[dougingraham]

Originally Posted by icec0o1

Which batteries are more energy dense? Maybe I missed something.

I would like to know also. I show the 3.4AH Panasonics as 266wh/kg and 691wh/liter. The follow up product which is supposed to have 4ah has a slightly lower voltage and an increased weight and calculates out to 252wh/kg and a staggering 768wh/liter. I don't see anything else even close to these. The closest cell I can find is a Dow/Kokam SLPB125255255H which is a 75A pouch cell and has a 160wh/kg and 346wh/liter. I think this is the cell John Wayland is using in his Silver Streak project.

Note: The wh/liter number is a little high on cylindrical cells because there is lots of wasted space between them when you start assembling packs. I should probably change the calculation on my spreadsheet to account for this.

[frodus]

Originally Posted by icec0o1

P.S.
I'm not arguing for the OP to build his pack from these. They could potentially be unsafe if you don't know what you're doing (as can any battery) and they are more difficult to make into a pack. I just didn't like that analogy which compared Tesla to companies like GM or Chrysler, forever stuck in the past. If a more dense battery came about, they would throw away the 18650's faster than you could say wh/kg. Elon didn't replace NASA by getting stuck with economies of scale.

You really read it out of context....no one said that. It could have been compared to ANY company and their previous packs. I mean Zero used Molicel batteries, now what do they use? Nano-tech lipo.

What he was saying is that Tesla ORIGINALLY (as in 5,6,7 years ago) designed their packs with 6500 18650 cells in a pack, because it was there and viable and available, they didn't design it around what "could" be.

But now, there are many other options available to not just manufacturers, but also us enthusiasts. So just because Tesla built a pack of 18650's, doesn't mean it's the best thing to do. Other batteries that would be just fine for a vehicle like this, exist, where they didn't before.

It wasn't a NOW analogy, it was a "past" compared to "present" analogy.

[icec0o1]

I think all of us would recommend for him not to use them, especially the smaller 14500 ones. So whether he uses the CALB cells or the 20AH A123 ones depends on his ability and options to make a pack out of them. (And whether he can still buy them for ~$20 a cell)

[frodus]

Exactly. All boils down to ability and time to put a pack of lots of tiny cells, and where the point of diminishing returns occurs.

[DJBecker]

Originally Posted by icec0o1

There is no more current technology than the Panasonic 3.4Ah 18650. Are you really arguing that if there was a better techonology/battery out there, Tesla wouldn't use it?

Telsa is on a tightrope. They don't have a lot of freedom to redesign right now.

They have a giant factory with their name in huge letters on the side, paid with federal stimulus money. It is located on I880 just a few minutes from the giant Solyndra factories that front I880. The Solyndra that famously closed with no warning, losing over a half billion of federal investment.

They stopped building roadsters quite a while ago, late spring or early summer 2011 (depending on how. Their focus is getting the new sedan ready for factory production, expected in May. That's a scary gap in having something to sell, and a huge risk. They aren't going to multiply that risk by changing any part of the design that doesn't absolutely need to change.

[tomofreno]

Originally Posted by DJBecker

Telsa is on a tightrope. They don't have a lot of freedom to redesign right now.

They have a giant factory with their name in huge letters on the side, paid with federal stimulus money...

They only bought part of the old NUMMI plant. Most is still owned by Toyota.

[DJBecker]

Originally Posted by tomofreno

They only bought part of the old NUMMI plant. Most is still owned by Toyota.

That's a minor detail of the financing. Most commercial real estate has a complicated own/lease/shell-corp structure. No doubt they got an advantageous deal on a freshly empty factory that had no other potential users. Telsa has their name in giant letters on the building, and they are the only company using it.

It doesn't change their situation. They have to get into production, swim or drown. They don't have the redesign flexibility that they might have had as a smaller company with lower profile and overhead.