Power inverters – devices that convert standard battery (DC) power to AC household power – are becoming more commonplace in the trucking industry. Depending upon whom you ask, that’s to the delight, or chagrin of fleet and maintenance managers, who often have a love/hate relationship with inverters.
“Inverters have always been a magnet of controversy,” says Steve Carlson, Xantrex’s OEM sales manager. Xantrex is a leading supplier of inverters, and Carlson says shipments have risen sharply since early 2012. The company expects this trend to continue in the next few years.
“Fleets know that drivers love them, as they provide an extra measure of creature comfort that helps with driver retention,” Carlson says. “But, they can be nervous about inverters and their potential to damage the truck’s electrical system.”
Carlson often fields questions from fleets about inverters. “The distrust of inverters is really a thing of the past, if -- and I stress if -- the right inverter and installation practices are followed. Inverters can be a great asset to drivers and fleets. The key is for fleets to do their homework and know what’s best for their operation prior to making a purchase. One size does not fit all, and inverter quality varies greatly.”
Carlson says the following questions typically rise above all others when fleets try to determine which inverters to purchase.
1. How big?
Far and away, Carlson says, “what size inverter do I need” is the Number 1 and most important question he hears from fleets.
“It’s easy to say, 'Get the biggest inverter on the market and you’ll be covered for all your needs,'” Carlson says. “But that’s not the best advice. Inverter sizes range from 300-watt cigarette lighter plug-in inverters to 5,000-watt units. Each fleet should do a survey on truck size and power usage and understand how their drivers will use an inverter – what items they want powered and what items will be used at the same time. That will help ‘right size’ the inverter for your operation.”
As an example, Carlson says drivers will often run a microwave, TV and laptop all at the same time.
“On each device you’ll see a wattage number,” he explains. “A microwave might be rated at 1,000 watts, a TV at 250 watts, and a laptop at 95. Add them up to see how much continuous power you’ll need, and then add 20%. So, in this case you’ll need just over 1,600 watts. Next, round up to find an inverter that meets your power needs. Xantrex, for example, offers an 1,800-watt unit, and that’s what we would recommend.”
While determining continuous power is an important consideration, so is “surge power.”
“Whenever you power up any device, the initial load is more – and sometimes double – what the continuous power requirement is,” Carlson says. “So the surge rating on quality inverters should be about double. So, an 1,800-watt inverter can handle a short 3,600-watt power surge requirement.”
Next, Carlson says to research how long the inverter can handle the surge. “The longer the better,” he says. “Some on the market can handle only a few milliseconds of surge before the power draw shuts down the inverter. Others can last five seconds or more, and that’s what you should look for.”
2. Type of Power: Sine or Modified Sine Wave
There are two types of inverters on the market, a sine wave and modified sine wave.
“Both work well in a truck environment, but for those running sensitive electronics (like CPAP machines) or products that are plugged into their own chargers –a drill or a toothbrush – sine wave is the preferred choice,” says Carlson. “Since sine wave is the same power as what you get at home, the voltage is consistent without spikes or drops. So, the device you’re powering reacts just as it would if you were plugged in at home.
“But, in most cases, modified sine wave power is just fine in operating most electronics and appliances with the exception of few sensitive applications.”
As for the price difference, Carlson says the gap has narrowed and today most higher wattage sine wave inverters cost about 15% to 20% more than a modified inverter.
“With a sine wave unit, you’ll notice a slight decrease in the efficiency rating, since electronics within the inverter use power to keep electrical levels consistent,” says Carlson. “It’s not much – we have an 87% efficiency rating on a Xantrex sine wave unit compared to 92% on a modified inverter. It’s like the difference between running a 6-cylinder car versus 4-cylinder car. That 4-cylinder car may get a bit better fuel economy, but the 6-cylinder is better in overall performance.”
How much power (watts) do you need?
- Microwave: 1,000
- TV: 250
- Hot Plate: 1,300
- DVD Player: 40
- Laptop: 95
- Hair Dryer: 1,500
- Electric Blanket: 200
- Portable Heater: 1,000 to 1,500
- Electric toothbrush: 2
Next Page: Can fleets install an inverter?