The Method to Charge a Lithium Polymer Battery

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The Method to Charge a Lithium Polymer Battery
Lithium polymer batteries must be properlychargedto prevent dangerous overcharges. (battery image by Sergey Juchkov from

Lithium polymer batteries are an adaptation of the familiar lithium-ion batteries used in laptop computers and other devices. However, "lipo" batteries, as they are often called, are encased in a flexible polymer casing, making them lighter and suitable for use in small devices like cellphones. It's critical to use the proper method to charge a lithium polymer battery, since overcharging can cause a fire or even an explosion.

Skill level:
Moderately Easy

Things you need

  • Lithium-ion battery charger

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  1. 1

    Purchase a battery charger specifically designed for lithium-ion batteries. Whether it's a regular or a polymer type, a lithium battery has a characteristic voltage drop when it reaches full charge. Lithium battery chargers have a sensor built in that detects this voltage drop and terminates the charging process, preventing a dangerous overcharge. You can purchase lithium battery chargers starting at about £13 at most electronics stores (price as of 2010).

  2. 2

    Remove the lithium polymer battery from its device and place it in the charger with the charger turned off. Follow the manufacturer's directions to connect the battery to the charger.

  3. 3

    Set the charging voltage. Most lipo batteries should be charged at slightly over 4 volts (check your battery specifications to make sure). A 4.2-volt setting will give you a 100 per cent charge. Do not set the voltage above the recommended maximum as this can result in an overcharge. Using a 4.1-volt setting produces an 80 per cent charge, but will lengthen the useful life of the battery if done a regular basis.

  4. 4

    Turn the charger on and allow the battery to charge. This usually takes two to four hours, depending on the battery and how much it is depleted. When charging is complete, turn the charger off and return the battery to the device it powers.

  5. 5

    Use the device immediately if you've chosen to bring the battery to full 100 per cent capacity. Leaving a fully charged lithium technology battery unused will shorten battery life.

Tips and warnings

  • Lipo batteries have an internal sensor that measures the amount of stored energy available. However, this sensor becomes inaccurate over time. About once a month, use the battery until it is completely discharged and then charge it to 100 per cent capacity. This resets the internal sensor. The device using the battery will then get correct data and provide you with an accurate estimate of remaining charge, thereby avoiding unexpected shutdowns.
  • If you need to store a lipo battery for long periods, charge or discharge it to 40 per cent capacity. This will prevent stored batteries from degrading and will maximise their useful life.

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