Review: Volvo B5RLE Hybrid

By: Matt Wood


Volvo has launched its first parallel hybrid bus onto the Australian market, going into service at Transperth. Matt Wood checks out the road manners of Volvo’s new leaner, greener route bus

The word ‘hybrid’ has quietly crept into our popular vernacular, sneaking stealthily through the door left open by automotive manufacturers. These days, what once was more likely to refer to a fruit tree in Nana’s backyard now stands for a clean, green and efficient mode of transport. Or so I thought until I came across a rather eccentric fellow drag racing a Toyota Prius.

He did actually manage a respectable 11.32 second quarter mile, however it was about as much fun as watching someone vacuum their lounge room very quickly.

But, while we’ve become accustomed to the hybrid badge appearing on cars, rarely have we seen the concept taken further into Australian public transport.

Testing times

There have already been some brave forays into diesel-electric bus hybridisation in Australia, with varying degrees of success. A BCI-Eaton hybrid appears to be languishing, and more recently, a New South Wales State Transit Authority (STA) trial using a Custom Coaches-Alexander Dennis (ADL) BAE series hybrid drive during 2011 and 2012.

The final results of that trial make for interesting reading. Especially when the BAE-equipped bus was being data logged and run alongside a Euro 5 Volvo B7 BLE as well as an older Volvo B12 BLE, both of which acted as the study’s control vehicles.

Interestingly, according to the NSW Transport trial report, the diesel-only B7 was actually more fuel efficient than the ADL hybrid. The trial hybrid also generated 4 percent more greenhouse gases than the B7 diesel and funnily enough had higher AdBlue consumption at 6 percent of diesel burn. While overall the ADL hybrid was generally found to be cleaner than its oil burning counterparts, it was also clear that at that time, the BAE series hybrid was no magic bullet, in terms of cost and reliability.

Skip to January 2013 and it’s Volvo’s turn to walk down the electric avenue with the Australian debut in Perth of the B5RLE parallel hybrid route bus. Western Australia’s Public Transit Authority (PTA) trial will see the B5 Hybrid assessed alongside the same B7 diesel that performed so well in the STA hybrid trial.

The B5 features Volvo’s I-SAM parallel hybrid driveline, using a 6-phase AC electric drive motor, which sits snugly between Volvo’s 216hp (159kW) four cylinder D5F215 engine and the 12-speed I-Shift automatic manual transmission (AMT).

There are a couple of schools of thought on the hybrid side of things. There’s the parallel hybrid that still uses the diesel engine for propulsion with the electric drive assisting or taking over completely at low speeds and, charge permitting for take-off. Then there’s the series hybrid which is driven by an electric motor at all times and uses a diesel engine to generate charge for the driveline and is in no way connected to the drive wheels. Because the start-stop nature of route work is ideal for energy recovery through the driveline it seems that either philosophy is applicable.

But there’s one major factor in favour of the parallel hybrid; if the electric drive malfunctions the vehicle will generally revert to running on straight diesel and get itself back to the depot. Whereas with a series hybrid drive if a spark drops the bus will stop.

Electric dreams

Which brings us to Volvo’s I-SAM hybrid drive which clearly is no prototype, given there are nearly 1,000 units operating globally at present and the double-decker variant of the B5 hybrid chassis is now a familiar sight on the streets of London, operating alongside, ironically enough, the aforementioned Alexander Dennis BAE series hybrid. The I-SAM drive is also available in Europe in Volvo FM and FE trucks, a clear indication Volvo Group has drawn its parallel line in the hybrid sand.

I had the chance recently to both inspect and drive the Volvo B5 hybrid before it went into service with the PTA where it will ply Perth’s free CAT route.

Apart from the leafy sticker job on the outside, the Volgren bodied hybrid looks pretty much like any other bus found on Perth’s streets, but once some of the covers are lifted, the vital ingredients of the electric Swede are revealed and provide an interesting insight into the technology required to run a heavy vehicle on both diesel and electricity, so brace yourself for some gobbledygook.

The I-SAM system draws energy from regenerative braking storing it in a lithium ion battery, the system cranks out a scalp tingling 600 volts AC which is then converted to 600V DC. This power is used to drive the bus and also to drive some auxiliaries such as the air compressor.

Power is also fed into a water cooled high voltage DC-DC converter, which converts the current into 24V DC to power the rest of the bus accessories.

This power is then used to power auxiliary systems such as air-conditioning, air compressor, power steering and water pumps for the three cooling systems on the bus. This all removes a hell of a lot of drag from the engine, which, for all its complexity only has one drive belt which in turn contributes to the drivetrain’s fuel efficiency.

All indications are that this will be the way of the future on most heavy hybrids. It should be noted that while 600V is more than enough to chargrill the average mammal, the thick bright orange high voltage cables are monitored by a HVIL safety that can sense when a cable is in danger of shorting and will shut the electric drive system down until the potential fault is rectified. One advantage of the high voltage generated by the system is that with so much power on tap there’s very little chance of voltage drop when the power is being used to drive accessories at the other end of the bus, which could prove handy for potential bendy-bus applications.

The cooling system is divided into three different circuits with three different radiators. Both the lithium battery and the AMT have their own radiators. The water pumps and thermo fans for these are electronically driven by power drawn from the hybrid drive. Keeping the battery at as close to 25C as possible prolongs battery life in a similar way to lead plate batteries.

Slipping behind the wheel of the hybrid and getting comfortable was an easy ask with the tilt and telescope steering column and Isri seat, and firing the beast up differed little from any other bus. The giveaway that something different was going on was a blue light on the dash to indicate that the ignition was on, and an eco-gauge on the dash-mounted digital readout of the B5 to let you know your battery levels as well as braking and energy recovery efficiency.

Zap, crackle and pop

The hybrid drive gives the B5 an astonishing amount of oomph that’s immediately on tap when accelerating. When the electric motor only is powering the bus the I-SAM system has a respectable 800Nm of torque and 120kW (160hp) of power on tap from a standstill. The diesel engine itself provides the same torque figure but develops 160kW (210hp) of power, which for a route bus is very handy when trying to merge into traffic when leaving a stop. However, the power comes on very smoothly reducing the chances of staggering standees and toppling shopping bags out back. As the torque curve of the electric drive falls, the torque curve of the diesel engine picks up between 1,200 to 1,700rpm adding to the B5’s city-paced performance.

Once the vehicle started to gather speed the diesel engine fired up, albeit very quietly and the 12-speed AMT started to climb through the ratios. The transmission seemed to perform very well, in fact the I-Shift AMT and the lack of a torque converter may have contributed to the Volvo’s standing start performance.

The Volvo driveline is eerily quiet on the road, especially when under electric drive power only. The Volgren body was also tight as a drum which only added to the sensation of gliding down the suburban back streets. Which raises a safety question being bandied about overseas in regards to electric vehicles — are they too quiet? One solution that springs to mind is maybe all hybrid buses should have to play music like an ice cream van when plying the city streets. It could prove very difficult — or very embarrassing — to be run over by a heavy vehicle playing ‘Green sleeves’.

A breath of fresh air?

While the Volvo had already ticked the power and noise boxes, road handling also came under scrutiny. The 11.5m-long, 65-passenger capacity bus also proved extremely nimble as I rolled down residential streets and around tight traffic islands and roundabouts. In fact, the green machine went everywhere I pointed it without even scrubbing a tyre side wall. Which brings up the power steering. The electric drive system provides surprisingly good feedback, with the steering servo motor idling at 1,200-1,500rpm but capable of 2,000rpm.

From the driver’s seat the Volvo comes up trumps, but the proof no doubt will be in the pudding in terms of reliability and running costs. Volvo claim only a 20 percent premium to purchase the Hybrid over a straight diesel unit, which compares favourably when purchasing and converting a bus to compressed natural gas (CNG), especially bearing in mind the extra infrastructure and maintenance CNG vehicles need.

The Volvo B5RLE trial in Perth may well be at the thin end of the wedge for hybrids in Australia, but maybe the question is more about the kind of urban landscape we want to inhabit.

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