# How Many AA Batteries Would to Take to Power a Human?

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So, how many AA batteries would it take to power a standard adult human for one day?

A Manganese/Alkaline AA cell it rated at about 2.4 amp-hours. If we assume 1.5 volts average this gives approximately 3.6 watt-hours (slightly optimistic). Since there are 3,600 seconds in an hour this is equivalent to 12,960 Joules.

A human consumes about 2,000 calories/day. A dietician calorie is equal to 1,000 engineering calories. A calorie is equal to 4.2 Joules. Therefore this is equivalent to 2,000 * 1,000 * 4.2 = 8.4 * 106 Joules per day.

Dividing one by the other you will need about 648 AA cells to power a human for one day.

This assumes that the power from the AA cell will go through the same inefficiencies as the chemical processes in a human. (A human runs at about 20% efficiency chemical energy to mechanical energy). If we can circumvent this inefficiency we would only need 20% of this number of cells - say 130 cells.

---From: Ben Gebeau

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