Military Embedded Systems

The battery’s role in the evolving military ground vehicle


November 20, 2023

Steve Carkner

Stryten Energy

Photo: Marine Corps Cpl. James Stanfield.

Military vehicles have rapidly evolved over the last few decades, equipped with more technology than ever for safer, more capable operations – requiring more power than ever. Manufacturers building energy-storage systems for modern military vehicles will need to tap the power of lithium batteries to more effectively power engine starts and silent watch capabilities, make hybrid engines viable, and ensure energy payload weapons function to their full potential.

Much like consumer vehicles, military vehicles have for decades relied on lead batteries for their most basic functions. Unlike most consumer vehicles, military vehicles produced in the 1970s and 1980s are still on the road today, and they still rely on lead batteries because these batteries are highly reliable – and they’re unlikely to go anywhere soon. The power demands of these older vehicles were low, mostly just engine starts, but upgrading these older vehicles may require increasing the existing energy storage, or possibly installing a second energy source that is dedicated to the new equipment.

As military vehicles have grown more complex, however, the battery’s role has also evolved, and innovative battery technologies present a variety of options for many applications. Today, energy is a resource that can be managed in real time and determines combat capabilities. In fact, it’s more appropriate to refer to modern-day batteries – many of which are often added to military vehicles in addition to the engine-start battery – as energy-storage systems. These next-generation batteries are networked in the vehicle and across the battlefield. They become part of the battle-management system and the “Internet of Battlefield Things.”

In the field, vehicles need batteries capable of running longer durations, while also delivering massive energy when necessary. The success or failure of a mission can depend on the success or failure of the battery. Let’s take a closer look at different options for vehicle energy sources and determine which are best for critical vehicle functions today, including engine starts, silent watch, hybrid vehicles, and energy payload. (Figure 1.)

[Figure 1 ǀ Modern-day batteries used in military vehicles are more appropriately called “energy-storage systems.” Stryten image.]

Engine starts and silent watch

Given the energy needs of today’s military ground vehicles, current 6T lead-battery technology [6T is a standardized form factor] is still used for engine starts. However, it will fall short of powering longer duration needs, such as critical electronic and cyberwarfare systems. A 50-amp load, still light by most military vehicle standards, may only be supported by a lead battery for 30 to 45 minutes without running the risk of deep cycle degradation issues or not leaving enough energy in the battery to start the engine.

Longer duration needs like silent watch applications regularly demand 80% or more of a battery’s capacity, which typically rules out lead batteries. Silent watch missions for modern military vehicles can require five times the electronic systems – including sensors, advanced communication systems, active-protection systems, electric power, and specialized battlefield systems – compared to older vehicles.

Even if duration wasn’t an issue, lead batteries still pose operational challenges: Draining a lead battery below 50% state of charge (SOC) significantly diminishes the battery’s life, and because lead batteries typically do not have built-in battery monitors, monitoring the SOC and general health of a battery becomes nearly impossible in the field.

Knowing all of this, what strategies can the military deploy for powering silent watch missions? Most solutions come with significant downsides:

  • Practicing tactical idling, or leaving the vehicle running most of the time, using lead battery for short bursts. This is inefficient and loud, plus it creates dangerous heat signatures that can be used to target the vehicle.
  • Installing an on-board generator – once again, these are loud, can be used by an adversary for targeting, and are prone to maintenance issues.
  • Installing fuel cells – these still require fuel, have a heat signature, and are sensitive to contaminants and abuse in harsh military environments.

Ultimately, lithium batteries look to be the leading option for both engine starts, and for longer duration needs such as silent watch. Moreover, lithium battery systems are “smart.” With a battery management system (BMS), SOC can be easily monitored to avoid loss of power in the field, as the batteries allow accurate coulomb [unit of electric charge] counting with a capacity and health measurement error of 2% or less. In addition, they have longer life than a lead battery, can double or even triple the time an engine can remain off, and have no heat signature.

More vehicle developers will likely look for dual sets of lithium batteries to power military vehicles. One set will be dedicated to engine starting with lower energy storage capacity and moderate instantaneous power, while the other set will power silent watch electronics with high storage capacity, but not necessarily high instantaneous power.

While the initial rollout of lithium batteries for silent watch is designed for larger vehicles, interest is growing for use in smaller transports like Humvees and light tactical vehicles. (Figure 2.)

[Figure 2 ǀ The Mine-Resistant Ambush Protected (MRAP) truck is used by the U.S. military for troop transportation; this MRAP is used by the U.S. Army Special Forces.]

Hybrid military vehicles

Silent watch also poses a challenge for diesel vehicles. Drivers want to move quickly for most of their journey to get close to the front lines and avoid detection once they get there. Diesel engines are not only loud, but they also create heat signatures detectable to the enemy.

Instead, there is a need for a hybrid engine, one powered by both electricity and fossil fuels, that enables quieter movement and a lower heat signature. Using a hybrid engine, a vehicle could make the first part of the journey using fuel and the last half mile using electricity for optimal stealth.

Hybrid vehicle batteries generally are going to be medium-capacity, with the ability to be charged and recharged many times. Much like engine starts and silent watch on larger military vehicles, the properties of a lithium battery make it a good option to power hybrid engines.

Coming up: energy payload weapons

Future combat systems may rely on nonkinetic directed-energy weapons to counter uncrewed aerial and hypersonic missile threats. More responsive and powerful lasers depend on the capacity and instantaneous power of next-generation energy-storage systems. This technology can quickly eliminate an enemy drone or disable an enemy vehicle with a small, focused strike on the vehicle’s core components, reducing danger while also reducing casualties.

High-rate energy storage-systems, often 100 C and greater (charge rates of 100 or greater than the battery energy capacity), are used to power energy-payload weapons. 100 C is a rate 50 times faster than most batteries available today. For context, the amount of energy being delivered in these exceptionally high-rate applications could power 20 homes, but the energy used in a weapon may only flow for a few seconds at a time.

While the exact types of energy-storage systems used to power these systems remain closely guarded, many in the industry are experimenting with lithium batteries, super capacitor banks, or a combination of the two.

Cutting-edge vehicles require cutting-edge power

Military vehicles have long been full of innovative technologies battling for their share of available power, but greater demands for energy capacity have pushed traditional batteries to their limit. Whether for moving troops safely and quietly, or ensuring weapon effectiveness, militaries have to rethink their energy strategies on the battlefield.

Lithium batteries could be part of the solution, as they can store more energy and deliver it over long periods of time, but they are also capable of concentrating it and emitting it quickly when under attack.

Steve Carkner is director of technology & business strategy at Stryten Energy. He has more than 30 years of engineering experience and is an inventor on dozen of patents. Prior to joining Stryten Energy, Steve served as head of innovation at Galvion, head of innovation at Revision Military; he was also founder and CTO at Panacis Inc. and served as director of product development at Blackberry. He holds a bachelor of science degree in electrical engineering from Queen’s University in Ontario.

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