How to Determine Charge Time for Rechargeable Batteries

Written by maxwell payne
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Rechargeable batteries are a type of battery that can be reused over and over again. These batteries store power provided by an external power supply and then use that stored energy to power the device when it is not connected to external power. Examples of devices that use rechargeable batteries include laptop computers, MP3 players, cell phones and cameras. The type of battery and its size, power output and charger can affect how long it takes to fully charge. There are two ways to determine charge time.

Skill level:
Moderately Easy

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Things you need

  • Stopwatch or timer
  • Internet access

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    Determine Charge Time by Using Battery Information

  1. 1

    Remove the battery from the device and look for the following information printed on the battery: battery size (such as AAA or D) if one is listed, type of battery (NiCd or NiMH), and the mAh number (such as 2400).

  2. 2

    Visit the website available in the Resources section of this article, which provides a calculator for finding out the recharge time for various batteries.

  3. 3

    Enter the mAh number in the top text box next to "mAh." If the mAh number on your battery has a decimal point, enter the numbers after the decimal point in the text box labelled "precision." Select your battery type from the left-hand side menu.

  4. 4

    Look at the battery charger and find the charger output (ma) rate. Select the matching rate from the right-hand side menu on the calculation website. After checking off this selection, you will see the amount of time it takes to fully charge the battery. This information is found in the top section of the calculator in blue text.

    Determine Charge Time Manually

  1. 1

    Disconnect the device's power supply or charger and use the device until the battery is nearly drained. This method of determining charge time is useful for devices that use battery technology such as lithium ion batteries.

  2. 2

    Reconnect the power supply or charger to the device. Keep the device on so that you can see when the battery is fully charged.

  3. 3

    Start the timer or stopwatch as soon as you reconnect the charger. Keep an eye on the device to watch for the status light or fully charged icon to appear.

  4. 4

    Stop the timer or stopwatch as soon as you see the status light change or the fully charged icon appear. The time displayed is the amount of time it took for the battery to be recharged.

Tips and warnings

  • Never try to use a higher-powered charger or a charger different than the one rated to work with the specific device. This can cause damage to the device or can be a fire hazard.

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