Slow draining battery on Subaru Forester 2005

[RonC6]

Yea, my problem was I left it on for a few months (forgot about it over winter) and it ran out of electrolyte .. and then whole garage smelled like rotten eggs. I believe it was on the 2 amp setting.

 

[Dick Foster]

As with almost anything, you want to get a tool designed for the purpose. Clearly the charger you used was okay for topping a battery up, say overnight but it wasn't a tender or maintenance charger.
There are a lot of batteries used in applications that see infrequent or seasonal use so naturally there are chargers designed for those applications. Boats etc. They all are programmed to top up then shut down so are safe to leave connected for extended periods of time.
Some even do preventative maintenance like occasionally checking for and desulfacaing the battery by applying rapid pulses which helps break down the sulfer crystals that coat the battery's anode plates.
The leading cause of battery failure is sulfication. The rotten egg smell is from the sulfer and sulfuric acid used in car batteries. As the coating builds up, the battery's internal resistance increases, which then decreases the current the battery can supply. It gets worse and worse until it eventually reaches the point of not having enough capacity to start the car.

 

[bmay10]

My 2005 Forester's battery drains slowly over several weeks. I put a slow charger on it to recharge, but it continues to slowly drain its charge. I read that the car has certain electrical functions with its computer that continue working even while not running. However my 2010 Forester doesn't have this same problem, so I suspect there is some short somewhere in the system that is causing a greater drain on the battery's charge. Any suggestions on how to diagnose this issue or how to locate a short?

You also might want to be sure the auto off is not ever turned on. I had to call roadside assisance becasue of this auto off button. Mine was same senerio wasnt driven much which the alternator did not run enough over time to charge battery fully. I bought a device that now leaves the auto off switch where I put it either on or off and stays that way when restarting

 

[Dick Foster]

You also might want to be sure the auto off is not ever turned on. I had to call roadside assisance becasue of this auto off button. Mine was same senerio wasnt driven much which the alternator did not run enough over time to charge battery fully. I bought a device that now leaves the auto off switch where I put it either on or off and stays that way when restarting

Autostopeliminator is a very good thing, not only for cars but for thier owners too. Auto stop is hard on batteries, engines and people.