Batteries.. not that reliable?

I recently went to London and noticed something odd while on the 137 bus to Clapham Common.

This was my second ever ride on the famous (or is that infamous) ‘Boris Bus’.   Or more correctly named the ‘New Routemaster’.   Lets skip over the whole hoo-har about how they were supposed to have conductors and how the rear door was supposed to be kept open.   Not sure of the injury stats for people hurting themselves on old routemasters but I doubt it was that high.

Anyway, my first ride on a Boris bus last year was very nice.   It was quiet, smooth and every so often on the ride along route 9 you would hear the engine fire up.   As expected, it is a hybrid with no direct drive from the internal combustion engine to the wheels.   It just keeps the batteries topped up.

But this was not the case this time.   The ride was noisy and it didn’t seem to be driving very well.   The driver was hammering the brakes but not pulling away like a London bus normally does.   Also I could hear the engine miss-firing!   Very strange!   Maybe this bus was faulty.

And then I saw this: New Routemaster’s battery problems mean many run on just diesel

Well that explains it!   The bus has a 75kWh lithium ion battery pack (I assume its not lithium polymer) and it looks like they are getting cooked.   This is 50% more than Rhys Millen’s Pikes Peak electric car!   (Although his has a MUCH faster discharge rate and didn’t actually make it to the top without encountering technical probs, better luck next year!)

Now it does say that the batteries are being replaced under warranty but the miss-fire was worrying.   They must be pushing the engine pretty hard as it was never intended to run the bus in normal service.   I fear they may be heading towards some expensive repairs!

And just to add insult to injury, the Solar Impulse plane has been grounded after its record breaking-ly long flight due to… you guessed it, a cooked battery.   DOH!

If you compare the Boris bus with a hybrid car, the old Mk1 Honda Insight has a 1kWh battery and the latest Toyota Prius has a 4.4kWh battery.   Tiny!   Designed to discharge at a much slower rate and moving a lot less mass.   A bus is 20+ tonnes.

Having dealt with lithium ion batteries at work I know how delicate they can be.   I made a slight boo-boo and set a pack charging at the wrong rate.   I’d forgotten to turn the current down from a previous test and tried to charge at twice the rated current.   Thankfully no fire but they got VERY hot and ended up going out the window.   And with hundred of cells (or 2400+ on Rhys Millens car!) it only takes 1 duffer to foul up the lot.

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