What are the critical components of a battery energy storage system?

In more detail, let’s look at the critical components of a battery energy storage system (BESS). The battery is a crucial component within the BESS; it stores the energy ready to be dispatched when needed. A battery contains lithium cells arranged in series and parallel to form modules, which stack into racks.

Can a lithium ion battery pack have multiple strings?

Whenever possible, using a single string of lithium cells is usually the preferred configuration for a lithium ion battery pack as it is the lowest cost and simplest. However, sometimes it may be necessary to use multiple strings of cells. Here are a few reasons that parallel strings may be necessary:

What is a battery energy storage system?

For this guide, we focus on lithium-based systems, which dominate over 90% of the market. In more detail, let’s look at the critical components of a battery energy storage system (BESS). The battery is a crucial component within the BESS; it stores the energy ready to be dispatched when needed.

Why is a single string battery set-up important?

A single weak or bad cell can exponentially lower the capacity of the entire battery pack. A properly engineered system can improve the overall reliability, but only when additional equipment and significant engineering time is invested. Whenever possible, a single string set-up should be considered.

Why does a battery pack have a different state of charge?

Additionally, because no two cells are exactly the same, different currents will flow through each battery pack due to differing internal resistances, creating difference in state of charge between the two strings.

How does a battery charger work?

This approach uses one battery charger per string. The BMS in each string directly controls the charger for that string, meaning that the charge can be controlled very precisely. Since the charging is handled and controlled by the charger on each string, each battery pack is only responsible for providing discharge current to the common DC bus.