June 26, 2012

AABC Europe 2012: better batteries with same chemistry.

The third European Advanced Automotive Battery Conference (AABC) took place 18-22 June 2012 in Mainz, Germany. Chaired by Bertrand Largy, Renault, Session 4 of AABTAM focused on battery pack engineering in automotive applications, aiming at making batteries safer, more reliable and better performing through better design, innovative cell-to-cell connection and modular approach.

Cell-to-cell connection by AVL

AVL has developed an innovative cell-to-cell connection to replace laser welding: cell tab clinching, easy and fast operation, the connection is un-detachable, double-sided and without pre-punch. The clinching connection method has been tested for electrical, thermal, mechanical measures: pull tests, climatic and humidity tests, vibration tests, electrical resistance tests and thermal behaviour tests. The connection passed all tests successfully.

Compared to laser welding, clinching as cell connection technology offers the following advantages:
  • Cost-effective tool (1/5 of laser welding)
  • Short cycle time (parallel execution + multiples points)
  • Possible direct combination of different materials (e.g. Al / Cu)
  • Insensitive to positioning tolerances
  • No heat input
  • Different material combinations and multiples layers can be connected with the same tool (e.g. Ap and 2p connections)
  • Cost reduction by eliminating parts

Safety of the Battery Pack – Renault experience

Batteries become unsafe because of electrical, mechanical or thermal abuse, or because of a cell internal defect. Masato Origuchi, EV Battery Development Group Leader at Renault, stresses the importance of having safety barriers at each level of battery components:
  • At the cell level with Cell intrinsic safety and manufacturing quality
  • At pack level with mechanical / thermal integration
  • At system level with Electronic control for “System Fail-safe”
  • At vehicle level with mechanical integration for crash safety

Renault has also conducted many tests regarding the behavior of electric vehicles and their batteries in case of a fire. The company worked with a fire department for fire extinguish test and has seen no significant difference from ICE vehicles. No violent phenomenon occurred and the fire was extinguished safely with water.

Modular approach in battery systems – BPCE experience

The BMW Peugeot Citroën Electrification (BPCE) has worked on a modular approach for batteries, including modular BMS. For Dr. Kai Ludwig, Manager Functions & Calibration R&D Battery, at BPCE, a “modular battery management system enables efficient development, integration & validation”.

On the hardware part, advantages in terms of costs are quite important as the battery management system (BMS) hardware covers 40% of total battery part costs.

But advantages are not only related to cost. A modular BMS HW:
  • Fits into a maximum number of battery geometries
  • Can be easily adapted to different function requirements
  • Supports different vehicle platforms
  • Covers long project time scales
  • Enables supplier competition
Software is also very important in the BMS, as its development cost represent a large part of R&D efforts (hardware + software = 44%). A modular BMS software:
  • Supports different battery configurations
  • Supports different vehicle platforms
  • Can be easily adapted to different type of cells
  • Covers long project time scales
  • Enables supplier competition for BMW hardware