Effective, safe and economical packaging for batteries, utilized through the US Navy and US Army activities, are becoming a greater issue everyday. Two major reasons for this challenge are (1) commercial cells are being packaged in a case suited for military applications and (2) the higher energy densities are raising the level of danger. In most applications, battery power is provided by several cells joined in series to form a set of cells. In this case, volumetric power density is a function not only of individual cells but of the assembled cell sets. Prismatic and pouch cells utilize space more completely than do cylindrical

Battery packaging ranges from the assembly of a battery containing 10 Watt-Hours of capacity for radios up to batteries with a storage capacity in excess of 1 Megawatt-Hour for underwater vehicle applications. A specific application is the development of small, quiet, unmanned Navy vehicles for military operations and surveillance.

This vehicle, Wide Area Surveillance Projectile (WASP), creates unique requirements for innovative battery packaging. The WASP micro air vehicle illustrates unique battery packaging. It replaces separate battery and wing structure components with a multifunctional structure/battery material system that supplies electrical energy for propulsion while carrying mechanical and aerodynamic wing loads. 1 This program is exploring materials that combine the function of structure with another critical system function such as power, repair, or ballistic protection.

The power supply for the WASP micro air vehicle must not only be rugged and reliable, but also as compact and lightweight as possible for Navy operations. The dual use of material, for structural integrity as well as for the wall of the battery itself moves in this direction.

However, another powerful factor is the type of battery that is chosen for the task. The accompanying charts (on the following page) illustrate the advantage of lithium batteries for energy supply where weight and volume are critical. The only other common battery type that is in the same energy output range is the zinc-air battery. However with its high internal resistance the zinc-air battery is not adaptable to high load applications such as are typical for most Navy systems.

Air crew systems needed a low-cost energy source for the PRC-112 Survival Radio used by the US Navy, Airforce and Marines. This need brought to light an opportunity to utilize commercial technology in a military application. The current energy source is a custom-designed primary battery. ACI, working with the US Army CECOM, has delivered a primary battery option based on nonrechargeabe lithium-ion batteries and rechargeable NiMH batteries.

The goal of the battery program was to provide air crews with a lower cost solution with similar capacity. The results indicate the primary version has approximately 90% of the life of the current battery. Designed to allow the insertion of COTS AAbatteries, the cost of use is significantly reduced. The US Army estimates a potential savings of $10M over the life of the program.

Lithium Batteries
Lithium rechargeable batteries for military applications have several advantages over current battery chemistries currently in use namely:

The disadvantages of lithium rechargeable batteries are:

Safety Considerations
Typical safety considerations that must be addressed when developing a packaging methodology for batteries are:

When considering lithium batteries for US Navy applications, S9310-AQ-SAF-010 Technical Manual for Batteries, Navy Lithium Safety Program Responsibilities and Procedures is followed. Other types of battery chemistry have similar testing requirements prior to use with the US Navy.

Comparison of Lithium and Alkaline Batteries for Navy Applications
Unfortunately, lithium batteries are relatively expensive, particularly with reference to the common alkaline batteries with their widespread commercial use. Thus it was of interest to directly compare the output of lithium and alkaline primary cells, in equivalent AA size packages. Data achieved at ACI and presented in the following graph clearly shows the greater power of lithium AA batteries (type L-91) in comparison with alkaline AA batteries. Note the voltage decrease of the alkaline battery as well as the shorter lifetime. The graph also presents data for the alkaline AAA cell, for comparison.

Battery Selection Criteria
The selection of the current battery type, based upon environmental conditions, use and storage, can either reduce or adversly impact the total cost of ownership of a system. The battery application determines the appropriate choice for battery type and chemistry. The criteria that must be considered in selecting the correct battery type for a given Navy application, and for choosing or designing an efficient, effective Navy product, can be summarized with the convenient mnemonic VITALES: 2

V oltage
I = Current
T emperature: operational and storage ranges, plus anticipated extremes
A ctivation mode (for reserve batteries)
L ifetime (storage and operation)
E nvironmental requirements
S ize: weight, volume, configuration

References
1 John McHale, Military & Aerospace Electronics, December 2002.
2 Discussion with Clint Winchester, December 2002.