Roland Perry wrote:
In message -septem
ber.org, at 09:13:08 on Mon, 20 Jul 2015, Recliner remarked:

http://www.theguardian.com/politics/...ries-london-bu
ses-add-to-boris-johnsons-problems

This confirms the observation that the Boris buses seem to run noisily on
diesel most of the time.

It's a pity that the Grauniad has angled this as a political
Wolmar-for-mayor story, though: whatever Boris's faults, technical problems
with a battery pack can hardly be blamed on him. But I wonder why the Boris
bus batteries are seemingly more troublesome than those in other hybrid
buses?

I doubt it's the batteries themselves, but it's quite plausible the
charging/discharging electronics wasn't quite right and this could have
shortened the life of the batteries (both the life each day, and the number of days).

Or I wonder if the batteries/electronics overheat, like the passengers?
Everything is squashed into quite a small volume under the rear stairs, and
maybe the ventilation is inadequate.

Maybe they just had a faulty component, which is what the story suggests:
"The battery packs are being upgraded as soon as possible and within
theThe battery packs are being upgraded as soon as possible and within
the warranty period, at no cost to TfL or the taxpayer.”
warranty period, at no cost to TfL or the taxpayer.”

Faulty design of component, rather than faulty manufacturing, I suspect.

Yes, I agree.


I'm not sure what you mean by the battery "life each day," though.

The "half hour" (see below).

These batteries are continually charged and discharged, almost at every
stop. They're not charged overnight and used all day.

They might start charging them en-route when they've reached some
specific level - like 50% perhaps.

It's got a 75kWH battery and a 130kW electric motor. So that's half an
hour flat out - which is less than I'd have expected.

And the actual battery capacity after a few thousand cycles is probably
much less.


Even when they were brand-new, the buses didn't run for more than about
five minutes without the noisy four-cylinder engine firing up.

That's been described as "something that's being worked on".

So the batteries are subjected to
hundreds of charge/discharge cycles very day, which can't be good for them.

They aren't full charge/discharge cycles, and that degree of punishment
should be factored into the overall design.

It should, but apparently wasn't.