What you need is a battery maintainer like the one I use is called the Battery Tender by Deltran it comes with a connector you attach to your battery then route the cable outside where it is convenient to connect to the charger without opening your covers or maintenance ports, it is dummy proof hookup and only connects one way so you cant get polarity wrong, I use mine on my motorcycles and it has more than doubled their life because the battery is always at peak charge when I go to start my cycles, it prevents self discharge from just sitting or temperature or drain conditions. You can get them at batttery warehouse type stores, motorcycle parts places and dealers, mail order, or possibly directly from Deltran in I believe Florida. Mind had a 5 year warranty with no troubles.