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Re: [EVDL] Press release on Firefly "Oasis" battery

I have seen a lot of numbers thrown around but 170wh/kg is what i have
always used. Here is a reference to support that.

massive link here

http://books.google.com/books?id=3YBPeJMKJHIC&pg=PA343&lpg=PA343&dq=lead+acid+theoretical+energy+density&source=web&ots=6hUXxmmdcq&sig=ku2h7tj1R515W7jPL7DgO3DC0kw


http://tinyurl.com/2j62ln

That puts the maximum theoretical right shy of the currently available
and way less than the theoreticals 200-300(phosphate) 400-600(cobalt)

by rough calculation
A123 are 70Grams , it takes 14.28 cells to be a kg. they are 2.3ah and
3.3V or 7.59 wh
This is 108wh/kg .

The theoretical is the active materials capacity. At zero charge there
is no electromotive force to do work, so you can't ever get that last
little bit out of a battery.
Lets say 80%. Then I haven't seen anyone get better than 50%. so 50% of
80% or 40% is my best guess. 40% of 170 is 68wh/kg. If firefly hits that
it will be a huge improvement. You have to have a case,separators and
electrolyte. The larger the battery, the more capacity per pound. That
is one of the reasons the A123 cells are so small capacity but they seem
to do pretty good.

Here are some trends. A123 thinks they will be able to double their
capacity in the next few years, they have press releases too.

Thundersky

LFP40aha is 3.2V 40ah and weights 1.5kg = 85wh/kg
LFP800aha is 3.2V 800ah and weights 25kg = 102.4 wh/kg

lithium cobalt (powerstream GMB18650H)
3.7*2.2 / .46 = 176wh/kg

Kokam 100216216H
40ah*3.7V /1.1 = 134wh/kg

Notice these numbers are about 40-50% of theoretical for the chemistry.
(except cobalt, no-one wants to put that much cobalt in a cell, the
amount chosen is the best tripple point of enough active material,
enough electrolyte and collector grid)

The point is not to get too excited and not to confuse theoretical with
practical.

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