Site acceptance testing (SAT) is the set of checks that prove a battery energy storage system works as a whole once it has been delivered, installed and connected at its final location. It follows factory acceptance testing, and it is usually the point at which responsibility and payment milestones move from the supplier to the owner. Commissioning is the wider programme around it: the staged energisation of the plant, the tuning of its controls, and the evidence that it can be handed over. This page sits under the Battery Energy Storage Systems hub.
FAT and SAT answer different questions
A factory test shows that a representative system, built and wired in controlled conditions, behaves as specified. It cannot show that the cable terminations were torqued on site, that the earthing grid is continuous, that the site network can carry the control traffic, or that the plant behaves correctly against the real grid. SAT closes that gap. A sensible test plan avoids repeating the whole of FAT, and instead repeats only what transport and installation could have changed, then adds everything that can only be tested on site.
Completion checks before energisation
Nothing is energised until the construction team has signed off the installation. The usual mechanical and electrical checks are:
- Visual and mechanical inspection of enclosures, racks, seals, drainage and transport damage, checked against the as-built drawings.
- Torque verification of power and busbar connections against the supplier’s values, normally marked after checking so a later inspector can see what was done.
- Insulation resistance testing of DC and AC cabling, and polarity checks on every DC string before it is connected to the pack.
- Earthing and bonding continuity across containers, frames and the site earth.
- Cable identification, phase rotation and protection relay settings against the approved design.
These checks matter more for a battery than for most plant, because a DC fault on an energised battery cannot be isolated by opening a switch upstream. The relevant installation standards are listed on the hub page, for example IEC 62485-2 for stationary battery safety.
Integration and control tests
With the plant energised in stages, the focus moves to the control chain. The battery management system, the power conversion system and the energy management system each passed their own tests at the factory, but on site they talk to each other over the real network and to the site controller or operator’s dispatch system. Typical tests confirm that:
- Cell, module and rack data reach the energy management system correctly, including alarms, warnings and trips from the BMS.
- Commands from the dispatch system produce the expected power response, in both directions, with the expected ramp and response times.
- Loss of communication, loss of auxiliary supply and emergency stop all drive the plant to a safe state.
- Limits set by the BMS, such as current and temperature derating, are respected by the converter.
Safety system function tests
Gas detection, smoke and heat detection, ventilation, and fire suppression are functionally tested rather than assumed. The tester triggers each detector or simulates its signal, then confirms the plant isolates, the alarm reaches the monitored panel, the ventilation or suppression responds as designed, and the local authority’s or insurer’s witnessing requirements are met. The reasons behind these systems are explained in Failures and Fires in BESS Systems and the large-scale test method in UL 9540A.
Performance tests that set the baseline
The capacity test and the round-trip efficiency test are the two most commercially important results of commissioning. A full charge and discharge at an agreed power measures usable energy, and the ratio of energy out to energy in gives the round-trip efficiency. Two details are routinely argued over: where the energy is metered (DC side at the battery, or AC side at the point of connection, which includes converter and auxiliary losses) and the temperature and starting state of charge during the test. Agreeing these in the contract before the test avoids disputes.
The result becomes the reference against which degradation and warranty claims are measured later, so it is worth recording the conditions in full. The link between test conditions and long-term performance is covered in BESS Ageing vs Duty Cycle.
Grid compliance tests
The network operator may witness tests that show the plant meets its connection agreement: power and reactive power capability, response to frequency and voltage disturbances, and protection operation. What these tests are checking, and why, is covered in the page on grid connection requirements for BESS. Testing guidance for storage commissioning is also set out in IEEE 2030.2.1 and IEC 62933-2-1.[1]
Handover documentation
A commissioning package normally includes the signed test records, the final protection and control settings, the as-built drawings, software and firmware versions, the alarm and trip list, the baseline capacity and efficiency results, and the operation and maintenance manuals. The software versions are easy to forget and matter, because a later firmware change can alter safety and control behaviour.
References
- BESS Commissioning Guide: Steps for Safe and Reliable Deployment, Sinovoltaics. Industry overview of commissioning stages; the project specification and the standards above take precedence.
See also: BESS Testing, BESS Factory Acceptance Testing, The Battery as an Asset