Finding a cordless impact wrench which fits your needs and has all the right features can be quite complicated. There are so many factors to consider, not the least of which is the type of battery used. There are three different types of batteries which can be used by cordless impact wrenches; nickel-cadmium (NiCad), nickel-metal hydride (NiMH) and Lithium-ion (Li-ion).
NiCad batteries are the oldest of the three batteries and can still be found today in some impact wrenches because they perform well in tough conditions. These batteries are also inexpensive with an impressive life cycle. Nickel-Cadmium batteries are the oldest types of batteries so some of their features and characteristics are old and dated; their capacity tends to be lowest among the other batteries and they also weigh more. These batteries should not be left to drop below 70% between charges; this affects their lifespan negatively. However, they should be drained out completely once every month to prevent the “memory effect”.
In summary, Ni-Cad batteries have a long lifespan (about 1,000 charge cycles) and the acceptable discharge is 15-20%. They have a low capacity of between 1.2Ah – 2.2Ad; they require regular checks and maintenance to avoid the memory effect and they are tough and durable.
Nickel-Metal Hydride Batteries
NiMH batteries spot some improvements over the Ni-Cad batteries. They are cheaper than the Nickel Cadmium batteries and have greater capacity and better energy density. They are also sensitive to storage and charging conditions though they weigh less than the Ni-Cad batteries.
Storing these batteries in unfavorable conditions and temperatures can damage the battery and reduce their lifespan. When left unused for a long time, these batteries are prone to damage. NiMH batteries should also be stored above 70% and a deep discharge should be performed once every three months to eliminate or reduce the risk of the memory effect.
Lithium-ion batteries are the newest and most used among the batteries. These batteries are more expensive than the Ni-Cad and NiMH batteries. They have a higher capacity and can charge more quickly and are the lightest among the three batteries. Lithium-ion batteries do not suffer from memory effect so regular maintenance of discharging is not necessary; proper care of Li-ion battery is equally important. These batteries should not be stored in too hot or too cold conditions and should be store with a 50% charge to improve their output and performance.