Normative document
NB-BESS Open Standard v1.1
Criteria for the designation of a system as an NB-BESS — No-Break Battery Energy Storage System.
Criteria for the designation of a system as an NB-BESS — No-Break Battery Energy Storage System.
This is a young initiative, founded in 2026 by PulseVolt. Conformance under this standard is by manufacturer self-declaration supported by documented evidence. It is not a certification issued by an accredited third-party body, and the NB-BESS designation is not a certification mark.
What this standard does require is third-party certification where it already exists: criteria N-7 and N-8 are met only through listings issued by a Nationally Recognized Testing Laboratory or equivalent. This standard adds requirements on top of those listings; it never substitutes for them, nor for the safety, electrical, fire and interconnection codes of the jurisdiction of installation.
This document defines the minimum criteria a stationary energy storage system must satisfy to be designated an NB-BESS (No-Break Battery Energy Storage System). Its purpose is to protect the meaning of the category: a buyer who writes "NB-BESS" into a specification must be able to rely on every criterion below being met, in the same way that "double-conversion UPS" or "Tier IV data center" carry reliable meaning.
The NB-BESS category sits at an intersection that no single existing standard covers. A system that satisfies the UPS performance and safety standards is not thereby an energy storage system; a system that satisfies the energy storage standards is not thereby free of transfer time. This standard requires both, and adds the requirements that neither family addresses: enforced protection reserve during economic dispatch, multi-source DC coupling, and instrument-grade power quality measurement at the load bus.
This document is published under an open license and may be implemented by any manufacturer at no cost. It does not reproduce the text of any referenced standard; referenced standards are cited normatively and must be obtained from their publishers.
Critical power path — the electrical path through which the protected load is served during normal operation.
Transfer time — any interval during which the protected load is not served by the system's power conversion stage.
Micro-interruption — loss or collapse of supply voltage lasting from milliseconds up to a few seconds.
Protection reserve — the portion of stored energy permanently reserved for ride-through and backup, and unavailable to economic dispatch.
Rated autonomy — the time the system sustains the protected load at 100% rated output from stored energy, from the protection reserve state of charge to the minimum permissible state of charge.
Load bus — the point of connection between the system output and the protected load, and the point of measurement for criteria N-1, N-2 and N-6.
Declaration of conformity — the manufacturer's signed statement, with supporting evidence, that a defined system family meets criteria N-1 through N-10.
Shall denotes a mandatory requirement. Should denotes a recommendation. May denotes a permitted option. A system shall meet all of N-1 through N-10 to be designated an NB-BESS; there are no partial, tiered or graded designations.
The following documents are referenced normatively. Where undated, the latest edition applies. These documents are copyrighted and must be obtained from their publishers; this standard cites them and does not reproduce them.
| Reference | Subject | Applies to |
|---|---|---|
| IEC 62040-3 | UPS — performance and test requirements; output classification (VFI / VI / VFD) | N-1, N-2 |
| IEC 62040-1 | UPS — general and safety requirements | N-8 |
| UL 1778 | Uninterruptible Power Systems | N-8 |
| UL 9540 | Energy Storage Systems and Equipment | N-7 |
| UL 9540A | Test method for thermal runaway fire propagation in ESS | N-7 |
| UL 1973 | Batteries for use in stationary applications | N-7 |
| IEC 62933 (series) | Electrical energy storage systems — terminology, parameters, safety | N-7 |
| NFPA 855 | Standard for the installation of stationary energy storage systems | N-7 |
| IEC 61000-4-30 | Power quality measurement methods — Class A | N-2, N-6 |
| IEC 61000-4-11 / -4-34 | Immunity to voltage dips, short interruptions and variations | N-2 |
| IEEE 1159 | Monitoring and classification of electric power quality events | N-6 |
| IEEE 519 | Harmonic control in electric power systems | N-2 |
| SEMI F47 | Voltage sag immunity for semiconductor processing equipment | N-2 |
| ITIC (CBEMA) curve | Voltage tolerance envelope for information technology equipment | N-2 |
| UL 1741 · IEEE 1547 | Interconnection of distributed energy resources | N-9 |
| Local electrical code | NFPA 70 (NEC), NOM-001-SEDE, or the applicable code of the jurisdiction | N-7 |
A system shall meet all of criteria N-1 through N-10 to be designated an NB-BESS.
Verification. (a) Single-line diagram review confirming that no path exists from any source to the load bus that bypasses the conversion stage during normal operation; a maintenance bypass is permitted only if it is manually initiated, externally interlocked and outside normal operation. (b) IEC 62040-3 output classification declared and evidenced. (c) Disturbance immunity testing per IEC 61000-4-11 / -4-34, or recorded field event logs from an operating installation, showing no deviation at the load bus outside the N-2 envelope. (d) Measurement resolution of at least one sample per half cycle at the load bus during the test.
Verification. (a) Power quality measurement at the load bus using instrumentation compliant with IEC 61000-4-30 Class A, recorded during representative upstream disturbances. (b) Comparison of the recorded load-bus envelope against ITIC and, where applicable, SEMI F47. (c) THD measurement at rated load. (d) Where field evidence is used in place of laboratory testing, records shall cover a minimum of 30 consecutive days of operation and include at least one classified upstream event.
Verification. (a) Nameplate ratings and published product family data. (b) Thermal design and continuous-duty documentation at rated output. (c) At least one reference installation, or a type test, at or above the 500 kW floor.
Verification. (a) Autonomy discharge test at 100% rated load from the protection reserve state of charge to the minimum permissible state of charge, with the measured time recorded. (b) Where generator extension is offered, documented integration scheme plus a demonstration that generator start, synchronization and load assumption produce no disturbance at the load bus outside the N-2 envelope.
Verification. (a) Energy management system documentation describing the reserve enforcement mechanism and the level at which it is implemented. (b) Functional test in which an economic dispatch command that would breach the reserve is issued and demonstrably refused or clamped. (c) Operating logs from an installation showing simultaneous optimization activity and reserve maintenance over not less than 30 days. This criterion is not addressed by any referenced standard and is specific to the NB-BESS category.
Verification. (a) Instrument specification and evidence of IEC 61000-4-30 Class A compliance for the measurement chain. (b) Sample event report from an operating system showing an upstream event, its IEEE 1159 classification, and the corresponding load-bus record. (c) Demonstration of export and of the retention period.
Verification. (a) Listing certificate and listing number from a Nationally Recognized Testing Laboratory or equivalent accredited body. (b) UL 9540A test reports at the applicable levels. (c) Installation-level conformity documentation for the jurisdiction, including authority-having-jurisdiction acceptance where required.
Verification. (a) Listing certificate or certificate of conformity from an accredited body. (b) Classification statement consistent with the evidence submitted under N-1.
Verification. (a) Single-line diagram showing source coupling topology and the point of common coupling. (b) Source transition test: with the load at not less than 50% of rated output, remove and restore each input source in turn while recording the load bus at IEC 61000-4-30 Class A resolution; no excursion outside the N-2 envelope is permitted. (c) Interconnection certification where export capability is offered. This criterion is not addressed by any referenced standard and is specific to the NB-BESS category.
Verification. (a) Alarm register with classification, trigger conditions and annunciation paths. (b) Protocol point list and integration documentation. (c) Demonstration of remote notification and of a successful read by a third-party client.
The verification paragraphs above state what must be shown. Annex A specifies how: apparatus, measurement points, procedures step by step, acceptance criteria and records to retain, for each of TM-1 through TM-10, plus the evidence index and the declaration of conformity form.
Conformance is by manufacturer self-declaration supported by documented evidence, reviewed and published by the initiative. It is not third-party certification, and the evidence trail is what gives the declaration its weight.
The manufacturer assembles the evidence listed under each of N-1 … N-10 for a defined system family, including listing certificates for N-7 and N-8.
The manufacturer submits a signed declaration of conformity with the evidence index and the declared values for rated autonomy, protection reserve and rated output.
On acceptance the system family is published in the public register, with its declared values and standard version, and the manufacturer may use the designation "NB-BESS v1.1 — declared conformance".
The designation shall always be stated with its standard version and with the words "declared conformance". It shall not be presented as a certification, an approval, or a mark issued by an accredited certification body. Declared values (rated output, rated autonomy, protection reserve) shall be reproduced accurately wherever the designation is used commercially.
Criteria N-7 and N-8 require listings that take time to obtain. Declarations submitted before 1 January 2028 may cite listings that are formally in process, provided the testing laboratory and file number are disclosed and the register entry is marked accordingly. From that date, completed listings are required for any new or renewed declaration.
PulseVolt — founding manufacturer. NB-BESS system family, declared conformant to v1.1. MW-class systems in continuous industrial service.
The register is short because the initiative is new. Any manufacturer whose systems meet N-1 … N-10 is invited to submit a declaration at no cost — contact the initiative.
The NB-BESS Open Standard initiative was founded in 2026 by PulseVolt, creator of the NB-BESS™ technology and category. The standard text is published openly and may be implemented by any manufacturer at no cost. PulseVolt administers the standard and the register during the founding phase; once three or more independent manufacturers hold accepted declarations, maintenance passes to a technical committee with one seat per declared manufacturer, and the founding administrator holds no veto.
Revisions follow semantic versioning. Substantive changes to normative criteria increment the major version and are announced with a transition period. Additions of references or clarifications increment the minor version. Current version: 1.1 (August 2026), superseding v1.0 — which contained the same architecture but lacked quantified thresholds and normative references.
Manufacturers, integrators and specifiers are invited to use these criteria in designs, RFQs and procurement documents. A vendor-neutral specification block, ready to paste into a tender, is published at nb-bess.com/rfq.
Open the RFQ template →