Under dash Relay box

[97ranger4x4]

Hey my truck died today at school, where I am still at now... The battery is completly dead and after trying to jump start it twice, I had no luck. I am going to have a load test on the battery (its 2.5 yrs old) done tonight. I did notice there was a black box under the dash that was clicking every 3 seconds even without the keys in the ignition. I think this is what might have drained my battery. Also I checked the lights and battery connections. everything was off and tight. battery had no corrosion on it and the alternator was replaced recently. Had no problems with it starting before.

So what is this black box? What does it do. I opened it up and it looked like it has 6 or so small relays.

Thanks,
Keith