A battery simulator is configured to provide large energy pulses for hot plug testing while maintaining the ability to quickly respond during random order testing. A simulator can comprise a plurality of cell simulators “cellsims” coupled to a DC power supply. Each cellsim can include a bidirectional DC converter, a bulk capacitor on the primary side of the converter, and a switchable discharge capacitor on the secondary side of the converter. The bidirectional DC converter enables the simulator to cooperate with a battery control module (BCM) to perform active cell balancing. Energy received from the BCM can be stored at the bulk capacitor. The discharge capacitor can be coupled to an output link to provide a high energy pulse to the BCM to simulate hot plug conditions, and can be decoupled from the link during random order testing. Output link voltage and current can be monitored for fault detection.