How to Charge a Lipo Battery

By William Adkins

Introduced in 1996, lithium polymer or "lipo" batteries are a variation of the familiar lithium ion battery. The polymer-based design eliminates the metal casing of traditional lithium batteries, making them lightweight and ideal for cell phones, PDAs and similar electronic devices. It is not difficult to charge a lipo battery, but it is vital that you follow steps. Improper charging can cause the batteries to overcharge. This will not only shorten a lipo battery's life, but it is also a serious fire hazard.

Use only battery chargers designed for lithium batteries. When a lipo battery is fully charged, the battery procedures a small but distinctive drop in voltage that tells the charger to shut off. Other types of battery chargers do not have this feature and will overcharge a lithium polymer battery, creating a fire hazard. A good charger will also have a voltage readout and timer as added safety features.

Test the voltage on each cell of a battery pack every 8 to 10 charges. Use a battery voltage tester to check each cell individually. If you charge a lipo battery pack with a cell whose voltage deviates from the others by 0.1 volt or more, the charger may not recognize a full charge and continue charging. This can cause the battery back to ignite or explode.

Put the battery in the charger and turn it on (make sure it's plugged in). Check the readout to see that all cells of a battery pack are charging. You should set the charger to 4.20 volts to fully charge a lipo battery. However, if you set the voltage slightly lower at 4.10 volts this will give you an 80 percent charge and greatly extend the life of the battery.

Allow sufficient time to charge a lipo battery. If it's fully discharged, you may need to charge a lipo battery overnight, but usually 4 to 6 hours is sufficient. Set the timer if the battery charger has one as an added safety precaution. Once the battery is charged, turn the charger off and reinstall the battery in the electronic device it powers.

Charge a lipo battery to 40 percent if you are going to store it. Fully charging lithium batteries without immediately using them shortens their life. They will lose a significant portion of the charge after a few days, so you may want to periodically bring the battery back to 40 percent if you are likely to need it on short notice.