Immersion Cooling Battery Storage: Benefits, Risks, and What to Ask
Immersion cooling battery storage places cells directly in an electrically insulating liquid, removing heat without a cold plate in between. The approach can improve thermal contact, so temperatures may be more even.
But its value depends on the complete system, not cooling alone.
An EV-oriented simulation study in Energies compared twenty dielectric fluids in a sixteen-cell 18650 module in 2026. It shows thermal and hydraulic trade-offs.
But it does not predict performance in a commercial stationary storage system.
What Is Immersion Cooling Battery Storage?
An immersion cooling battery storage system uses a dielectric fluid to control cell temperature. A dielectric fluid is an electrically insulating liquid.
Cells or small groups of cells sit inside the fluid. As a result, heat moves from the cell surface straight into the liquid.
This sets immersion apart from two other approaches, so the table below compares all three.
| Cooling approach | How heat is removed | Main design consideration |
| Air cooling | Air moves around cells or modules. | Airflow and heat-transfer surface set performance. |
| Cold-plate liquid cooling | Heat passes through a plate into a separate coolant loop. | Thermal contact between the cell and the plate matters. |
| Immersion liquid cooling | A dielectric liquid touches the cell surfaces directly. | Fluid properties, flow, insulation, and material compatibility become central. |
Here, the key difference is direct versus indirect cooling, because immersion exposes more of the cell surface to the coolant.
Cold plates, by contrast, rely on fixed contact areas and interface layers.
If you want more depth on air and cold-plate options, see our liquid vs air cooling guide for BESS.
How the Cooling Loop Works
Immersion cooling battery storage designs use one of two ways to remove heat, but the choice depends on operating conditions, fluid properties, and system design.
Single-Phase Immersion Cooling
In a single-phase system, the fluid stays liquid as it absorbs heat. Pumps then carry it to a heat exchanger.
There, the heat moves to another cooling loop. Once cooled, the fluid returns to the battery enclosure.
But performance depends on more than the fluid. The design must spread coolant evenly, otherwise low-flow regions or localized hot spots can form.
Fluid viscosity, flow rate, and circuit geometry influence pressure drop and pumping power, while heat capacity helps set the flow needed to carry the heat. An IEEE paper covers single-phase immersion for both stationary arrays and vehicle batteries.
Two-Phase Immersion Cooling
In a two-phase system, the fluid boils as it absorbs heat. The vapor then condenses and returns as liquid.
This uses latent heat, which is the energy absorbed when liquid turns to vapor. As a result, it can absorb a lot of heat.
Still, it needs careful vapor and pressure control. That adds fluid-selection and vapor-management requirements, so it is not the best fit for every project.
Performance depends on the fluid, heat load, flow conditions, and heat-rejection design. Therefore, neither approach guarantees a particular cell temperature.
Benefits of Immersion Cooling Battery Storage and Their Limits
The benefits of immersion cooling battery storage include heat transfer, even temperatures, and safety gains. However, each needs proof at system scale.
Lower Peak Temperatures and Potentially More Uniform Cooling
Immersion touches a large share of each cell surface. As a result, it can cut the uneven heating seen with small cooling contact areas.
In the Energies simulation, the air-cooled case reached a peak cell temperature of about 45.6 °C. With a 25 °C coolant inlet, however, the best immersion fluids held the simulated peak near 28.6 °C, about 17 °C lower.
These results apply to a modeled sixteen-cell 18650 module, not a full stationary storage rack. In fact, the example shows lower peak temperature, not a measured gain in cell-to-cell uniformity.
Even temperatures matter because big cell-to-cell gaps drive uneven aging. Our guide to cell temperature gradients in BESS explains safe ΔT limits.
Lifetime Claims Need Evidence
Since heat speeds up battery aging and unwanted side reactions, good temperature control supports longer life.
But immersion cooling does not prove longer life by itself. In fact, a peer-reviewed review found few studies on lifetime, fluid stability, and compatibility.
Because of this, any life claim should name the exact cell, fluid, and system tested.
Possible Limits on Failure Spread
When one cell fails, its heat can set off its neighbors. Fluid in direct contact can soak up heat around the failing cell, so it may slow that spread.
Still, tests and models offer some support. For example, a 2025 SAE study validated its propagation model using a seven-cell module, then applied it to a full-scale module.
The authors reported strong agreement with experimental data and delayed or mitigated propagation. However, those results apply only under the studied conditions.
This is a possible benefit, not a fireproof guarantee. Since a cell can fail internally, immersion cooling should not be relied on to prevent it.
Therefore, safety depends on the fluid, the flow rate, and the system design.
The Dielectric Fluid Is a Critical Engineering Component
In immersion cooling battery storage, the fluid is the heart of the design. Because it touches cells, seals, and hardware, its electrical, chemical, and thermal traits all matter.
Fluid Selection Criteria
- Electrical insulation: The fluid must block electrical current well, so cells stay isolated.
- Heat transfer: Thermal conductivity and heat capacity set how much heat the fluid can carry.
- Viscosity: Resistance to flow drives pumping needs.
- Material compatibility: The liquid must work with the enclosure, seals, hoses, and other wetted parts, because leaks or swelling can follow.
- Stability: Fluid behavior over time and at high heat must be known, since aging can change it.
- Flammability and fire behavior: Test the exact formulation. Do not assume it is safe because it is called dielectric.
Dielectric fluids often carry less heat than water-glycol coolants. Direct contact makes up some of the gap, but the design may still need more flow.
Cooling Performance Versus Pumping Demand
The Energies study compared twenty fluids. Mineral oil gave one of the lowest peak temperatures but also the highest flow resistance.
In the mid-height flow case, mineral oil showed about 12 Pa of pressure drop, while a synthetic hydrocarbon needed about 7.5 Pa. One fluorinated fluid needed only about 1.2 Pa.
The study called the synthetic hydrocarbon (PAO4) a good compromise in its qualitative comparison. Rankings changed when the authors used a combined thermal-hydraulic index.
Because these values come from a small simulated module, the trade-off matters more than the numbers. Therefore, no fluid should be chosen from this study alone.
Pumping Energy and System Efficiency
Better heat transfer does not guarantee lower total energy use in immersion cooling battery storage. Because pumps must overcome fluid resistance, viscous fluids raise that load.
Pump input power follows a simple relation:
Pinput = V̇ × Δp / η
Where V̇ is flow rate (m³/s), Δp is pressure drop (Pa), and η is pump and motor efficiency. P is electrical input power (W).
For illustration, consider a hypothetical loop, not measured data. If it moves 0.001 m³/s at 50 kPa with 50% efficiency, it draws 100 W.
At a fixed flow rate, pressure drop in laminar flow rises roughly in line with viscosity. Higher viscosity therefore increases pumping power unless the design cuts flow.
Compare the whole cooling system, including pumps, heat exchangers, and heat rejection, because cell temperature alone hides this cost.
Challenges of Immersion Cooling Battery Storage
The challenges of immersion cooling battery storage are mostly about proof, maintenance, and cost. None is a dead end, but each needs a clear answer.
Long-Term Material Compatibility
Initial thermal results are only the start, since the fluid must stay stable. Seals, hoses, glues, and coatings must also handle long exposure.
The 2022 review named fluid stability and compatibility as research gaps. Those gaps matter because projects must run for many years.
Cost and Complexity
Systems may need special fluids, sealed enclosures, and pumps. Two-phase designs also need vapor handling.
In addition, research lists cost, viscosity, pumping loss, and complexity as barriers to wider use.
The useful question is not which approach cools best, but which approach meets thermal needs at the lowest defensible lifetime cost.
The Large-Cell Evidence Gap
The Energies study modeled 18650 cells at 1C with single-phase cooling. It was also framed around electric vehicles.
The small-cell studies cited here do not establish performance for large prismatic LFP systems. Therefore, buyers should request evidence for the proposed cell format, chemistry, and system setup.
If you want a wider view of cooling choices at project scale, see our C&I BESS thermal management guide.
Safety Evidence for Immersion Cooling Battery Storage and UL 9540A
Safety claims for immersion cooling battery storage need test data, not sales language. UL 9540A evaluates thermal runaway characteristics, fire propagation, and associated heat and gas hazards, as UL Solutions describes.
UL 9540 sets product-safety rules and the basis for certifying the whole storage system. Meanwhile, our UL 9540A test method guide explains how the test works.
Ask which UL 9540A edition and test levels were used. Then ask whether the fluid and circulation system were present. Also ask whether any parts were disabled or modified to start the event.
Then ask how the tested setup relates to the product you will receive and the planned site.
Ask too what happens if pumps stop or heat rejection fails. Without flow, much of the cooling benefit may fade.
Finally, check how the design fits wider certification needs. If you need the main standards, see our BESS certifications guide.
Buyer Due-Diligence Checklist
These questions help buyers separate proven results from broad claims about immersion cooling battery storage. So ask each one in writing.
- Temperatures: What cell temperatures and cell-to-cell gaps did you measure under our operating conditions?
- Energy use: How much power does the full cooling system draw, including pumps and heat rejection?
- Materials: What long-term tests support the fluid and every wetted material?
- Interruptions: What happens when flow or heat rejection stops?
- Failure behavior: What test data shows behavior during a cell failure in the proposed setup? Include the UL 9540A edition, test levels, and any modified parts.
- Test scale: Which results came from lab cells, and which came from full modules or complete systems?
- Cell format: Were tests run on the same cell format and chemistry we are buying?
- Service: How is the fluid checked, filtered, topped up, and disposed of?
Together, these questions cover the thermal, pumping, material, lifetime, and safety gaps found in published research.
Outlook for Immersion Cooling Battery Storage
Immersion cooling battery storage has strong thermal appeal because direct contact can even out temperatures. It may also help limit failure spread.
But its commercial value depends on the whole system. Fluid choice, pumping load, material life, safety evidence, and cost all matter.
Treat it as one more design option, not an automatic swap for air or cold plates. So its benefits must be proven for your use case.
Frequently Asked Questions About Immersion Cooling Battery Storage
These short answers cover common questions about immersion cooling battery storage.
How does immersion cooling battery storage work?
Cells sit in a dielectric fluid that absorbs heat from their surfaces. Then a pump or a boiling cycle carries that heat to a heat exchanger or condenser.
Is immersion cooling battery storage better than cold plates?
Not automatically. Immersion offers direct fluid contact, but buyers should compare thermal performance, auxiliary energy, serviceability, safety evidence, and lifetime cost for the proposed designs.
Does immersion cooling prevent thermal runaway?
Immersion cooling should not be assumed to prevent thermal runaway. It may help limit heat transfer to neighboring cells, but that benefit requires validation for the specific system.
What is the difference between single-phase and two-phase immersion cooling?
Single-phase cooling keeps the fluid liquid, while two-phase cooling uses boiling and condensation to move heat. The two-phase design therefore adds fluid and vapor-control needs.
Does immersion cooling use more energy?
It can. Viscous fluids raise pumping load, so compare total cooling-system energy, not just cell temperature.
Is immersion cooling proven for large LFP storage systems?
The small-cell studies cited here do not settle that, so ask suppliers for proof on your cell type and full system.
Further Reading on Immersion Cooling Battery Storage
These SunLith guides add context to immersion cooling battery storage decisions.
- Liquid vs Air Cooling System Use in BESS: Choosing the Right Thermal Management
- C&I BESS Thermal Management: Optimizing Performance, Safety & Lifespan
- Cell Temperature Gradients in BESS: Safe ΔT Limits and What Causes Uneven Heating
- UL 9540A Test Method: Complete Guide for BESS Manufacturers
- BESS Certifications Explained: What You Need to Know Before You Buy or Sell
Sources
The research behind this guide to immersion cooling battery storage is listed below.
- Computational Fluid Dynamics Analysis of Battery Immersion Cooling: Impact of Dielectric Fluid Thermophysical Properties. Energies 2026, 19(12), 2770
- Roe et al. Immersion cooling for lithium-ion batteries: a review. Journal of Power Sources, 2022, 525, 231094
- Thermal Management of Li-Ion Batteries With Single-Phase Liquid Immersion Cooling. IEEE Open Journal of Vehicular Technology, 2020
- Multiscale Modeling and Validation of Thermal Runaway Propagation in Immersion-Cooled Battery Systems with Full-Scale Application. SAE Technical Paper 2025-01-8166
- UL 9540A Test Method for Battery Energy Storage Systems. UL Solutions