Sounds like you need to clean your battery connections! replace the battery cables and clean the battery terminals and that should do it. Consider an Optima or some kind of gel cell gas recombinant battery to eliminate this problem all together. I used to fight this same problem until I switched to the Optima. I have never had the problem again, and the Optima has been there for 5+ years. They really are great batteries.
'85 CJ-7, fuelie '73 401, NV 4500, Atlas III 4.3, 14 bolt FF rear, Dana 60 front, full width axles, Detroits F&R, 4 wheel discs, spring over front, coils and reverse 4link rear, 100 in wheelbase, 42 inch Swampers on hummer beadlocks.