So you are saying the battery isn’t what is subject to damage but rather electrical components in the vehicle? Would that be just a computer or other sensitive electrical components? Or all?
I have to keep the batt. cables off on the ‘59 as it is. Got an electrical leak somewhere I haven’t been able to trace.
No, I think that as you said the battery should be okay but when a battery is still connected to the car body it’s part of a circuit. I suspect that might result in a momentary surge being applied to a battery during an EMF, Potentially damaging the battery. But disconnecting a battery, or even having a spare sitting around, should nullify any such danger.
Aside: imagine the shock to Americans having to live without smart phones for even an hour?