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How to Calculate Battery Discharge Rate

Almost everywhere you look you can find a wide range of batteries from tiny, coined-shaped ones that power hearing aids to the much larger ones found in your car. Generally speaking, the larger the battery, the higher its capacity and the longer it will take to discharge. How long this will take depends on its current-time rating. This rating is usually marked on the battery or may be found by consulting with the manufacture. The rating is in milliamp-hours or amp-hours depending on the size of the battery. The discharge time depends on both this rating and the load on the battery.

Calculator

Instructions

- 1
  Locate the milliamp-hour rating stamped on the battery and record this value. Let's use an example of 2,500 milliamp-hours (also often shown as "mA hours"). This would be a typical value for a higher quality AA battery.
- 2
  Locate the current rating marked on the device that you will be powering with the battery. You will need to know this value, since the battery discharge rate will depend on how much current is being drawn from the battery. This value will be expressed in amps or milliamps. For the example, we'll use 100 milliamps (also often shown as "mA").
- 3
  Divide the value in Step 1 by the value in Step 2. In this example, this is 2500/100 = 25 hours. Therefore, the battery will power the device, or discharge, for 25 hours.

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