Secondary batteries are rechargeable. The initial cost of these batteries is usually higher than with primary batteries, but they begin to have a significant economic advantage in power-hungry applications that would rapidly consume alkaline batteries.
Secondary Battery Types
The most common type of secondary battery is the lead-acid battery. The lead-acid battery is the oldest type of rechargeable battery, found in most of the world’s automobiles. It is relatively low-cost and reliable, but it has the lowest energy to volume and energy to weight ratio of the major types of secondary batteries. This makes it popular for energy storage applications in which weight and space aren’t a major concern — like backup power for solar photovoltaic systems. But for mobile applications that rely heavily on battery power, the lead-acid battery is being rapidly superseded by newer battery types.
The lithium-ion battery has emerged as the most serious contender for dethroning the lead-acid battery. Lithium-ion batteries are on the other end of the energy density scale from lead-acid batteries. They have the highest energy to volume and energy to weight ratio of the major types of secondary battery. That means you can pack more energy into a smaller space, and the weight will also be lower.
Lithium-ion batteries are still new compared to lead-acid batteries. The knock on them had been cost, but those costs have plummeted over the past decade, and are projected to continue declining.
The other two major types of secondary batteries are nickel-based, and both fall between lead-acid and lithium-ion in terms of energy density. The nickel–cadmium battery (Ni-Cd battery) uses nickel oxide hydroxide and metallic cadmium as electrodes. Ni-Cd batteries are great at maintaining voltage and holding charge when not in use. But these batteries are well-known for “memory” effects that take place when a partially charged battery is recharged. This degrades the capacity of the battery over time.
Ni-Cd batteries were once popular in portable power tools and portable electronic devices. But nickel-metal hydride (Ni-MH) batteries have largely supplanted them in these applications due to lower costs and higher energy density. In addition to having up to three times the capacity of a Ni-Cd battery of the same size, Ni-MH batteries don’t have the “memory” effect of Ni-Cd batteries.
Selecting the Right Battery