Secondary Batteries (Rechargeable batteries) play an important role in our lives and many daily chores would be unthinkable without the ability to recharge an empty battery. In this regard, there are different types of secondary batteries that vary in their specific energy, life, load characteristics, safety, price, self-discharge, maintenance requirements, and disposal. These different types of secondary batteries have been explained below:
Lead Acid Battery — This is one of the oldest & the most well-known rechargeable battery systems. It is rugged and economical in price; has a low specific energy and limited cycle life. Lead acid is used for wheelchairs, golf cars, personnel carriers, emergency lighting and uninterrupted power supply (UPS) systems. The sealed Valve Regulated Lead-Acid (VRLA) Battery is popular in the automotive industry as a replacement for the lead–acid wet cell. The VRLA battery uses an immobilized sulphuric acid electrolyte, reducing the chance of leakage and extending the shelf life.
Nickel-cadmium (NiCd) Battery — This is used in applications which require a long service life. Other characteristics of NiCd batteries include high discharge current, extreme temperatures and economical price. Main applications are power tools, air crafts and UPS systems.
Nickel-metal-hydride (NiMH) Battery — Owing to many environmental concerns, NiCd batteries are being replaced by other types. One of the most practical replacements for NiCd is the NiMH battery. It has higher specific energy that NiCd, with fewer toxic metals. NiMH is used for medical instruments, hybrid cars and industrial applications. NiMH is available in AA and AAA cells for consumer use.
Lithium-ion (Li‑ion) Battery — This is one of the most promising battery systems. It is used for portable consumer products as well as electric power trains for vehicles. Li-ion batteries are more expensive than nickel and lead acid systems, and need protection circuit for safety.
The lithium-ion family is divided into three major battery types, which are named by their cathode oxides – these include cobalt, manganese and phosphate. The characteristics of these Li-ion systems are as follows:
Lithium-ion-cobalt or lithium-cobalt (LiCoO2): This has high specific energy with moderate load capabilities and modest service life. Applications include cell phones, laptops, digital cameras and wearable products.
Lithium-ion-manganese or lithium-manganese (LiMn2O4): This is capable of high charge and discharge currents, but has low specific energy and modest service life. It is mainly used for power tools, medical instruments and electric power trains.
Lithium-ion-phosphate or lithium-phosphate (LiFePO4): This is similar to the lithium-manganese system. It has a nominal voltage of 3.3V/cell, and offers a long cycle life. It has a good safe record but exhibits higher self-discharge than other Li-ion systems.