Advanced Lithium Ion Systems for Military Vehicles

These rugged, long-lasting battery systems are applicable for hybrid electric drive vehicles.

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



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Advanced Lithium Ion Systems for Military Vehicles

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Defense Tech Briefs Magazine

This article first appeared in the August, 2009 issue of Defense Tech Briefs Magazine (Vol. 3 No. 4).

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Overview

The document titled "Advanced Lithium Ion Systems for Military Vehicle Applications" discusses the advancements in lithium-ion battery technology developed by Saft America, Inc. for military applications. It highlights the significant benefits of lithium-ion batteries over traditional battery technologies, such as lead-acid and nickel-metal hydride, particularly in terms of energy and power density, which leads to reduced weight and volume for hybrid electric vehicle (HEV) systems.

The report focuses on the VL34P cell, a high-power lithium-ion battery designed to meet the demanding electrical power requirements of military vehicles. This cell is characterized by its high rate capability, allowing it to support applications requiring silent watch and hybrid electric propulsion. The VL34P cell demonstrates a specific power of over 6,000 W/kg under continuous discharge and can achieve pulse discharges of 8,000 to 12,000 W/kg, making it suitable for both manned and unmanned military vehicle applications.

Key performance characteristics of the VL34P cell include a nominal capacity of 33 Ah, a mass of 0.94 kg, and an energy density of 280 Wh/dm³. The cell can deliver a maximum continuous discharge current of 500 A at 25°C, with a peak pulse current of 1,900 A for short durations. The document also emphasizes the cell's low internal resistance, which enhances its performance, particularly in hybrid vehicle applications that operate within a specific state of charge range.

The report outlines the testing conducted on the VL34P cell, which confirms its excellent rate capability and cold temperature performance, with 85% of capacity delivered at -30°C. The cell's design improvements, including enhanced electrochemical properties and packaging, contribute to its high performance and lower heat generation, which is crucial for maintaining cell life and efficiency.

In conclusion, the document underscores Saft's commitment to developing advanced lithium-ion battery systems that cater to the unique needs of military vehicles. The ongoing efforts to reduce costs and improve performance, led by key personnel at TARDEC, aim to make these battery technologies more accessible and effective for military applications. The collaboration with the U.S. Army and continuous feedback from customers are vital for the ongoing development and enhancement of these battery systems.