Formula 1 ESS and battery technology

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ESS (Energy Storage Systems) and batteries are crucial for the performance of a Formula 1 race car. Thay have been hybrid since 2014, when major regulation changes came into the sport. The addition of an electric battery creates the need for new technologies and development that requires speciliased knowledge. Bold has been involved in a number of projects for the design of battery packs and supply of components for Formula 1 ESS Batteries. We have designed F1 battery packs from concept packaging to detail drawings of individual components.

Formula 1 Hybrid systems

The rule change of 2014

In 2014 FIA introduced new regulations that mandated using a turbocharge internal combustion engine with the addition of an energy recovery system (ERS). This system was composed of an ESS (Energy Storage System) or battery and two electric motor generator units: the first motor is mechanically connected to the internal combustion engine crankshaft to recover kinetic energy; the second motor is linked to the turbine shaft to recover energy from the exhaust gases.

Although energy recovery systems had been used in Formula 1 since the 2009 season, with KERS, the rule changes of 2014 were a major revolution. A much complicated system was needed and the complexity was such that even the leading engine suppliers struggled to adapt.


The mechanical energy recovery motor is called Motor Generator Unit Kinetic (MGU-K) and has a maximum power of 120 KW (161 hp). This motor is a three phase motor with permanent magnets that can either generate or harvest energy from the internal combustion engine.

Another generator is connected to the turbo compressor shaft to generate electrical energy from it. The energy released in the exhaust gases spins the turbo compressor at high rotational speeds. In turn, this motor can also spool the turbine to reduce what is known as turbolag, This motor is known as Motor Generator Unit Heat (MGU-H).

This energy generated by both electric motors is stored in a battery. The MGU-K harvests energy mainly during breaking and the MGU-H can harvest energy at any point. When the car accelerates, the energy is released to boost to the internal combustion engine with he addition of the 161 hp of the MGU-K. This brings the total power plant of an F1 to more that 1000 hp and higher than 50% thermal efficiency.

The amount of power that can be released by the MGU-K is limited by the technical regulations to 4 MJ per lap. The maximum harvest energy per lap is 2 MJ by the MGU-K and unlimited by the MGU-H. The location of the cell block must be under the fuel tank and inside the monocoque. The unit is protected by the monocoque itself and a structural plate underneath the battery. That full coverage prevents damage to the battery in case of a crash. The cell block mass must be between 20 and 25 kg.

The characteristics of the internal combustion engine are:

  • Cylinders: 6
  • Capacity: 1.6 litres
  • Maximum rpm: 15,000
  • Maximum fuel flow rate: 100kg per hour at 12,000-15,000rpm

Energy Recovery Systems (ERS):

  • Power output: Additional 161bhp
  • Maximum harvest energy: 2MJ per lap
  • Maximum energy output: 4MJ per lap
  • Battery weight: Limited to 20-25kg
The basic concept of a Formula 1 hybrid system
The basic concept of a Formula 1 hybrid system. (Image copyright ©: Renault Sport F1)

Motorsport and Formula 1 battery technology

ESS for motorsport are high power batteries which means they will be charged and discharged at a really high rate when the car is running. The battery state of charge changes significantly throughout the lap and can also be fully depleted during a single lap, for example in qualifying.

Batteries have ion-lithium cells with different chemistries depending on the budget and performance required. Some engine suppliers use pouch cells and others use can type cells.

All motorsport batteries will be cooled to keep temperatures in the safe operating window of the cells. Both water and oil based fluids are used depending on the design of the battery pack and aerodynamic characteristics of the car. The cooling systems of the battery are usually combined with the cooling of the electric generators.

Formula 1 ESS batteries

Battery enclosures for Formula 1 and motorsport

Most batteries for motorsport are contained in structural composite boxes that protect and support the cell block, cooling and electronic elements that from the battery pack.

There are different design strategies for safety of the pack with minor alterations in the way the metallic elements of the enclosure are connected amongst each other. Different levels of insulation might be preferred depending on the cell type and whether the power electronics are inside or outside the battery pack.

Some cars have the inverter and DC/DC electronics outside the battery pack. These elements, also require protection boxes which usually are made out of aluminium or composite materials.

The enclosures are purged with innert gas to prevent moisture condensation affecting the electronic components and high voltage elements. Therefore, enclosures must be designed to be leak proof. Pressure tests must be done to ensure there are no leaks so the inert gas is permanently contained.

Bold can perform pressure tests, as well as design and supply pressure test fixtures and kits. Electronic enclosures are usually tested to IP67 to guarantee an adequate safety protection level.

All battery packs for international motorsport competitions will be subject to transport regulations UN38.3 for lithium ion batteries. This tests puts the battery pack through a series of environmental, electrical, vibration and shock tests that simulate different conditions the battery might see during transport and operation. Hence, these tests will also be considered in the structural studies during the design phase.

Bold has experience in designing battery packs to comply with all regulations and requirements that teams have for the normal operation and production of the battery. Given the dangers of chemical runaway of the lithium ion cells, safety is a major element when designing the battery pack. Much of this experience can only be learned after having worked in numerous projects and seen first hand the requirements on the race track.

Battery enclosures for motorsport

Battery Enclosure Materials for Motorsport and Formula 1

For motorsport Bold uses composite materials to build battery enclosures. These materials offer a range of advantages that make them the best candidate for this application over machined aluminium:

  • High strength to weight ratio
  • Good impact resistance properties
  • Electrically conductive and insulated material variations can be combined in the same part
  • Relativelly low non-recurrent costs and quick turn around from design to finished product

The most common material for this application is carbon fibre and epoxy prepregs with the addition of some electrically insulation layers out of other materials. Other materials are used to create a Faraday cage effect to protect internal and external electronics from electromagnetic radiation caused by the inverter power modules and high voltage elements.

Composite materials for battery enclosures

Battery Enclosure Materials for Automotive and Industry

For high volume production, that is a hundred parts a day or more, Bold uses composite materials too. However, the process for making those is fully automated. In order to be able to implement this process, parts have to be designed accordingly. Bold works together with customers to develop the appropriate design features for high volume and low cost part production.

These automated processes offer the following advantages:

  • Hundreds of parts a day or more form a single manufacturing station
  • Highly automated process
  • Possibility to have long reinforcing composite materials for optimum strength to weight ratio and safety
  • Possibility to have metallic inserts embedded in the composite substrate of the part

Contact Bold for any question or requirement you might have about design and production of battery and power electronic enclosures. We will be pleased to support your team and work together to make great products.

Battery Cooling systems for Formula 1

Bold has experience in designing compact systems for cooling battery units. There is a variety of cooling systems and materials that can be used. We have used clever design features that allow ease of assembly in intrincate and busy battery compartments. The internal pipes of the cooling system can be made through machining, laminating, additive manufacturing or injeciton. Depending on the application and sector, Bold adapts the design to fit the requirements of our customers and provide the best solution for every project.

We have used additive manufacturing to produce aluminium cooling pipes for small volume production (up to 100 parts). The freedom of DMLS over moulded or machined cooling manifolds can reduce losses in the cooling system, thus reducing pumping energy requirements and weight. This has been implemented already and has been validated in testing. That is specially advantageous for small and compact units in motorsport.

Bold can simulate through CFD (Computerized Fluid Dynamics) the performance of your cooling system to optimize the unit. We can dimension the cooling requirements from individual cell testing and design the entire system to keep the cells at the correct operating temperature using air or liquid coolants. Heat exchangers are used to achieve the desired cooling temperature in high performance systems.

Bus bars for batteries for Formula 1

Every battery system has custom made bus bars to carry the electric power amongst different points in the battery system. Given cell blocks are increasing in power and getting squeezed in volume, bus bars will be ever more complex in shape.

Bold has experience in bus bars up to 600 mm long and 5 axis machining in one piece, with special coatings including gold plating and silver plating amongst others.

To electrically insulate the conductive material for safety inside the battery, we have used a number of techniques, ranging from composite material wrapping to powder coating. Bus bars can also be cooled using non conductive fluids.

A concern with bus bars is that they can crack and fail due to vibration at certain frequencies. For most applicatins involving vehicles and movility, bus bars will be exposed to some degree of vibration and this might cause structural issues. The consequences of a bus bar breaking are a big concern for any battery, especially related to safety. Knowing the correct material alloys to be used will greatly improve safety, whilst maintaining low electrical resistance and weight.

Another important aspect of cell battery and bus bar design is how to perform structural analysis on the units. There is a great deal of trade offs that need to be done and having strong previous experience is a big bonus. Contact Bold for specialist advice about design and supply of bus bars to your specification.

Power electronics enclosure for Formula 1

The knowledge derived from the battery enclosure range of products is also used in other applications. These include electronic boxes, such us inverter units for generators or electronics in general.

Bold has done a preliminary design in composite materials to reduce the weight of an aluminium enclosure for a Formula E inverter. The approximate weight reduction is in the order of 60%, which equates to saving in the region of 1750 g. This is a massive weight saving whilst keeping the performance of the aluminium enclosure in terms of structure and electrical properties.

These type of boxes can be produced using manual layup for low volume production or other proprietary processes for high volume. Bold has experience in tooling design for both approaches and can work together with customers to improve design for manufacturing. This will lead to a better product at a lower cost.

Experience is especially important for composites and batteries, which are two very specialised fields where the value of experience is a premium due to the performance and safety levels required.

High Power three-phase connector

Bold developed a set of three-phase plugs and sockets to connect the MGU-H and MGU-K motors to a Formula 1 battery pack and E-dyno testing equipment.

These connectors are significantly smaller than commercially available solutions and allowed much better packaging between the chassis and the battery pack. These connectors have now been manufactured in the hundreds. The connectors are rated to 300A and 1000 VAC. The plug body dimensions are approximately 20 x 60 mm in cross section.

Honda, high power connector

Bold can design and produce connectors for any application where volume and weight are important. In some sectors, the design is limited by the commercially available options which can be limiting the design of a new unit.

The freedom that a customized connector provides will enable a better product and might be a differenciating factor for the end customer. The cost of developing a custom connector is not significant when producing medium to high quantities of parts.


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