Section 6.1 – Access and Basic Mechanical Protection

Powerwall 3 complies with the entirety of this section, which covers enclosure material and access as well as the maximum energy allowed within a single container (20 kWh).

Section 6.2 – General Safety Requirements

This section includes the following requirements:

Section 6.3 – Safety of Battery Assemblies for Protection Against Fire and Burns

This section sets out requirements for quantifying the arc-flash energy potential from the DC circuits in the battery enclosure, and links enclosure and installation requirements based on those declared energy values.

The battery circuits within the Powerwall are sealed within module enclosures, and are not accessible for installers or for field servicing. Nonetheless, Powerwall has redundant overcurrent protection in the battery circuit which has a significant impact on limiting arc-flash energy. Using the calculation methodology described in AS/NZS 5139 which the PAS recommends, Powerwall’s battery DC arc flash incident energy is determined to be well under 1 cal/cm². This energy level is below the threshold defined in the PAS both for additional enclosure requirements and for additional installation requirements or precautions.

Section 6.4 – Safety of Cells and Monobloc Batteries

This section requires lithium-ion battery-based systems to comply with BS EN IEC 62281 related to the safety cells and batteries during transport. The Li-Ion battery cells used in Powerwall 3 are certified to IEC 62281.

Section 6.5 – Protection Against Fire

This section covers installation requirements for indoor/outdoor installations, fire resistive materials, ventilation, setbacks and energy thresholds. Most of these requirements are consistent with the guidance provided in the Powerwall installation manuals.

The PAS states that “where practicable, storage batteries should be installed outdoors.” Powerwall 3 is suitable for outdoor installation, providing an installer with a ready means to comply with this section.

For indoor installations, the PAS states that any location in which a battery is installed shall have fire resisting separation (from specific indoor locations, via walls, ceilings and floors) of at least REI 30 to BS EN 13501 series (30 min to BS 476 series for load bearing capacity, integrity and insulation). Due to the wide variation in building construction, it is not feasible to provide detailed guidance on specific locations, and installers will need to look at each location on a case-by-case basis. Many of the common locations selected for a Powerwall may meet the requirements stated in the PAS – for example NHBC specifies a minimum of REI 30 / 30min fire resistance for attached or integrated garages**.

** NHBC 2024, 10.1 Garages, 10.1.6: Resistance to fire spread

Section 6.5.3 – Ventilation

The PAS states that interior locations where ESS units are installed shall have fresh-air ventilation to outdoors. Ventilation systems should not compromise the fire resistance of the battery enclosure, and outdoor ports of the ventilation must be at least 1 m from doors, windows, ventilation ports, and escape routes. An informational note also points to BS EN IEC 62485 for further guidance.

Issue

This requirement is well intended but, broadly applied, ignores distinctions that are addressed in other installation and product standards. For example, the validation and testing section of IEC 62933-5-2 acknowledges that requirements should depend on chemistry-specific accumulation and cites off-gassing measurements in large-scale fire testing as a means to determining venting requirements. It cites an Annex describing UL 9540A large-scale fire testing as a means to do this. All Powerwall products have demonstrated through UL 9540A testing that under normal operating conditions (charging or discharging) there is no production of hydrogen or other flammable gasses.

Recommendation

While many of the common locations where Powerwall is typically installed may already comply with this requirement, Tesla considers the PAS approach to be unnecessarily broad-brush. The UL 9540 and 9540A certification requires that the Powerwall installation manual address any and all ventilation requirements based on the results of the testing under normal and failure conditions. Tesla’s position is that the PAS should acknowledge the use of these rigorous type tests and their findings as an alternative to a blanket ventilation requirement.

Section 6.6 and 7.3 – Protection Against Impact

The PAS requires that storage batteries (Section 6.6) and power conversion equipment (Section 7.3) installed in locations subject to vehicle damage (garages, driveways and similar locations) shall have a minimum degree of protection against external mechanical impact. PCE equipment is required to have an impact protection rating of IK08 in accordance with IEC 62262 (equivalent to 5 Joules), and storage battery enclosures a rating of IK10 (20 Joules). Powerwall is tested for compliance with the IK08 rating, in accordance with the requirements in IEC 62933-5-2 and IEC 62477-1. Therefore, installers wishing to meet the requirements of the PAS should consider additional protection (barriers, enclosures, or equivalent) in these locations.