NASHVILLE, Tenn. – As trucks are stuffed full of more electric and electronic gadgets, the trucking industry needs to consider new ways to supply power to equipment, according to a panel presenting at the Maintenance Council of the American Trucking Association’s spring meeting. That could mean the introduction of everything from new battery models to fuel cells, to simply reconfiguring the way traditional batteries are linked together.

Consider some of the drains on traditional power supplies. A radio will draw one to three amps per hour, a CB will take another 1.5, a fridge with a compressor that runs 50 per cent of the time will draw 3.5 amps, while blower motors running on high will draw a full 22 amps.

Even when a truck’s engine is off, various devices tend to draw six to three amps per hour, while at low idle you can expect to lose 36 to 56 amps, said Freightliner’s Paul Menig. At high speed there could be a drain of 40 to 61 amps.

But a 135-amp alternator seldom puts out its full capacity. When idle speeds drop to 600 rpm, it’s more likely to put out 50 amps, he said.

“That’s a problem when you look at loads coming out of the vehicle.”

Part of the solution may be in the power that’s supplied.

Perhaps three batteries devoted to starting and one for so-called convenience items are enough for today. But that series will be further strained. With two devoted to starting and two batteries for convenience, there may be enough power for gadgets, but the two batteries may not offer enough power to turn over high-horsepower engines in cold weather, Menig added.

While gel cells used in marine applications have been tested as a solution to the heavy-amp draws from accessories, they haven’t held up to the constant vibration of over-the-road use, he said.

Using four starting batteries for all-purposes will work, but they will survive only 250 cycles, Menig said. The best solution in his opinion is to use four dual-purpose batteries with a low-voltage disconnect that turns off non-critical items – such as dome lights, cigar lighters and sleeper power – when the power drains so low that the truck might not start.

Optimized idle systems could automatically start and stop the engine to maintain power, but drivers aren’t crazy about the noise as they sleep, particularly because of the shaking that comes as an engine powers down, he said. For that matter, the engine may not run long enough to fully re-charge the battery.

Auxiliary power units, meanwhile, are seen as noisy, heavy and expensive, Menig said. Still another option is shore power, such as that offered by Volvo and Freightliner, but the number of truck stops that offer these power sources is limited.

“A/C inverters are not the answer to the problem,” Menig added. “Some inverters will decrease in output as time goes by.”

A 1200-watt inverter will take 100 amps out of a battery, and that will require much larger wires to carry the load. That can be a safety issue, he said. Freightliner is now installing 1100-watt Trace models.

Fuel cells, super capacitors able to start 14-litre engines at -40 Celsius, or air starters are all possible solutions, but they’re also in the future.

But there’s no question that advancements are rapidly placing greater drains on power supplies. Only six years ago, when mechanical engines were still available, there were 32 circuits and an 85-amp alternator, noted Mark Kachmarsky, Mack’s manager of vehicle electronics. Today there are two electrical distribution locations – a cab and engine power distribution module – in addition to such things as ABS modules. There are four 70-amp power relays, up to 64 circuits, and 130-amp alternators are the norm.

Where electrical schematics for a Mack truck were once printed on seven sheets of paper, the company now prints 19 sheets of information.

More is coming. Brake by wire will put an added drain on power supplies, and steer-by-wire designs that replace driveshafts with a servo motor on the steering gear are both a real possibility. Then there’s the research into electronic valve actuation, and the possible need to heat everything from exhaust catalysts to windshields.

And each will have a draw of its own. n