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Battery cooling and thermal management

We create, make and sell specialty ester base oils that can be used in dielectric fluid formulations, used in electric vehicles for the direct immersion cooling of vehicle components. 

Our range of esters help formulators and original equipment manufacturers (OEMs) optimise thermal performance and contribute to fluid stability and material compatibility in a final formulation. Our base oils offer exceptional lubricating properties, for when formulators want to use a single fluid for lubrication and cooling – such as in an e-motor or electrical transmission. 

Our dielectric product offering is marketed under the brand of Xenitron™ – a brand representing high quality, high performance and sustainable dielectric base oils. 

What is a dielectric fluid? 

A dielectric fluid is an electrically non-conductive liquid that has a very high resistance to electrical breakdown. These fluids are typically used to cool and insulate electrical components. 

This method of cooling is more efficient than alternative methods - such as forced air cooling - as the thermal conductivity and specific heat capacity of the liquid is higher than that of air, making the fluid more efficient at removing waste heat.

Dielectric fluids can be used in full submersion and spray systems, where electrical components are in direct contact with the fluid. They are already used to cool and insulate transformers, capacitors, high voltage cables and switchgear, providing electrical insulation and suppressing electrical discharge. 

In electric vehicles, dielectric fluids can be used to cool the battery, electric-motor, power electronics and electric transmissions. The fluids must have high thermal conductivities and low viscosities to aid efficient heat transfer and pumping efficiency.

Why are new methods of cooling needed? 

Air cooling is the traditional cooling approach in most vehicles today, alongside in-direct water (ethylene glycol) cooling. However, these methods are no longer efficient enough to manage temperatures in high performance batteries and power electronics that need to be charged at very high rates.

For higher-performance applications, direct liquid cooling can be used. In direct cooling, water cannot be used as it will short circuit electronics. Water-glycol cooling systems also introduce weight and pose a risk if they leak. Direct cooling is therefore a preferred method that is safer, more efficient and more cost effective versus air and in-direct cooling. 

Direct immersion cooling using dielectric fluids in electric vehicles

Driven by the need to electrify, the automotive sector is now focused on creating highly efficient, power dense and lightweight electric motors, batteries and power electronics.

Effective thermal management is now the key challenge to overcome in unlocking maximum performance.

Over the next 5-10 years, direct liquid immersion cooling will become increasingly important as forced air cooling and indirect liquid cooling will not continue to meet the high-performance needs of the market.  

Direct cooling of electronics in EVs will occur in the following areas:

Fast charging and high-performance use of batteries

Many electric cars are capable of being charged at very fast rates (high coulomb rates, C-rates) with further increases planned for future models. This causes the battery to heat up significantly. High temperatures reduce the lifespan of lithium-ion batteries and very high temperatures increase the risk of thermal runaway. Cooling is therefore necessary to reduce the temperature during fast charging or when demand on the battery is high.

Cooling during charging increases the efficiency of charge transfer and reduces degradation of the battery, allowing the battery to retain capacity over its lifetime so that maximum EV range can be maintained.

Electric motor(s)

E-motors are up to 94% efficient and so small improvements in efficiency can result is large gains in EV range. Improvements in efficiency are delivered through effective cooling (reducing the effect of resistive heating) and improved lubrication.

Power electronics 

The power electronics transfer power from the battery to the motor and are also responsible for controlling the current going into the battery during charging. Temperatures can increase during charging or when significant demands are placed on the battery (for example during spirited driving, or at high ambient temperatures).

High temperatures increase electrical resistance which in turn increases temperature, as a positive feedback loop. Cooling is crucial to the efficiency and longevity of the power electronics. Trends to reduce the size of power electronics produce additional challenges for cooling and dielectric fluids can overcome these challenges.

What? Why? How?  Alternatives
Batteries To prevent degradation

Air cooling

Cold plate cooling

Direct immersion cooling
Power electronics To prevent overheating Heatsinks Direct immersion cooling
Electric motors To minimise current resistance Cooling jackets

Spray cooling

Drip cooling

Whitepaper: Properties of esters for use as dielectric fluids

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CFD study: Immersion cooling of batteries

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Data sheet: Xenitron™ 3221

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What makes our esters suitable for formulation into dielectric fluids?

We are world leader in esters. When we set out to develop dielectric fluids for direct immersion cooling, we used our knowledge of ester chemistry to design molecules that would outperform alternatives. Our research and development programme led us to identify esters that have: 

  • High thermal conductivities
  • Very high flashpoints
  • Non-toxic
  • Excellent dielectric properties
  • Low viscosities
  • Low volatilities
  • Halogen free
  • Oxidatively stable
  • Low pour points
  • Biodegradable or bio-derived. 

Today, we are working on the development of improved chemistries to meet the new needs of the industry. In doing so, we want to establish close partnerships with our customers to develop market leading materials for next generation fluids. Speak to us to get access to our latest development products.  

A shared dielectric fluid for motors, transmissions, and gearboxes


As customer demand for electric cars grow and competition increases, there is a downward pressure on prices and manufacturers seek to reduce costs. Range is also a significant issue for EVs to be accepted in the market and one of the easiest ways to increase range is to reduce mass. A trend in electric vehicles is to combine the coolant loop from the motor with that of the lubricant used in the transmission or gearbox. This simplifies the cooling system and reduces the number of fluids required. This saves weight, complexity, and cost.  

To achieve a dual-function fluid, the dielectric fluid must also have specific lubricating qualities including:  

  • Balanced friction and traction  
  • Low viscosity
  • Good oxidation stability

With over 70 years experience in tribology and lubrication, our capabilities are aligned to help you meet your goals in next generation fluids.

Recommended products

Xenitron™ 3221

A dielectric base oil suitable for blending into PAO and mineral oil dielectric fluid formulations.

Our team is here to answer your questions