Batmobile has a proximity alarm and can power generators.

Setting the proximity alarm to alert him to unexpected intruders, he ran charge wires from the Batmobile’s engine to a small generator. It, in turn, was attached to a single, unimposing antenna hidden among the rest.

He set the Batmobile to neutral, then gunned its engine. Moments later the generator hummed with power. Shortly thereafter he reported his progress.