The Development of an Isothermal Control Platform (ICP) for the Precise Regulation of Battery Temperatures using Multiple Zone Control

"The characterisation of batteries is critical in the development of Li-ion battery chemistries. This influences the designs of modules and the associated thermal management systems which handle the heat generated during their use in electric vehicles. Consequently it is fundamental to understanding whether or not particular battery chemistries and constructions are capable of providing enough power in a safe manner to drive a vehicle under both normal and extreme conditions of use. The design of a cooling system which prevents batteries from overheating is a necessary requirement in every electric vehicle and impacts on both safety, battery longevity and vehicle range. It is therefore imperative that a precise understanding of battery behaviour is established to minimise shortfalls that come about as a result of inaccuracies in the design data obtained from charging and discharging experiments.

It was determined recently by researchers at Imperial College (ICL) in London, that there are significant inaccuracies with data obtained from such experiments on Li-ion cells when carried out in isothermal chambers that maintain a constant temperature environment. This was noted to be a problem at lower temperatures, such as those encountered during the winter in many parts of the world. It was clear that the temperatures of the batteries under test were deviating significantly, as the main method of heat removal was through convection. This resulted in significant misinterpretations of their behaviour and performance and is of great concern as this indicates that the current methods which use isothermal chambers are flawed to a significant extent, yet are relied upon exclusively by the Li-ion battery and the electric vehicle industries.

An alternative means of achieving a more constant temperature is by direct contact with the battery. This will exchange heat through conduction in a much more controlled and direct manner, avoiding the above mentioned inaccuracies altogether.

Bletchley based Thermal Hazard Technology (THT - a trading arm of Heath Scientific Co. Ltd.) are considered to be World leaders in Safety Calorimetry and in particular within the Li-ion battery and electric vehicle sectors. It is considered that bringing their expertise to bear upon this problem will lead to the successful development of a much needed testing platform which will provide a means of obtaining much more reliable data for use in the design and development of batteries and electric vehicles."