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NEWS | March 20, 2023

Carderock Engineers File Patent for Lithium 6T Top Cap Invention

By Todd Hurley, NSWC Carderock Division Public Affairs

Naval Surface Warfare Center, Carderock Division engineers in the Expeditionary and Developmental Power and Energy Branch recently developed and filed a patent for their invention, a Lithium 6T (Li6T) Top Cap, which is a modular, field-reconfigurable direct current (DC) power distribution device that can be installed and mounted on top of a Li6T battery in less than 30 seconds.

The inventors are Matthew Huffman, technical area lead, Kevin Lin, electrical engineer and James Mulford, mechanical engineer.

The device consists of an additively manufactured shell with interfacing connectors that installs on top of a Li6T battery’s positive and negative terminals. It allows users to utilize the direct current capabilities of the Li6T battery in a manner that also complies with the charging, discharging and safety specifications of the battery. The device utilizes a NATO slave connector for charging the Li6T battery from an external direct-current power source, and four paralleled ITT Cannon connectors for providing power to downstream DC loads. All five connectors utilize externally-accessible circuit breakers for high visibility, ease of resetting, and protection against overloads while charging or discharging. A prominent side-mounted emergency stop button allows the user to easily turn on and shut down the device with one hand.

“This came about as a Carderock concept,” Huffman said. “This product is an in-house, hand-built prototype designed right here at Carderock. We originally discussed the origins of this product back in 2018, but it took many years for it to gain an appreciation for the concept.”

That appreciation arose when the need came from the Warfighter for a newer, safer battery charging method.

“The Marine Corps asked us if we could develop a prototype that could mount on top of Li6T batteries and act as a direct replacement to the lead acid batteries,” Mulford said. “This product has a lot of advantages over the lead acid batteries, such as its clever battery management system that we are pulling information directly from and displaying on our user interface screen for situational awareness. It also provides an inherent protection of exposure against live voltages.”

Some additional advantages consist of its ease of use, novel integration of functionality and minimalism — this device is significantly smaller, lighter and capable of accepting more DC power charge than existing Li6T charging and discharging devices. Most military generators require a forklift to move, whereas this device is man-portable and can be easily packed into a rucksack for field use.

“One thing to note is that Li6T, unlike lead acid batteries, have more energy inside of them,” Lin said. “Unlike a car battery where you can only use it for starting, lights and ignition, you can use this independently and you can deeply charge and discharge this. That means you can use this for other purposes such as providing DC power to loads downstream.”

This device’s ease of use is critical and involves a specific part of the patent — the screws that are used to attach the Li6T Top Cap to the Li6T battery.

“The bottom of the Top Cap is where the patent really lies — with the floating screws,” Lin said. “There are two screws that are different sizes. One is a 3/8”-16 threaded hole and the other is a 5/16”-18 threaded hole, which means the positive and negative screws install directly into the positive and negative terminal threaded holes. Essentially, you can’t place the Top Cap on incorrectly or backwards. These screws can move around several millimeters to accommodate for mechanical tolerances. When you put the Top Cap on the battery and tighten the screws, not only are the terminals now protected, but they are now compressed onto pads for the best possible transfer.”

This device’s ease of use also comes into play with its user interface. The three engineers designed the user interface on the product to be as intuitive as possible.

“We designed this user interface with simplicity in mind,” Lin said. “It is meant to show the user all the essentials of the battery at a glance. There are no additional pages, so what you see is what you get.”

Additionally, the Top Cap is the only device that incorporates a color user interface screen.

“There are active electronics within the device, such as the color user interface screen,” Mulford said. “This screen provides data such as battery voltage, input and output current, charge and discharge, total power in or out of the battery, internal temperature in both Celsius and Fahrenheit and the available capacity based on the state of charge.”

The inventors recently demonstrated the device at the Pentagon Energy Expo in Washington, D.C., from Sept. 21-22, 2022, where they received fantastic feedback, according to Mulford. They currently have three upcoming demonstration events: two in March at Marine Corps Base Quantico in Triangle, Virginia, supporting the Expeditionary Energy Office, and another event in April with the Technology Operational Experimentation Exercise at Marine Corps Base Camp Lejeune in North Carolina.