Kingsport man designs his own hybrid

Rick Wagner • Nov 7, 2008 at 12:00 AM

David Hrivnak, an industrial engineer at Eastman, holds the electric plug that recoils back into his 2004 Chevy Avalanche. Hrivnak has placed a supplemental electric motor in the vehicle and has battery cells located behind the truck step bars. It improves his gas mileage from about 14 mpg to 17 mpg. Erica Yoon photo.


KINGSPORT — David Hrivnak isn’t trying to reinvent the wheel. But he’s succeeded in making the wheels on his vehicle roll around town a little more efficiently, using an electric-assist system he hopes to mass market.

About two years ago, the Eastman Chemical Co. industrial engineer and self-described tinkerer began to think about ways to get more mileage out of his white, four-door 2004 Chevrolet Avalanche.

He bought it for the room and hauling capacity, as well as scout activities.

However around town, Hrivnak’s V-8 gas-powered vehicle averaged about 14.9 miles per gallon. But he began plans to convert it to a gas-electric hybrid that plugs into the 110-volt outlet in his garage each night.

After the conversion, he’s averaged about 17.2 mpg.

“The plan is to develop a kit to improve gas mileage and pay American companies who make the motor, controller, computer interface, chargers and batteries, rather than pay for imported oil,” Hrivnak said.

So who undertakes such a do-it-yourself project?

The Pittsburgh native, 49, is married with two children, East Tennessee State University sophomore Kirk Hrivnak and Dobyns-Bennett High School junior Brian Hrivnak.

The elder Hrivnak received his bachelor’s degree in engineering at Virginia Tech and his master’s of business administration at ETSU.

He has worked at Eastman and lived in Kingsport for 25 years.

“I love tinkering,” Hrivnak said when asked if he was an inventor, adding that he is known among colleagues at Eastman as “semi-eccentric.”

His brother, Eastman mechanical engineer Steve Hrivnak, said David Hrivnak is a life-long tinkerer and problem solver.

“To be truthful, he probably should have been a mechanical engineer, not an industrial engineer. He’s always tinkered and messed with things all his life,” Steve Hrivnak said. “Solving a problem is pure joy.”

Recharge for 50 cents

Getting power to the batteries was simple, or so David Hrivnak thought.

The retractable power cord comes out of the lower part of the Avalanche’s grill. It draws about seven kilowatts of power over five hours to recharge fully discharged batteries. David Hrivnak said that works out to about 50 cents a day for recharging.

That worked well while at Myrtle Beach, where he plugged in at a parking garage where electric golf carts were being recharged.

However, once at home, he forgot and drove off with the plug still attached. After that, he fixed an outlet in the ceiling so he could readily see if the cord was still plugged in.

That 50 cents a night isn’t too hard to absorb at home since he lives in an energy-efficient passive solar home. He’s designed two such passive solar homes in the past 25 years, including the one he lives in now.

“He’s always been very efficient,” Steve Hrivnak said of his brother.

The first passive solar home was an earth burm design.

According to his brother, he’s also helped build Habitat for Humanity homes internationally and is scoutmaster for Troop 51 that meets at First Broad Street United Methodist Church. He is a member of Holy Trinity Lutheran Church.

He also has helped his brother recently move and rebuild a log cabin.

On the current solar home, David Hrivnak used insulated concrete forms for the walls, structural insulated panels for the roof and put almost all the windows on the south side. During heating season, those windows allow the sun to heat inside tile floors and other surfaces, and at night the blinds or curtains are closed to keep cold air outside and warm air inside. In the summer, the blinds or curtains are closed to keep warm air outside and cool air inside.

He said the annual heating and cooling cost for the home is about $120 a year.

Put another way, he said his family electric bill is about half the bill of houses of similar size, reaching something like $65 a month in the peak heating season and running about $40 when there is no heat or cooling required.

“We designed and built both of our houses. We were the general contractor on both of them,” said Brenda Hrivnak, David Hrivnak’s wife.

As for the Avalanche, in theory the project could attempt to use a power inverter to try to recharge the electric motor batteries through the 12-volt system of the gas truck engine, but he said that would be inefficient since too much power would be lost in the conversion from the alternating current of the alternator to the direct current, back to AC and then back to DC for the electric motor batteries.

He said a gas engine is about 30 percent efficient, an alternator is about 70 percent and DC to AC and back to DC about 70 percent efficient, so the overall efficiency would be about 15 percent.

“The reason I plug it in is a power plant is about 70 percent efficient, electrical transmission 90 percent and the chargers about 90 percent for an overall efficiency of ... 57 percent or about 4 times more efficient than trying to run the gasoline motor to charge.”

Also, putting the electric motor batteries on the same DC circuit as the gas engine battery would overload the alternator since the electric-assist motor runs on 72 volts.

“You cannot really get enough power out of 12 volts. So you cannot use a 12-volt alternator to charge 72 volts,” he said. “Then it takes a lot of power to move a vehicle. As you saw the motor will draw 500 amps at 72 volts. That is the same power as 3000 amps at 12 volts. So a typical alternator at 125 amps and 12 volts would provide only 4 percent of the electricity you need to really run on electric.”

From 14.9 to 17.2 mpg

After the conversion earlier this year, the truck has gone to about 17.2 miles per gallon around town as he continues to tweak the conversion that has operated about 4,500 miles.

“About two years ago, I was starting to think about — that’s when gas prices started going up — what could I do to make the truck more fuel efficient,” Hrivnak said.

He got the electric-assist vehicle up and running in February and after replacing an electric motor with a twisted shaft in July has been motoring along ever since.

“I’m sure it would have failed,” Hrivnak said of the old motor, which vibrated because of the twisted shaft but found a new home using only the good shaft in an all-electric Karma Ghia conversion in Kentucky. That application requires only one shaft, not two.

“I won’t say I helped him a lot. We spent a lot of lunches looking at drawings and talking,” Steve Hrivnak said of time he spent with his brother on the project, adding that the first motor was not aligned quite right and had a shaft two weak for the application.

The new electric-assist motor in the Avalanche has a stronger shaft. One end goes to the transmission, which was the one that twisted on the first motor, while the other goes to the differential.

The electric motor has its own computer control and is powered by 12 deep-cycle, marine-type batteries. It is programmed to engage only at speeds of 40 mph or less, since that is where gasoline engines are less efficient.

So in interstate driving, where the four-door truck with a bed averages about 20 mpg, the vehicle uses strictly gas.

“The reason we use so much gasoline is it’s great. It has an incredible amount of energy,” Hrivnak said, adding that 800 pounds of lead-acid batteries are required to carry the same amount of energy as a gallon of gas.

“Once you’re going 40 miles an hour, then the electricity doesn’t help at all,” Hrivnak said.

However, during stops or short trips at a destination, as well as in regular around-town driving, the electric motor helps propel the vehicle.

He said the project also has lots of local connections. Fleming and Fleming, which does business as Fleming Tune Up, helped with the motor installation. Owner Tandy Fleming said he helped measure for the alignment of the motor share to get an idea of the kind of bracket needed and worked on the shaft balance and bushings needed.

Another Kingsport business, Johnson-Hilliard, made the battery boxes and brackets to install the motor, while FleetPride and Bowman Driveshafts got the new driveshafts built and Tabco in Surgoinsville powder coated the battery boxes.

Seeking wide appeal

Hrivnak said the commercial potential for the conversion is massive since about 5.5 million General Motors vehicles on the same platform are on the road today, including the Chevrolet Silverado, Avalanche, Suburban and Tahoe full size model and their GMC cousins such as the Sierra.

In addition, he said the system is adaptable to other makes and models as long as there is enough room for the motor, batteries and other components.

So Hrivnak hopes to turn his system into a commercially viable one and market it.

Before that happens, however, he said a few problems must be addressed.

For one, he said that “throttle bias” his wife doesn’t like must be addressed. He said she’s been very patient with his tinkering with the vehicle.

“At steps along the way, he’d have me drive it and ask if I noticed anything,” she said.

Because the computer for the electric motor picks up information from the computer controlling the throttle body of the gas engine rather than the throttle itself, he said the vehicle has a lag and then a discernable “surge” when the electric motor kicks in during low-speed acceleration.

He can monitor everything from a display panel near the floorboard, which among other things reports the amperage the electric-assist motor is drawing and the voltage in the batteries he said generally last about 25 or 30 miles of in-town driving — enough to get to and from work and a few side trips since he lives about two miles from his office.

The electric motor, supplied by NetGain Technologies and designed with input from Hrivnak, is about a 10 percent boost in power, so he said fixing the throttle bias would make the vehicle operate more smoothly.

For more information on that company and its engines, go to http://www.go-ev.com/EMIS.html. A man near Denver has made a few conversions highlighted at www.salidaconversions.com.

To mass market Hrivnak’s kit, he said the electric motor itself also needs improvement.

“I think we’re going to need a a third-generation electric motor with a little more torque to it,” Hrivnak said.

He said that lithium ion batteries, which have double the power with half the weight, hold great promise for all electric or hybrid vehicles using electric, although he said the Avalanche has plenty of space for the batteries and they should last four to six years.

Another, perhaps the biggest obstacle to overcome, is the cost and potential federal income tax incentives.

The system he uses cost about $7,500 in component parts, which he hopes to reduce to about $4,000. Buying in larger quantities would cut per-unit costs, but he said that would be hard to do with the higher up-front costs of selling only a few units, which he said is the perennial problem of “which comes first, the chicken or the egg?”

The recent “bail-out” legislation passed by Congress and signed by President Bush includes a $7,500 tax credit for new hybrid electric vehicles.

However, Hrivnak said he’s not sure his system would be included since it’s a conversion of a traditional gas-powered vehicle.

“It’s kind of like a build-your-own hybrid,” Hrivnak said.

So the next time you see a white Chevrolet Avalanche around Kingsport, it may have a retractable cord in its grill and a smiling engineer at the wheel.

For more information, go to www.hrivnak.com or e-mail dhrivnak@chartertn.net.

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