There's no free lunch, even at the technology bar. Individual drivers as well as fleets interested in boosting driver comfort have been bellying up for lots of inverters. But these handy devices that let drivers plug in everything from laptop computers to kitchen appliances can cause problems if used without heeding some good technical advice.

J. Stanley Saunders, marketing director-aftermarket for Delco Remy America, cautions that while inverters are a great way to inexpensively enhance driver comfort, unauthorized or improper use of the devices can cause potentially expensive problems.

Inverters convert stored energy from a truck's batteries into AC electrical power, providing a simple way for drivers to tap their truck to power personal gear in the cab.

Drivers like inverters so much that sales of the devices have surged in recent years. Saunders reports sales are growing 20-30% per year.

As handy as the devices are, Saunders says trouble can result when a driver uses an inverter that lacks protective safeguards for the electrical system or installs it improperly.

“Inverters are really a boon to those who jump-start trucks,” he reasons. “A lot of drivers don't know to look for inverters that have battery protection. This simple feature shuts the inverter off before battery levels get too low. Without this feature, the inverter sucks the life out of the battery, and the truck will need a jump start. It can cost a fleet $200 or more each time the truck is jump started.”

On top of that, according to Saunders, each time battery voltage drops below a recommended level, battery life is shortened considerably. “And those problems multiply,” he says. “If your battery is taxed by heavy draw-downs, then your starter works harder. So does your alternator. All three devices end up wearing out faster.”

But trying to avoid these problems by banning inverters is not the answer — drivers may use their own.

“By following a no-inverter policy, fleets are helping to create an underground where drivers make temporary installations,” points out Bob Jeffries, regional sales & service manager for Delco Remy.

“Unfortunately, electrical problems are resulting from these jerry-rigged installations,” he continues. “The average fleet jump-starts 10% of its trucks each month. Furthermore, an average of 15% of those jumps are due to excessive electrical loads in the cab.”

Saunders and Jeffries reason the answer is to allow inverters — good ones, that is. They recommend that fleets purchase, or at least allow their drivers to, inverters that include a low-voltage battery cutoff, which shuts down the AC power before the battery is depleted.

“A good inverter will cut the power at 11.8 volts with a load, which is enough power for the driver to start his truck,” Saunders advises.

Other important features they say to look for are ground-fault circuit interruption and rating of wattage at “continuous” power rather than “peak” power designed to handle a surge in power.

According to Saunders, the most popular inverter with drivers is a 300-watt unit that costs about $40 at truckstops and plugs into a cigarette lighter.

“The problem [with these 300-watt units] is a lighter is designed for plug-ins of up to 150 watts,” Jeffries says. “When the load exceeds that, problems can arise.”

Naturally, higher-wattage inverters with battery-protecting features cost more than the plug-ins. But fleets willing to pony up to give drivers the AC power they want and the safeguards they need will end up protecting their equipment and extending battery, starter and alternator life. “That,” Jeffries sums up, “is a payoff a fleet can't afford to ignore.”