Certifications

What UL 1973 is for

UL 1973 is the standard an authority having jurisdiction in the United States or Canada will name when they ask whether a stationary battery is safe to install inside a building. It is a safety standard: it says nothing about how much energy the product delivers or how long it lasts.

The testing works at three levels. At cell level it applies electrical abuse (overcharge, forced discharge, short circuit), thermal abuse and mechanical abuse (impact, crush, drop), then looks at whether the cell vents, ruptures or ignites. At module level it repeats a subset of those tests on the assembled pack. At system level it reviews the enclosure, the wiring, the protective functions of the battery management system, and — since the 2022 revision — the behaviour of the system when a single cell fails.

What it means for a buyer

• Insurability. Commercial insurers increasingly ask for the UL 1973 listing before they will accept a battery inside an occupied building. Without it, the installation may be technically compliant and still uninsurable.
• Permitting. The fire code pathway in most US jurisdictions references UL 1973 or UL 9540. A product without it turns a straightforward permit into a variance application.
• A real BMS specification. The listing forces the manufacturer to document the over-voltage, under-voltage, over-current and over-temperature thresholds and to prove they operate. That documentation is what makes a warranty claim auditable later.

What it does not cover

UL 1973 alone does not qualify a complete energy storage system for installation. That is the job of UL 9540, which takes the UL 1973 listed battery and evaluates it together with the converter and the system controls.

How we apply it

Our rack-mounted lithium modules are listed to UL 1973 at cell, module and system level. The listing file, the test reports and the BMS safety function documentation are issued with the quotation rather than held back until after the order, because the permit application usually runs in parallel with the procurement.

Certificate numbers are specific to the certification body and the manufacture site, and are provided in the compliance pack accompanying each shipment.

The difference between UL 1973 and UL 9540

UL 1973 certifies a battery. UL 9540 certifies a system.

That distinction matters in practice because a UL 1973 listed battery wired to an inverter that is not evaluated with it is not a listed energy storage system, and a permit reviewer can reject it on exactly that basis. UL 9540 evaluates the assembly: the battery, the converter, the controls, the enclosure, the wiring methods and the interaction between them.

What the evaluation adds

• Component compatibility. The converter’s charge profile has to be shown to stay inside the battery’s published operating window, including under fault conditions.
• Enclosure and separation. Clearances, ventilation and the physical separation between the battery and the electronics are assessed against the installation location — indoor, outdoor, or in a dedicated room.
• Control interface safety. The communication link between the battery management system and the converter is treated as a safety-relevant interface, not a convenience data feed.
• Thermal runaway propagation. The system evaluation references UL 9540A test results for the specific cell and pack configuration, which is where many projects without documentation stall.

Why the listing usually decides the project schedule

UL 9540 is the document the fire marshal asks for. A system without it can still be installed in some jurisdictions, but it is treated as an engineered installation requiring local analysis — which typically adds weeks or months to the approval and can require additional fire suppression.

Sourcing a UL 1973 battery and a separately listed inverter does not produce a UL 9540 system. The combination has to be evaluated together, which is why we quote the battery and the converter as a matched pair rather than as two independent line items.

How we apply it

Our hybrid converter and rack-mounted lithium modules are offered as a UL 9540 evaluated combination. The system listing document, the UL 9540A test summary for the cell and pack configuration, and the installation separation requirements are issued with the quotation.

Where a customer wants to integrate our converter with a third-party battery, we supply the converter’s own documentation set and confirm in writing which system-level evaluations remain the integrator’s responsibility.

What changed with the SB supplement

UL 1741 has been the inverter safety standard in North America for decades. The SB (Supplement B) edition is the one that matters now: it adds certification against the grid support functions defined in IEEE 1547-2018.

The older edition effectively certified an inverter that would shut down when the grid misbehaved. The SB edition certifies an inverter that is expected to help — injecting or absorbing reactive power to hold voltage, curtailing active power as frequency rises, and riding through a disturbance instead of tripping offline.

What it means in practice

• Interconnection approval. Most US utilities now reference UL 1741 SB and IEEE 1547-2018 in the interconnection agreement. Equipment listed only to the earlier edition is frequently refused, or approved with conditions that shift risk onto the site owner.
• Certified default settings. The standard defines default volt-var and frequency-watt curves, and requires the equipment to implement them without a custom firmware build for each utility.
• Ride-through capability. Instead of a blanket trip, the inverter rides through a defined voltage and frequency envelope, which matters on weak feeders where a nuisance trip takes down a whole site.
• Rapid shutdown. The requirement for a readily accessible rapid shutdown device on the PV side is part of the same listing family and is enforced at inspection.

Where it overlaps with IEC frameworks

A product designed only for the European market will typically hold IEC 62109 and an EN 50549-1 declaration, which does not satisfy a US utility interconnection review. The reverse is also true. Exporting equipment between the two regimes means holding both, which is why our converter carries UL 1741 SB alongside the IEC and EN documentation.

How we apply it

Our bidirectional power conversion system is listed to UL 1741 SB with grid support functions implemented across volt-var, volt-watt, frequency-watt and configurable ride-through. The type test certificates and the certified default settings are issued with the quotation so the interconnection application can be filed without waiting for the hardware.

Factory configuration against a specific utility’s characteristic curve is performed before dispatch, and the settings record ships with the unit.

Where it sits in the international framework

IEC 62619 is the standard that a European, Middle Eastern, African or Asia-Pacific regulator will typically name for an industrial lithium battery. It is written for industrial applications — stationary storage, forklifts, mining equipment, marine — as opposed to the consumer-oriented IEC 62133 series.

The structure is familiar to anyone who knows UL 1973: cell-level abuse testing, module-level repetition, and a system-level review of the battery management system’s protective functions. The two standards are close enough in intent that many manufacturers test once and submit to both, but they are not interchangeable and a listing under one does not satisfy the other.

The tests that matter commercially

• Overcharge. Confirms the cell vents or shuts down rather than ignites when the charger misbehaves — the failure mode that causes most stationary storage incidents.
• Internal short circuit and thermal abuse. Establishes how a single failing cell behaves and, with the BMS, whether the failure stays contained.
• Over-discharge protection. Often underestimated. A deeply discharged LFP cell that is then recharged is a fire risk, which is why the BMS cutoff has to be proven rather than assumed.
• BMS functional safety. The protection thresholds and the logic that acts on them are reviewed as a safety function, not as a feature.

What it does not do

IEC 62619 does not cover transport. A battery can hold a valid IEC 62619 certificate and still be illegal to ship without a UN 38.3 test summary. It also does not cover the complete system — that is IEC 62933 for grid-connected electrical energy storage systems.

How we apply it

Our lithium modules are tested to IEC 62619 at cell, module and system level. The test report, the certificate and the BMS protection threshold documentation are issued with the quotation alongside the UL 1973 listing, because a project that ships between North America and the IEC markets frequently needs both in the same tender pack.

Where a customer’s regulator requests a specific accredited body, we will confirm the issuing laboratory’s accreditation scope before the test programme starts rather than after.

What it covers, and what it does not

IEC 62477-1 is a horizontal standard: it defines the safety requirements for power electronic converter systems generally, without reference to what the converter is doing. Solar inverter, battery inverter, motor drive, DC converter — the hazard analysis is the same.

That is also its limitation. A converter that holds IEC 62477-1 is safe as a piece of equipment, but the standard says nothing about grid interaction. That is IEC 62109 for PV-connected converters, EN 50549-1 for connection to European low-voltage networks, and the UL 1741 family in North America.

The hazards it actually addresses

• Electric shock. Insulation coordination, creepage and clearance distances, protective earthing continuity, and the touch-current limits for accessible metalwork in normal and single-fault conditions.
• Energy hazards. Stored energy in DC link capacitors, which is why a converter carries a discharge time and a warning label that an installer is legally obliged to respect.
• Thermal and fire hazards. Temperature limits on components and enclosure surfaces, and the assessment of what happens if a semiconductor fails short.
• Mechanical hazards. Enclosure strength, lifting provisions for heavy units, and stability for floor-mounted equipment.

Why a buyer should ask for it specifically

Tenders frequently list “IEC certified” without naming a standard. A converter can be certified to a narrow component standard and still lack a system-level safety assessment.

Asking for IEC 62477-1 by name establishes that the equipment as supplied — not a subassembly — has been evaluated for the electrical, thermal and mechanical hazards an installer and an operator will actually be exposed to. It also makes the required installation clearances and earthing arrangements a documented deliverable rather than a judgement call on site.

How we apply it

Our power conversion equipment is evaluated to IEC 62477-1 in addition to the application-specific standards it carries. The certificate, the clearance and creepage documentation, and the installation instructions required by the standard are issued with the quotation and repeated in the manual shipped with the unit.

Where a project specifies an IEC 62477-1 evaluation by a particular accredited body, we confirm the laboratory’s accreditation scope before the test programme is committed.

What CE marking actually is

CE marking is not a certificate and it is not issued by the European Commission. It is a self-declaration by the manufacturer that the product meets every directive that applies to it, backed by a technical file and, where the directive requires it, by a notified body assessment.

The legal weight sits in the declaration of conformity — a signed document naming the manufacturer, the product, the directives applied and the standards used. Signing it accepts liability. That is why the document, not the logo on the nameplate, is what a European buyer should ask for.

Which directives apply depends on the product

Product type	Directives typically in scope
Electronic converter, 50–1 000 V AC	LVD, EMC, RoHS, REACH
Hydraulic pump on a machine	Machinery Directive, RoHS, REACH
Hazardous-area transmitter	ATEX, EMC, RoHS, REACH
Battery module	EMC, RoHS, REACH, battery and transport regulation

A single product can sit under three or four directives at once, and the declaration has to name all of them. A declaration that lists only the EMC Directive for a mains-powered converter is incomplete, and a procurement audit will find that.

The technical file

Behind the declaration sits a technical file: drawings, risk assessment, test reports, component certificates, and the standards applied. Under most directives the manufacturer must hold it for ten years and produce it on request to a market surveillance authority.

Buyers rarely see the file. They should still ask which standards are cited against each directive, because that is the difference between a declaration supported by testing and a declaration supported by a template.

RoHS and REACH

These two sit alongside the new-approach directives and are the most common source of last-minute problems in industrial supply. RoHS 3 restricts ten substances including the four phthalates added in 2015; REACH requires disclosure of substances of very high concern above 0.1 % by weight.

Both are declaration-based and both are enforced at customs. A supplier who cannot produce a current RoHS declaration and a REACH SVHC position will stall a shipment, whatever the technical documentation says.

How we apply it

Every product line carries a declaration of conformity naming each applicable directive and the standards cited against it, together with the RoHS 3 and REACH positions. For hazardous-area equipment we hold the ATEX and IECEx certificate sets and the notified body numbers.

Where a product is supplied as part of a larger assembly, we state explicitly which obligations transfer to the machinery builder — an area where responsibility is routinely blurred and disputes later arise.

Why this is the first document anyone asks for

A lithium battery is a Class 9 dangerous good. Before it can be offered for transport by air, sea or road, the shipper has to hold a UN 38.3 test summary covering the exact cell and the exact pack configuration being shipped.

The summary is not the test report. It is a one-page declaration naming the cell manufacturer, the cell model, the pack model, the tests performed and the laboratory. It travels with the shipment. A forwarder who cannot find it will refuse the booking, and an airline that finds a discrepancy between the summary and the goods can reject the consignment at the gate.

The eight tests

Test	What it simulates
T.1 Altitude simulation	Reduced pressure in an unpressurised cargo hold
T.2 Thermal cycling	Temperature swings in transit and storage
T.3 Vibration	Handling and vehicle vibration
T.4 Shock	Impacts during handling
T.5 External short circuit	Terminal short during transport
T.6 Impact	Crush or impact on a cell
T.7 Overcharge	Charger fault (battery assemblies)
T.8 Forced discharge	A cell driven into reverse by a failing string

The trap most projects fall into

UN 38.3 is issued per cell model and pack configuration. Changing the cell supplier, changing the number of cells in series, or changing the protection circuit means the existing summary no longer covers the product.

This is why a cheap battery can arrive with a valid-looking test summary that does not match the goods. Procurement teams that verify the cell model named on the summary against the cell model in the bill of materials catch this before the container is loaded instead of at the port.

How we apply it

Every lithium module we ship has a UN 38.3 test summary covering the specific cell and pack configuration supplied, with the cell manufacturer and model named. The summary, the classification entry (UN 3480 for cells and batteries shipped alone, UN 3481 where packed with or contained in equipment) and the required packaging instruction are issued with the quotation.

We supply the documents in the format the forwarder needs before the booking, on the basis that a shipment held at origin costs more than the entire certification programme.

Why a system certificate matters to a buyer

ISO 9001:2015 certifies the management system, not the product. On a specification sheet it is the least technically interesting line and, in practice, the one that decides whether everything else holds up.

The standard requires a documented process, records that prove the process was followed, a defined way to handle non-conformance, and corrective action that traces back to a root cause. Applied honestly, that is what allows a customer to order the same part number eighteen months later and receive something functionally identical.

What it makes possible

• Traceability. A serial number resolves to a production batch, a test stand record and a material certificate. The value of that is not the paperwork — it is being able to close an investigation with evidence instead of a hypothesis.
• Supplier control. Incoming inspection and approved-supplier status are system requirements, which is what stops an unapproved cell or seal supplier appearing in a delivered unit.
• Corrective action. A field failure triggers a documented root cause process. The output is a design or process change, not a replacement unit and an apology.
• Repeatability across sites. Where production is split between facilities, the system is what keeps the specification identical between them.

What it does not prove

ISO 9001 does not certify product performance, does not replace type testing, and does not by itself satisfy any safety directive. A supplier can hold ISO 9001 and still ship a product that fails its own datasheet.

The certificate is a necessary input to a supplier qualification, not a substitute for one. Used properly, it is the reason the rest of the compliance documentation can be trusted.

How we apply it

Our quality management system has been certified to ISO 9001:2015 for over two decades, covering design, manufacture, test and dispatch. Certificate scope, the issuing certification body and the validity dates are provided in the supplier qualification pack.

Testing records for pressure-containing equipment, calibration certificates for instrumentation, and material certificates for wetted parts are issued with each shipment and cross-referenced to the serial number on the unit.