2007 – Year of the electric car

[bystander]

From the website of an Austrailian science magazine:

http://www.cosmosmagazine.com/node/957

Interesting quote:

The company claims that their battery shows a cycle life in excess of 20,000 charges and discharges while still retaining 85 per cent of its capacity to store energy. If proven, this would be a revolutionary breakthrough, especially since Altairnano also claims their battery can be recharged not in hours, but in less than 10 minutes.

Be careful interpeting the comparitive power density (4x, found elsewhere in the article) over regular Lithium chemistry batteries, as that does not affect overall capacity (when comparing weight or bulk) in as meaningful a way.

[bentbiker]

Originally Posted by bystander

Be careful interpeting the comparitive power density (4x, found elsewhere in the article) over regular Lithium chemistry batteries, as that does not affect overall capacity (when comparing weight or bulk) in as meaningful a way.

Quite interesting article on a public company. I didn't understand your comment above. Why would you not expect an equal size battery with 4X the current power density to not affect overall capacity?

[bystander]

Originally Posted by bentbiker

Quite interesting article on a public company. I didn't understand your comment above. Why would you not expect an equal size battery with 4X the current power density to not affect overall capacity?

The "power density" spec. tells how quickly the power can come out, not how densely the power can be packed inside a given mass or volume. These high power density cells are approx the same weight and mass as existing solutions, not 1/4 the size or weight.

Used in an intuitive sense, "power density" ought to mean more power in less space or weight. But it doesn't work that way. It's more like how densely the power can be packed in the opening of the storage container, not the container proper.

The term "4x power density" on a battery is analogous to trying to empty a gallon container through a 1/4 x 1/4 inch hole, vs a 1/2 x 1/2 inch hole. No matter what size the hole is, it's still a gallon container.

If all your application needs is short, wide bursts power, it's a plus. If you need a fair amount of power for a considerable time, it's a wash.

Due to regen braking requirements, a storage battery may be sized larger to allow for more efficient conversion of the braking energy. With these "4x" type cells, that part of the design can be reduced.

On a PT, The Saphion pack is as heavy and bulky as it is because it has to have a minimum power density to maintain it's margin of safety. The mass is so large, it also allows for a 20-24 mile range.

If you simply designed a 5-6 mile Saphion pack at 1/4 the weight, bulk, & cost for the PT, it would not work well, because the power density would also be reduced to 1/4. The margin of safety needed to maintain balance and traction would not be there, as it requires a certain level on-demand power. This is one of the fundamental reasons why the p-series did not get Saphions.

This new "4x" power density type cell would allow for a smaller pack with great safety overhead. But it would not offer greater range because the capacity is not denser, it's the rate of energy flowing in and out that is denser.

[bentbiker]

Originally Posted by bystander

The "power density" spec. tells how quickly the power can come out, not how densely the power can be packed inside a given mass or volume. These high power density cells are approx the same weight and mass as existing solutions, not 1/4 the size or weight.

Used in an intuitive sense, "power density" ought to mean more power in less space or weight. But it doesn't work that way.

Gotcha! Thanks . . . kw/kg, not kw-hrs/kg.

[polo_pro]

There's also volume issues. Even if they can pack in 400 kwh into 10 pounds of battery, the 10 pounds of battery might take up a cubic foot of space. That type of battery couldn't be used on a segway even though it might perform up to spec wonderfully in every other way (discharge rates, charging times, heat dissipation, etc).

[bystander]

Originally Posted by bentbiker

Gotcha! Thanks . . . kw/kg, not kw-hrs/kg.

Didn't mean to hammer you with the re-edit. I wasn't seeing your response when I went back and fleshed out my point in the above post.