A high-voltage battery pack for an onsite power generation system includes battery modules configured to provide a voltage of at least 170V. High-speed switches and a high-speed current detection circuit are serially coupled between the battery modules and the positive and negative output terminals of the battery pack. A control circuit is operatively coupled to the current detection circuit so that when the current detection circuit detects a fault condition, the control circuit opens one or more of the switches to thereby electrically isolate the battery modules from the positive and negative output terminals of the battery pack. The battery pack is configured so that the at least 170V provided by the battery modules can be provided to an AC stage of the onsite power generation system without an intervening DC/DC converter and/or a transformer.