On silent watch, power is security

As military vehicles carry growing amounts of complex technology, so their power needs are growing. Traditional lead-acid batteries are no longer up to the job.

The military has numerous ways of carrying out reconnaissance – from very long-distance tools such as satellites to closer observation by troops on the ground. An increasingly common option is the ‘silent watch’ mission. This potentially high-risk operation involves bringing a vehicle and a team of soldiers close to their target to gather intelligence. Based on what they learn, if they need to act quickly, then the troops are where they are needed. If not, they can return to base without raising the alarm.

For this to work, a silent watch mission should, of course, be silent – or as close to it as possible. That means not running the engine while in position, which reduces noise and heat signatures, lowering the risk of detection and also conserving fuel and reducing emissions.

However, a modern military needs complex equipment to carry out the ‘watch’ part of the mission. Whether it’s communications equipment, sensors, optical and imaging tools or weapons and targeting systems, a contemporary military vehicle carries a lot of kit and it needs power. Without the engine to provide that power, the equipment needs a battery – and outdated batteries frequently create problems.

Replacing lead-acid

Over the course of a mission, lasting up to eight hours, there is obviously no way that a traditional lead-acid vehicle battery could power the necessary equipment, not to mention charging up any personal technology that soldiers might have with them. By the time the crew is ready to return to base, the battery would be dead. A worse problem is that each deep discharge of a lead-acid battery damages it so that its life gets progressively shorter with each mission, thus increasing the likelihood that the battery will fail and leave soldiers stranded.

To avoid that, vehicles have to have some other power option – often an externally-mounted or towed generator. These are usually smaller diesel engines than in the vehicle, designed to run quieter and consume less fuel. However, they are still cumbersome, heavy and inefficient but, so far, they have been the best solutions available.

That has changed in recent years as lithium-ion batteries have been developed as a realistic replacement. In comparison with lead-acid batteries, they are far better suited to silent watch missions – being able to provide power for long periods without running the vehicle engine. They offer higher energy density, longer life and, therefore, a lower total cost of ownership than lead-acid.

They are also better suited to extreme conditions, which means they can operate reliably in the extremely hot or very cold temperatures in which a modern military often finds itself.

Finally, Li-ion batteries offer smart capabilities that bring other benefits. Self-monitoring, for example, means that a battery will neither be replaced before its end-of-life nor fail when the crew needs it most. If the battery is close to failing it can warn the crew. And it can be programmed to disconnect itself from silent watch at the end of a discharge to guarantee that there is enough power to restart the engine.

Lithium-ion brings peace of mind

Saft’s Xcelion 6T was designed specifically for this purpose. It is a drop-in replacement for a lead-acid battery with all the benefits of Li-ion as well as additional smart features. For example, the ‘battle override’ mode will ignore some of the battery’s normal operating limits if necessary, without compromising the overall safety limits of the battery. That means, for example, that if the crew needs to use the battery in very high temperatures, perhaps to escape a dangerous situation, the battery will deliver the necessary power.

Producing a battery that can meet these needs is not easy. Reliability is paramount, but these batteries also have to operate in extreme conditions and do so safely. A Li-ion battery that catches fire if it is struck by a bullet is not something you want on a military vehicle. Saft uses superphosphate chemistry, a proprietary iron phosphate-based chemistry that is the safest on the market today. Equally, with the range of environments in which a modern military might need to operate, these batteries have to be able to function in very hot and very cold places without performance suffering.

The GDELS Mowag Piranha V armored personnel carrier, due to be deployed by the Danish military in 2018, will be powered by the Xcelion 6T. Its uses are not limited to military vehicles, however. The fact that the 6T fits in the same space as a lead-acid battery means it is also being looked at by the emergency services and as a battery for hybrid generators in disaster regions.

A silent watch mission puts soldiers in situations involving long periods of waiting, sometimes punctuated by short, rapid bursts of activity. It’s a common combination in armed forces work – and a stressful one. The last thing service personnel want to worry about during such a tense mission is whether they will have sufficient power to move their vehicle when the time comes. With a lithium-ion battery, that worry is removed, leaving the crew to concentrate on their mission.

Xcelion 6T update

In August 2019, Saft launched the Xcelion 6T Type 1-A battery that is designed to meet the stringent standards of MIL-PRF-32565 Rev B set by the U.S. military, and provides unsurpassed cold cranking performance and safety. This newest Xcelion battery will enable U.S. military and defense contractors to seamlessly replace legacy lead-acid battery technology with lower weight, enhanced performance Li-ion batteries that are maintenance-free