If I were to purchase a Model S with the 160 or 230 mile range pack, is it possible to expand the battery pack to 300 if that becomes desirable someday?
Based on what I've learned so far, the battery pack will be interchangeable, and doing so will take less than 5 minutes.
I think it's safe to assume you'd be able to upgrade at any time.
It won't be something you can do in your driveway though: it will need to be done in a garage environment, probably a Tesla service shop.
Unless Tesla has come up with a way to let their Rangers do this in the field....... hmmmm........
Upgrade to bigger battery wont be cheap either. You are not swapping new battery to new battery there, so you probably will have to pay full price for it, which after five years will still be something like $20k. (8% drop in price every year for $400/kWh * 90kWh battery, though that drop might be a lot bigger if DBM kolibri battery manufacturing cost isn't hoax).
I always assumed that all battery packs were the same and only differed in their contents, with some having more cells than others.
That being the case, one would simply add more cells, in any quantity one would desire. That's the way it should work, but don't know that it does.
The 160 mile range and 230 mile range battery pack will use the same batteries. The 300 mile range pack will have a different battery.
Here is a blog entry by Paul Scott containing information that he received during the unveiling of the Model S.
The Tesla S Revealed
I asked Tesla's Chief Technical Officer, J.B. Strauble, whether they would be using the same battery tray for all three options and he confirmed they would. The 160 mile version will not use all the room in the tray, the 230 mile version would be full and the 300 mile version would be using a different type of LiIon battery with more energy capacity. While J.B. was unable to divulge the battery company by name, he did say it was a name we'd recognize and was based in Japan.
This information was revealed in March 2009, since then me know the battery company is Panasonic.
"one" would certainly not be able to add modules etc. to the sealed unit "oneself". Tesla might be able to do such an ungrade, but there's some serious structural, electric, and electronic complexity to messing with the ESS.
It would perhaps be possible to design a battery pack that was able to accept that kind of mod, but it would have to be built-in from the getgo.
Plus there's the cooling systems, the cutouts, the battery mounts...... etc, etc, AD infinitim.
For what it's worth, Musk has floated the idea of renting a 300 mile pack from a Tesla store, so presumably they are easily interchangeable.
Same external dimensions and connections, different contents. That's the point of those battery packs. They are interchangeable and made for fast swapping.