[clett]

*FINALLY* SION have made a public demonstration of their Lithium-Sulphur cells. At WinHEC last week they showed that one of their LiS cells could power a Tablet PC for a whole 8 hour working day!

The cell specs are currently 350Wh/kg - a huge improvement on what's available today. (eg the energy density of the NiMH cells in the '04 Prius is about 46 Wh/kg).

What could this mean for battery electric vehicles? Below is a Toyota RAV4 - EV. Range is about 110 miles on the existing NiMH batteries (65 Wh/kg).

Swap these for the SION cells and you've got an instant upgrade to 350Wh/kg and a range of 592 miles!

Shame they've only managed a cycle life of 300, though I expect this will improve with some more development (still good enough for over 175,000 miles though!).

 

[Daniel]

... Shame they've only managed a cycle life of 300, though I expect this will improve with some more development (still good enough for over 175,000 miles though!).

That's assuming you drive every cycle to near-depletion. In real life you are likely to recharge long before depletion. However, if the batteries are not too expensive, replacing them once during the life of the car may be acceptable.

 

[kennyb]

How much do these batteries cost per kwh? Do you know?

 

[Daniel]

At the Fargo street fair this month I spoke with one of the members of the team that built North Dakota State University's solar-powered racing car. They used NiMH batteries and I asked why they had not used Li-Ion or some other form of lithium battery. He said there were two reasons:

1. Cost. Lithium batteries are much more expensive. There is a separate category in solar-car racing for teams that have unlimited funds, and they can do whatever they like. But the NDSU team is in a category for teams with real-life budgets. Obviously, the cost of these batteries will decline with time.

2. Safety. Lithium batteries can explode if they overheat, and since a car puts a pretty heavy load on the batteries you have to monitor the temperature throughout the battery pack and have pretty sophisticated control over both charging and discharging currents, which can limit both the energy available to the wheels and the re-charging rate.

None of this is a barrier to the development of an EV, but it adds time and expense to the development project, and will add expense to the car.