Solutions for Vehicle Communications and Power Interconnectivity

By Robert Grzib | January 17, 2023

The increasing demand for mobile tactical power and communications capabilities presents new interconnect and cable assembly design challenges.

The increasing demand for mobile tactical power and communications capabilities for military use presents new interconnect and cable assembly design challenges. In addition to demanding the utmost in durability and universal connectivity, military requirements make the optimization of finite in-vehicle space critical. Alternative interconnect designs and MIL-Spec components maximize performance while addressing the Department of Defense (DOD) requirements for powering in-vehicle radios, GPS devices, and chargers. 

Legacy in-vehicle communications and power systems’ size and capabilities

Single-channel vehicle-mounted military radios were developed in the 1930s to supersede visual and light signals, foot and motorbike couriers, homing pigeons, and messenger dogs. These early tactical communications radios were big, heavy, and bulky and therefore commonly mounted in Jeeps, armament carriers, and trucks. Their outsized physical dimensions, high-current power demands, and complexity relegated their usage mainly to single-purpose “signal corps” vehicles. For situations in which longer-range communications capabilities were needed, radios were installed in special “radio vans,” the predecessors to today’s military mobile radar vehicles.

In-vehicle communications and power systems optimize performance and limited interior space 

The vehicle that initially compelled engineers and military contractors to create application-specific power interconnect components was the U.S. military’s High Mobility Multipurpose Wheeled Vehicle (HMMWV), commonly referred to as a Humvee. First introduced 1988, over 280,000 Humvees were manufactured. The vehicles were specifically designed for the SINCGARS (Single Channel Ground and Airborne Radio System) family of VHF-FM combat-net radios (CNR) to provide the primary means of command and control for infantry, armor, and artillery units. The radio had no charging or additional ancillary systems requiring power. Over 500,000 SINCGARS were manufactured in a variety of form factors and were typically employed in military vehicles. As they were strategically installed in the center of the vehicles’ forward dash, they eventually began to encroach into the driver compartment. Despite multiple attempts to re-configure the available mounting area in so many units, it was determined that optimization of the existing space was significantly more cost-effective. Any solution would require standardized MIL-DTL-55181 connector interfaces and similar performance specifications (e.g., voltage drop, contact compatibility, shell plating equivalency, and environmental durability).

The JLTV (Joint Light Tactical Vehicle) program is the current U.S. Armed Forces and United States Special Operations Command initiative to part-replace the Humvee in frontline service. These state-of-the-industry combat vehicles need multiple auxiliary power sources for additional radios, chargers, and accessories. While radio installation in the JLTV is more integrated, the vehicle’s crew compartment is narrower than the HMMWV and requires specialized space-saving power source multiplication. Though a vertical stacking design is most regularly used, a JLTV-specific, side-by-side, cable-mounted connector box is frequently specified to optimize limited space and support heat dissipation.

Vertical-stacking cable-mounted connectors 

Cable-mounted MIL-DTL-55181-compatible stacking connectors were developed to minimize footprint while maintaining both plug and receptacle contacts. The stacking connector’s front-mounted plug contacts can be mounted to a power receptacle, which allows additional plugs and cables to be mated to the connector’s rear-mounted receptacle contacts. When mated to a battery, power is distributed to the cable attached to the stacking connector and the “piggybacked” cable. Notably, the stacking connector can also function identically to a standard plug when a secondary piggybacked cable is not connected. This enables the removal of the battery powered by the stacked cable for use in another vehicle to further maximize the safety of ground troops.

Single-point-mounted dual-exit splitter

As multiple designs are required to address the divergent applications, dual-exit, single mounting point plugs were developed to provide a straightforward, low-cost alternative to traditional “Y” cables. This design incorporates a single-plug MIL-DTL-55181-compatible body mounted on a permanent interconnect to distribute power to two exiting cables connected to ancillary radios or chargers. While the single-point-mounted dual-exit splitter is less space-efficient than the stackable design, it is a more efficient solution for applications in which standard cables are utilized regularly as a fixed configuration within the vehicle. In addition, the single connector interface supports mating and un-mating as needed.

Connector head splitter

Dual head splitter receptacles enable the powering of two devices from a single cable, without requiring additional interior vehicle space. The configuration allows two sets of MIL-DTL-55181-compatible receptacle contacts to share power from one source cable. As this innovative interconnect is a single-piece design, it is a simpler and lower-cost solution to multiple external “Y” cable assemblies.

Multi-power access units

These engineered components provide two power outputs from a single input. The unit’s body incorporates a cable adaptor and a MIL-spec-style receptacle to facilitate power splitting from a single MIL-DTL-55181-compatible plug connected to the power source. This is an ideal configuration for height-constrained applications or when a preexisting preconfigured cable or wire harness is needed (mating interface to the receptacle interconnect). While versatile, the units’ physical size and functionality are more permanent than those previously discussed.

Alternative orientations for cable plugs 

Conventional QPL-qualified MIL-DTL-55181 connectors are configured for 90° mounting to the source interconnect. This configuration is less than ideal due to dashboard or panel-mounting space constraints or overlapped “wire stacking,” which can induce electromagnetic interference (EMI). The connectors’ right-angle orientation is also impractical for in-line cable interconnection. Straight-backshell MIL-DTL-55181-compatible versions of right-angle interconnects were engineered to avoid the obstruction of other installed power connectors, and to provide an optimal solution for in-line and extension cable interconnects.

Interconnect innovations driven by military ground vehicle development

Up-armoring programs such as Armor Survivability Kit (ASK), and Fragmentary Armor Kits (FRAG5 and FRAG6) did not allow conventional signal and power interconnects to be utilized for dismounted soldier connectivity. Extended-body MIL-DTL-55116-compatible interconnects allowed for conventional interior termination while providing exterior mating and enhanced survivability.

HUMMWV interior designs evolved as a result of multiple armed conflicts that highlighted advantages to mounting bulkhead feed-through interconnects, now a requirement. An easy to install and terminate extended body MIL-DTL-55116-compatible bulkhead connector is now available which accommodates the increased thickness of the vehicles’ interior surfaces.

The future of ground vehicle tactical power and communications connectivity 

Advances in computer design, contractor prototype evaluations, and ancillary power requirements for tactical communications devices are now commonly preconfigured in most military vehicles and armor. Additionally, USB and quick-charge mobile interconnects are also included in tactical radio designs, as are traditional MIL-DTL-55181 interfaces. However, it is estimated that it will take the military over a decade to field roughly 58,000 JLTVs to the Army and Marines. As this number is significantly below the quantity necessary to totally replace the Humvee, the solutions explored in this article are offered to help MIL-spec component specifiers and design engineers today and in the foreseeable future.

Visit CDM Electronics to learn more.

Robert Grzib
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