Batteries can greatly increase the portability and practical applications of power tools. "Secondary cell" refers to a rechargeable battery. Nickel-cadmium and lithium-ion batteries designed for use in cordless power tools are secondary cells. Their rechargeable property makes them handy for use in the field where you cannot easily access an electrical outlet. Many consumers employ two rechargeable cells while in the field; they use a backup battery while another recharges, allowing for uninterrupted use of a cordless power tool.
Lithium-ion batteries operate at different efficiencies than nickel-cadmium batteries. In general, nickel-cadmium batteries last longer than lithium-ion batteries. The typical lithium-ion battery lasts for approximately three years, while nickel-cadmium batteries last for around five years. Lithium-ion batteries designed for use in power tools offer around 500 charge/discharge cycles while nickel cadmium portable power tool batteries offer up to 1,000 charge/discharge cycles.
DeWalt manufactures secondary cells engineered for use in their cordless power tools. They make a few models of lithium-ion and nickel-cadmium batteries that are interchangeable. You can use them in any one of several DeWalt cordless power tools. Their "XRP" line of cordless power tool batteries features a lithium-ion and a nickel-cadmium battery. Their "Compact" batteries series also features a lithium-ion as well as a nickel-cadmium cordless power tool battery. Each battery model in both lines of DeWalt cordless power tool batteries is an 18-volt secondary cell. The XRP lithium-ion power tool battery takes approximately an hour to charge and weighs 1.5 pounds The XRP nickel-cadmium battery takes an hour to charge and weighs a hefty 2.4 pounds. DeWalt's Compact lithium-ion battery recharges in around 30 minutes and weighs in at one pound. The nickel cadmium battery in DeWalt's Compact series takes an hour to charge and weighs around 1.7 pounds.
Certain types of batteries are more prone to "memory effect" than others. When you don't periodocally discharge certain batteries, large crystals can form on cell plates. The accumulation of crystals can damage a battery's electrical storage area (memory effect). Lithium-ion cordless power tool batteries are much less likely than nickel-cadmium batteries to be compromised due to memory effect. A nickel-cadmium cordless power tool battery can easily lose storage capacity throughout the life of the cell if you don't regularly discharg it.