Using battery-electric tractor units for bulk tipping work poses a new challenge for engineers, with a number of hurdles required to be overcome to make the combination work. However, many companies are working on solutions and Richard Simpson meets one that has embraced the conundrum
Bulk transport profit margins are highly sensitive to payload and vehicle utilisation – and switching to battery power poses a number of new operational and engineering problems. The operator now has to consider range and recharging within the daily schedule so as to minimise impacts on productivity. Also, time must be spent recharging. In most haulage operations there is an opportunity to undertake this process during either loading or unloading. However, bulkers load quickly and unload even faster. Productivity is further compromised by reduced payload. The unladen weight of the tractor unit is a tonne or more (depending upon battery specification) than the diesel equivalent.
Then there’s the question of axle weight: the greater weight of the tractor unit means that less of the trailer weight can be imposed on its rear axle(s) than can be taken by a diesel.
Nevertheless, pioneering operators are putting electric trucks into service on this demanding work. British tipper specialist Weightlifter has supplied half-pipe trailers for use with electric tractor units to a couple of operators in the aggregates market, and two modified grain bulkers to Voltloader.
A VOLT FROM THE BLUE
Voltloader is a Cambridgshire-based start-up that launched early last year with the objective of transitioning UK’s heavy goods haulage to zero emissions. “The technology to decarbonise road transport is available, but government targets are too far away to incentivise their widespread adoption now,” explains David Rose, the founder of the business.
“Our goal is to build a 100% electric network within regional agricultural supply chains – and we aim to lead and show what can be done,” he adds. “The present focus is on grains and oilseeds from farm to store and store to mill: this is a regional business moving millions of tonnes annually, so ideally suited to electrification.
“It’s a niche, but a huge niche! We intend to take our offering into wider agri and other parts of the supply chain, such as distribution,” explains Rose.
“We also see many opportunities in other sectors such as construction and waste recycling.”
The current fleet comprises two Volvo FM Electric 4x2 tractors matched to modified Weightlifter tri-axle grain trailers. While the 6x2 tractor is optimum for most bulk tipper applications, Rose says that changes when you go electric.
“A 4x2 40-tonne electric tractor qualifies for a two-tonne concession, so permitted weight is actually 42 tonnes,” he explains. “Subtract the extra weight of a 6x2 tractor and the disparity in payload is not so great – 0.5 to one tonne – and the shorter, cheaper and more manoeuvrable 4x2 tractor is a better choice for this work.”
SPEED OF OPERATION
Rose chose to go with Volvo after considering spec and price of all the offerings from major manufacturers but, crucially, Volvo also had the fastest speed to market. Voltloader was also able to lease the vehicles on a package that included all maintenance and a 100% uptime guarantee. The lease included the vehicle batteries. “That means the technical and financial risk lies with the manufacturer,” he says.
Each truck has six 90kWh batteries: the most that Volvo offers. Thanks to the battery weight, even with the two-tonne allowance, payload parity has not been achieved.
“The standard industry unit load is 28-29 tonnes on a diesel 6x2 tractor. We can approach 25 tonnes with the current equipment, so there is still room for improvement. This will probably come at least partly through tweaks to the legislation, although there is potential for further reducing unladen weight,” Rose speculates. “We’ve saved a bit already by specifying ali wheels. We’ve also pared weight from the tractor by fitting a fixed fifth-wheel without coupling ramps.”
Meanwhile, overloading the tractor’s single rear axle is an issue. “Weightlifter installed an internal bulkhead, so there is an empty void at the front of the trailer. This configuration reduces its nominal capacity from 72 cubic yards, which we could never fill without overloading, to 60 cubic yards. The first metre of load-length is empty and this imposes more weight onto the trailer bogie and prevents a drive-axle overload.” A factory-installed ePTO on the truck drives a conventional Harsh wet kit to tip the trailer.
PAYLOAD PROBLEMS
Operationally, there are constraints beyond the shortfall in payload, but these are not as serious as some might believe. With maximum battery capacity installed, the trucks typically run between 140 and 150 miles at a time: enough to do two or three loads.
Rose sees this distance expanding in the future: “We started off calculating routes on the basis of returning to base with 20% left in the batteries. As we’ve grown more confident, we’ve been able to cover as much as 175 miles – and still come back with batteries
15% full.”
If operations permit, the trucks can return to base for a top-up charge mid-shift. “An hour on our Ultrarapid 200kW charger puts some worthwhile charge back into the batteries. In fact, it can take the batteries from low to full in 90 minutes,” Rose reports. The Ultrarapid charger is backed by a pair of AC 43kW chargers.
Rose also has arrangements to use truck chargers at two other East Anglian hauliers who have electric trucks – and is working with customers to have chargers installed at their premises. “The key to successful electric truck operation is going to be operators sharing their chargers,” he contends.
Voltloader’s depot site, on an industrial estate, was chosen with this in mind. “It has a good electrical connection and lots of truck traffic passing the door,” he says.
While the environmental argument for electric trucks is self-evident, the economic case for their adoption is more complex.
“Using our own chargers versus diesel, we estimate our fuel costs are reduced by one-third. But you will need to install your own chargers and will pay a premium to use third-party chargers,” says Rose. “The major factor is the price of the truck, which can be two or three times that of a diesel. This is obviously absorbed over time on leased vehicles, but we need EV prices to come down to make operations economic at current transport rates. There are reports that we could see vehicle price parity by 2030.”
PRETTY PARALLEL PERFORMANCE
Journey times are pretty much unchanged from diesel. “The trucks have the equivalent of 666hp, so power is not a problem,” Rose reports. “Excessive speed would certainly have an impact on range. However, most of our work is on rural roads, so speed isn’t much of an issue. We encourage the drivers to drive gently: the more work that can be done with the regenerative brake, the more energy is saved, and this means anticipation is key.
“Drivers love them,” he adds. “They are easier to drive than a diesel and there is far less noise and vibration.
“The FM cab is ideal for use on an electric truck. It’s a good aerodynamic match for our Weightlifter trailers – and its relatively small volume means less energy is drawn to heat it in cold weather. Cold ambient temperatures do impact on the batteries, but a useful feature on the FM is a facility to control the heater remotely, which means the cab interior can be pre-heated while the truck is still tethered to the charger.
“Our trucks operate with the trailer sheet closed, even when empty, but an unsheeted trailer would certainly create greater drag, as would a double-deck curtainsider,” he warns.
