Hybrid vehicles are all the rage today. A shopper can find almost any kind of personal motor vehicle in hybrid form, ranging from ultra-small economy cars to full-size SUVs and pickups. Those modest-sized hybrids, relatively speaking, could well be joined by some significantly larger cousins: Class A motorhomes.
Winnebago and Fleetwood are now showing concept-vehicle hybrid Class A motorhomes — and these concepts present some exciting new possibilities for RVers.
Both the Winnebago Adventurer (www.winnebagoind.com) and the Fleetwood Hybrid (www.fleetwoodrv.com) are based on the Freightliner ecoFRED chassis, a front-engine diesel-powered unit with an integrated electric motor/generator and a bank of lithium-ion batteries. The concept vehicles we viewed were displayed to gauge dealer reactions to the products and the jury is still out on how soon one or both of these rigs will hit the dealer lots.
This chassis is not new technology. It’s been in successful use as a commercial chassis employed by large companies with fleets of trucks for close to a decade, so this is a tried-and-proven system.
The ecoFRED is similar in many respects to a conventional Class A chassis. Its primary power is a 300-hp Cummins ISB 6.7-L engine mounted in a pair of steel rails. Leaf springs front and back support solid axles and carry power disc ABS-equipped brakes. The chassis is rated at 27,000 pounds Gross Vehicle Weight Rating and 37,000 pounds Gross Combination Weight Rating, healthy figures that enable the coach manufacturers to place good-sized bodies on the rails.
From the engine back the “similar” aspect changes dramatically. Next to the engine there’s an auto clutch, which is more or less a standard clutch used in conjunction with a manual transmission, but it’s power-activated and automated. Next there’s the electric motor/generator unit wired to an inverter and powertrain control unit, plus a hefty 340-volt lithium-ion battery pack, then an Eaton 6-speed manual transmission with power-activated and automated gear changes.
In use, the manual transmission setup works like an automatic transmission. The rig’s powertrain control unit engages the clutch and makes appropriate gear changes as needed, and the driver doesn’t need to do anything normally associated with manual-transmission operation.
The big difference occurs when the electric motor part of the drive kicks in. Unlike smaller hybrids, the ecoFRED diesel engine prime mover is always running. It’s the electric motor that kicks in and out, depending on load requirements, to provide the extra propulsive power that reduces the diesel engine use.
When the driver first accelerates the electric motor provides boost at a time when the diesel is running at a fairly low power point. This is what results in the usual lag in acceleration for a normal diesel-powered coach. An electric motor produces 100 percent of its torque regardless of its rpm, so that torque is immediately there in full force to help get the coach moving. That electric torque will also be applied when the driver mashes the pedal to take on a steep grade, for example, among other situations.
The electric drive is also set up to act as a regenerative battery charger. When the motorhome is coasting and not using the electric motor it becomes a generator and helps recharge the batteries. Dynamic braking is another standard feature with the electric motor. This latter feature is designed to reduce brake system wear and tear and improve coach safety.
The lithium-ion battery pack also supplies the coach with 120-volt AC power via an inverter, so no auxiliary generator is required. To avoid depleting the batteries, an Auxiliary Power Generation unit senses the battery level and automatically starts the main engine to charge the batteries if the coach is parked at a campsite, for example.
The technology as it applies to motorhomes is new enough that company representatives are understandably a bit cagey when quoting any specifics about fuel economy increases for the hybrid rigs. Estimates range from as low as 7- to 8-percent on up in excess of 40-percent fuel economy savings. If we did any gambling we’d guess that something closer to the lower end of the spectrum would be realistic, but we could be wrong and pleasantly surprised by higher figures, as well.
The added-value extra cost to the consumer is also uncertain, but we heard estimates from about $30,000 to $40,000 more compared to a similarly-equipped coach on a standard chassis.
It doesn’t take much math to conclude that the break-even point for a hybrid motorhome is far, far down the road, well past the miles and time driven by the usual owner. However, today’s hybrid product development can lead to better things later, and the manufacturers’ first baby steps in hybrid Class A motorhome technology will yield even better, more sensibly energy-conscious rigs for tomorrow’s consumers.
Photos: At the heart of the Freightliner ecoFRED chassis are the 340-volt lithium-ion battery pack (right) and the control unit (left) which also contains an inverter to supply 12-volt AC power to the coach.
Winnebago’s Adventurer hybrid motorhome concept uses a Freightliner ecoFRED diesel/electric chassis with electric power to augment the front-end diesel engine.
Copyright, Motor Matters, 2009