Aside from putting weights in the trunk at ice lake race events (where tire traction is extremely limited), and race events where all cars have to weigh the same, I think it is unheard of to have extra ballast in a production car. The benefits of less weight are just too great to give up.
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Probably because they haven't finalized the design yet? It wouldn't suprise me if they have not yet built a car with a 40kWh pack.
stopcrazypp
Well-Known Member
The lithium version of the Tango had 200lbs of lead weight ballast added to it:
http://tangocars.blogspot.com/2010/06/gratitude.html
Of course, that design isn't conventional (the car has a high risk of rollover without proper ballast).
stopcrazypp
Well-Known Member
I take it is for the same reason why they didn't post 1/4 mile and hp numbers for the smaller packs. They likely do not have an actual prototype of these packs yet, so they can't really tell you the weight of it. But from my estimates it is virtually impossible for the 40kWh pack to weigh roughly the same as the 85kWh (it will have at least 1/3 less cell weight) unless they don't go with 18650 cells anymore (unlikely given that gives them production efficiency and consistency).
gg_got_a_tesla
Model S: VIN 65513, Model 3: VIN 1913
Would that mean that they'd have to do separate crash testing for the 60 and 40 packs along with the EPA-5-cycle tests ahead of November/December?!
My rep told me that the 40kwh is the same weight as the 85, as they are actually adding weight to make up for the battery difference. Seems wasteful but is likely being done to avoid additional crash testing.
Take this with a grain of salt, I've been told a number of, um, falsehoods by Tesla reps so far.
Sent from my SGH-T959V using Tapatalk 2
Take this with a grain of salt, I've been told a number of, um, falsehoods by Tesla reps so far.
Sent from my SGH-T959V using Tapatalk 2
scole04
Member
That is hilarious if true. It would defiantely be a first.
Anywho...
Im P3552 with a 40kwh pack. Patiently waiting....well maybe not patiently lol...
ddenboer
MODEL X #1770
I had heard from a Tesla engineer that the battery tech on the 40 is slightly different, and heavier, hence the same weight.
When they do crash testing on other cars, do they do it for each model? Say a 4-cylinder Honda Accord is going to weigh differently than the V6 Honda Accord?
I thought the 40kw and 60kw used the same battery? So the 60Kw has 50% more cells than the 40, While the 85KW has a different higher output chemistry, but the same number of cells as the 60kw.
I thought the 40kw and 60kw used the same battery? So the 60Kw has 50% more cells than the 40, While the 85KW has a different higher output chemistry, but the same number of cells as the 60kw.
That seemed to be the plan a couple years ago, but I never got the final word on that. One year ago, at the Beta event, an engineer told me they were keeping their options open. That for example the 60 kWh pack might in fact include fewer of the same cells as the 85 kWh pack. He implied that it would depend on certain variables at the time they were to go into production. I suggested, for example, that since they were getting so many of the cells for the 85 kWh packs, it might end up being cheaper for them to get more of those cells at volume than to use the lower capacity cells for the 60 kWh pack. He seemed to agree. I suppose something similar might hold for the 40 kWh pack. Anyone ever get a final word on that?
If they are adding ballast, I think it has more to do with maintaining the center of gravity rather than just the total mass. See for example these videos where they stress that the Model S suspension is specifically designed for its low CoG.
[video=vimeo;18443539]http://vimeo.com/18443539[/video]
Tesla Model S Innovations
This is a very good question which unfortunately Tesla doesn't address for some odd reason. The cells used in the 85kwh pack have quite a bit better capacity loss resistance than the roadster cells, if one is going by the published Panasonic graphs.
It's quite possible that Tesla hasn't decided yet because of the lack of information on how many 85kwh cars are going to be sold in relation to the smaller packs. If for example Tesla doesn't have many takers for the 40kwh or 60kwh packs, than using a different chemisty for those smaller packs doesn't make much sense because it would be much cheaper to use one kind of cell than have to mess with multiple varieties. IMHO, It will come down to the bean counters deciding which route to take.
It's quite possible that Tesla hasn't decided yet because of the lack of information on how many 85kwh cars are going to be sold in relation to the smaller packs. If for example Tesla doesn't have many takers for the 40kwh or 60kwh packs, than using a different chemisty for those smaller packs doesn't make much sense because it would be much cheaper to use one kind of cell than have to mess with multiple varieties. IMHO, It will come down to the bean counters deciding which route to take.
Not a first. Supposedly the Tango had to add ballast mass when changing its batteries to Li-ion from lead acid.
Commuter Cars - Tango - Page 4
stopcrazypp
Well-Known Member
I have them right here (the 85kWh Model S uses the cells on the bottom graph, NCR18650A):
http://www.teslamotorsclub.com/show...or-Model-S/page2?p=61317&viewfull=1#post61317
It's taken from here (page 2):
http://industrial.panasonic.com/www-data/pdf2/ACI4000/ACI4000CE25.pdf
The 40kWh pack might use cells more similar to the top graph (cheaper cells with less capacity), but I'm not so sure about that anymore after the EPA results came out for the 60kWh (which shows Tesla might choose to use the same cells for all three versions).
