Volvo Buses enters Hong Kong market with tri-axle electric double-decker

Volvo Buses has unveiled a new all-electric urban double-decker bus tailored specifically to the needs of the Hong Kong market. Debuting at the ReThink Hong Kong exhibition, the Volvo BZL DD Electric is notable for being the first tri-axle version of the Swedish manufacturer’s self-propelled BZL Electric platform family developed for double-decker buses. The bodywork of the 12-metre vehicle is supplied by Egypt’s MCV, while the driveline and the aforementioned rolling chassis come from Volvo.

With the new model, Volvo joins Wrightbus and Alexander Dennis in Hong Kong’s electric bus market: both British manufacturers already offer locally adapted, all-electric tri-axle double-decker models around 12 metres in length. Interestingly, the two manufacturers, now clearly competitors, previously sold large numbers of double-decker buses in Hong Kong as Volvo bodywork partners as well, albeit with conventional diesel drivetrains. Since then, however, their paths have visibly diverged, while MCV has in recent years become Volvo’s primary bodybuilder for the Hong Kong market too. It is therefore no coincidence that the new tri-axle (6×2) version of the Volvo BZL Electric chassis family is making its debut under the Egyptian manufacturer’s bodywork.

The design of the vehicle has been shaped primarily by Hong Kong’s specific operating requirements and regulations. Because of the city’s extremely high passenger volumes (and its British colonial past), high-capacity tri-axle double-deck buses have traditionally been used there, while the hilly terrain, closely spaced stops and subtropical climate place heavy demands on the electric driveline and auxiliary systems alike. The tri-axle layout, already customary in the Hong Kong market, plays a particularly important role when paired with electric drive: the additional load capacity provided by the third axle and the higher 24-tonne gross vehicle weight can offset the significant extra mass of the batteries, meaning electrification does not necessarily entail a substantial reduction in passenger capacity.

500 kWh LFP, two electric motors

The energy storage system of the 12,000 mm long, 2,550 mm wide and 4,400 mm high bus is based on lithium iron phosphate (LFP) batteries, with a total nominal capacity of exactly 500 kWh. The vehicle uses flat-pack battery units, each with an energy storage capacity of 39 or 44 kWh and a mass of 234.5 or 263 kg respectively. Among the advantages of LFP chemistry, the manufacturer highlights high thermal stability and a long service life even with frequent charging cycles. The batteries are protected by a steel protective frame and thermal protection made from heat-resistant materials, while their condition is monitored by Volvo’s own BMS at cell, module, battery pack and full system level, continuously checking parameters including temperature, current and pressure. A separate liquid-based cooling and heating system ensures the correct operating temperature. The traction system operates at a voltage level of 600 V.

The vehicle’s twin-motor driveline uses two Volvo EPT802 electric motors, each with a maximum output of 200 kW, giving the system a combined peak output of 400 kW. Maximum torque at the wheels is 31,000 Nm. The driveline is coupled to a two-speed automated manual transmission, which uses the electric motors to synchronise speeds during gear changes. The system has also been dimensioned for operation under heavy loads on steep routes; the hill-start assist function prevents the vehicle from rolling back on gradients of up to 20%.

The front axle is a Volvo RFS-L unit, the driven rear axle is a ZF AV133, while the third, tag axle is fixed. Compared with the steered auxiliary axle used on tri-axle buses, this is a simpler and less expensive design, reducing the extra cost and maintenance requirements associated with installing a third axle, although it does involve a compromise in manoeuvrability – albeit one that remains acceptable thanks to the relatively short wheelbase. The vehicle is equipped with electronically controlled air suspension and, naturally, disc brakes on all wheels. The electronic braking system (EBS) is complemented by anti-lock braking (ABS), traction control and electronic stability control, while during deceleration the so-called brake blending function coordinates regenerative and mechanical braking.

Up to 120 passengers

Volvo’s Hong Kong product page lists a maximum passenger capacity of 118, while the detailed technical specification gives 120 passengers, including 82 seats. The minor discrepancy between the two factory figures is presumably due to the specific interior layout or configuration.

One of the key technical issues in Hong Kong operation is the energy demand of air conditioning. Accordingly, the BZL DD Electric is fitted with a high-performance Denso electric air-conditioning system, which, in addition to cooling the passenger compartment, is also linked to battery thermal management. The system uses a high-voltage electric compressor and a dedicated battery-cooling function.

The bus can be charged at up to 250 kW via a CCS-standard plug-in connector. In addition to the charging socket located as standard at the left rear, a second socket can optionally be installed on the right-hand side, although only one can be used at a time. The design therefore primarily supports operation based on overnight depot charging, but the 250 kW charging power may also allow opportunity top-ups during the day.

Arrives with a substantial safety package

The Hong Kong-market BZL DD also receives a significant share of Volvo’s current active safety systems. The equipment includes, among other features, collision warning combined with city emergency braking, intelligent speed assistance, a side collision risk monitoring system, monitoring of the area directly in front of the vehicle, lane keeping and lane-change support, as well as a driver alertness monitoring function. Due to the electric driveline, the batteries and high-voltage network also have their own dedicated monitoring and protection system.

The bodywork of the Volvo BZL DD Electric – which, in line with local practice, is built as standard with a 2-2-0 door arrangement, supplemented by an emergency exit door at the rear on the right-hand side in the direction of travel – is produced by MCV. The cooperation between the two companies is not new: in recent years Volvo has assigned an increasingly important role to the Egyptian manufacturer in bodying its complete buses, while it has focused primarily on the chassis, electric driveline, energy storage, vehicle control and related services. Based on the images, the bodywork of the newly unveiled double-decker electric bus is virtually identical to that of the facelifted version of the MCV eVoSeti model built on the diesel-powered Volvo B9L chassis, which, while perhaps not an everyday sight, has been a familiar presence on the roads of Hong Kong since 2023.

At the same time, the arrival of the tri-axle version is an important expansion of the BZL Electric chassis family. With it, Volvo is entering a high-capacity electric bus segment in Hong Kong where ensuring passenger capacity comparable to that of traditional diesel double-deckers is a fundamental requirement during the transition to electric operation. The market significance of the model therefore lies less in the electric drive itself than in the fact that Volvo is now offering it in a tri-axle configuration adapted to the specific weight, capacity, climate and performance demands of Hong Kong operations.

Photos: Andrew Mak, CGI graphics: Volvo Buses