The Minnesota Streetcar Museum built their own electric speeder a couple decades ago. It uses a motor and controller from a Cushman or a golf cart, several deep-cycle batteries and a welded frame above four speeder wheels. It can travel several miles on a full charge (not sure exactly how long, since the line is only a mile and a half), and reaches speeds around 20 mph. It'll also pull a respectable load of ties, the tower car, volunteers, and/or tools at 15 mph.
We use the electric speeder both because of noise issues (the museum's in an upscale neighborhood), and also because we're used to electric equipment. You probably won't get as long of a range as the equivalent weight gas speeder though, unless you get into funny business with regenerative braking and such.