My car started right up today
 

I store my car in the garage for the winter months. Usually I leave the battery in the car all winter but I disconnect the cable from the negative terminal. In the past, the car has always needed to be jumped to get it started in the spring but this year I just reconnected the negative side and it fired right up without any jumper cables needed. This is the first year that I have disconnected the negative side. In the other years I've left everything attached. Could not having the negative side attached kept the battery from dying over the winter?

Yes, it can prevent battery drain.

I detach my 03 elantras in between me running it to keep it alive. If I dont it sometimes needs a jump.

I always take the battery completely out in mine and keep it on a shelf next to my workbench in the basement all winter. :) Never had to jump the car after I put it back in in the spring.

There is parasitic loss as well as things like the ECU, radio, and clock that use the battery full time. There may be more items.