The higher energy and power density of Li-Ion battery technology offers a significant reduction in the weight and volume for hybrid electric vehicle (HEV) battery systems compared to lead acid and nickel metal hydride technologies. Saft’s High Power Li-ion battery technology has demonstrated specific power of over 6,000 W/kg under continuous discharge, and a pulse discharge of 8,000 to 12,000 W/kg.

This technology has been steadily improved as advances in electrochemistry are proven and implemented. The VL34P cell was recently developed to provide the dual performance of power and energy suited for military vehicle applications. This cell has been used in series hybrid applications to support battery-only operation, silent watch, and drive assist. The performance characteristics of the cell make it an ideal candidate for integration into battery systems for hybrid electric drive vehicles.

The cell incorporates improvements in many aspects of the cell design. The electrochemical design has been updated to improve the performance of the cell for high rates and low temperatures. It has been repackaged to improve the volumetric and gravimetric power and energy densities, while moving to lower-cost components and processes. Improved packaging and assembly methods have also allowed for a significant reduction in the internal resistance of the cell, resulting in improved power, improved energy, and lower heat generation. This allows for a uniform temperature distribution within the cell, and a means of effectively removing heat from the cell to improve cell life.

The VL34P cell has been shown to be well suited for use in military vehicle applications. The high power of the cell is able to support the charge and discharge power profiles of hybrid vehicles. The low cell resistance allows for simple cooling methodologies for the modules and batteries. Implementation of controls in the battery systems for vehicles provides an excellent means of effectively monitoring and integrating the battery within the vehicle controller.

Iron phosphate is suitable for high-power applications that require an added level of redundant safety to extreme abuse. The requirements of the application must be considered, as there are tradeoffs in lower power and energy, poorer low-temperature performance, and less stability at high temperatures for storage.

This work was done by Scott Ferguson, Kamen Nechev, and David Roller of SAFT America, Inc. for the Army Research Laboratory. ARL-0071

This Brief includes a Technical Support Package (TSP).
Advanced Lithium Ion Systems for Military Vehicles

(reference ARL-0071) is currently available for download from the TSP library.

Don't have an account? Sign up here.