renergize a battery

[robert shreveport]

Can a Battery 5-6 yrs. old from interstate battery company be brought back to a reusable life. It was a 650 cold cranking amp. Looks like the top might have 2 places that could be opened. Have never looked at the electrolyte level. Car is always in a garage and probably once a month charge it at a 2 amp charge until the green light on charger says Fully Charged. Last summer (2013) was when I started having to charge it some. The car is used very little. Have a 1 wire alternator on it and ampmeter always show a plus when running. What battery group should I replace it with. When I bought car 12 yrs. ago the battery in it was held down with battery holder and when I replaced the battery I must have bought the wrong group number because the battery hold-down would not work any longer. Thanks for all replies.