While it can vary a lot with usage habits, an energy consumption of 9-10 watt-hrs / km is typical on normal direct-drive setups. When comparing between battery chemistries, one of the most relevant metrics is the Energy Density in watt-hrs / kg. Li-ion is ~110 whrs/kg, and Li-Polymer is up to 160 whrs / kg. Knowing these values makes it easy to project the weight of a pack without having to look up data from the manufacturer. The gravimetric energy density of LiFePO4 battery is 130Wh/kg, four times higher than that of Lead-acid battery, 35Wh/kg.