Nickel-metal hydride and lithium polymer batteries are rechargeable, versatile and used for small energy-draining devices. Hearing aids, radios, electronic toys and model planes all require these batteries to work at peak efficiency. Batteries are classified according to the materials used to make them. NiMH and LiPos offer some unique benefits over the other types.
Pros of Nickel-Metal Hydride Batteries
NiMH batteries have a high capacity, up to 11,000 milliampere hours over a specific period of time. Containing no toxic materials, they are environmentally friendly and can be tossed in the garbage when they no longer hold a charge. These batteries are often marketed as rechargeable and can be recharged hundreds of times. When used in a high-energy-usage devices they provide a lot of power from the moment the device is turned on.
Cons of Nickel-Metal Hydride Batteries
These batteries are more expensive than the average alkaline battery. They tend to cut power suddenly when they run out of charge, rather than slowly running down. They also self-discharge quickly. If you leave a NiMH battery sitting in a drawer for a couple of months, it's going to discharge its energy and need recharging before use. Makers of some NiMH batteries also design the batteries so they can only be recharged using the manufacturer's charger.
Pros of Lithium Polymer Batteries
LiPo batteries are much lighter than other batteries. The standard 3.7-volt, single-cell LiPo weighs about 3.2 grams. LiPo's are also sold as rechargeable batteries and can be recharged several hundred to thousands of times, if care is taken to maintain the battery. They also feature high discharge rates, meaning they can provide power to devices requiring a lot of energy within a short period of time. Model plane enthusiasts like LiPos for this reason.
Cons of Lithium Polymer Batteries
While these batteries offer lots of capacity and many recharging cycles, they do have some important drawbacks. All lithium batteries, including LiPos are at risk of exploding or catching fire if overcharged, overheated or damaged. They should never be charged unsupervised. Also, LiPo batteries require special chargers for recharging. LiPos require specific care and maintenance and are thus take more time than the standard battery. Relatively new to the market, LiPo batteries are more expensive than other batteries.