On Mon, 19 Dec 2011 11:37:34 -0000
"Recliner" wrote:
According to the Autocar review of the bus, the 4-cylinder diesel
generator has a max power of only 182bhp (which is less than my car),
which is used not only to charge the battery, but also to power the air
compressor for the brakes and steering. The battery is rated at 75kWh.

Its quite enough to move a double decker on the relatively shallow inclines
of a motorway even accounting for losses in converting to electical power.
Most buses arn't rated at much more than that anyway. If it can't cope with
steady running on a motorway with loads of nice cold air to keep it cool
god knows how it'll manage in 30C in summer slowly cooking in a london traffic
jam.

B2003

wrote in message

On Mon, 19 Dec 2011 11:37:34 -0000
"Recliner" wrote:
According to the Autocar review of the bus, the 4-cylinder diesel
generator has a max power of only 182bhp (which is less than my car),
which is used not only to charge the battery, but also to power the
air compressor for the brakes and steering. The battery is rated at
75kWh.

Its quite enough to move a double decker on the relatively shallow
inclines of a motorway even accounting for losses in converting to
electical power. Most buses arn't rated at much more than that
anyway. If it can't cope with steady running on a motorway with loads
of nice cold air to keep it cool
god knows how it'll manage in 30C in summer slowly cooking in a
london traffic jam.

You're assuming that it overheated, rather than my guess that the
battery was running low. I presume that they run the engine for optimum
economy, rather than for max power.

On Mon, 19 Dec 2011 11:55:54 -0000
"Recliner" wrote:
You're assuming that it overheated, rather than my guess that the
battery was running low. I presume that they run the engine for optimum
economy, rather than for max power.

I shouldn't make any difference. Once the battery is flat it runs off the
engine just like every hybrid car ever built.

B2003

wrote in message

On Mon, 19 Dec 2011 11:55:54 -0000
"Recliner" wrote:
You're assuming that it overheated, rather than my guess that the
battery was running low. I presume that they run the engine for
optimum economy, rather than for max power.

I shouldn't make any difference. Once the battery is flat it runs off
the engine just like every hybrid car ever built.

This is a range-extender hybrid, unlike most existing hybrid cars. In
other words, it's more like the Volt, not the Prius (ie, not all hybrid
cars are the same). So the only drive to the axle is from the 174bhp
motor, powered by the battery, with the generator just acting as a
part-time charger, which runs at optimum revs when it runs at all. If
the engine isn't charging the battery as fast as it's discharging, the
bus will have to stop or slow down for long enough for the charge to
accumulate again.

Autocar comments that the engine needed to run most of the time during
its short road test, probably because it wasn't getting much benefit
from regenerative braking, unlike on a normal bus route. This does
suggest that the engine isn't really up to powering the bus for a
sustained run at motorway speeds (unless the engine is pushed hard,
which would destroy the excellent economy and green claims). Wright
claims 11.2mpg for the Boris Bus, compared to 8.6mpg for Wright's Gemini
2 Hybrid (and 4.3mpg for a Citaro G bendy bus). The CO2 figures are also
much better (640g/km, compared to 864 and 1300, respectively).

On Mon, 19 Dec 2011 12:57:20 -0000
"Recliner" wrote:
This is a range-extender hybrid, unlike most existing hybrid cars. In
other words, it's more like the Volt, not the Prius (ie, not all hybrid
cars are the same). So the only drive to the axle is from the 174bhp
motor, powered by the battery, with the generator just acting as a
part-time charger, which runs at optimum revs when it runs at all. If
the engine isn't charging the battery as fast as it's discharging, the
bus will have to stop or slow down for long enough for the charge to
accumulate again.

No reason it should have to stop - the power could be directed straight from
generator to motor bypassing the battery. In fact thats what any sane drive
system should do since there's no point directing power into the battery if
its just going to be used up again immediately. Also unless a radical new
battery technology has been invented the motor would almost certainly be able
to drain the battery faster than the generator can charge it so I suspect the
generator will be running most of the time anyway regardless of traffic
conditions. The plus side as you said is it can run at an optimal rpm and
regenerative braking can regain some of the energy lost.

If they haven't designed the system so it can run on generator alone with a
flat battery then shame on them.

B2003

In message , at 14:04:52 on Mon, 19 Dec
2011, d remarked:
If they haven't designed the system so it can run on generator alone with a
flat battery then shame on them.

If the brief was "in stop-start traffic in London", then engineering it
for an extended flat-out run on a motorway might not be appropriate.
--
Roland Perry

"Roland Perry" wrote in message
...
In message , at 14:04:52 on Mon, 19 Dec
2011, d remarked:
If they haven't designed the system so it can run on generator alone with
a
flat battery then shame on them.

If the brief was "in stop-start traffic in London", then engineering it
for an extended flat-out run on a motorway might not be appropriate.

Wouldn't it have been easier to string a couple of wires up above the bus
routes and dispense with carrying a generator and batteries around on the
bus?

)

Ian1

On Dec 19, 1:29*pm, wrote:

I shouldn't make any difference. Once the battery is flat it runs off the
engine just like every hybrid car ever built.

Though with only 182bhp for a vehicle that size, probably quite
slowly.

Most hybrid cars, by contrast, have an engine that is more than
adequate to power the car on its own.

Neil

on Mon, 19 Dec 2011, Neil Williams remarked:
I shouldn't make any difference. Once the battery is flat it runs off the
engine just like every hybrid car ever built.

Though with only 182bhp for a vehicle that size, probably quite
slowly.

Most hybrid cars, by contrast, have an engine that is more than
adequate to power the car on its own.

I recall the Parry People Mover coming up as possibly another vehicle
whose "top-up" internal combustion engine might not be enough to propel
it on its own.
--
Roland Perry

On Mon, 19 Dec 2011 06:38:28 -0800 (PST)
Neil Williams wrote:
On Dec 19, 1:29=A0pm, wrote:

I shouldn't make any difference. Once the battery is flat it runs off the
engine just like every hybrid car ever built.

Though with only 182bhp for a vehicle that size, probably quite
slowly.

All double deckers in london are underpowered anyway. Anyone who has been
stuck in a car behind one crawling its way up highgate hill or around southgate
will testify to that.

B2003