Battery compartment sensor ?

I have a 98 Neon (SOHC w/air). There is some kind of sensor inside the battery compartment, that enters from below the compartment. It is held in place witha larde hex nut. Unfortunately, I broke this sensor while removing the battery compartment, now I need to get a new one, but I don't exactally know what it does, or what it's called. Can someone shed some light for me ?
Thanks !

Its called the 'battery temperature sensor'. If your auto parts place tells you its a dealer item and it turns out to be expensive - you can probably find one at any junkyard having a Neon. Since lead-acid batteries are less efficient in colder weather, the charging system has to charge the battery at a higher rate in winter, and this sensor is what does that.

The sensor on the neon doesn't do anything though, AFAIK.

I just replaced mine because it went bad my check engine light and battery light were on. Auto zone wanted $21 for it I bought it at the dealer for $15. Didn`t have the nut either I just put a zip tie on it to keep it from falling down and banging around.