Ragone chart

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Ragone chart showing energy density vs. power density for various energy-storing devices

A Ragone chart (also called Ragone plot) is a chart used for performance comparison of various energy-storing devices. On such a chart the values of energy density (in W·h/kg) are plotted versus power density (in W/kg). Both axes are logarithmic, which allows comparing performance of very different devices (for example, extremely high and extremely low power).

The Ragone (pronounced "ra-GOH-nee"[1]) chart was first used to compare performance of batteries. However, it is suitable to compare any energy-storing devices,[2] as is shown in the graph on the right. The chart is named after David V. Ragone.[3]

Conceptually, the vertical axis describes how much energy is available, while the horizontal axis shows how quickly that energy can be delivered, otherwise known as power, per unit mass. For example, powering a small light bulb may require low amounts of power, but the power should be delivered steadily enough to operate a flashlight for minutes or hours of use. Conversely, a high-speed electronic switch inside a computer may require very little energy to activate; yet it must be delivered rapidly enough to complete the transaction in mere microseconds. These two types of loads would be represented at opposite corners of the Ragone chart.

\text{Energy density} = \frac{V \times I \times t}m,
\text{Power density} = \frac{V \times I}m,

where V is voltage (V), I electric current (A), t time (s) and m mass (kg).


  1. ^ http://books.nap.edu/openbook.php?record_id=11065&page=81
  2. ^ T. Christen, M.W. Carlen (2000). "Theory of Ragone plots", Journal of Power Sources 91(2), 210–216.
  3. ^ "Review of Battery Systems for Electrically Powered Vehicles", D. V. Ragone, SAE paper 680453, 1968.