A vehicle having a traction battery disposed within a battery housing is provided. The battery housing is in selective fluid communication with the cabin of the vehicle. An accessory battery separate and distinct from the traction battery is also provided. A closeable barrier system is electrically connected with the accessory battery and is configured to fluidly isolate the battery housing from the cabin when closed. At least one controller is configured to, in response to a trigger condition, disable the traction battery and increase an output of the accessory battery to close the barrier system to isolate gas in the battery housing from the cabin.