ESR750 Li-Ion Depending in model, the on board Li-Ion battery power consist of 2, 3, or 4ea 25.9V Li-ion polymer battery packs wired in series, one or two packs per side within the aluminum battery pan. As the battery packs take up less room than the previous SLA (sealed lead acid) batteries in the ESRex and Hoverboard, further weight and deck thickness is also reduced to create the sleekest, lowest standing height, lightest, highest range electric portable transportation devices in the world. New Improvements for 2008! After several years of very successful service the "Electric Speed Racer" ESR 750 Go-Ped product line has been greatly improved for 2008. Along with an innovative new self adjusting chain tensioner, the heart of the 2008 improvements are from a new, and much more efficient motor. The new ESR motor has the following enhancements; Significantly thicker and much more powerful Rare Earth magnets. Brushes and heat producing components are now better located within the new and better heat transferring aluminum "E Head". All precision sealed ball bearings at each end of the motor shaft replacing previous brass bushings. Commutator/brush drag cut in half. Larger armature copper wire diameter for reduced resistance and unwanted heat. Higher motor RPM operation to improve efficiency. The result is a significantly lower operating temperature resulting in significant ESR range and reliability and brush life increases. The new ESR750H and ESR750EX come now equipped with a new 11/80 sprocket ratio and 108 chain length to take optimum advantage of the new motor for the world's best speed, range and hill climbing ability versus electric vehicle weight.