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A Comprehensive Approach to FAT and SAT for BESS

The battery energy storage system (BESS) market is booming. Lithium production is expected to increase five times by 20301 and, right now, battery technology is evolving by leaps and bounds. The day-to-day work of BESS project development is revealing, however, that standards and guidelines are falling behind on multiple fronts – safety and performance testing protocols, test timing, and the enforcement of certification requirements.

1Home, A (December 15, 2022). Column: Lithium still super-charged as supply chases after demand. 
Reuters. Lithium still super-charged as supply chases after demand

We at Blanboz believe that, despite their great efforts, standards organizations have not had a chance at keeping up with the development and innovation in this thriving industry. The resultant gap benefits suppliers and vendors, leaving customers without argumentative strength to establish procedures and to propose changes to guarantee safety and performance conformity. All the inherent risks, then, are passed on to the customers.

We have, therefore, partnered with experts from the old oil & gas industry to bring their sector experience of high standardisation into conjunction with our vast experience in the BESS field, while trying to make the most of existing standards to improve safety and to guarantee intended performance. Our partnership has established a comprehensive approach to evaluate and witness factory acceptance tests (FAT) and site acceptance tests (SAT), focused on the battery perspective at cell, module, rack, and system levels. We based our methodology on international standards, predominantly International Electrotechnical Commission (IEC) standards relating to FATs and SATs for BESS. Our approach has been proven to de-risk our customers’ projects in the procurement, construction, and operational stages. This note in our blog series summarises our findings, from the battery-related standard standpoint of view, and we hope that it might support your projects or open discussions.

The rational application of the available standards and the utmost understanding of their content and scope are important. IEC standards are developed at an international level by expert organisations from around the globe. A BS EN designation on a standard means that it has been fully adopted by Europe and the UK. In parallel, Underwriters Laboratories (UL) is a standards-developing organisation fully accredited by the American National Standards Institute (ANSI) and the Standards Council of Canada (SCC), and their standards also function as an important global reference in the BESS industry, particularly for fire safety and testing methodologies in stationary battery applications.

When it comes to BESS testing, applicable standards can be separated into two groups:

  • Performance standards: for evaluating the capabilities and reliability of the system (or subsystems) under particular conditions.
  • Safety standards: for assessing and reducing the common risks and hazards of electrochemical energy storage.

FATs and SATs are a staple of energy projects’ quality plans. They are initially justified by the fact that the client is buying (or installing) equipment, and therefore the system’s original safety and performance parameters must be verified. At the system level, these tests are specifically detailed in the IEC 62933 family of standards which takes into consideration the different types of energy storage systems (ESS) – mechanical, electrical, and electrochemical. Here, we cover the parameters and standards associated with electrochemical batteries.

Standard IEC TS 62933-3-1:2018 is a planning and performance assessment technical specification for ESS. It establishes what kinds of tests are needed to measure compliance with system specifications:

  • From a performance standpoint, BS EN IEC 62933-2-1:2018 and the published document (PD) IEC TS 62933-2-2:2022 are the general specifications for parameter testing for an ESS, including a BESS.
  • From a safety standpoint, FAT and SAT requirements specifically for electrochemical ESS, or BESS, are established in BS EN IEC 62933-5-2:2020, which specifies the test program to be carried out in the installations’ initial life stages. This standard’s scope is equivalent to the combined ANSI/CAN/UL 9540 standard along with the ANSI/CAN/UL 9540A test methodology. BESS manufacturers could certify their products under these three safety standards.
Figure 1 - Safety and performance standards for BESS (system level) testing.

As batteries are the core element of a BESS, its components and electrochemical operating principle are inherently the most hazardous part of the system, and are thus where most of the safety measures should be focused. Standard BS EN IEC 63056:2020 is dedicated specifically to the assessment and testing of lithium batteries for use in a battery storage system. This standard falls under the umbrella of standard BS EN IEC 62619, which addresses the safety of rechargeable lithium cells and batteries for industrial use. Our opinion is that the tests mentioned in BS EN IEC 63056:2020 and BS EN IEC 62619:2022 should be performed for all batteries used in a BESS (or at least a sample as specified in these standards). Additionally, these two standards make a call to the performance standard IEC 62620:2014 regarding marking and capacity testing for the batteries. A battery OEM can certify its products (cells, modules and/or racks) under standards BS EN IEC 63056, 62619 and 62620. We found this combination the best option since most of the tests established look for potential triggers of fire, explosion or other dangerous situations, and these tests are required to be performed at the factory. We strongly recommend that test result reports be made available to the buyer and reviewed by an accredited independent engineer. We can help you with the latter.

It is worth mentioning that the ANSI/CAN/UL 1973 battery safety standard is equivalent to the three IEC battery standards mentioned before. Cells and batteries could also be certified using standard UL 1973. See figure 2 for the test standards available for BESS batteries.

Figure 2 - Safety and performance standards for batteries (cells, modules, and racks) testing.

In broad terms, the course of action for acceptance testing consists of:

  • Type testing: done during manufacture or at the end of the production line of the major BESS components, to assess the standards conformity of representative production samples.
  • FAT: done on complete and/or partially assembled subsystems, prior to their transportation to the site.
  • SAT: done on the complete, installed system after commissioning.

Depending on the complexity of the BESS and other constraints such as manufacturing delays or component unavailability, some tests could be undertaken in either of FAT and SAT, before or after commissioning, and the results included in the installation’s operation manual as complete examination records.

Consequently, we always push for detailed FAT and SAT procedures for the system whilst assessing the batteries, in technical requirements (i.e. in the Employer Requirements or Minimum Functional Specification). We have established comprehensive and versatile FAT and SAT protocols considering the clients’ needs, and the availability and usual constraints of suppliers, along with always emphasizing safety without ignoring performance.
Our core methodology is pragmatically categorised into three levels, as shown in Figure 3:

  • Pink Boundary: The establishment of the need for safety and performance FATs and SATs for BESS, and general guidelines as per the mentioned standards.
  • Purple Boundary: Performance tests for a completely assembled BESS, usually conducted at the point of connection (POC) with the grid. For safety, the system must be evaluated as a whole, but every subsystem that composes it should individually be proven safe. Type tests, specific subsystems´ FAT and functioning tests should be performed for the major components of the system.
  • Orange Boundary: Assessment of the BESS’s primary subsystem, which comprises the batteries and the power conversion system (PCS). If the PCS is not available, the batteries should be tested according to the applicable standards.
Figure 3 - FAT & SAT Logic based on test standards and typical architecture of a BESS.

List of Standards

BS EN IEC 62619:2022. Secondary cells and batteries containing alkaline or other non-acid electrolytes – Safety requirements for secondary lithium cells and batteries for use in industrial applications.

BS EN 62620:2015. Secondary cells and batteries containing alkaline or other non-acid electrolytes – Secondary lithium cells and batteries for use in industrial applications.
(This standard is identical to IEC 62620:2014).

BS EN IEC 63056:2020. Secondary cells and batteries containing alkaline or other non-acid electrolytes - Safety requirements for secondary lithium cells and batteries for use in electrical energy storage systems

IEC TS 62933-3-1:2018. Electrical energy storage (EES) systems - Part 3-1: Planning and performance assessment of electrical energy storage systems - General specification.

BS EN IEC 62933-2-1:2018. Electrical energy storage (EES) systems - Part 2-1: Unit parameters and testing methods - General specification.

PD IEC TS 62933-2-2:2022. Electrical energy storage (EES) systems - Part 2-2: Unit parameters and testing methods - Application and performance testing.

BS EN IEC 62933-5-2:2020. Electrical energy storage (EES) systems - Part 5-2: Safety requirements for grid-integrated EES systems - Electrochemical-based systems.

ANSI/CAN/UL 1973:2022. Batteries For Use in Stationary And Motive Auxiliary Power Applications.

ANSI/CAN/UL 9540 Ed. 1-2016. Energy Storage Systems and Equipment.

ANSI/CAN/UL 9540A Ed. 4-2019. Test Method for Evaluating Thermal Runaway Fire Propagation in Battery Energy Storage Systems.

About the Authors

Tomas Gomez – Guest, Mechanical Engineer with more than 13 years of experience in oil & gas project construction. Eager about my newfound purpose: helping with the transition to clean energy and decarbonizing through quality engineering.

Andres Blanco – Project Consultant | Managing Director at Blanboz, engineer with almost 15 years of experience in the renewable energy field, with the last seven to eight of these years fully dedicated to BESS through the full project life cycle. Electricity for all - Batteries lead the charge. Further information at, if you want to contact me please do so at,