The U.S. Army takes significant pride in its vehicles, many of which have become synonymous with power and performance. Indeed, modern combat requires that ground forces be able to rapidly maneuver across the battlefield. Meanwhile, the automotive sector is shifting away from traditional internal combustion engines to electric powertrains. Most major automotive companies have committed to developing electric vehicles, with some even planning to phase out internal combustion engines altogether.
Given that the U.S. Army has committed to leveraging commercial innovation, it is natural that it considers the use of electric vehicles. Electric drivetrains offer several advantages over traditional drivetrains for military applications. However, the usage of electric vehicles will be limited until several key issues are resolved.
Over the past three years, the U.S. Army has started to actively evaluate electric vehicles. Last week, General Motors Defense demonstrated an electric prototype of its Infantry Squad Vehicle. The prototype leveraged commercial General Motors technology, producing more power than the standard diesel version while achieving a range of 70-150 miles. Additionally, in April, the U.S. Army awarded contracts to six companies to study different methods to power a future fleet of 225,000 electric military vehicles. These contracts are part of a larger effort to oversee a long-term transition plan to electric vehicles.
While sustainability is a key selling point for electric vehicles in the automotive sector, it is less applicable to the military. U.S. Army vehicles use diesel engines that run on JP-8, a form of jet fuel. In a deployed environment, the bulk of the power is created from generators which also burn JP-8. Hence, the usage of electric vehicles simply adds an intermediate step in converting JP-8 into vehicle propulsion. Additionally, jet fuel is also becoming greener, as the aviation industry is “going green” by using synthetically generated jet fuel.
However, electric vehicles offer numerous tactical advantages on the battlefield. First, electric motors provide more torque at lower speeds than diesel engines, improving vehicle acceleration, towing capacity, and climbing ability. Additionally, the noise and thermal signatures from an electric drivetrain are substantially less than those from a diesel engine. Modern acoustic sensors and infrared cameras can detect a diesel engine from multiple miles away; as such, a reduced signature is key for surviving on the modern battlefield.
Regardless of these advantages, there are still numerous technical hurdles that must be overcome prior to the U.S. Army widely using electric vehicles. The largest issue is battery weight. A diesel engine can convert 1 gallon of JP-8 into the energy stored in 140 lb of Li-Ion batteries. As such, the 23 gallon fuel tank of a Humvee would equate to 1.7 tons of batteries, more than half the current weight of the vehicle. This issue becomes amplified for larger vehicles which would require even more batteries. Furthermore, many of these vehicles are already at the upper limits for the allowable weight on some roads and for air-transport. To maintain the existing weights, the vehicles would have to sacrifice its range, weapon systems, or armor.
The second issue is related to charging. Currently, soldiers load their vehicles with extra fuel canisters to refuel during a mission, allowing them to extend a mission. However, when an electric vehicle depletes its batteries, it must be able to find a place to recharge. Since recharge options will not be likely in deployed environments, another vehicle must drive out to the vehicle with a generator and recharge the batteries. Meanwhile, the recharging process can take substantial time, during which the vehicle and its crew are vulnerable to an attack.
The third issue is safety. Although JP-8 is flammable, it is more stable than Li-Ion batteries — lithium burns quickly and aggressively. Additionally, a small amount of physical damage to an individual battery cell can result in the thermal runaway, resulting in the entire battery pack catching fire. A small roadside bomb or a well-placed bullet aimed at the battery pack could cause the entire vehicle to rapidly catch fire.
All of these issues will eventually be resolved by the automotive sector, which is spending billions of dollars into researching better batteries. Eventually, a new battery chemistry will be available with a higher energy content, faster charging time, and more durability. However, although several chemistries are showing promise, it will still take significant time for the infrastructure to be in-place to produce these batteries at scale.
On the near term, the U.S. Army can take advantage of electric vehicles through hybrid power trains. Hybrid options allow for quiet, resilient, and powerful vehicles that are less constrained by battery technology. Last year, the Army awarded the University of Wisconsin to investigate hybrid drivetrains for tactical and combat vehicles. Additionally, multiple companies have produced prototypes of hybrid combat vehicles.
Right now is an exciting time for the automotive industry as electric vehicle technology are establishing a market foothold. Given that the Army is attempting to leverage advances in the commercial sector, it seems natural that they will evaluate the use of electric vehicles in their ground vehicle fleet. Despite their tactical benefits, the technical challenges associated with the batteries will likely limit the usage of electric vehicles in military applications.