This picture is of a box under one of the back seats of a city bus. The box is very roughly a foot on a side.

Does anyone know what the Ultra-Cap is used for in the bus?

 

Is it a hybrid bus? We have hybrid buses in my area, but they say hybrid on them and the roof area is extra thick, as if they're keeping the energy storage devices in the roof.

 

Is it a hybrid bus? We have hybrid buses in my area, but they say hybrid on them and the roof area is extra thick, as if they're keeping the energy storage devices in the roof.

No, a Diesel bus.

 

No, a Diesel bus.

I'm guessing the bus, like many ocean going cruise liners and locomotives, has a diesel engine which runs a generator which provides power for an electric motor. The ultra capacitor stores energy while the vehicle is idling, and provides current to accelerate or climb hills.

 

I'm guessing the bus, like many ocean going cruise liners and locomotives, has a diesel engine which runs a generator which provides power for an electric motor. The ultra capacitor stores energy while the vehicle is idling, and provides current to accelerate or climb hills.

I don't think the bus is Diesel-electric. I would think they would say so on the outside in big print.

Also, it does not make any funny sounds. The smaller, hybrid or electric (I'm not sure which) mall buses sometimes sound like they are stripping gears.

 

In a Prius, the motor/generator on the engine goes into generator mode when dynamic-braking, and the current produced is jammed into the battery pile pretty much as fast as it can handle it without bursting into flames. Everything about a bus is bigger, including the current produced when braking. There is too much current for batteries to absorb safely, so it goes into a supercap array that can handle a much greater di/dt. Also, the charge/discharge profile is very different for a bus. With thousands of cycles per day, normal batteries wouldn't last a week. The energy storage density of any rechargeable battery chemistry decreases with each cycle, while a well-built capacitor is capable of near-infinite cycles with much less degradation.

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There is too much current for batteries to absorb safely, so it goes into a supercap array that can handle a much greater di/dt.

Why does the rate at which the current is changing such a big deal? I would think it would be the magnitude of the current itself (dq/dt) that would matter much more.

 

Also there are many Prius in use as taxis with hundreds of thousands of miles on the original batteries. They don't last forever, but they last a reasonable amount of time. Part of the trick is they only use a fraction of the capacity of the batteries.

 

Its used to start the bus since it reduces the battery count from 4 to 2.

 

Its used to start the bus since it reduces the battery count from 4 to 2.

Ohhh I like that. Lower weight, higher reliability.

 

Its used to start the bus since it reduces the battery count from 4 to 2.

So, how does it do this? By lowering the output resistance of an existing battery? By doubling the battery voltage?

I think older buses used compressed air to start the engine. I assume this is the modern equivalent?

 

They use

So, how does it do this? By lowering the output resistance of an existing battery? By doubling the battery voltage?

I think older buses used compressed air to start the engine. I assume this is the modern equivalent?

I think that you can find the answer here:
http://www.koldban.com/Kapower_Information_Center_s/28.htm

 

I think that you can find the answer here:
http://www.koldban.com/Kapower_Information_Center_s/28.htm

Yes! I will need some time to digiest it, though.

 

I ran across this:

http://www.koldban.com/v/vspfiles/assets/images/documents/TR0003.pdf

It basically says that the supercaps are there to ensure that there is sufficient energy to start an engine in spite of anti-idle laws.

 

Oh, I see that the article I found is on the Kold Ban site that ISB123 recommended, so it may be redundant.