News | Nov 21, 2019

Solar can save the US Army $17 million in vehicle batteries

U.S. businesses can help by licensing, manufacturing the Army's patent-pending charge controller

Hundreds of tactical wheeled vehicles sit in the motor pool at Fort Bliss, Texas.

Travis McNiel/Army

A research team is figuring out how small solar panels can keep tens of thousands of vehicle batteries from going dead while they sit in parking lots.

In a U.S. patent application made public on Thursday, U.S. Army researchers Ernest Luoto, Brian Frymiare, and David Carrier describe a smart controller that can govern power distribution from a small solar panel to a bank of batteries.

Through technology transfer, it’s a business opportunity that could save taxpayers millions.

The Army has a vast fleet of tactical wheeled vehicles staged at Army bases across the world, think Humvees, MRAPs, LMTVs, and 5-ton trucks, and about 75% are driven less than 3,000 miles per year.

Because the trucks spend so much time sitting in the motor pool lot, the lead-acid batteries slowly drain. To keep the trucks ready to roll, the U.S. Army has to spend about $26 million per year replacing them.

“Recent Army Sample Data Collection and Analysis (SDC&A) data shows (tactical wheeled vehicle) batteries being replaced every 13 months on average, yet the expected minimal life of the battery is three years, with an expected full life of approximately 6 to 8 years when treated properly,” they wrote for a research symposium.

Solar charging, they say, could extend a vehicle battery’s life 3-to-5 times, saving the Army about $17 million per year.

But modern Army trucks contain powerful radios and other electronic systems, powered by strings of 12 and 24-volt batteries connected in series and in parallel.

For example, some of the trucks require four large 120-amp-hour batteries to deliver both 12- and 24-volt outputs. The different loads placed on the vehicle’s battery bank lead to voltage imbalances.

Research has shown that a one-volt difference between the two 12-volt battery strings is not uncommon, but that one-volt difference in a battery is the difference between being 100% charged and approximately 20% charged.

The discrepancy can cause problems. And that’s where the Army’s new, patent-pending controller comes in, switching the solar panels on or off, moving the charge between the individual batteries, and preventing sulfation and overcharging.

A battery disposal yard at Kandahar Airfield, Afghanistan. In fiscal 2016, more than 373,000 vehicle batteries were replaced at a cost of more than $80 million to DOD. (Chip Herrell/Army)

To transfer the Army’s research and inventions to the private sector for commercialization and in many cases sales back to the military, U.S. technology transfer laws allow and encourage government agencies to license their technologies to U.S. businesses.

TechLink, the Department of Defense’s national partnership intermediary for technology transfer, regularly helps businesses review the commercial potential of Army technologies and navigate the licensing process.

To learn more about technology transfer and the Army’s smart controller for solar-powered battery maintenance, contact Dr. Brian Metzger, senior technology manager at TechLink, at brian.metzger@montana.edu or 406-994-7782.