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Diesel-Electric Hybrids


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One thing going for the parallel system is the limp home capability when the inevitable malfunction occurs.

I'd reckon half the faults in a BAE hybrid require a tow.

Makes sense and these parallel hybrid systems bring it up in their selling points:

"No downtime. If a component fails, the hybrid motor ceases and the vehicle continues operating using internal-combustion engine."



"The safety and reliability of a parallel hybrid system — runs “parallel” to the engine and transmission so if the system is down the vehicle still drives."

The Allison system is known to be a parallel system but on their website they point out that it is two-mode:

"two-mode parallel hybrid operates automatically as a parallel hybrid or series hybrid"


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I think it's extremely important to thoroughly investigate the environmental and the financial impacts of the batteries these vehicles use and will use over their lifetime.

If the mining required to extract the rare metals required to assemble these batteries is environmentally negative is it really beneficial to use them? What if there are "human rights" abuses involved in their extraction?

Will the batteries actually last as long as the manufacturers claim?

If the batteries do last the 7 years the manufacturers claim, is it worth it for transit authorities to reevaluate their fleet replacement cycle from 12 to 14 years? Given the the high initial cost of the purchasing a hybrid vehicle should TA's consider keeping them longer, possibly rebuilding the bodies and some of the subsystems to maximize their investment, say three battery cycles or 21 years?

The TTC seemingly replaces battery cells frequently, so the idea of 7 year battery life is laughable to me.

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I bet the additional weight of the batteries means the body does not last as long to begin with.

You can spin numbers any way you want - while the ETS trolleybus debate went on, they brought up environmental issues with our coal powered electricity (which of course also powers everyone's houses and the LRT), but took diesel fuel at face value and did not take into consideration the emissions for extracting oil, and the transport costs to get the fuel to the garages, etc.

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Good points all.

It seems to me that climate change from carbon emissions is a bigger threat than any risk from battery toxicity so I am eager for more hybridization. (But while batteries are so expensive it seems that only routes with 4 or more stops per km are worthy of the expense)

Regarding battery replacement, can Bus Medic, or anyone with good info, speak to how long hybrid batteries (whether Allison, BAE or other system) are lasting in the real world?

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My point was, is the extra cost of purchasing and maintaining a hybrid fleet really offer significant environmental improvement over a clean diesel fleet? If the true costs of operating a hybrid fleet including all costs and benefits properly calculated and weighed out, would they end up costing more or less than operating a trolleybus network using buses with EPU technology?

I'm sure that even if a trolleybus network was operated off of a partly coal fired electricity grid they would still be more environmentally efficient than diesel buses, or diesel/electric hybrids used improperly (on routes with less than 4 stops per km).

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I'm sure that even if a trolleybus network was operated off of a partly coal fired electricity grid they would still be more environmentally efficient than diesel buses, or diesel/electric hybrids used improperly (on routes with less than 4 stops per km).

I think you are right that trolleybuses are more efficient. I am eager for more electric buses, preferably trolley, but also battery electric and hydrogen electric.

The problem is that all of them are still too expensive--unless you already have the trolley network in place and have cheap electricity, etc.

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  • 3 months later...

This article (about new XDE40s for Champaign-Urbana MTD) claims that the hybrid premium has decreased. I hope the reporter got it right but I'm not sure he did.


"At one time the difference in the purchase price of the hybrids versus conventional diesel buses was as much as $100,000, but it's now about $600,000 apiece for the hybrids to $550,000 for a conventional coach."

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  • 1 month later...


"When the PSTA board of directors authorized the purchase of the first diesel-electric hybrid buses in 2008, the bus manufacturer, Gillig Corp., claimed that the hybrids would use 20% less fuel on average than PSTA’s regular diesel buses. Since their deployment in 2009, the hybrids have experienced an average increase of 56% in fuel economy over the agency’s standard diesel buses.

The new 40-foot hybrids cost about $600,000 each, which is approximately one-third more than a standard diesel unit. However, overall savings in fuel and maintenance are expected to make the lifetime cost (over a 12-year period) of the hybrids equal to that of the regular diesel models."


(By my calculations, the 56% increase in fuel economy means that these Gillig Allison hybrids are using about 36% less fuel than the agencies standard diesel buses)

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  • 2 months later...

They cost more, but the Maryland Transit Administration (MTA) says that when it comes to hybrid buses you get what you pay for.

You get a lot:

With their current diesel fleet major road calls occur every 5,695 miles versus every 18,556 for the hybrid fleet.

Fuel mileage is 20 percent higher,

brake life is 25 percent longer,

and hybrids are found to be 50 percent quieter than diesels,” said MTA Administrator Ralign T. Wells.

Source: Metro Magazine


The MTA uses New Flyer hybrids with the Allison hybrid system. Other TA's with similar buses do better than 20% better on fuel mileage, probably because their duty cycle is more stop-and-go.

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  • 5 months later...

Very interesting. Go hybrids go.

On that same note, Volvo is introducing its hybrid articulated bus in Euope, with a 4 cylinder 5 liter engine!


Volvo Buses to introduce hybrid articulated bus


Volvo Buses will now strengthen its model program with a new articulated bus with hybrid technology. The Volvo 7900 Articulated Hybrid bus will have capacity for 154 passengers and up to 30% lower fuel consumption than the current diesel model.

“Many European cities have requested buses that combine high capacity with low fuel consumption and low environmental impact. With the Volvo 7900 Articulated Hybrid bus, we will meet customers’ requirements with a solution that will also fulfill the high demand on operational safety and reliability,” says Johnny Lidman, Product Manager Europe at Volvo Buses.

The new articulated bus has the capacity for up to 154 passengers, which is four more than the previous diesel model and more than any other hybrid bus in the market. Compared with the dual-axle Volvo 7900 Hybrid bus, fuel consumption will decrease by 15% per passenger in a fully occupied bus.

The Volvo 7900 Articulated Hybrid bus is equipped with Volvo’s new five-liter 240 hp diesel engine. It is approved for Euro 6 norms and will generate extremely low emissions. The emissions of nitrogen oxide will decrease by 87% and particle emissions will reduce by 50% compared with Euro 5. The bus also has a newly developed, efficient system for heating and ventilation. Thanks to the location of the battery package near the central axle, the weight of the 18-meter bus will be evenly distributed, making it possible to increase the number of passengers.

Reduced fuel consumption by up to 30%

As with Volvo Buses’ other hybrid buses, the Volvo 7900 Articulated Hybrid bus is a parallel hybrid, where an electric motor and diesel engine can be used jointly or independently. At bus stops, the bus will operate silently and completely emission free on electricity. The energy generated during braking is stored in the battery and then used to generate electricity for the electric motor. The technology will reduce fuel consumption and climate-impacting emissions by up to 30% compared with current diesel model. Since 2010, Volvo Buses has sold more than 1,200 hybrid buses in 21 countries with the same hybrid drivelines.

The first Volvo Hybrid 7900 Articulated will reach the customers in the spring of 2014.

All single-deckers low floor hybrids from 2014

From 2014, all single-decker buses with low floors in Volvo Buses’ model program for Europe will be hybrid buses. The hybrid program includes both low-floor buses Volvo 7900 Hybrid (4×2) and the Volvo 7900 Articulated Hybrid bus, as well as the Volvo B5LH Double-decker.

Facts about the Volvo 7900 Articulated Hybrid bus

Triple-axle articulated bus with low floor.

Length: 18 m.

Number of passengers: up to 154.

Diesel engine: Volvo D5 for Euro 6 norms (240 hp and 900 Nm).

Electric motor: (150 kW max) Volvo I-SAM parallel hybrid system.

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