With the BL36 kit, we like to use the formula: 20/20, which means your bike will go 20 mph for 20 miles, but that is under the following conditions: 26" wheel with thin, slick street tires, 150 lb. rider, flat riding terrain, and no stops or starts. In the real world, you will probably get 15 miles per battery pack charge with the standard battery pack, and about 10 miles more (25 miles +) with the extended range battery pack. The BD36 will have 35% less range than the BL36 with the same battery pack: standard pack = about 11 miles; extended range pack = about 19 miles.