The cylindrical plug of a low-voltage, high current capacity connector assembly has an axially positioned sleeve wiping contact and a transversely positioned U-shaped channel member to provide two pairs of planar wiping contact surfaces parallel to the plug axis and substantially perpendicular to the plug housing surface. The socket component, which will accept standard low-voltage, low current car appliance plugs, includes an internally mounted, closed face pin contact and a barrel contact having depending ears positioned to engage the protruding sides of the plug U-shaped channel member. The socket also has an internal boss and housing lip to prevent electrical activation of a standard automotive cigarette lighter plug, and the plug component of the connector assembly has the sleeve contact recessed to prevent contact following insertion into a conventional cigarette lighter socket. The mobile power tool and appliance operating system includes a portable lead-acid battery pack having a high current capacity socket compatible with existing low current plugs used with appliances intended to operate from automotive cigarette lighter sockets. Matable high current capacity plugs are attached to power tools and appliances through retractable cords. The battery pack is receivable in a 120 VAC powered charging base having a self-contained charging circuit including a transformer and a voltage regulator.