Car batteries are not a problem, they do have internal resistance. Now take a wet cell NiCd cell, internal resistance tends to approach zero, for almost all currents and at almost any state of charge. Now add to this the demand of a jet starter motor/generator, which can both source and sink 8kA for around a minute without failure, and consider that the charge circuit is not temperature compensated, and the battery does have a negative temperature coefficient. That is why jet aircraft have a single very strict limitation of no more than 2 start attempts before removing battery and replacing, they do tend to go thermonuclear. Not good when you are sitting on top of it, and right next to it is a evaporating coil for the airconditioning, fed conveniently with LOX from the cryotank next to it, and used to give the pilot both oxygen and pressurise his g suit.