Cell

What sucks about our cars is that when water runs down the front windshield and onto where the panels meet the edge of the windshield, it seeps down and through the back of the battery area and into the bottom. That is where you see the rust and mineral build up in that photo. So if the Z was driven in the winter, chances are you will find the same build up in that spot.

This is also the same reason why using the grommet where all the wires enter the cabin as a way to hook up gauges are a bad idea. The grommet will be worthless and leak water into the cabin unless it is sealed off again with some sort of sealant.