Ni-Cd (nickel-cadmium). Ni-Cds offer a fast charging rate and can achieve good longevity, with more than 1,000 charge/discharge cycles. Ni-Cds can suffer from reduced performance if you recharge them before they have been completely discharged. Some Ni-Cd battery chargers include circuitry to discharge Ni-Cds before charging. Ni-Cds require a break-in period. Many manufacturers recommend up to three charge/discharge cycles before the battery will reach optimum performance.
NiMH (nickel-metal hydride). NiMHs are capable of 30 to 40% higher storage capacity than equivalent Ni-Cds, but they support fewer charge/recharge cycles; 300 to 500 charging cycles is the norm. NiMHs do not require a deep discharge before charging, so you can top off a battery before a planned prolonged use. Continually deep discharging a NiMH can shorten its life, although an occasional full discharge will ensure optimal energy storage. NiMHs take longer to charge than equivalent Ni-Cds and can be damaged by overcharging or by charging when the battery is hot. Smart NiMH battery chargers can prevent overcharging and/or charging when a battery’s internal temperature is high.
Li-Ion (Lithium-Ion). Li-Ion batteries provide the highest energy density available, nearly double the energy available from Ni-Cds. They are also low maintenance. They don’t require a deep discharge, they don’t require a break-in period, and they don’t suffer from battery memory. You can charge a Li-Ion at any time without affecting battery performance, but because Li-Ions generally have a charge/discharge life of 300 to 500 cycles, you can shorten a battery’s life by topping it off too often. Most Li-Ion manufacturers expect battery lifetimes of up to three years, however, some consumers report failures in as few as 18 months. Li-Ion Polymer.
Li-Ion Polymer batteries, sometimes referred to as Li-Polys or LiPos, are essentially the same as Li- Ions. The main difference is that Li-Ion Polymers are much thinner, with cell heights as small as 1mm. Li-Ion Polymers are also very lightweight, and more resistant to overcharging and leaking. They are more expensive to produce than Li-Ions, however, and have a lower energy density. Li-Ion Polymers are most often used in lightweight, high-value electronics, such as cell phones.
