Technology has infiltrated modern trucks at numerous levels. Today’s rigs bristle with electronic controls and a growing number of devices to enhance safety and make the driver’s workplace more comfortable. With each additional device comes an increased electrical power draw, putting added pressure on the truck’s batteries and charging system.

Yet, despite the technological revolution in the rest of the vehicle, truck electrical systems have stayed unchanged in their basic design since trucks were first invented. Lead-acid batteries remain the primary electrical power source and must be constantly charged by an engine-driven alternator.

Fleets operating in a wide variety of applications are finding this system inadequate to handle the electrical draws their trucks are seeing in daily operations. “When I started here in 1985, a 75-amp alternator was plenty for the trucks we were running,” says Jim Cade, Vice President of Maintenance for Ryder System’s 200,000-plus North American fleet. “Now we won’t spec anything under 130 amps. The demands on vehicles keep going up. We need more amps all the time.”

Cade is joining the growing ranks of fleet managers looking at intelligent DC power management to cope with higher electrical demands and avoid premature failures of batteries, alternators, and starters.

Higher electrical demands in today’s trucks come from advanced electronics, such as communications technologies, as well as additional loads under the hood from a proliferation of electronic control modules to monitor, diagnose, and control a growing number of functions.

Just a decade ago, a typical truck had a cumulative current draw of 30 amps. A typical over-the-road truck today can have a current draw of 60 to 80 amps.

“Nearly everything in the cab comes at an electrical cost,” says Will Watson, Vice President, Sales & Marketing for Intra Technologies., a Tukwila-Wash. specialist in DC power management technology. “Add in simple items like blower motors and a stereo system to advanced electronics and the cumulative effect is tremendous.”

A fleet’s problems start when the ignition is turned off, the alternator stops charging and the battery takes over. Parasitic loads from electronic controls, communication systems, in-cab appliances, and other electrically-powered devices will slowly drain the batteries so that there isn’t enough power to start the truck.

“Jumpstarts are a growing problem in the trucking industry. Fleets are paying an average of over $200 each time they have to restart a stranded truck with dead batteries,”adds Watson.Even if a driver can get a truck to restart after it has been parked for an extended period, he may still be doing damage to the batteries. “If you allow batteries to drop below a 50% state of charge, you shorten battery life significantly,” says Watson. “To get maximum battery life, you need to keep them at a constant state of maximum charge.”

Keeping batteries in a healthy condition requires intelligent power management, a way to monitor electrical loads and turn off the least important loads before the batteries have drained too much. Intra uses patented switching technology to do this. “Think of it as a switch with brains,” says Watson. “It allows you to manage the loads in a way so that there is less impact on the driver and on maintenance costs.”

Intra’s switch is incorporated into a low-voltage disconnect (LVD) system available as an aftermarket item. “Our LVD is a solid-state unit that monitors battery levels, automatically disconnecting non-critical power loads when battery voltage reaches critical levels,” explains Watson. “Our latest version provides the driver with an audible warning before it starts cutting power. That gives the driver the option to turn off the device of his or her choice. As soon as the driver turns it off, the system resets itself and won’t do anything until power has dropped to low levels again.”

Long-haul fleets testing LVDs have seen their potential for reducing electrical maintenance costs, according to Watson. A large truckload fleet ran LVDs on sleeper-equipped tractors for two years and compared maintenance to similar non-LVD equipped tractors. The tractors without LVDs averaged a 20-month battery life while the LVD trucks managed almost 36 months out of batteries. The LVD trucks also had an 18% increase in alternator life and a 38% decrease in jumpstarts.

The savings are also there, Watson claims, for short-haul and P&D fleets where trucks experience deep discharges due to frequent stopping and starting. Ryder’s Cade says he’s seeing growing problems with leasing clients making a lot of deliveries in residential areas. “The driver will shut the engine off to be kind to the neighbors, but then will leave lights on or use a liftgate for a while. After the second or third stop, the batteries will have drained enough so that the truck won’t start.”