What it means and how it affects the life cycle

The rated capacity of a battery represents the amount of electrical charge that can be delivered by a fully charged battery. This value is measured under specific temperature and load conditions until a predefined end-of-discharge voltage is reached.

However, some batteries do not immediately reach 100% of their rated capacity. To achieve this full capacity, they must complete several discharge and recharge cycles, a process that allows the internal components to settle. Once this condition is achieved, the battery can offer its full rated capacity for most of its useful life.

The decline in capacity and the end-of-life limit

As the cells age, the capacity of the battery tends to decline gradually until it reaches 80 percent of its initial capacity, which is considered the end-of-life limit. This decline accelerates as the battery nears the end of its use cycle, making its remaining life more difficult to predict.

Within the battery, deterioration is manifested by an increase ininternal impedance. This phenomenon varies depending on the chemistry of the battery. For example, in lead-acid batteries, the increase in impedance is caused by recrystallization of the negative electrode, sulfation, and corrosion of the positive electrode grid.

How internal impedance affects performance

A significant increase in internal impedance occurs before obvious capacitance losses occur. During the early stages of aging, impedance can increase to as much as 25% of the initial value, but the battery still manages to provide nearly100% of capacity.

With an increase in internal impedance between 25% and 50%, deterioration accelerates, causing a decrease in capacity. Exceeding 50%, the battery likely becomes unusable.

Prevent failure with early diagnosis

A battery failure during a grid outage can cause serious problems, especially when relying on it to keep a system running temporarily. Fortunately, such situations can be avoided with regular maintenance and internal impedance monitoring.

Adelsystem's CBIs offer an effective solution. These devices measure the internal impedance of the battery when it is fully charged, thus monitoring the onset of any increases that could lead to a failure. With early diagnosis, the right countermeasures can be taken, ensuring the functionality of the system and preventing unwanted outages.