid ±6A capability. Static losses are about 1 Watt per cell section, so with an array of 24 cells, the likelihood of a 12V supply reversal is minimal and the power level scales well for use with an off-the-shelf 12V/300W supply like the TDK-Lambda SWS300-12.

Conclusion

Building a battery simulator is a practical solution to providing a high density and easily transported BMS development tool. A 24-cell simulator can be packaged in a 2RU rack-mountable chassis complete with a 12V bulk supply, and provide precisely adjustable voltages in the 1.9V to 4.2V range with ±6A capability.

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