Will a battery lose its charge sitting in storage?

Depending on the batteries type of plate and grid alloy, batteries will have a self-discharge or internal electrochemical “leakage” of between 1% and 15% per month. This will cause the battery to become sulfated and fully discharged over time. Higher temperatures accelerate this process. A battery stored at 95˚ F (35˚ C) will self discharge twice as fast than one at 75˚ F (23.9˚ C). Discover™ Advanced AGM or Gel batteries will naturally discharge at approximately; 2% per month when stored at 8˚C/46˚F; 3% per month when stored at 20˚C/68˚F; 5% per month when stored at 30˚C/86˚F; 10% per month when stored at 40˚C/104˚F.