OER Parts offers a wide selection of Battery Accessories for your 1978 Mercury Cougar. OER Parts offers 1978 Mercury Cougar Battery Tender, 1978 Mercury Cougar Battery Managment System, 1978 Mercury Cougar Dual Battery System Controller Set, and 1978 Mercury Cougar Battery Relocation Set. Battery Mat Battery Topper Battery Terminal Protectors Battery Post Cleaning Brush Battery Terminal Puller