Cummins Teams With TM4 On Class 7/8 Plug-In Hybrid Diesel Bus Platform

MAY 15 2017 BY MARK KANE 12

Cummins and TM4 have announced a joint effort to develop a plug-in hybrid powertrain for Class 7/8 transit buses.  Reportedly the new set-up can reduce fuel consumption by at least 50% over conventional hybrid buses.

Above: The system consists of a gen-set (Cummins’ Euro 2019 B4.5 internal combustion engine coupled with TM4’s LSG130 electric generator), an external ultrafast charging infrastructure, a power collector, a 111 kW-h onboard Li-ions battery, a TM4 SUMO electric motor directly connected to the axle’s differential, a small fuel tank and all power electronics and controls that allow the system to work.

As some background on the partners, TM4 it is one of the largest suppliers of electric powertrains, already delivering roughly 5,000 units in China last year, while Cummins is well known from its internal combustion engines, which have started to turn to plug-in hybrids recently, perhaps already seeing that electrification is the only way to go.

The two intend to use optimized engines as range extenders (see image).

Unveiling of the joint plug-in hybrid powertrain is scheduled at UITP, taking place in Montreal, from May 15-17th, 2017.

According to the pair, up to 35 km (22 miles) of all-electric range, charged up in 5 minutes – 450 kW fast charging is the target.

“With their expertise in internal combustion engines and related products, Cummins researchers will optimize the powertrain by selecting the engine with the best architecture to use as an electric commercial vehicle range extender, using the engine to manage the charge level of the all-electric drive battery pack. The range extender will be integrated, using advanced vehicle controls, with the electrified powertrain and other applicable technologies.”

Said Robert Baril, Managing Director of TM4 said:

“TM4 has always innovated to serve the market needs. Today, our customers can buy battery electric or hybrid buses with limited EV range. Our goal is to offer a system that can achieve 35 km EV range and benefit from the 450 kW fast charging infrastructure to recharge in less than 5 min. The range extender allows for peace of mind and significant flexibility. We are honored to be partnering with Cummins and hope to bring this product to market in the near future,”.

Wayne Eckerle, VP, Cummins Research and Technology said:

“The close integration and control of the electrified powertrain with an appropriately selected engine is critically important to developing a plug-in hybrid electric vehicle system.  We believe that through the team’s efforts we can become a  significant player in electrification of commercial vehicles by providing complete systems to benefit our global customers. ”

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12 Comments on "Cummins Teams With TM4 On Class 7/8 Plug-In Hybrid Diesel Bus Platform"

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Math smells funny, maybe it’s me:
“35km”, on “5 minute” charges.

Thinking back to the last truck article, assuming .5mi/KWh, the 111KWh battery would need about 42KWh at each stop. In 5 minutes, that suggests a sustained 500KW.

I guess it’s me. They’re using a small enough DOD window that the taper may not be too bad. Maybe 15% charged to ~55%. Would this mean the 450KW would have to be delivered at or above, 800 volts?

Just thinking it through. I had a little bit of money in CMI, when I thought their LNG design was going to succeed. That was before oil prices sank.

I don’t see this reducing emissions that much for an on the highway class 7/8 truck. In fact it could be worse than a regular semi truck.


The series setup won’t be as efficient on the highway as a regular diesel semi because of the conversion losses. Plus

..the EV range is so low it won’t cut emissions much since most miles will be on the range extender.

On the other hand it doesn’t need a 120,000$ battery pack either.

Can’t wait for the Sept reveal of Elon’s electric semi

This is for buses driving fixed routes with access to quick charging. The range extender won’t run much.

Thx David, slaps forhead. I missed that

Seems a bit like overkill for around town. No RE required.

Didn’t Proterra kind of ditch the small battery huge charger concept for just a bigger battery?

On the other hand, you could put a smaller diesel engine couple with a Stirling motor or a Rankin cycle turbine to recuperate some of the wasted heat altogether running a generator to generate the power to move the hauler.
Seems complicated, but much less than any F1 engine that couple KERS or MGU-K plus an MGU-H.

That would probably put the absolute efficiency over 55%.
Not perfect but better than usual.

I would connect the engine/alternator to the motor through a clutch. That allows full power when you need it.

Great hybrid, which is perfect for city but routes. Almost every bus route in my city here, would not need to burn any fuel at all, and powering up for 5 mins at the end of route would work really well.

TM4 is a company here in Canada (Quebec), but I see they manufacture their motors/inverters in China.

There ought not be another non electrified bus built.

Whats its lap time on the nurburgring?

There are several fully electric buses out there. They’re perfect for city driving. No need for an REX in my point of view. Give it a 200km (124mile) range and you can charge it at the end of the route for 5min too. It will never run out of power.

I must be missing something…

JJF, should read “bus”, apologies on that. Fixed!