A lot of the recent noise on the adoption of alternative traction for trains has concerned passenger vehicles.

Hydrogen or batteries are viewed as an effective method for short journeys, or perhaps in urban settings where issues of noise and emissions are becoming more of a concern.

In the freight sector, the focus tends to be on the last mile, where locomotives can operate on batteries or, perhaps, a smaller power unit when overhead line electrification is not available. But trials in California could change this.

Battery-powered locomotives built by Wabtec could be hauling-heavy haul freight trains in North America, South America, and Australia in the next few years as the manufacturer looks to expand its alternative power offering for the rail industry.

Initial trials with a battery locomotive over a three-month period at the start of 2021 have already proven successful. The FLXdrive 1.0 locomotive was tested by BNSF on the 560km route between Barstow and Stockton between January and March.

The 192-tonne battery locomotive, coupled between two Tier 4 diesel locomotives, was fitted with 18,000 lithium-ion battery cells offering 2.4MWh of battery storage. The locomotive consist was tested on heavy mining trains and it is this market which Wabtec believes could be the initial user of such locomotives.

FLXdrive covered more than 21,400km during the trial, running through the hilly terrain in California’s San Joaquin Valley. Not only is the terrain a challenge, but the region is also classified as a non-attainment area, where air quality is worse than the National Ambient Air Quality Standards. This trial was partly funded through a $US 22.6m grant from the California Air Resource Board awarded to Wabtec, BNSF, and the San Joaquin Valley Air Pollution Control District.

Two months after the trial ended, Wabtec confirmed that the FLXdrive locomotive delivered more than an 11% average reduction in fuel consumption and greenhouse gas emissions for the entire train, the equivalent of 23,469 litres of diesel fuel saved, and around 69 tonnes of CO₂ emissions reduced.

“20 years ago, we invented Trip Optimiser. That was really developed thinking about the potential for hybrid technologies to come.”

Mr Alan Hamilton, Wabtec vice-president of engineering

The locomotive was charged overnight and was then able to recharge throughout the trip using regenerative braking. Wabtec’s Trip Optimiser manages the overall train energy flow and distribution. This is effectively an intelligent cruise control system programmed via artificial intelligence (AI) to respond to every twist and grade of the track in the most energy-efficient way possible.

When thinking about implementation of the technology, Wabtec vice-president of engineering, Mr Alan Hamilton, explains it is not about one locomotive, rather it is about the entire formation.

“It’s not uncommon to have four or five locomotives on a train, and therefore because of the huge amount of energy that is being utilised we’ve developed a lot of different energy-saving technologies over the years,” Hamilton says. “20 years ago, we invented Trip Optimiser. That was really developed thinking about the potential for hybrid technologies to come.”

Wabtec battery-powered locomotives could be used on three continents in the next few years.

At the dawn of the new millennium Wabtec [then General Electric] had already been experimenting with batteries for many years. However, Hamilton says at that time it was obvious the technology was not suitable for the type of energy needed for a heavy haul locomotive.

However, Trip Optimiser started to show average fuel savings of 10%, and fast forward to 2021 Hamilton says battery technology is now much more practical due to the huge investments that have been made worldwide mainly driven by the automobile sector. “Now you can get energy density and pricing and safety that we can start to deploy on these types of trains,” Hamilton says. “But you still need to control it. It’s this overall Trip Optimiser control that now has another lever that it can utilise and say, well not all braking is bad.”

Initial trials showed that another 11% of energy could be saved by being able to recover that dynamic braking, save it and use it when appropriate. “We also show that we could actually use that energy in different ways,” Hamilton continues. “We can use that energy whenever we want it, we can use it as average fuel savings. We could use it to pull the train into the yard on zero emission mode, and do all sorts of different things.”

However, it was recognised that making the entire train operate in this fashion would be timely and expensive, so a different way of thinking was required, according to Hamilton. This involved using diesel locomotives and adding a pure battery locomotive to the mix before treating it as a complete energy management platform. “What’s on the FLXdrive is basically the same type of ac traction system that we have on our other locomotives, but instead of engine and alternator, now we basically have a bank of batteries that’s on the top deck.”

Hamilton believes that while the overnight static charging will be an initial way of operating these locomotives, eventually there could be charging carried out on the move perhaps via stretches of discontinuous electrification. This, he says, could dramatically extend the range of the batteries.


Hamilton says the locomotive was seamlessly integrated into the BNSF network and that no special operation was needed. Instead, it just went out and performed its duties, which Hamilton says is a credit to BNSF. “We had a hypothesis based on modelling, based on understanding of how these trains run, how much energy we should be able to save if we deploy this and so we validated that model - we actually exceeded our expectations and by doing that we also showed we could do it in a very safe manner.”

“Eventually we are going to have more and more energy on these locomotives which will mean at some point, maybe not having diesel on the train.”

Alan Hamilton

Three months is a short period for a trial, admits Hamilton, but he says it was enough to show that the locomotive could be integrated into day-to-day operations. “It didn’t need to be run by a team of engineers; the operator was able to control it,” he says. Range anxiety - concerns over how far the train could run between charges - was real Hamiton adds. However, the diesels were there in case anything went awry. Longer term, that may not be the case.

“Eventually we are going to have more and more energy on these locomotives which will mean at some point, maybe not having diesel on the train,” Hamilton says. “The way we end up charging the batteries is two-fold. One, of course, is along the way. Anytime we are braking, we’re working on how we recapture that energy for the battery electric locomotive intelligently, how we put the energy back in the battery, and then at its final destination when it’s laid up.”

It is unlikely that FLXdrive 1.0 will be used by itself. Hamilton points to the large-scale of North American freight trains, which can be more than 1600m long with 6000 tonne plus trailing loads.

“We’re already thinking for certain routes even in North America, where maybe two or three FLXdrives could be able to complete zero emission operation,” he says.

“The current FLXdrive 1.0 that we demonstrated is very modest in terms of the size of the battery. It is 2.4MWh. That is a lot of energy compared with a car, but when you think about the amount of energy that these trains use, that is a very modest amount. Our FLXdrive 2.0 that we are working on is more than 6MWh, so you can imagine what that will do potentially for fuel savings on certain routes - maybe almost a 30% fuel saving, and again the geography is very important.”

It is not just heavy haul freight locomotives where battery technology could be deployed. “Yards that are within very densely packed, urban areas where the regulatory environment and local or federal governments might be giving incentives, even though this might not be economically attractive, but due to what this technology can bring for that area of that city, it makes sense to do it,” he says.

Hamilton tells IRJ of the work taking place in Wabtec’s laboratories. “Batteries are one piece of the puzzle but what we’re doing right now is total energy management,” he says. “We are even thinking about hydrogen technologies in the future.”


This work is not just about the prime mover, rather it is also about the controls, or where the power comes from, with drawing power from the grid under consideration. “It’s really a combination of these technologies that I think in the future is going to make sense,” Hamilton says, adding that while he believes smart electrification and hydrogen will have a place in future strategies, batteries will be the choice in all these situations because it can capture wasted energy and reuse it.

However, he warns that it is important to optimise how this technology is utilised. “A locomotive, unlike a car or iPhone or anything else that is using batteries, has a very long life so we need to be able to design our system, so it doesn’t stay stagnant over time,” Hamilton says.

“How can you intelligently upgrade the system in a safe, high performing and economical way? It’s very important from the system design, and the mechanical and electrical integration, that you’re thinking of what will come and, even though you don’t know exactly what that will be. You’re designing the interface so that it can take advantage of tomorrow’s technology with your design today. It’s very important to future proof.”

“Batteries are one piece of the puzzle but what we’re doing right now is total energy management. We are even thinking about hydrogen technologies in the future, and other types of technologies.”

Alan Hamilton

Days after Wabtec spoke to IRJ about FLXdrive 1.0, it was confirmed that the manufacturer and General Motors (GM) are set to collaborate in the development and commercialisation of GM’s Ultium battery technology and Hydrotec hydrogen fuel cell system in Wabtec locomotives.

A non-binding memorandum of understanding (MoU) has been signed to advance a shared vision of zero emissions transport with the objective of using Wabtec’s expertise in energy management and systems optimisation to develop a heavy-haul locomotive solution that can use GM technology.

Ultium Cells, GM’s joint venture with LG Energy Solution, launched the Ultium battery technology back in March 2020 and this is now the centrepiece of the auto manufacturer’s transition to electric vehicles. Ultium is unique to the industry, claims GM, and is based on large-format, pouch-style cells that can be stacked vertically or horizontally inside the battery pack, optimising storage and thus making them suitable for locomotives.

GM is also supplying Wabtec with its Hydrotec hydrogen fuel cell power cubes, which will be manufactured by Fuell Cell Systems Manufacturing in Brownstown, Michigan, a manufacturing joint venture of GM and Honda.

“The real benefit of the MoU is that GM is a leader in battery and hydrogen technologies, which complements Wabtec’s expertise in the heavy-haul rail and energy management,” Wabtec spokesman, Mr Tim Bader, told IRJ. “The two companies can develop battery and hydrogen solutions specifically tailored to the rail industry’s demanding environments. They will be based off the Ultium and Hydrotec platforms. Additionally, GM has the battery and hydrogen production capabilities to accelerate and scale for the manufacturing needs of Wabtec’s locomotives.”


So where will these battery-powered locomotives be used? Hamilton says their operation likely will not be limited to North America.

“Right now, we’re in negotiations and discussing with many different customers,” he says. This includes mining customers in South America and Australia. Hamilton says lines operated by mining customers make a lot of sense because the ore is being mined high up and is then hauled down to a port.

“The other thing with mining customers is often it is a captive and very predictable type of operation, so it is something that has great, great potential,” Hamilton says.

Getting the project to full production will take a couple of years after testing of FLXdrive 2.0, which is being built at Wabtec’s Erie plant in Pennsylvania, begins in the second half of 2023. “I think that we have the potential with customers, both in North America and around the world, to think about how we develop this technology in a safe and responsible manner,” Hamilton says. “As it reaches maturity and costs continue to come down, there’ll be more and more opportunities for the technology to be deployed.”