Discussion:
New electric buses
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s***@potato.field
2016-12-08 14:42:44 UTC
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I noticed some brand new (66 plate) single decker pure electric buses around
Waterloo today. They look very nice (apart from the huge battery pack on the
roof) and certainly have a good turn of acceleration off the line. I notice
however that their unladed weight is > 12 tons which is more than a lot of
double deckers, presumably because of the battery. I wonder how efficient that
actually makes them when you calculate it all the way back to the power
station?
--
Spud
Recliner
2016-12-09 13:57:45 UTC
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Post by s***@potato.field
I noticed some brand new (66 plate) single decker pure electric buses around
Waterloo today. They look very nice (apart from the huge battery pack on the
roof) and certainly have a good turn of acceleration off the line. I notice
however that their unladed weight is > 12 tons which is more than a lot of
double deckers, presumably because of the battery. I wonder how efficient that
actually makes them when you calculate it all the way back to the power
station?
I suspect that the box on the roof isn't the heavy battery pack. The
whole back half of the bus has a high floor, and given the absence of
a diesel engine, I think that's where the batteries live. It means
that there are only a couple of step-free seats; the others are all in
the high back end.

They presumably have regenerative braking, so the weight won't make
too much difference to the efficiency. But it explains why there won't
be any double-deck battery buses.

Of course, they're being used to eliminate local pollution in the city
centre, not to save energy. But they apparently have a much lower
running cost, no doubt partly because they need less maintenance.

They're not as quiet as I expected; obviously there's no engine noise,
but the transmission has a loud gear whine.
s***@potato.field
2016-12-09 14:30:45 UTC
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On Fri, 09 Dec 2016 13:57:45 +0000
Post by Recliner
I suspect that the box on the roof isn't the heavy battery pack. The
whole back half of the bus has a high floor, and given the absence of
a diesel engine, I think that's where the batteries live. It means
Wonder what the roof thing is then. Its pretty large , way too large to be
an aircon unit. Perhaps its braking resistors for when the regen braking can't
cope?
Post by Recliner
They're not as quiet as I expected; obviously there's no engine noise,
but the transmission has a loud gear whine.
Thats probably the noise of the motors themselves I would imagine. There's
probably little if any transmission to speak of.
--
Spud
Recliner
2016-12-09 16:20:53 UTC
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Post by s***@potato.field
On Fri, 09 Dec 2016 13:57:45 +0000
Post by Recliner
I suspect that the box on the roof isn't the heavy battery pack. The
whole back half of the bus has a high floor, and given the absence of
a diesel engine, I think that's where the batteries live. It means
Wonder what the roof thing is then. Its pretty large , way too large to be
an aircon unit. Perhaps its braking resistors for when the regen braking can't
cope?
Yes quite likely. Could also be the aircon or cooling radiators for
the batteries, which are likely to get quite hot. There might be more
of a clue if you can see one from above; for example, you can see the
hydrogen cylinders in the open-top box on the roof of the
hydrogen-powered buses.
Post by s***@potato.field
Post by Recliner
They're not as quiet as I expected; obviously there's no engine noise,
but the transmission has a loud gear whine.
Thats probably the noise of the motors themselves I would imagine. There's
probably little if any transmission to speak of.
There's a reduction gearbox, which probably makes more noise than the
motor(s). There may also be some sort of prop shaft and differential.
s***@potato.field
2016-12-09 16:36:35 UTC
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On Fri, 09 Dec 2016 16:20:53 +0000
Post by Recliner
Post by s***@potato.field
Wonder what the roof thing is then. Its pretty large , way too large to be
an aircon unit. Perhaps its braking resistors for when the regen braking
can't
Post by s***@potato.field
cope?
Yes quite likely. Could also be the aircon or cooling radiators for
the batteries, which are likely to get quite hot. There might be more
of a clue if you can see one from above; for example, you can see the
hydrogen cylinders in the open-top box on the roof of the
hydrogen-powered buses.
Seemed to be completely enclosed IIRC.
Post by Recliner
Post by s***@potato.field
Thats probably the noise of the motors themselves I would imagine. There's
probably little if any transmission to speak of.
There's a reduction gearbox, which probably makes more noise than the
motor(s). There may also be some sort of prop shaft and differential.
If the motors and traction controllers are similar to that on trains they could
be pretty noisy. Doubt there's a prop shaft - transverse mounting makes the
most sense to me with the diff built in.
--
Spud
DRH
2016-12-09 19:05:44 UTC
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The Red Arrow BYD / Alexander-Dennis Enviro200EV buses have iron-phosphate batteries at the rear and in the roof pod, which also incorporates the aircon unit. The driveline comprises two 90kW wheel-hub motors and water cooling system plus regenerative braking system.

There are also five BYD double-deck battery buses in (intermittent) use on route 98.

DRH
Recliner
2016-12-09 21:06:38 UTC
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Post by DRH
The Red Arrow BYD / Alexander-Dennis Enviro200EV buses have
iron-phosphate batteries at the rear and in the roof pod, which also
incorporates the aircon unit. The driveline comprises two 90kW wheel-hub
motors and water cooling system plus regenerative braking system.
There are also five BYD double-deck battery buses in (intermittent) use on route 98.
Thanks, that's interesting. Were the additional batteries in the roof pod
added to increase the range? They sound like an afterthought.
DRH
2016-12-10 08:21:51 UTC
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Post by Recliner
Post by DRH
The Red Arrow BYD / Alexander-Dennis Enviro200EV buses have
iron-phosphate batteries at the rear and in the roof pod, which also
incorporates the aircon unit. The driveline comprises two 90kW wheel-hub
motors and water cooling system plus regenerative braking system.
There are also five BYD double-deck battery buses in (intermittent) use on route 98.
Thanks, that's interesting. Were the additional batteries in the roof pod
added to increase the range? They sound like an afterthought.
No, I think it is to balance the weight. They appear to be split 50/50 with the very back of the bus.

DRH
Recliner
2016-12-10 09:36:12 UTC
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Post by DRH
Post by Recliner
Post by DRH
The Red Arrow BYD / Alexander-Dennis Enviro200EV buses have
iron-phosphate batteries at the rear and in the roof pod, which also
incorporates the aircon unit. The driveline comprises two 90kW wheel-hub
motors and water cooling system plus regenerative braking system.
There are also five BYD double-deck battery buses in (intermittent) use on route 98.
Thanks, that's interesting. Were the additional batteries in the roof pod
added to increase the range? They sound like an afterthought.
No, I think it is to balance the weight. They appear to be split 50/50
with the very back of the bus.
OK, that makes sense. They must put quite a lot of weight on what's
normally a flimsy body structure, though. Or do those buses have monocoque
bodies, with no chassis?
DRH
2016-12-11 08:34:50 UTC
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Post by Recliner
Post by DRH
Post by Recliner
Post by DRH
The Red Arrow BYD / Alexander-Dennis Enviro200EV buses have
iron-phosphate batteries at the rear and in the roof pod, which also
incorporates the aircon unit. The driveline comprises two 90kW wheel-hub
motors and water cooling system plus regenerative braking system.
There are also five BYD double-deck battery buses in (intermittent) use on route 98.
Thanks, that's interesting. Were the additional batteries in the roof pod
added to increase the range? They sound like an afterthought.
No, I think it is to balance the weight. They appear to be split 50/50
with the very back of the bus.
OK, that makes sense. They must put quite a lot of weight on what's
normally a flimsy body structure, though. Or do those buses have monocoque
bodies, with no chassis?
I think they have separate chassis and body. The two earlier BYD ("Build Your Dream") buses tried on the Red Arrow routes, EB1 and EB2, had bodies built by BYD itself. They had batteries in a pod on the roof and in two large cabinets over the front wheels. The new ones have a bog-standard Enviro 200MMC adapted diesel bus body, but possibly strengthened to cope with the extra weight of the batteries.

DRH
Basil Jet
2016-12-10 11:55:48 UTC
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Post by DRH
Post by Recliner
Post by DRH
The Red Arrow BYD / Alexander-Dennis Enviro200EV buses have
iron-phosphate batteries at the rear and in the roof pod, which also
incorporates the aircon unit. The driveline comprises two 90kW wheel-hub
motors and water cooling system plus regenerative braking system.
There are also five BYD double-deck battery buses in (intermittent) use on route 98.
Thanks, that's interesting. Were the additional batteries in the roof pod
added to increase the range? They sound like an afterthought.
No, I think it is to balance the weight. They appear to be split 50/50 with the very back of the bus.
Putting weight on the roof to improve the balance?
Recliner
2016-12-10 12:30:58 UTC
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Post by Basil Jet
Post by DRH
Post by Recliner
Post by DRH
The Red Arrow BYD / Alexander-Dennis Enviro200EV buses have
iron-phosphate batteries at the rear and in the roof pod, which also
incorporates the aircon unit. The driveline comprises two 90kW wheel-hub
motors and water cooling system plus regenerative braking system.
There are also five BYD double-deck battery buses in (intermittent) use on route 98.
Thanks, that's interesting. Were the additional batteries in the roof pod
added to increase the range? They sound like an afterthought.
No, I think it is to balance the weight. They appear to be split 50/50 with the very back of the bus.
Putting weight on the roof to improve the balance?
Without that counterweight, there would be very little weight on the
front wheels.
Neil Williams
2016-12-11 22:29:23 UTC
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Post by Recliner
Without that counterweight, there would be very little weight on the
front wheels.
How, out of interest, does that differ from a normal rear-engined bus?

Neil
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Neil Williams
Put my first name before the @ to reply.
Recliner
2016-12-11 22:52:00 UTC
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Post by Neil Williams
Post by Recliner
Without that counterweight, there would be very little weight on the
front wheels.
How, out of interest, does that differ from a normal rear-engined bus?
The batteries are several tonnes heavier than an engine+fuel tank.
DRH
2016-12-12 10:24:39 UTC
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Post by Recliner
Post by Neil Williams
Post by Recliner
Without that counterweight, there would be very little weight on the
front wheels.
How, out of interest, does that differ from a normal rear-engined bus?
The batteries are several tonnes heavier than an engine+fuel tank.
The 12m BYD/ADL Enviro 200EV's GVW is 18,600kg.
The near-equivalent 11.8m Enviro 200 diesel bus is 14,400kg.

Probably the bulk of the extra weight is batteries.

There are two other electric buses that were tried briefly on the Red Arrow routes and are now being transferred to route 108. These are Irizar i2e's which appear to have all the batteries in a full-length roof pod. They thus appear to be rather taller than normal single-deck buses, and have similarities to the hydrogen buses on route RV1.

Whereas the original BYDs had a pronounced but not unpleasant whine from the electric motors, the newer ones are quieter but the Irizars were very quiet indeed - an impressively smooth ride.

DRH
Neil Williams
2016-12-13 00:52:00 UTC
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Post by Recliner
The batteries are several tonnes heavier than an engine+fuel tank.
Didn't know that. Might explain why the MK battery buses allow fewer
standees (only 7) than the otherwise identical diesel versions (which
allow a crush-load - the number permitted is more than you would
physically fit on).

I wonder how, given the UK's generation profile, this affects their
carbon footprint?

Neil
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Neil Williams
Put my first name before the @ to reply.
s***@potato.field
2016-12-13 09:41:55 UTC
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On Tue, 13 Dec 2016 00:52:00 +0000
Post by Neil Williams
Post by Recliner
The batteries are several tonnes heavier than an engine+fuel tank.
Didn't know that. Might explain why the MK battery buses allow fewer
standees (only 7) than the otherwise identical diesel versions (which
allow a crush-load - the number permitted is more than you would
physically fit on).
Isn't there a maximum number of standing for diesel buses which is routinely
ignored anyway? Can't see the driver enforcing that 7 in the rush hour. Anyway,
surely the bus suspension and handling characteristics should be designed so
it can take as many passengers as a diesel of the same size?
--
Spud
Neil Williams
2016-12-13 16:06:59 UTC
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Post by s***@potato.field
Isn't there a maximum number of standing for diesel buses which is routinely
ignored anyway?
There is, but on most buses these days it is higher than a crush-load.
Post by s***@potato.field
Can't see the driver enforcing that 7 in the rush hour.
I only had it brought to my attention by a driver having a loud
conversation about it and why he did enforce it because he valued his
driving licence - though in reality in MK crush-loaded buses are rare
as not enough people use them.
Post by s***@potato.field
Anyway,
surely the bus suspension and handling characteristics should be designed so
it can take as many passengers as a diesel of the same size?
So you'd think but apparently not. Some must do, though, as the Red
Arrows would be a bit useless if they couldn't take a standing
crush-load.

Neil
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Neil Williams
Put my first name before the @ to reply.
Offramp
2016-12-13 19:28:10 UTC
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Someone who employs is an employer. Someone who is employed is an employee.
s***@potato.field
2016-12-12 09:39:45 UTC
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On Fri, 9 Dec 2016 11:05:44 -0800 (PST)
The Red Arrow BYD / Alexander-Dennis Enviro200EV buses have iron-phosphate =
batteries at the rear and in the roof pod, which also incorporates the airc=
on unit. The driveline comprises two 90kW wheel-hub motors and water coolin=
g system plus regenerative braking system.
Wheel hub motors? They're a poor idea as they massively increase unsprung
weight. Also I'm surprised they could fit motors powerful enough in the wheels
with enough cooling for a bus tbh. Hope westminster has increased its pothole
budget.
--
Spud
Recliner
2016-12-12 13:11:03 UTC
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Post by s***@potato.field
On Fri, 9 Dec 2016 11:05:44 -0800 (PST)
The Red Arrow BYD / Alexander-Dennis Enviro200EV buses have iron-phosphate =
batteries at the rear and in the roof pod, which also incorporates the airc=
on unit. The driveline comprises two 90kW wheel-hub motors and water coolin=
g system plus regenerative braking system.
Wheel hub motors? They're a poor idea as they massively increase unsprung
weight. Also I'm surprised they could fit motors powerful enough in the wheels
with enough cooling for a bus tbh. Hope westminster has increased its pothole
budget.
They do increase the unsprung weight, though they also save the weight
of the live axle, differential and half the prop shaft. Incidentally,
the units also include a reduction gearbox.

But these heavy buses plod along at low speeds in dense urban traffic,
so I don't think the unsprung weight will be nearly as serious a
problem as it would in a higher speed vehicle.
s***@potato.field
2016-12-12 14:02:02 UTC
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On Mon, 12 Dec 2016 13:11:03 +0000
Post by Recliner
of the live axle, differential and half the prop shaft. Incidentally,
the units also include a reduction gearbox.
Christ, they must be heavy. Obviously a clever piece of engineering and I'm
trying to figure out how you can have a reduction gearbox with a hub mounted
motor because the whole point of the latter is the motor shaft is fixed to
the chassis while the rest of the motor is attached to the hub and rotates.
Post by Recliner
But these heavy buses plod along at low speeds in dense urban traffic,
so I don't think the unsprung weight will be nearly as serious a
problem as it would in a higher speed vehicle.
I suppose so.
--
Spud
r***@cix.compulink.co.uk
2016-12-13 10:24:59 UTC
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Post by s***@potato.field
On Mon, 12 Dec 2016 13:11:03 +0000
Post by Recliner
of the live axle, differential and half the prop shaft. Incidentally,
the units also include a reduction gearbox.
Christ, they must be heavy. Obviously a clever piece of engineering and
I'm trying to figure out how you can have a reduction gearbox with a hub
mounted motor because the whole point of the latter is the motor shaft is
fixed to the chassis while the rest of the motor is attached to the hub
and rotates.
AC electric motors are very light compared to axles and transmissions.
--
Colin Rosenstiel
s***@potato.field
2016-12-13 11:44:51 UTC
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On Tue, 13 Dec 2016 04:24:59 -0600
Post by r***@cix.compulink.co.uk
Post by s***@potato.field
On Mon, 12 Dec 2016 13:11:03 +0000
Post by Recliner
of the live axle, differential and half the prop shaft. Incidentally,
the units also include a reduction gearbox.
Christ, they must be heavy. Obviously a clever piece of engineering and
I'm trying to figure out how you can have a reduction gearbox with a hub
mounted motor because the whole point of the latter is the motor shaft is
fixed to the chassis while the rest of the motor is attached to the hub
and rotates.
AC electric motors are very light compared to axles and transmissions.
Not compared to a normal wheel though.
--
Spud
Recliner
2016-12-13 12:29:28 UTC
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Post by s***@potato.field
On Tue, 13 Dec 2016 04:24:59 -0600
Post by r***@cix.compulink.co.uk
Post by s***@potato.field
On Mon, 12 Dec 2016 13:11:03 +0000
Post by Recliner
of the live axle, differential and half the prop shaft. Incidentally,
the units also include a reduction gearbox.
Christ, they must be heavy. Obviously a clever piece of engineering and
I'm trying to figure out how you can have a reduction gearbox with a hub
mounted motor because the whole point of the latter is the motor shaft is
fixed to the chassis while the rest of the motor is attached to the hub
and rotates.
AC electric motors are very light compared to axles and transmissions.
Not compared to a normal wheel though.
No, but a normal diesel bus also has the live axle, differential and
half the prop shaft as unsprung weight. The BYD site says:

"BYD's self-developed wheel-hub motor is adopted in the BYD ebus. It
is installed in the rear drive axle together with regenerative braking
technologies. Compared with a normal motor, the rear drive axle system
in the BYD ebus has no gear box, no transmission shaft, and no
differential mechanism. The power from the motor is directly
transmitted to the wheels, so that significant improvements are
achieved in transmission efficiency and reductions in noise and
vibration. In addition, the bus weight can be cut by 300kg, and
interior space is greatly saved."

http://bydeurope.com/innovations/technology/index.php#motor

I note that the reduction gear has a 17.7 ratio, and the bus has a
very low top speed -- 70 km/h (little more than 40mph) -- so the
unsprung weight isn't going to matter very much. You can see from the
illustration that the permanent magnet synchronous motor is inboard,
driving through the slim gear box that's between the motor and the
wheel.
s***@potato.field
2016-12-13 14:13:30 UTC
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On Tue, 13 Dec 2016 12:29:28 +0000
Post by Recliner
differential mechanism. The power from the motor is directly
transmitted to the wheels, so that significant improvements are
achieved in transmission efficiency and reductions in noise and
vibration. In addition, the bus weight can be cut by 300kg, and
interior space is greatly saved."
Cut by 300Kg? Is that including the batteries? I doubt it.

Odd suspension design though. They had the opportunity to make give each wheel
fully independent suspension, yet they didn't bother, instead deciding to join
the sides by some sort of plate looking at that diagram. Quite why you would do
that when you don't need to baffles me frankly.
--
Spud
Recliner
2016-12-13 15:00:20 UTC
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Post by s***@potato.field
On Tue, 13 Dec 2016 12:29:28 +0000
Post by Recliner
differential mechanism. The power from the motor is directly
transmitted to the wheels, so that significant improvements are
achieved in transmission efficiency and reductions in noise and
vibration. In addition, the bus weight can be cut by 300kg, and
interior space is greatly saved."
Cut by 300Kg? Is that including the batteries? I doubt it.
Yup, me too.
Post by s***@potato.field
Odd suspension design though. They had the opportunity to make give each wheel
fully independent suspension, yet they didn't bother, instead deciding to join
the sides by some sort of plate looking at that diagram. Quite why you would do
that when you don't need to baffles me frankly.
Having that bogie-like frame probably makes it easier to mount on the
chassis.
Basil Jet
2016-12-09 16:06:54 UTC
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Post by Recliner
Post by s***@potato.field
I noticed some brand new (66 plate) single decker pure electric buses around
Waterloo today. They look very nice (apart from the huge battery pack on the
roof) and certainly have a good turn of acceleration off the line. I notice
however that their unladed weight is > 12 tons which is more than a lot of
double deckers, presumably because of the battery. I wonder how efficient that
actually makes them when you calculate it all the way back to the power
station?
I suspect that the box on the roof isn't the heavy battery pack. The
whole back half of the bus has a high floor, and given the absence of
a diesel engine, I think that's where the batteries live. It means
that there are only a couple of step-free seats; the others are all in
the high back end.
They presumably have regenerative braking, so the weight won't make
too much difference to the efficiency. But it explains why there won't
be any double-deck battery buses.
This can't be right! Pushing a bus that's twice as heavy through the
streets has to use twice the energy, and regen braking won't change that
equation.
s***@potato.field
2016-12-09 16:15:31 UTC
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On Fri, 9 Dec 2016 16:06:54 +0000
Post by Basil Jet
Post by Recliner
They presumably have regenerative braking, so the weight won't make
too much difference to the efficiency. But it explains why there won't
be any double-deck battery buses.
This can't be right! Pushing a bus that's twice as heavy through the
streets has to use twice the energy, and regen braking won't change that
equation.
Probably depends how effective the regen braking is. I suspect in london
traffic with its slow stop start the answer is "not very" as regenerative
braking doesn't work very well at slow speeds.
--
Spud
Recliner
2016-12-09 16:15:38 UTC
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Post by Basil Jet
Post by Recliner
Post by s***@potato.field
I noticed some brand new (66 plate) single decker pure electric buses around
Waterloo today. They look very nice (apart from the huge battery pack on the
roof) and certainly have a good turn of acceleration off the line. I notice
however that their unladed weight is > 12 tons which is more than a lot of
double deckers, presumably because of the battery. I wonder how efficient that
actually makes them when you calculate it all the way back to the power
station?
I suspect that the box on the roof isn't the heavy battery pack. The
whole back half of the bus has a high floor, and given the absence of
a diesel engine, I think that's where the batteries live. It means
that there are only a couple of step-free seats; the others are all in
the high back end.
They presumably have regenerative braking, so the weight won't make
too much difference to the efficiency. But it explains why there won't
be any double-deck battery buses.
This can't be right! Pushing a bus that's twice as heavy through the
streets has to use twice the energy, and regen braking won't change that
equation.
The energy cost is mainly to accelerate the bus, and much of that is
recovered with regen brakes. The rolling resistance is not only
relatively small, but these inner city buses don't spend much time
coasting along.
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