Originally Posted by valerun
smooth - your PM box is full ;-))
Sorry about that cleared out some PM's.
Originally Posted by Hockeydad
Is it not possible to keep the # of cells etc. the same but replace the actual cells in each pack with Tesla-like batteries so the BCM still sees it as the same number of overall cells? The temperature issue is just an assumption right now, we don't know how the current temperature control system on the Fisker could handle the heat put off by Tesla batteries. One thing I do know is that when it's cold in Toronto, the batteries sure do lose a lot of power so it's a shame some of that heat isn't used to keep the batteries running at a constant temperature.
It's not like I don't want an easier solution or believe we won't be able to replace our battery with something better but wouldn't it be nice to have more than one solution to depend on?
There has been tons of research done on the Panasonic 18650 form factor batteries and the amount of precise control necessary to ensure that these cells are kept at the optimal temperatures (not only for efficiency but to ensure thermal runaway is not a problem as the chemistry is much more volatile than the A123 chem). The Karma enclosure in its current form cannot handle the Tesla batteries and without a massive R&D effort this is the path of most resistance. The amount of custom software, controls, hardware etc to make this work would be significant. If you are bent on a different form factor than the pouch batteries the Karma currently uses then the A123 AHR32113 cylindrical or 18650 batteries may be a good choice. I know that BMW uses the AHR32113 in their active hybrids. Problem is the BCM and all related hardware that is in our current battery enclosures will probably be useless and have to be re-engineered.
Here is some good reading on the Tesla thermal management (a bit dated for the Roadster but same principles apply for the Model S etc)
On a different note I have not measured any of the 15 Karma modules at this point but they look to be around 15L with 1.3kw per module and around 345lbs in just cells (collectively). The power density seems to be really low by modern standards (on par with the NIMH EV1 27kwh in 300l volumetric capacity). There is definitely room for improvement just using A123 technology. Of course weight may be an issue but that is a whole different topic.