was the largest nimh cell that exists?

[giguana]

this is a bit on the theoretical side-could they make some big cells like car batteries?

 

[Ian]

this is a bit on the theoretical side-could they make some big cells like car batteries?

The Toyota Prius hybrid petrol-electric car uses NiMh batteries for short term energy storage, I have no details but am sure that they are of a much higher capacity than a typical car battery, especially considering the fact that they are lightly loaded to maximise life.

On an even larger scale one variant of the GM EV1, a high performance electric vehicle designed to comply with proposed Californian zero emissions legislation, had its 100kW motor powered by a large NiMh battery.

And on a truly massive scale there is the Brush-Hitachi diesel-electric hybrid locomotive currently in its prototype stage. Despite having spies in the Brush factory I still don't know the battery chemistry but NiMh is a possibility, I am however told the battery and management system occupy an entire railway carriage and have a maximum output measured in megawatts.
If this massive battery is indeed NiMh then the quantities of materials used in its manufacture go some way to explaining the world nickel shortage.

As far as I know the largest readily available cells are F size, a little larger than the familiar D size.


EDIT. I have discovered that the Brush-Hitachi locomotive uses Li-ion batteries with a total capacity of 48 kWh, weighing 1 tonne and able to deliver a peak power of 1 MW. Life is estimated at 8 years. I wonder at what age the cut-outs will start.

 

[giguana]

Brilliant! it may possibly be a gas-electricity conversion reactor, there was one on television that looked like a giant radiator with a series of plates that turn something like compressed gas or hydrogen into electricity, it was about the size of a train carriage and they were showing it because it was the first "giant battery" to power an apartment block. that said, with a bike trailer on the back of a bike it would be possible to get a battery that does 100 miles

 

[Jeremy]

The Prius NiMH cells are small prismatic case cells (at least they are in my '05 Prius), with a capacity of only 6.5Ah (most car batteries are around 40Ah). The voltage of the pack is 273V though, so there is plenty of power available.

The battery in a hybrid isn't required to drive the car for any length of time, it's only there to even out power demand, by absorbing excess and delivering a high peak torque, primarily for pulling off and accelerating. This allows a big car to get away with a small engine, one that runs on a modifed Atkinson cycle (which would be unusable with a conventional transmission). The Prius will only cover 2 or 3 km on battery power alone.

Jeremy

 

[flecc]

EDIT. I have discovered that the Brush-Hitachi locomotive uses Li-ion batteries with a total capacity of 48 kWh, weighing 1 tonne and able to deliver a peak power of 1 MW. Life is estimated at 8 years. I wonder at what age the cut-outs will start.

It does have one advantage over us, it doesn't have to climb steep hills.

Very steep in railway circles is something like 2% (1 in 50). I think my Li-ions would last well if that was the steepest I ever faced.
.

 

[Ian]

The Prius NiMH cells are small prismatic case cells (at least they are in my '05 Prius), with a capacity of only 6.5Ah (most car batteries are around 40Ah). The voltage of the pack is 273V though, so there is plenty of power available.

Thanks for clarifying that Jeremy, I was assuming the battery would be of high capacity to provide the high peak power demands. In fact the Hitachi hybrid rail traction system also uses a battery with a surprisingly small capacity relative to the high peak power demands, if 48kWh can ever be called small!

It does have one advantage over us, it doesn't have to climb steep hills.

But it doesn't have pedals either Flecc, so no passenger contribution.

On a serious rail related note perhaps the fare increases announced today will make electric cycling more attractive to some commuters.