Subsea and UUV Pack Qualification: Governed Rows and Named Voids

Application: unmanned underwater vehicles and subsea autonomous systems | Last verified: July 31, 2026

Correction to Issue #6. The Evidence Ladder treated the UUV public record as one broad structural void. That was too coarse a reading. ABS governs lithium battery installation in underwater vehicles at subclause granularity, and a DVP written as though no installation rule exists will fail survey on grounds that were published the whole time. The void is narrower than Issue #6 described and it sits in identifiable parameter classes, mapped below.

Start with the failure modes. A subsea pack fails by seal ingress under sustained differential pressure, by heat with no exit path from a sealed one-atmosphere housing at duty, by a cell venting into a fixed free volume with no route to atmosphere, and by runaway walking through a module whose cell spacing was set by volumetric packing efficiency rather than thermal isolation. All four are pack-level, installed-condition failure modes, and all four are conditioned to some degree by the hydrostatic environment the pack sits in. No published standard sets a number for any of them.

The governance is real and it is specific. ABS mandates a risk analysis before installation, enumerates the protection functions the BMS must perform, requires third-party cell certification as an entry condition, requires pressure testing to design depth, and requires a vehicle trial. What the battery lane never does is state a value. It sets no pressure margin over design depth, no hold duration, test SOC, cycle count, temperature limit or propagation criterion. The obligation is written down. The acceptance level is yours to set and yours to defend in front of a surveyor. Last week's eVTOL card described an asymmetric multi-authority problem, with EASA supplying clause-level test conditions, the FAA supplying aircraft-level safety objectives, and neither supplying a pack performance threshold. Subsea inverts the shape. One authority, deeply prescriptive about process, silent about values.

Governing and adjacent documents

Document	Edition / status	Role for a UUV pack
ABS Rules for Building and Classing Underwater Vehicles, Systems and Hyperbaric Facilities (PDF)	January 2025 text inspected; January 2026 edition published	Primary installed-system lane. §10/11.5 battery installation; §19/33.3 mission power; §19/37 vehicle trials
IEC 62619:2022, Ed. 2	Current; IEC stability date 2026	Industrial secondary cell and battery safety. Scope names marine vehicles. Silent on submergence
UN 38.3 / UL 1642	Imported by ABS	Third-party certification prerequisite to the installation claim
ISO 21173:2019	Current, confirmed 2025	Hydrostatic pressure test of submersible pressure hulls, accessories, buoyancy materials. Housing lane, not pack lane
ISO 20682:2026	Ed. 1, published February 2026	AUV risk and reliability. Expressly excludes AUV batteries from scope
NAVSEA S9310-AQ-SAF-010	Rev 3, November 3, 2020, public release	Navy lithium battery safety certification. Public propagation-test construction and a submarine containment criterion
BV NR 610 §3.3.3 / IMCA D 002	NR 610 December 2018; D 002 Rev 1.1, February 2024	Diving-systems lane. NR 610 §3.3.3 states qualitative battery-in-pressure-housing provisions and refers users to IMCA D 002; D 002 clause content is not publicly disclosed, title and revision only, retrieval required

Revision status. The ABS January 2026 change notice lists the clauses altered since January 2025. Neither §10/11.5, §19/33 nor §19/37 appears on it, which supports treating the subclause text below as unchanged. It does not prove it. A change notice is not consolidated rule text. On IEC 62619, the reviewed public material shows Edition 2 current with a stated stability date of 2026 and discloses nothing about an Edition 3 or a circulating amendment. Check the IEC TC 21 published work programme before the edition year goes into a released DVP.

Two kinds of missing number

Every absent value below carries one of two tags, and the tag tells you who owes the answer.

Governed but program-valued. ABS requires the test and defines the article under test. The acceptance level is a vehicle-program input. Design depth is the clean case. A row like this is not "TBD pending standards research." It is "TBD pending program decision," and a written rationale closes it. There is no citation to go find.

Genuinely unaddressed. No reviewed standard, class rule or public government specification establishes a test condition or acceptance criterion for this parameter in a subsea pack. There is nothing to cite. Anything you borrow has to carry a statement of the originating scope of what you borrowed it from.

Energy density and capacity

DVP needs: gravimetric (Wh/kg) and volumetric (Wh/L) energy density at installed-pack level, housing and compensation hardware included, plus delivered capacity at mission temperature and depth.

Governs: ABS §19/33.3 requires an onboard power source with capacity adequate for the planned mission duration (published rule text). That is an adequacy showing against a mission profile the program declares. It is not a threshold.

Missing: mission duration, reserve policy, end-of-mission SOC definition, and any density figure at all. Governed but program-valued. No reviewed standard sets an energy-density floor for any class of UUV, and it is hard to construct one that would mean anything. A 15 kg inspection vehicle and a 10-tonne extra-large UUV do not share a mission envelope.

Power capability

DVP needs: continuous and peak discharge C-rates by operating mode (transit, hover, payload duty cycle, recovery), charge C-rate, and charge-window temperature limits.

Governs: ABS §10/11.5.4(a) enumerates the protection functions the BMS must implement. Item (ii), charge control preventing overcharge, undercharge and voltage reversal. Item (iii), discharge control preventing overdischarge. Item (v), overcurrent and short-circuit protection (published rule text). The rule mandates that the function exist. It says nothing about the limit the function enforces.

IEC 62619:2022 Clause 6.2 uses a 0.2 It A capacity-confirmation rate at 25 ± 5 °C ambient, per the public preview text. It A is the IEC reference-current notation, rated capacity divided by one hour. That is a test-method rate under laboratory ambient. It is not a duty requirement and should never be transcribed into a DVP as one.

Missing: everything a power row needs. Genuinely unaddressed. No reviewed standard establishes C-rate acceptance for any UUV mission phase. The limits your BMS enforces under §10/11.5.4 are program-valued, and the ABS Surveyor, meaning the class society's attending engineer who signs the survey, will expect each of them justified against the mission profile.

Cycle life and calendar life

DVP needs: cycle count at stated DOD and temperature, calendar capacity retention at stated storage SOC and temperature, and the maintenance or replacement interval those two produce for the class file.

Governs: nothing quantitative. ABS §10/11.5.1(e) requires suitability for marine service, supported by service experience or by test data demonstrating suitability for underwater applications (published rule text). That is an evidence obligation with no threshold attached. BV NR 610 §3.3.3 requires planned examination and renewal of batteries installed in pressure housings and specifies no interval (published rule text, December 2018).

Missing: cycle count, DOD basis, temperature basis, calendar criterion, interval. Genuinely unaddressed, and only loosely structured by §10/11.5.1(e). Bring evidence. Sufficiency is the Surveyor's call.

Operating envelope, pressure

Whether the pack sits in a one-atmosphere housing or in a pressure-compensated one changes what this row is testing. Write the row twice.

DVP needs: design depth, qualification test pressure and any margin above design depth, pressurization and depressurization rates, hold duration, electrical duty during the hold, instrumentation, and a defined pass condition.

Editorial conversion, offered to size the load rather than to be cited: seawater adds roughly 1 bar per 10 m of depth, so a 3,000 m design depth puts on the order of 300 bar of differential across a non-compensated pack boundary. That is the figure the ISO 21173 structural factor below would multiply.

Governs, pressure-exposed packs: ABS §10/11.5.6(a) applies wherever the battery is exposed to pressure greater than one atmosphere. It requires pre-service pressure testing to the vehicle's design depth, demonstration of satisfactory operation at that condition, and testing to the Surveyor's satisfaction (published rule text). The clause governing the most consequential row on this card carries one number, and it is the applicability trigger.

Governs, one-atmosphere housings: §10/11.5.3(b)(i) requires purging or inert-gas charging provision so that oxygen stays below the flammable limit. Item (ii) requires explosion-proof electrical equipment inside the housing. Item (iii) requires water-intrusion, fire, pressure and temperature sensors "as appropriate," with audible and visual alarms on manned vehicles (published rule text). Housing pressure integrity is a structural article and gets qualified separately from the pack.

Adjacent lane, borrowed scope labeled: ISO 21173:2019 supplies the structural pressure-test logic. Its public preview reports:

Test-medium temperature 10–30 °C at ambient pressure 0.084–0.106 MPa (§4.4)
Pressurization no slower than the rate produced by diving; hold at maximum working pressure for at least the design operating time at that pressure; depressurization no faster than the surfacing-rate basis (§5.2.2)
Test pressure at 1.1–1.25 × maximum working pressure for an unmanned pressure hull and buoyancy materials

Those parameters govern hull, accessories and buoyancy materials. They address cell operation not at all, nor thermal rejection, nor seal behavior under cyclic load, nor leakage response. A program that borrows the 1.1–1.25 factor should record in the DVP that the factor's originating article is structural.

The nearest battery-adjacent published factor is historical. Lloyd's Register submersible rules of July 2019, Pt 6, Ch 1, §9.5.2, described an external battery housing as either a pressure vessel rated for 1.4 × hydrostatic pressure at maximum operating depth or a pressure-equalized container with a bladder (historical reproduced rule text, locator only). Current LR rules are the July 1, 2026 edition and the clause text sits behind the Regs4ships licensed portal. Treat 1.4 as a prompt to go retrieve that text rather than as a citable requirement, and note that it applied to the housing, not to exposed cell operation.

Confirmed negative, DNV and BV. No current public DNV clause was found establishing a battery-specific external-pressure multiplier, hold duration or submerged propagation criterion. DNV's July 2025 edition entered force January 1, 2026, and the July 2026 edition enters force January 1, 2027, with operative text behind the authenticated Rules and Standards Explorer. That is a public-access negative. It does not demonstrate that no such requirement exists. BV NR 610 §3.3.3 states no numerical hydrostatic factor whatsoever.

Missing: margin over design depth, ramp rates for the pack test, hold duration, electrical duty during the hold, and the numerical content of the phrase "satisfactory operation." Governed but program-valued under ABS, with no consensus factor from any reviewed class society available to anchor it. Pressure-compensated architectures reduce the differential across the pack boundary; they do not remove the qualification question. The architecture survey in this issue's publication summary is the context for how compensation changes what the pressure row is actually verifying.

Operating envelope, temperature and thermal rejection

DVP needs: operating and storage temperature limits at cell and module level as installed, demonstrated heat rejection at worst-case duty in the real thermal environment, and internal condensation control.

Governs: ABS §10/11.5.4(b) requires real-time module temperature monitoring, and §10/11.5.3(a)(i) requires the housing to be located as far as practicable from heat sources (published rule text). IEC 62619 defaults to a 25 ± 5 °C test ambient (public preview). NAVSEA S9310-AQ-SAF-010 Rev 3 §13-3.2 defaults rechargeable-battery testing to 25 ± 5 °C, 29 ± 2 inHg and 30–90 % RH unless another condition is approved (published public-release manual).

Missing: all three of those defaults are one-atmosphere laboratory conditions. No reviewed standard establishes thermal-rejection acceptance for a pack sealed in a one-atmosphere housing at depth, or for a pack immersed in dielectric fluid inside a compensated housing. Genuinely unaddressed. The conductive and convective paths differ enough between the two architectures that a single thermal row cannot honestly cover both. Split the row and state the architecture in each. Humidity is a second unaddressed case: the NAVSEA 30–90 % RH band is a chamber setting, and no reviewed source speaks to condensation inside a one-atmosphere housing whose walls sit at seawater temperature while the pack runs at duty.

Mechanical

DVP needs: shock and vibration profiles for launch, recovery, transit and surface handling, plus verification of impact protection.

Governs: ABS §10/11.5.3(a)(ii) requires the housing to be mechanically protected from direct impact and, where the vehicle is transported while in service, protected from acceleration and shock loads. §10/11.5.2(b) requires the installation to prevent inadvertent terminal shorting (published rule text). No profile, no amplitude, no duration, no axis count.

Missing: the profile. Genuinely unaddressed in the subsea lane. Programs routinely borrow MIL-STD-810 methods. If you do, name the method, name the tailored profile, and name the originating platform environment that profile was written to represent, because no MIL-STD-810H method was drafted against UUV launch and recovery through the splash zone. The shipboard and transportation methods it does contain were written for installed or in-transit equipment. What carries the DVP row is the tailoring rationale, not the method number.

Safety, abuse tolerance and propagation

DVP needs: abuse-test article definition (cell, module, or installed pack in its housing), initiating-failure selection with justification, propagation acceptance criterion, vent-path and free-volume verification, and containment demonstration at the housing boundary.

Entry conditions. ABS §10/11.5.1(c) requires independent third-party certification to UN 38.3, UL 1642 or another recognized national or international standard, performed by a competent test facility. §10/11.5.1(d) requires an approved quality-assurance program (published rule text). Read the scope of those certifications carefully. Both named articles are cell-level or shipping-configuration, and neither involves external hydrostatic pressure or describes an installed pack. A program can therefore close a mandatory ABS input completely and still hold no evidence at all about the failure mode it is actually afraid of. Whether the "another recognized standard" alternative admits a pack- or system-level certification in place of cell-level UL 1642 is not established in the reviewed public text. Confirm the acceptable certification article with the attending Surveyor before you select one.

Overcharge, external short circuit, forced discharge. Addressed at cell and shipping-configuration level through the UN 38.3 test series, at ambient pressure. No reviewed source establishes a submerged or compensated-housing equivalent of any of the three. Genuinely unaddressed as installed-pack abuse conditions.

IEC 62619 abuse clauses. The public preview does not expose the abuse-test clause set, so clause numbers and any pressure-related limitation remain unconfirmed. Retrieve the licensed full Edition 2 text before citing IEC 62619 as abuse coverage for anything beyond the internal cell assembly of a one-atmosphere housing.

Installed-system provisions (all published rule text):

§10/11.5.3(a)(iii) — pressure relief for gas generated by a malfunctioning battery, with discharge routed as far as practicable from heat sources, compressed-gas cylinders and acrylic windows.
§10/11.5.3(a)(iv) — electrical circuits insulated and isolated from housing structural elements.
§10/11.5.2(a) — in a manned vehicle, battery installation outside the occupied pressure boundary unless equivalent safety is demonstrated.
§10/11.5.3(b)(iv) — A-60 rating under the IMO Fire Test Procedures Code, or equivalent, where the battery housing is contiguous with a human-occupancy pressure vessel or with the vehicle's pressure hull. A-60 is the IMO structural fire-integrity class requiring 60 minutes of insulation against a standard fire curve.
§10/11.5.2(c) — pre-installation risk analysis covering the installation and both normal and emergency operating procedures, using the ABS Guidance Notes on Risk Assessment Applications for the Marine and Offshore Industries or an equivalent method.

Missing from those provisions: no reviewed source establishes a vent flow rate, a free-volume basis, a burst-disc or relief set pressure, or a defined test article for demonstrating the A-60 boundary claim with a live battery on the hot side. Genuinely unaddressed. Being able to quote the rule text does not close the row.

Propagation. No reviewed standard, class rule or government specification establishes a thermal-runaway propagation test condition or acceptance criterion for a UUV pack under external hydrostatic pressure. Genuinely unaddressed, and the largest single void on this card.

NAVSEA supplies the nearest borrowable public construction. §13-3.9 requires propagation testing that represents real-system cell spacing, orientation, free volume, packing and wiring, with the initiating failure chosen from internal short, localized thermal abuse, overcharge, external short or puncture on the basis of the preliminary hazard analysis and CONOPS. §13-3.3.1 requires thermocouples rated to 800 °C, voltage and current instrumentation, data acquisition and audio-video recording. Table 13-1 gives a submarine-platform pass condition: complete containment of all gaseous, liquid and solid material and flame from the maximum credible event, measured temperature below 100 °C, internal pressure below 50 % of the venting-mechanism or rupture condition (published public-release manual). Two constraints bound the borrow. The manual's default test environment is approximately atmospheric, and its authority runs through the Navy Lithium Battery Safety Program, which the manual itself distinguishes from platform fielding and integration. The July 2026 Authorization for Navy Use list confirms continued reliance on the manual and requires relevant underwater equipment to be manufacturer-certified for maximum operating depth, without supplying a battery pressure multiplier or a hold duration.

Immersion propagation. What exists here is two peer-reviewed experiments, not a protocol. A 2024 study compared identical 21700 modules in air versus paraffin-series insulating oil at 100 % SOC with overcharge triggers (Data in Brief 54, 110304). A 2026 study in No. 5 industrial white oil found that full immersion delayed the triggered cell's runaway by roughly 1,600 s and then, once the oil ignited, raised peak heat release rate from 16.76 kW to 366.62 kW (Energy 347, 140289). Different fluids, different enclosures, different triggers, no shared acceptance threshold, both at one atmosphere. That second result is the reason a DVP cannot assume immersion is a conservative condition. UL 9540A Sixth Edition, March 13, 2026, supplies cell, module and installation-level propagation methods for stationary storage and does not extend to submerged or compensated systems.

Environmental protection

DVP needs: enclosure integrity, water-intrusion detection, salt exposure, post-immersion functional acceptance.

Governs: ABS §10/11.5.3(b)(iii) requires water-intrusion sensors "as appropriate" in one-atmosphere housings (published rule text). MIL-STD-810H Method 512.7 remains the common borrowed enclosure-integrity lane, and as Issue #6 covered, it establishes none of the following: sustained-pressure cell behavior, submerged thermal rejection, electrolyte containment after cell failure, output stability through a pressure excursion. Note the ABS qualifier as well. "As appropriate" delegates judgment to the design and to the Surveyor, which makes this a documented rationale in the DVP rather than a checkbox.

Missing: any IP-class equivalence for a depth-rated pack, and any post-immersion functional acceptance criterion. Genuinely unaddressed.

EMC

DVP needs: conducted and radiated emissions and immunity for the pack as both source and victim inside the vehicle electrical system, including BMS telemetry integrity near sonar and acoustic-modem bands.

Governs: nothing in the subsea battery lane. ABS §10/11.5 contains no EMC provision, and no reviewed subsea standard addresses pack-level EMC. Where a program carries an EMC requirement, it originates in the vehicle electrical system specification or with the customer. Editorial inference: this belongs in the vehicle EMC plan with the pack scoped as source and victim, not as a standalone pack DVP row.

Transport

DVP needs: shipping-configuration qualification of the pack or its subassemblies, plus the certified state of charge and packaging configuration.

Governs: UN 38.3, imported by ABS §10/11.5.1(c) as a certification prerequisite (published rule text). Settled, unambiguous, and disconnected from anything the pack does at depth.

Gaps summary

Parameter	Category	Working-group activity
Design depth, pressure margin, ramp rate, hold duration, test duty	Governed but program-valued (ABS §10/11.5.6(a))	None identified in reviewed public material
Mission duration, reserve policy, energy density	Governed but program-valued (ABS §19/33.3)	None identified
Allowable BMS voltage, current, temperature limits	Governed but program-valued (ABS §10/11.5.4)	None identified
C-rate acceptance, charge rate, charge-temperature window	Genuinely unaddressed	None identified
Cycle life, calendar life, replacement interval	Genuinely unaddressed	None identified
Propagation under external hydrostatic pressure	Genuinely unaddressed	None identified
Propagation and containment in dielectric-fluid immersion	Genuinely unaddressed	None identified
Vent flow rate, free-volume basis, relief set pressure, A-60 test article	Genuinely unaddressed	None identified
Thermal rejection at depth, both architectures; internal condensation	Genuinely unaddressed	None identified
Overcharge, external short, forced discharge as installed-pack conditions	Genuinely unaddressed	None identified
Shock and vibration profile, launch and recovery	Genuinely unaddressed in subsea lane	None identified
Post-immersion functional acceptance	Genuinely unaddressed	None identified

ISO 20682:2026 excludes batteries for the use of AUVs from its scope by name, alongside electrical motors and autonomous underwater gliders. Someone drew that boundary on purpose; it is not an annex that got left out. The public ISO/TC 8/SC 13 work programme at cutoff listed five projects under development, covering ocean-industry classification, blue carbon, ocean-bottom seismometers, macrofauna and vegetation. Nothing on batteries or pressure-exposed energy storage. IEC's public committee mapping puts maritime electrical standards with TC 18, whose published strategic business plan covers ships, offshore units and subsea equipment and identifies no pressure-exposed battery-pack qualification project. The negative is bounded by reviewed public material and nonpublic preliminary work items may well exist. Nothing visible suggests the propagation void closes on a schedule any current program can plan around.

Before you freeze a row

Four retrievals this card cannot substitute for:

The consolidated ABS January 2026 rulebook via Rule Manager, which will also settle the exact §19/33.3 subclause designation and the current title of the referenced Guidance Notes.
The Lloyd's Register July 2026 submersible clause text via Regs4ships, to confirm or retire the historical 1.4 housing factor.
DNV's operative underwater-vehicle clauses via the authenticated Rules and Standards Explorer.
The licensed IEC 62619:2022 abuse-test clauses, per the Safety row above.

ABS tells you what to test and then holds you to a written justification for every number you bring. It supplies none of them. Build the pressure-envelope, thermal and propagation rows on the assumption that you will defend a program-derived value with your own test data and your own rationale, because no published threshold exists to stand behind. On our reading of §10/11.5.6(a), the Surveyor's satisfaction is the only acceptance criterion the rule actually names.

This card synthesizes publicly available standards, class rules and technical analyses. It is a starting point for internal design review and validation planning, not a compliance determination.

Things to follow up on...

IMCA D 002 retrieval: The one document in the reviewed landscape whose title promises exactly what this card lacks is IMCA D 002, Battery Packs in Pressure Housings, Revision 1.1 of February 2024 with its last technical revision in March 2021 — the public catalog page discloses no pressure multiplier or propagation protocol, so a member-access pull is the highest-value next retrieval for anyone writing a pressure-envelope row.
DNV January 2027 entry into force: DNV's July 2026 edition does not enter force until January 1, 2027 unless parties agree to apply it earlier, which gives programs selecting DNV as their class basis a defined window to check whether any battery-specific external-pressure clause appears before the transition.
UL 9540A Sixth Edition scope drift: UL 9540A published its Sixth Edition on March 13, 2026 with cell, module and installation-level propagation methods for stationary storage; worth watching whether subsequent revisions extend the installation-level method toward enclosed or fluid-filled configurations, since it is currently the most mature published propagation-test architecture that a subsea program could argue from.
NAVSEA controlled-issue verification: The July 2026 Authorization for Navy Use list still cites NAVSEAINST 9310.1C and S9310-AQ-SAF-010, confirming continued program reliance — but it does not establish that the publicly posted Revision 3 PDF is the current controlled TDMIS issue, which matters if you intend to borrow the Table 13-1 containment criterion into a defense-adjacent DVP.