While the electrical and mechanical components of hybrid vehicles are reasonably mature, the main obstacle for full Hybrid Electric Drive (HED) maturation with the military are the batteries. The main drawbacks of current batteries are their sensitivity to extreme environmental conditions (heat, freeze, humidity). To prevent freezing the batteries are contained in an environmental chamber, which maintains the temperature at operational conditions. This method enables the vehicle to operate from -40C to +65C degree temperature range.
Battery cost is another aspect causing slow adaptation of HED. Current designs are using lead-acid, which are widely available and lower-cost batteries. Nickel Metal Hydride (NiMH) batteries provide twice the energy storage of lead-acid, but only half the power surge, therefore, they can drive a vehicle twice as far but not as fast. Lithium-Ion cells are delivering the highest performance but their cost is still prohibitive for mass-production. Fuel cells are also considered, but such technology is still far from maturation for large scale applications.
Lithium-ion batteries would give a vehicle four times the energy capacity with power density equal to lead acid. They could also power a command and control shelter for 12 hours. The cost of such batteries is still too high and current battery research is examining issues such as the cost of raw materials, materials processing, cell packaging, and module packaging in an effort to make the process more economical. R&D is also addressing lithium-based battery performance limitations, which include the reduction in discharge pulse power at low temperatures and the loss of power over time. Lithium Technology Corporation and T/J Technologies are developing such large format rechargeable Lithium batteries, under a $5.1M U.S. Army TACOM Life Cycle Management Command contract.
Another aspect of the new hybrid and electrically powered vehicles will be the power management. Although these vehicles will pack significantly more power than current vehicles, they will also consume more power – by employing more sensors, radios, computers, active suspension systems, electric gun turrets, nuclear/biological/chemical protective systems and other mission equipment. Future vehicles could also mount electrical armor protection, which will significantly increase power demands. These future vehicles will require an automatic load management, matching power demands with resources, drawing available power from generators, batteries and other sources.
HED Providing Mobile Power
The use of HED powered vehicles in power generation role is evaluated by the ONR under a 3 year program focusing on 20, 30, and 60 kW power generation provided by modified Humvee and MTVR vehicles. The biggest generator typically towed by a Humvee provides 15 kW. In contrast, the hybrid Humvee demonstrator can produce 75 kW. When supplemented by common lead-acid batteries the vehicle can provide 500 to 600 kW. This capacity opens new opportunities for the employment of power-hungry weapon systems – such as a mobile solid-state 100 kW laser currently under development. Another program will evaluate the RST-V capability to convert as a 60 kW mobile power generator, thus reducing battlefield logistical tail.
Additional parts of this article:
- Military Applications of Hybrid Cars and Trucks
- Technical Principles of Hybrid Electric Drive
- Plug-in Hybrid Electric Vehicles (HED) the Humvee example
- Hybrid Electric Vehicles (HED) Powered Trucks
- Hybrid Electric Drives (HED) For Armored Fighting vehicles
- Power Sources and Batteries for Hybrid Electric Drive (HED) Vehicles