Engine/Transmission (1998.5 - 2002) Battery tray thingy. What is it?

[HookMeUp]

I changed out my batteries today and noticed under the drivers side battery there was a disk that is spring loaded in the bottom of the tray. What is it?

 

[ThrottleJockey]

Is there a wire attached to it? The battery temp sensor?

 

[HookMeUp]

Yes there is a wire attached. Don't know ...

 

[FourBarR]

it is the battery temp sensor. used by the computer to determine battery charge rate.