Assessment: IEC 62619 Acceptance Test Reveals 7 Deviations in 20 MWh Large-Scale Storage — Acceptance Rejected

Assessment type: Acceptance assessment / Safety inspection System size: 20 MWh / 10 MW LFP (5 containers) Region: Lower Saxony Period: Nov 2024 – Feb 2025
Assessment summary:
IEC 62619 Acceptance Test — Sequence (Large-Scale Storage 2.4 MWh) Visual inspection Labeling ✓ Pass Insulation Riso > 1 MΩ ✓ 4.7 MΩ Capacity ≥ 95% rated ✓ 97.3% Short circuit Shutdown ✓ 3.2 ms Overcharge protection ✓ Pass Thermal management ✓ ΔT < 5K Result: 6/6 PASSED Test duration: 4 days | Test temperature: 23 ± 2°C | Test specimen: CATL EnerOne 2.4 MWh

What was the reason for the inspection?

An energy provider in Lower Saxony planned the commissioning of a 20 MWh container large-scale storage system (LFP technology, 5 containers at 4 MWh/2 MW each) for primary frequency response (FCR) and arbitrage trading. Before grid connection, the operator commissioned an independent acceptance assessment to verify conformity with IEC 62619 (safety requirements for industrial lithium-ion batteries) and VDE-AR-E 2510-50 (stationary energy storage systems).

Test catalog (excerpt of key test items)

Test areaStandard referenceTest scope
Cell safetyIEC 62619 Ch. 7Certificate check, sample discharge
BMS functionsIEC 62619 Ch. 8Overvoltage, undervoltage, overtemperature, short circuit
Ventilation / HVACVDE-AR-E 2510-50 Ch. 6.3Airflow volume, pressure differential, gas detection
Fire protectionVDE-AR-E 2510-50 Ch. 6.5Suppression system, early fire detection, escape route
Electrical safetyDIN EN 62477-1Insulation resistance, protective conductor, touch protection
Grid connectionVDE-AR-N 4110Protection settings, NA protection, reactive power capability

What deviations were identified?

Class A findings (safety-relevant — acceptance blocking)

#FindingMeasured valueRequired valueRisk
A1Ventilation in Containers 2+4 undersized384 m³/h≥800 m³/hGas accumulation during cell venting
A2BMS overtemperature shutdown delayed8.2 s≤2 s (IEC 62619)Thermal runaway propagation
A3Gas detector Container 3 not calibratedAlarm at 2.8% LELAlarm at 25% LEL ±5%False alarm or non-detection

Class B findings (operationally relevant — remediation required)

#FindingDetails
B1Insulation resistance Container 5 borderline1.2 MΩ (limit: ≥1 MΩ, new value: >10 MΩ)
B2Protective conductor connection Rack 7 to container housing missingTouch voltage of 38 V measurable
B3BMS firmware outdated (v2.1 instead of v2.4)Known bug in SOC calibration below 5 °C
B4Early fire detection: aspirating smoke detector not tested per DIN EN 54-20Certificate expired
Most critical finding (A1): The ventilation system in Containers 2 and 4 delivered only 48% of the minimum airflow required by VDE-AR-E 2510-50. In the event of a cell venting event (outgassing of flammable electrolyte vapors), the concentration would exceed the lower explosive limit (LEL) of 2.7 vol.% within 12 seconds — with correct ventilation, only after 47 seconds. The BMS evacuation time (shutdown + ventilation) is approximately 30 seconds.

What recommendations were issued?

Expert recommendation: Reject acceptance until complete remediation of all Class A findings. Estimated remediation costs:
MeasureCost (estimated)
Ventilation retrofit Containers 2+4 (fan units + ducts)EUR 62,000
BMS firmware update + temperature shutdown test (all 5 containers)EUR 28,000
Calibration + certification of gas detectors (5x)EUR 8,500
Insulation fault finding + protective conductor connectionEUR 12,000
Re-inspection by expert assessorEUR 18,000
Project management / commissioning delay (4 weeks)EUR 56,500
TotalEUR 185,000
Expert assessment: The findings indicate quality deficiencies in system integration — not cell defects. The cell supplier (CATL) delivered flawless cells with valid IEC 62619 certificates. The problems lie in the container integration by the system integrator (EPC contractor). A liability claim by the operator against the EPC is, in the expert's assessment, justified.

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Last updated: 2026-06-16 | Author: Christoph S. Prestele, TUV-certified expert assessor | PV-BESS-Assessor.com