Hybrid vehicles
Electric vehicles - batteries
With the development of hybrid and electric vehicles, the issue of electricity storage in batteries is becoming a priority. Breakthrough technologies are required to secure our long-term economic future in this field. Valérie Sauvant-Moynot, Head of the Electrochemicals and Materials Department, and Julien Bernard, “Battery” project manager, explain IFP Energies nouvelles' activities in the field of batteries.
- What research is being conducted by IFP Energies nouvelles in the field of batteries?
V-SM : We're working on accumulators capable of storing large quantities of energy, such as nickel metal-hydride or lithium-ion batteries, as well as supercapacitors offering greater power. These studies are being conducted as part of hybrid and electric demonstrator vehicle projects and prototype vehicles for testing and validating innovative technologies.
Our research has two objectives: to develop models capable of describing the electrochemical and thermal phenomena at work in batteries that can be integrated into simulation platforms in order to determine the dimensions of the vehicle architecture and improve real-time diagnosis of batteries' state of charge.
- Why is it necessary to assess the state of charge and “health” of batteries?
V-SM : In hybrid vehicles, the battery is responsible for intermittent and reversible energy storage. In order to optimize management, knowledge – precise and at any given time – of the battery's energy reserve or “state of charge” is crucial so that the information can be used to maximize the battery's “health”, in other words its lifespan. Yet, at present, it is still difficult to obtain a reliable real-time assessment of these two parameters. This is leading manufacturers to adopt large safety margins by reducing the working range of batteries. If the onboard system responsible for monitoring these parameters (BMS) was more precise, it would be possible to drive for longer, to reduce the size of the battery, which is currently oversized, to change it less frequently and hence to reduce costs.
- Have you made progress in this field?
V-SM : Internally first of all, then as part of the ANR (Agence nationale de la recherche) ALIDISSI project that we led in 2008-2009 alongside the CEA, the CNRS and M², we have developed an onboard diagnosis method based on measurement of electrical impedance. This involves applying a current to the battery then recording the voltage in order to deduce this measurement, which has proved to be a precise and reliable indicator of the battery's state of charge and health. Already validated in the laboratory, this research may soon lead to a prototype sensor.
- Another problem is battery ageing...
J-B : That's right. We are studying this phenomenon as part of ANR research projects. This involves simulating the ageing of hybrid vehicle batteries on test benches by reproducing and speeding up the operating conditions, especially those corresponding to vehicle acceleration and braking. These data are then integrated into models that are used to predict the lifespan of these components in real conditions of use. We also take into account the battery immobilization phases during which the battery deteriorates.
- Can you cite some examples of demonstrator vehicle projects?
V-SM : One example is the ADEME (Agence de l'environnement et de la maîtrise de l'énergie) demonstrator fund ELLISUP project, led by Irisbus-Iveco, which aims to produce an all-electric 12-meter prototype bus by 2012. We are involved in this project in several ways: characterization of battery components, thermal modeling of the pack and dimensioning of the cooling system, and, finally, the development of control algorithms.
J-B : We are also working on the HYDOLE project led by PSA Peugeot Citroën. This vehicle is designed to operate in all-electric mode during the week, when motorists are commuting to work, but uses a hybrid or IC mode the rest of the time, particularly at weekends. With the CEA and EDF, we are comparing several battery technologies, by subjecting them to various operating and ageing tests on test benches.
+ Industrial development > Engines > Hybrid vehicles