A look at the Fluence Gridstack Pro Battery Energy Storage System (BESS). In particular the specifications for the Gridstack 5000 Series 5XX.
Fluence say that the pack is designed to be flexible and reduce the time it takes to introduce new battery technology from a growing base of global battery manufacturers.
Initially we have assumed it is using the Envision AESC 530Ah LFP cell as the smaller Fluence units already use a USA produced AESC 305Ah cell.
This pack is grid forming capability allowing it to be used partially or fully off-grid.
Pack
Metrics
- Energy Density
- Gravimetric = 124 Wh/kg
- Volumetric = 132 Wh/litre
- Power Density
- Discharge = 31 Wcont/kg
- Charge = 31 Wcont/kg
- Round Trip Efficiency = 87% AC
This post has been built based on the support of and sponsorship from: Quarto Technical Services, Eatron Technologies and About:Energy
Specifications
- Model/Pack = 5000 Series 5XX
- Energy = 5644 kWh (total)
- Discharge Power
- Continuous = 1411 kW
- Charging Power
- Continuous = 1411 kWfast
- Pack Mass = 45,500 kg
- Total Cell Mass = kg
- Cell to Pack Ratio = %
- Pack Dimensions
- 2896 x 6058 x 2438 mm
- Volume = 42,772 litres
- IP Rating = IP55
- Cooling = litres/minute
- Type = liquid
- Aux Power at 4 hour rate = 17 kW
- Certification
- UL1741, UL1741SA/IEEE1547, NFPA68/69/72/855, UL 9540A Cell, Module, Unit
The cooling power is described as Aux. Peak Load and hence the actual cooling power will be multiplied by a Coefficient of Performance (CoP) for the chiller unit. CoP values typical range from 2 to 4.
Safety
With regards to fire safety the system shows passive and active systems:
- Steel outer housing
- fibreglass insulation to reduce heat propagation from outside
- active vents
- deflagration panels
- Sensing
- gas: CO and H2
- smoke detector
- thermal detector
To validate its safety at this scale, the system underwent rigorous testing using fully charged batteries. The large-scale fire tests were conducted at Safe Laboratories in North Carolina under the observation of CSA Group.
These tests far exceeded the requirements of the current UL 9540A standard and aligned with emerging safety standards, including the forthcoming NFPA 855 (2026).
Four enclosures containing live batteries were set up using minimum spacings, with the deflagration panels on the center enclosure opened. A fire was deliberately ignited in the center enclosure and allowed to fully develop without the use of fire suppression or firefighting intervention.
The results confirmed that Gridstack Pro 5000 enclosures are designed to prevent propagation of battery fires under the conditions tested, even in tightly spaced layouts.
No enclosure-to-enclosure propagation occurred, and surrounding battery cells remained within safe limits.
Fluence complete safety evaluation on Gridstack Pro 5000, Fire and Safety Journal Americas [2]
Cell
The cell is the AESC HC-L530A 3.2V 530Ah Lithium Iron Phosphate (LFP) and although we don’t have a specification sheet we do have a detailed reference from Basen Green [3].
Metrics
- Energy Density
- Gravimetric
- Volumetric
- Power Density
- Discharge
- Charge
Specifications
- Standard Capacity = 530Ah
- Nominal Voltage = 3.2V
- Standard Energy = 1696Wh
- Operating Voltage = 2.5–3.65V (T > 0°C)
- 2.0–3.65V (T ≤ 0°C)
- ACIR (1kHz): 0.18 ± 0.05 mΩ
- Cycle Life: ≥10,000 cycles to 70% SOH
- at 25 ± 2°C under standard charge/discharge
- Temperature
- Charging = 0–60°C
- Discharging = -30–60°C
- Storage = -40°C to 60°C
- Cell Mass: 9.53 ± 0.30 kg
- Dimensions
- 73.10 x 274.60 x 212.60
A preload force of 50–800 kgf is required during testing and assembly. End of life swelling force is quoted as up to 75,000N at 65% SOH.
The preload for testing has a wide range, most LFP cells quote 300kgf for testing. The end of life swelling force is very high compared to a typical NMC / Graphite cell being ~30,000N at 70% SOH.
References
- Built for the next era of utility-scale energy storage, Fluence
- Fluence complete safety evaluation on Gridstack Pro 5000, Fire and Safety Journal Americas
- Introducing the AESC 530Ah LFP Cell: Powering the Future of Energy Storage, Basen Green
Global Standards Certifications for BESS
The Global Standards Certifications for BESS container based solutions is significant. As Battery Energy Storage Systems become critical to modern power infrastructure, compliance with international standards ensures safety, performance, and interoperability across components from cells to containerized systems.