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I went away for a long weekend and when I returned, my car battery was completely dead. No lights, no crank, nothing. I had to call for roadside assistance to get a jump start. This isn't the first time this has happened after leaving the car unused for a few days. I'm now determined to figure out how to stop this from happening again and have been researching preventing battery drain issues specific to our climate. I found a guide that explains how heat can increase self discharge and how modern cars with always on electronics can slowly drain a battery even when parked. It also suggested checking for parasitic draws and considering a battery maintainer if the car sits unused often. My question is, how can I tell if my battery is just old and weak, or if there's actually something in the car draining it? I don't want to buy a new battery only to have the same problem. Any advice on diagnosing parasitic drain would be really appreciated.