This diesel bus converted to electric is half the price of a new model!

The Mercedes Citaro converted to electric during its visit to Marseille / Image: AP-HL

The “retrofit” isn’t just reserved for vintage cars and SUVs. Larger machines can also ditch their heat engine in favor of an electric motor. Retrofuture, one of the leaders in conversion in France, has thus embarked on the modernization of urban buses. It presents a first model, which operators could very well acquire.

New, a 100% electric city bus is extremely expensive: count between €500,000 and €650,000 depending on configuration and options. Renewing the entire fleet of a big city like Marseille (600 buses) would require a budget of… 300 million euros. A difficult amount for communities to take on. But then, how can they green their fleet without pulverizing their finances?

The “retrofit” is one of the solutions. This Anglicism designates the transformation of a thermal vehicle into an electric vehicle. Clearly, the gasoline or diesel engine is removed and replaced with a zero-emission drive chain. On an urban bus, operating costs “between €250,000 and €300,000” assures Arnaud Pigounides, founder and director of Retrofuture. The Parisian start-up, until then specialized in converting passenger and utility cars, is now starting the electrification of diesel buses and trucks.

A new electrical life after 18 years of service

It proposes a first model, in partnership with the reformer German Pepper Movement. This is the Mercedes Citaro, a very established bus in French urban transport networks. Retrofuture is currently touring 40 cities in France to introduce it and inform operators about the benefits of the retrofit. We visited the machine during its visit to Marseille.

Volvo Marseille electric bus

An entirely new bus, of which only the design betrays the period of origin. Manufactured in 2004, this example has more than 668,000 km on the odometer. It is experiencing new life since replacing its old diesel engine with an all-electric one.
At the rear, the removal of the block left enough space to install several water-glycol-cooled NMC batteries with a total capacity of 240 kWh under 650 Volts. The set weighs 980 kg and offers a standard range of 250 km. This radius of action is quite sufficient, as an urban bus travels an average of 120 km per day in France.

Under the engine hatch, batteries replace the diesel unit.

Charging power up to 150 kW

A Combo CCS port was added next to the fuel port, which was retained to power the optional biodiesel heating system (standard, a 25 kW heat pump provides heating and air conditioning). The bus accepts a maximum charging power of 150 kW, enough to fill up in less than 3 hours. Propulsion is provided by two asynchronous electric motors of 125 kW and 485 Nm of torque each, placed on the rear axle.

Buss electric retrofit e-trofit Germany

As surprising as it may seem, the Citaro still weighs 12,300 kg empty. He didn’t swell during his transformation. Maintaining the vehicle’s original mass and power is in fact mandatory to homologate a conversion. Engineers therefore had to perform specialized equilibrium and distribution calculations.

Two months waiting for a converted bus, one year for a new bus

Converting a bus requires 700 hours of work, or 6 to 8 weeks. This is shorter than that of a new electric model, whose wait between ordering and delivery is sometimes up to a year, explains Arnaud Pigounides. The manager also insists on the economics of the retrofit. Because if it’s half the cost of a new one, you can also benefit from the bonuses (up to €30,000) applicable to zero-emission buses.

At best, a transport operator can get a retrofitted electric model as efficient as a new one, from… €220,000. Conditions only: the machine must be at least 5 years old according to regulations and listed in the Retrofuture catalogue.

The company currently offers the Mercedes Citaro C1 and C2 and will soon face the Iveco Crossway. An offering that is slowly growing because you need to develop an expensive conversion plan for each model: “20 million euros for a bus and 1 million euros for a private or utility vehicle, including 200,000 euros just for homologation”details Arnaud Pigounides.

Retrofitting, better for the local economy and the environment

In addition to a reduced purchase cost, conversion has other advantages. Since the transformation operations are carried out by approved regional workshops, it promotes employment and the local economy. It also saves a lot of resources.

According to a study by the Agency for the Environment and Energy Management (ADEME), opting for a converted bus over a new electric model reduces greenhouse gas emissions by 37% over the entire life cycle. Transforming a diesel bus into an electric one cuts emissions by 87%, according to that same study, which was based on a standard 12-ton model.

Focus on trucks and hydrogen

Retrofuture, which has converted 20,000 vehicles since its inception three years ago, plans to convert 300,000 in ten years. In parallel with the development of a bus offering, the company will offer its first adapted truck models in 2023. The Mercedes Actros MP3, MP5 and Atego will be the first to benefit from it. For the first time, they will have the option to choose between battery-powered or hydrogen-powered electric propulsion. Retrofuture will indeed be able to replace your diesel engine with a fuel cell.

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