Description:
OBJECTIVE: Develop bipolar lead acid batteries that provide lighter weight and lower volume, for military vehicle applications. DESCRIPTION: Lead acid batteries are used in nearly all military ground vehicles. Many times, the size and weight of these batteries become prohibitive to meeting vehicle architecture and performance requirements. Bipolar lead acid technology offers a significant reduction in size and weight through the elimination of up to 50% of the inert lead grids. Traditional lead acid military batteries utilize a mono-polar construction, in which each cell consists of two plates (positive and negative) and each plate consists of a heavy lead metal grid pasted with active material. These plates are paired up to make a cell, and these cells are connected in series with metal connectors. In a bipolar design, each plate has positive active material on one side and negative active material on the other. Cells are created by stacking bipolar plates together so that the negative of one plate is paired with a positive of another plate, with each cell separated by the bipolar plate material. This construction alone offers an almost 50% reduction in inactive plate material. Additionally, the elimination of metallic connectors connecting the cells further reduces the weight and decreases the batteries internal resistance. Further improvements to the bipolar design can be accomplished through the investigation of alternate plate material and appropriate sealing techniques. An optimal bipolar plate material would be lightweight, inexpensive, and corrosion resistant. An appropriate sealing technique would prevent electrolyte from crossing between cells. Once an optimized bipolar lead acid battery design is established, the intended application would be a military vehicle starter battery. The current military lead acid batteries have an energy density of around 40Wh/kg , a specific energy 100 Wh/L and are capable of at least 120 deep discharge cycles. Some common military vehicle batteries are the 6T, 4HN, and 2HN, as well as some commercial form factors (Group 31, Group 75/86, Group 78, etc). A successful battery design would demonstrate improvements in energy density (60Wh/kg), specific energy (150Wh/L) and deep discharge cycle life (300 cycles). Additionally, the ideal final design would fit a standard military form factor and meet or exceed the weight, capacity, cold cranking amps, life cycle, and battery resistance requirements for that standard PHASE I: A successful Phase I would result in the development of bipolar lead acid cells that demonstrate 70Wh/kg energy density, 200Wh/L specific energy, and 50 deep discharge cycles on the cell level. Deliverables would include at least 5 bipolar lead acid cells for laboratory testing. PHASE II: A successful Phase II would scale up or otherwise optimize the cells developed in Phase I to fit a specific military form factor. These cells would be assembled into a multi cell string or battery module that demonstrate the feasibility of reaching the end goal of 60Wh/kg energy density, 150Wh/L specific energy, and 300 deep discharge cycles. Deliverables would include at least 3 bipolar lead acid strings/modules for laboratory testing. PHASE III: A successful Phase III would result in the development of bipolar lead acid battery that adheres to a standard military form factor and meets or exceeds military the specifications for weight, capacity, CCA, internal resistance, and cycle life. This battery should demonstrate 60Wh/kg energy density, 150Wh/L specific energy, and 300 deep discharge cycles. Potential military form factors include the 6T, 2HN, and 4HN as described in the military specifications MIL-PRF-32143B and MIL-B-11188H. Potential military applications would be any commercial lead acid start battery, such as Group 31, Group 75/86, Group 78, etc., as defined by Battery Council International. Deliverables would include at least 2 batteries for laboratory testing.
