Mercedes testing new hybrid bus with world's largest lithium battery
Mercedes-Benz has begun demonstrating its new Citaro G BlueTec hybrid bus with what is claimed to be the world's largest lithium ion battery pack application. The new Citaro G is an 18-meter articulated bus with a series hybrid drive system. A smaller 4.8-liter diesel engine replaces the typical 12-liter engine used in such applications and drives a generator which provides electricity to hub motors mounted at the center and rear axles. The 771 lb lithium battery pack provides 180 kW and is charged both from the generator and from the regenerative braking. The bus can operate for short distances on battery power alone and reduces diesel fuel use and CO2 emissions by a estimated 30 percent compared to a standard bus of this size.
[Source: Daimler]
PRESS RELEASE:
New Mercedes-Benz hybrid bus in operation
* 250 customers test the Mercedes-Benz Citaro G BlueTec Hybrid city bus
* World's largest lithium-ion battery in vehicle operation
* Diesel consumption and CO2 emissions reduced by up to 30 percent
* Citaro G BlueTec Hybrid – future-oriented technology for the city
* 40 years of Daimler hybrid buses
More than 250 customers from 15 countries recently had the opportunity to experience at first hand the Mercedes-Benz Citaro G BlueTec Hybrid articulated bus in operation for the first time. Experts from European transport operations praised a number of features of the 18-metre long hybrid city bus, including its completely emission-free operation on some stretches of the route, its quiet, practically jerk-free drive system, its unique vehicle concept incorporating four electric wheel hub motors, and also its use of the world's largest lithium-ion vehicle battery. This battery stores the energy from the diesel generator and the electrical energy recuperated during braking.
As a result the Mercedes-Benz Citaro G BlueTec Hybrid reduces diesel consumption by up to 30 percent, with a commensurate reduction in highly topical CO2 emissions. The new hybrid bus has successfully completed extensive practical trials over recent months, including several weeks of winter trials under extremely tough operating conditions near the Arctic Circle. The first vehicles will be delivered to the transport operators before the end of this year. Given appropriate public sector support for hybrid technology, market insiders expect a potential annual demand for at least 300 hybrid buses in western Europe, which would enable diesel fuel consumption, CO2 emissions and pollutant emissions in the cities to be drastically reduced. In North America the Daimler bus brand Orion already has 1700 hybrid buses in day-to-day operation, which makes it the world market leader for hybrid technology in commercial vehicles.
Mercedes-Benz Citaro G BlueTec Hybrid
The Mercedes-Benz Citaro G BlueTec Hybrid has a technologically very sophisticated, serial hybrid drive system which allows emission-free driving under battery power alone over short distances. The drive system is installed in an articulated Citaro G bus, and drives the centre and rear axles by means of four wheel hub motors – a combination that makes this articulated hybrid bus unique.
The diesel engine in the serial hybrid bus does not act as a primary drive unit, but rather drives the generator to produce electric power as required. This energy is stored by maintenance-free lithium-ion batteries mounted on the roof. The batteries are not only fed by the diesel generator, but also with energy recuperated during braking.
The energy generated by recuperation when braking on the approach to bus-stops or traffic lights is used both to supply the vehicle at standstill and when moving off. This means that the hybrid bus is able to operate purely under electric power, and therefore practically without emissions, when stationary and under acceleration – with a significant reduction in noise as well.
Power is transferred to the wheels of the Citaro G BlueTec Hybrid by four electric wheel hub motors on the centre and rear axles. Even under heavy operating conditions, the 320 kW total output of the wheel hub motors is ample for an articulated bus.
Downsizing is among the greatest advantages of the serial hybrid system in the Citaro: instead of the large, 12-litre six-cylinder in-line engine normally employed in an articulated bus, a more compact unit with a displacement of 4.8 litres is used. As a result the engine weight is reduced from around 1000 kg to just 450 kg or so.
World's first lithium-ion battery in this output category
The lithium-ion battery used in the articulated Citaro G BlueTec Hybrid is in an output category of its own. The battery system generates 180 kW and is comparatively light in weight at under 350 kg. Major advantages over conventionnal battery systems include a higher energy density combined with a high storage capacity and a low battery weight.
Changes in the automobile industry are increasing the demand for clean, efficient and economical vehicles. According to forecasts, the market volume for powerful lithium-ion batteries is set to exceed the 10 bill. euro mark over the next decade, with the market for battery materials exceeding 4 bill. euros. In Germany alone, the government envisages at least one million electric cars populating the roads in the cities by 2020.
40 years of Daimler hybrid buses
With diesel-electric hybrid vehicles from Orion in North America, Mercedes-Benz in Europe and Mitsubishi Fuso in Asia, Daimler not only has the longest, but also the most extensive experience with alternative drive systems for commercial vehicles. The new Citaro with hybrid drive is a major step towards great economy and emission-free driving. Despite fuel savings of up to 30 percent, this complex hybrid technology nonetheless requires incentive financing. The support of politicians and the public sector in the form of subsidies is required to make the one-third higher costs for this technology in large-scale production worthwhile for both customers and manufacturers.
Reader Comments (Page 1 of 1)
jharlan 11:12AM (3/30/2009)
The US has lost the leading edge. Will we ever be able to catch up? After all we are the world leaders in selling *&&^%^%$ derivatives!
Reply
rar 11:30AM (3/30/2009)
I agree with your derivative comment, you do know that GM has been producing the two mode hybrid bus since 2003.
http://www.autobloggreen.com/2008/01/22/dc-auto-show-1-732-more-orders-for-gm-hybrid-buses/
The question for this bus is, will any public transportation company be able to afford it?
harlanx6 12:38PM (3/30/2009)
Very good point, rar. Lithium batteries are affordable in your laptop, but might just cost more than the rest of the bus.
Matt 11:30AM (3/30/2009)
Guess you haven't seen the aptera or volt lately... I'd say we're ahead.
Reply
damien 11:52AM (3/30/2009)
Too little too late.
They had their chance to be the worlds best automaker and they blew it with the EV1.
I own a 1977 GMC camper special, it still runs great. Why? Because GMC used to produce great products. Since then they started producing cars with a bunch of planned obsolescence, with little to no fuel economy improvements (made them even worse is some cases), and they started putting all their production and marketing efforts in SUVs. Anybody with half a brain could realize that these decisions were in the opposite direction that the industry needed to go. They were doing it to ensure that North Americans would continue to waste as much gas as possible.
And ya wow the Volt and the aptera are SO amazing, but way too late. You think anyone who has owned a GMC lemon within the last 10 years, and then switched to more reliable Asian cars are going to take a risk of owning GMC again? Hell no!
Matt 12:12PM (3/30/2009)
Don't be so sure, I think Americans want to support their domestic automakers. Just look at the success of the new Chevy Malibu and the Ford Fusion. They are making a genuine effort and putting real design resources to work for these new platforms. They can and will succeed, and those that blindly bash them because of past mistakes may just as well bash VW for having been started by Hitler. They are headed in the right direction now, and that's all that matters.
randomdude 3:52PM (3/30/2009)
Apparently much of the knowledge used to build the Volt comes from Germany (Opel). *wink*
Chris M 4:42PM (3/30/2009)
The GM Volt project is in some ways international, with information coming not just from Opel in Germany and GM in Detroit, but also from Saab in Sweden, LG Chem of Korea, and possibly even AC Propulsion in California. And don't forget that GM was inspired by Tesla Motors, also from california.
Matt 5:14PM (3/30/2009)
SAAB, Opel, Vauxhall, Holden, Daewoo, Buic, Cadillac, Chevy, GMC, Hummer, Oldsmobile, Pontiac, and Saturn... All GM, but the Volt is an American project. Germany, Sweden and Korea get a consolation prize for helping because GM pooled its resources to get the research and development done. Furthermore, if we let GM die, it will all go to waste and will never really happen. If big blue goes under you don't have to worry about where the parts came from, because the people who put them together will be out of work.
why not the LS2LS7? 1:15PM (3/30/2009)
I'm sure the amount of fuel saved is very significant. But I'm surprised it only saves 30%. In city use I would think it would be closer to 50%.
Reply
jeff 2:10PM (3/30/2009)
Something doesn't make sense. At first I thought they meant to say 180kW-hours, but that would weigh a lot more than 700lbs and would give this thing way more all electric range than it needs (probably like 200 miles or something). So I don't think they give the battery capacity, though you can make a guess based on that weight: probably about 50kWh for 350kg.
But a pack this size should be able to put out way more than 180kW of power. That's about the size of the Tesla battery, and the bottleneck for power is the motor, definitely not the batteries. Li-ion batteries can typically put out way more power than their motor can handle. While the energy density of li-ion batteries is usually around 150 Watt-hours/kg, the power density is much higher, usually at least 2000 Watts/kg. That would mean this battery should be able to dump out 700 kW.
Besides, it'd be really weird to have a series hybrid where the batteries can't provide all the required power on their own and are dependent on the range extender for almost half the power. it would make more sense if the range extender could output 180kW, that sounds about right for a 4.8L diesel. That also sounds about right for a series hybrid with motors capable of outputting 320kW. Its probably a charge sustaining hybrid, with the 180kW engine sized for approximately the average power requirements of the motors, while the motors can peak to 320kW thanks to the battery buffer.
Reply
Matt 2:31PM (3/30/2009)
I think plug in capability would be a huge bonus here. They could charge the buses at night which would at least let them go on electricity alone for the first few hours of their route. You might be able to have them charge when waiting at the main terminal too between routes. This would mean massive fuel savings...
jeff 2:35PM (3/30/2009)
I agree that the more you run off energy from the grid the better, but I don't think this is how this particular bus works. There's no mention of it being a plug in. I agree though, set up a fast charge station at one end of a 10 mile bus route, and you could pull off a pure EV bus pretty well. In my city, most of the buses routes have a subway station at one end, so there's already a pretty massive electrical hookup somewhere inside! Just tap a couple extension chords right onto the rails!
3PeaceSweet 3:30PM (3/30/2009)
So the downsizing of the diesel engine saves as much weight as is added by the battery pack?
If the wheels are all electrically driven you can do without the transmission, drive shaft and differential etc all saving weight.
Add in some fast charging capacitors to the bus and some fast charging capacity at the busiest stops (longest) and you minismise the fuel requirements.
Add in some CNG injection to the diesel engine to further reduce NOx / PM when the diesel is running.
Reply
Chris M 4:37PM (3/30/2009)
If the article is correct, downsizing from the 12 liter to the 4.8 liter droppped the weight from 1,000 Kg down to 450 Kg, a savings of 550 Kg. Since the battery pack was "under 350 Kg", that indicates a total weight saving of about 200 Kg. I say "about" because it doesn't give the additional weight of the motors and generator, or the weight savings from not having a transmission.
One minor quibble. This isn't "the worlds largest LiIon battery pack", as the ones used in hundreds of Tesla Roadsters are bigger, both in weight and in power output. Perhaps it is the "worlds largest LiIon battery used in a series hybrid bus".
Arend 4:24AM (4/03/2009)
The e-traction bus ( http://www.autobloggreen.com/2009/03/26/dutch-e-traction-bus-combines-series-hybrid-setup-with-wheel-mot/ ) has a larger litium-ion battery than this bus. it uses 30 lithium-ion batteries with a total weight of 585 kilo,s.
I would really like to know which batteries they use because i haven't found such a high capacity battery yet wich such a low weight.
arend
Reply