OER Parts offers a wide selection of Battery Accessories for your 1977 Mercury Monarch. OER Parts offers 1977 Mercury Monarch Battery Tender, 1977 Mercury Monarch Battery Managment System, 1977 Mercury Monarch Dual Battery System Controller Set, and 1977 Mercury Monarch Battery Relocation Set. Battery Mat Battery Topper Battery Terminal Protectors Battery Post Cleaning Brush Battery Terminal Puller