energy storage system

Providing a reliable power option


Energy Storage Systems (ESS) already have a significant role with power grids. They are a backup resource to help manage fluctuations for power grids or provide storage for renewable energy that is later transferred to the power grid. ESS are moving from a supporting role to the main stage for better grid management for many utilities.


Another role for ESS is supporting the growing residential and commercial EV charging stations infrastructure. The fast adoption rate of electric vehicles (EVs) is driving the growth of fast-charging stations that will require not only the power grid to provide power but energy storage systems too. EV charging stations with ESS make charging more cost-effective by drawing energy from the grid during low-demand periods and releasing power to charge EVs during peak-demand periods.


Currently, Europe is leading the way with having the most ESS as part of its power grid infrastructure. North America, China, and India are part of fast-growing markets driven by government incentives for grid expansion, reliance on renewable energy, and the increased demand for EVs, according to a February 2020 MarketsandMarkets Report.


What are Energy Storage Systems?

In simple terms, ESS is the capture of energy produced at one time for use later to help maintain a steady supply of energy. These systems are comprised of internal electronics, AC/DC panels, power inverters, HVAC systems, operating software/hardware, battery modules, thermal management system and a fire suppression system. A typical system fills a standalone metal container and is moved into place to support an operation. The metal containers can be small enough to hang on a garage wall at a personal residence or as large as a shipping container. Multiple storage systems can be linked together and run by a control system to help manage the flow of energy for the grid system or act as a stand-alone system that is powered by solar or wind.


What batteries are the best choice for ESS?

Modern ESS are moving away from traditional lead-acid batteries in the battery modules to alternatives that have a higher energy density, higher power density, increased cycle life, and longer calendar life. As prices have decreased, Lithium-ion battery modules have become an attractive option for use in ESS.


To help you choose the most appropriate Lithium-Ion cells to use to create the battery module for your ESS, the Flex Advanced Battery Systems Team (Battery Team) can help. We have a deep understanding of the types of cells, cell chemistry, application requirements, and in-house performance characterization and aging evaluations that provide the best match for any mechanical and electrical requirements.


Building a reliable ESS

As mentioned above, the list of components for ESS is short, but the success of the system relies on the manufacturing of long-lasting, reliable battery modules. A battery module is a group of identical individual electrochemical cells configured in parallel and subsequently in series to provide desired voltage, capacity, or power density.


There are three choices of cell packaging that are used to create a typical battery module.

  • Cylindrical cell This cell is what most people think of for a battery. Your typical size AA battery is a single cell used in the home, commercial and industrial applications. The cell is created by rolling up sheet-like anodes, separators, and cathodes and packed in cylinder-shaped containers. This battery style is the most popular because they are inexpensive and easy to manufacture. Another benefit of the cylindrical shape is that internal pressure from side reactions can be distributed evenly.

  • Prismatic cell This cell is created by layering the sheet-like anodes, separators, and cathodes into a metallic or hard-plastic housing in a rectangular form. The cell’s design improves space utilization and allows for a flexible design. As industry shifts towards electrification, these cells are incorporated into battery packs for electric vehicles, energy storage systems, and other heavy-duty applications.

  • Pouch cell The cells are packaged in flexible foil for a minimalist approach to packaging; they are lightweight and easy to fit into any available space of a given product. These batteries are used in more applications every day due to their versatility, but they must be handled carefully due to their non-rigid packaging.


Manufacturing long-lasting Lithium-ion battery modules

The module manufacturing process is determined by the type of battery cells used to create the battery modules to meet an application specification. And the best way to manufacture Lithium-ion battery modules is by an automated manufacturing line that relies on a laser welding system.


For example, manufacturing modules using cylindrical cells begins with the scanning and installing individual cells into a rigid cell holder to keep the cells in place. After the cylindrical cells are loaded into the module holders, battery tabs for electrical connection are laid across the top and laser-welded into place. Flex utilizes precision automated laser welding systems to weld the metal tabs across the cells to connect them, which ensures superior repeatability, improves the throughput compared to mechanical spot welding, and reduces the risk of cell puncture.


During the processing on the automated lines, the modules are balanced, have their voltage checked, and are screened for tab resistance after welding. All these quality checks ensure that the module is reliable and fully functional before the remaining electrical and internal components, software, hardware, and metal enclosure are added.


The manufacturing process for prismatic cells and pouch cells is similar. The individual battery cells are scanned and tested before they are stacked on one another or side by side. Once the predetermined number of cells are in place, the endplate and side plates are added to the module and laser-welded into place. Laser welding offers the precision application of the slag material to prevent the welds from becoming too big and altering the final dimensions of the module.


The next step is adding the busbar, a low-resistance metallic bar to connect all the positive and negative ends on the cells, which is again affixed using laser welding. The busbar helps to distribute the power while the module is in use. The slag material must be evenly applied to minimize gaps which can cause a power blow-out or slow energy transfer. The precision of laser welding helps to achieve maximum connection efficiency.


Before the top of the enclosure is installed, the battery module undergoes several tests to ensure it meets all the requirements. Once the module passes all the quality checks, the enclosure top is added, and the completed battery module is passed on to final test.


We have regional manufacturing sites with dedicated battery module automation lines in place with precision laser welding capabilities. These sites already have experience handling and storing battery cells to meet safety and environmental requirements. You can read more about our advanced manufacturing capabilities here.


Tap into our global resources for your next ESS project

After working with you to identify the suitable battery cell for your battery module and completing the manufacturing process, we can help you build out the rest of the ESS. The HVAC controllers, AC/DC panels, inverters, electronic components, thermal management system and metal tamper and environmental proof enclosures can be manufactured in-house or supplied by other Flex manufacturing sites to ensure high-quality components are used for your product. We have access to regional and global vendors to help source fire suppression systems to complete your system. Finally, we have the resources and technical expertise to assemble your system from top to bottom and quality test the entire system before sending it to your customer.


We provide solutions for your ESS

We can help you design and build a new ESS or update your existing systems to meet the growing demand for electrification of industrial applications. The automated manufacturing lines with laser welding capabilities efficiently assemble battery modules for your ESS. Our integrated manufacturing approach brings together components to be assembled at our world-class facilities. The final product moves your ESS from a supporting role to leading role for you and your customers.


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