Lithium polymer is the newest battery type. They have up to four times the battery capacity of nicad batteries, but they are very fragile. They contain lithium which is a metal which ignites on contact with air, so if the battery balloons and the covering pops or the covering of the battery is punctured, it will ignite and explode.
LiPo batteries can be charged at a maximum rate of 1C.
LiPo batteries are very sensitive to overcharging. They should They should NEVER be overcharged, and ALWAYS be charged in a fireproof container and should NEVER be left unattended because they have been known to ignite in some circumstances.
LiPo batteries should not be discharged below 3 volts per cell because they can be damaged by overdischarging. They should not be fully discharged at the end of the day; you should leave some charge in them. Thunder Power recommends long-term storage with about a 40% charge left in the cell; this minimizes cell deterioration and prevents the cell's voltage from dropping too low. They should be stored in a cool place in a fireproof container.
LiPo batteries are fairly fragile. You should avoid dropping them (especially onto concrete or asphalt) because this can cause cell damage. LiPo batteries have beeen damaged in a crash and have spontaneously ignited up to 30 minutes later. Any LiPo batteries which have been in a helicopter that has crashed should be kept in a fireproof container for a few hours for observation.
Do not attempt to charge or discharge a ballooned battery pack. The proper way to dispose of a bad lipo cell is to take a container and fill it with water, then keep adding salt and stirring until no more salt will dissolve (reached saturation). Drop in the cell and leave for at least TWO WEEKS. Also, please search for "lipo disposal" in the RC Groups forums for the latest safety information on this technique.