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# Long description

This chart shows the energy density of four different types of rechargeable battery. It has a y- axis labelled ‘volumetric energy density’ in watt-hours per litre, with a scale running from zero to 400. A red upward-pointing arrow next to the axis is labelled smaller size. The x- axis is labelled ‘specific energy density’ in watt-hours per kilogram, with a scale running from zero to 250. A red arrow pointing to the right is labelled ‘lighter weight’. There are four coloured shapes indicating the properties of the batteries. A blue circle is labelled ‘Lead acid’. The range of volumetric energy densities is between 30 and 90 watt hours per litre and that for the specific energy density between 20 and 60 watt hours per kilogram. A green ellipse is labelled ‘nickel cadmium’. The range of volumetric energy densities is between 70 and 180 watt hours per litre and that for the specific energy density between 40 and 90 watt hours per kilogram. A blue ellipse is labelled ‘nickel metal hydride’. The range of volumetric energy densities is between 110 and 290 watt hours per litre and that for the specific energy density between 85 and 130 watt hours per kilogram. An orange ellipse is labelled ‘lithium ion’. The range of volumetric energy densities is between 240 and 380 watt hours per litre and that for the specific energy density between 125 and 215 watt hours per kilogram.