Dan5 wrote:That is why I used other EVs and packs as comparisons.
Dan, thanks for all of the information. I learned a lot attempting to track down sources. Understandably, manufacturers are very tight-lipped about battery chemistry, and all we really find is a tremendous amount of unsourced conjecture from inquisitive folks like us.
I don't agree that one can infer the comparative energy density of a battery cell technology based on the energy density of a battery pack:
- First there are differences of scale. The BMW i3 battery pack has roughly 1/4 the capacity of the 85kWh Tesla Model S, so considering some fixed components that do not scale, it is highly probable that a pack of 1/4 identical cells will be more than 1/4 the weight
- There is volumetric efficiency. A 1' x 1' x 1' empty cardboard box weighs more than 1/4 the weight of a 1.6' x 1.6' x 1.6' empty cardboard box, but has 1/4 the volume.
- There are varying design objectives for a given battery pack. For instance, to make cooling highly efficient, and the battery pack less explody, BMW chose to use a freon refrigerant cooling system in the pack, which surely must add some weight. (see http://darrenortiz.com/website_pdfs/BMWi3PG.pdf)
Back to the original question - does anyone have a source indicating the i3's battery chemistry? I can only find two (thanks, Buskraut!), and neither is from a manufacturer. They both point to NMC:
I have been unable to find any source that suggests otherwise.
Actually that was the reason I used the Model S as a comparable vehicle, it also has a water cooling system to keep the batteries cool. I think Tesla and BMW are both capable of designing a cooling system that is lightweight, but still provides adequate cooling.
The Tesla is a very conservative number and one would assume that the "plate design" that BMW uses actually decreases the weight.
Remember Tesla is using a bunch of these cells called 18650's (essentially the orientation of the cells you find in laptops) and as such have about 11% of the weight that is coverings.
The only odd balls would be the leaf- air cooled and the MiEV.
I think we did narrow it down, Altair is not the supplier, neither is Toshiba- means it is not lithium titanate
A123 is not the supplier- means it is not iron phosphate
Panasonic is not the supplier that means it is not NCA
The criteria for cobalt oxide does not fit.
The Volt is like 83 Whr/kg and has liquid cooling (We all know about the crash test where the coolant leaked 2 weeks later and short circuited the battery) and that is manganese oxide
So it's 12% more than manganese oxide (pure) battery, but not quite as much as a pure NCM battery.
I found this paper, this may be something that they did- doping with Cobalthttp://www.electrochem.org/dl/ma/206/pdfs/0416.pdf
Makes sense, Samsung works with NCM and NCA
Also I narrowed down one of the authors.
Atsuo Yamada is involved in the Samsung grouphttp://www.researchgate.net/publication ... _electrode
If only we could link him further...