Excuse the dirt...I've been driving it instead of showing the last few years... I haven't looked inside this battery in years, but recently it's become slow cranking so I took a look. What's going on here? The outer end cells appear to be refillable, while the center cells appear to have a smaller 'case' inside. Do you think I can refill the ends and charge it up, or is this a smaller 'sealed' battery enclosed inside the repro case?