JRP3
Hyperactive Member
Well none of us are using paper so... Plus a discussion board with no discussion is just a blank screen.
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Well none of us are using paper so... Plus a discussion board with no discussion is just a blank screen.
LargeHamCollider
Battery cells != scalable
They're not going to be able to make adjustments that are smaller in size than 1 module, module size has definitely already been set and is likely around 9.2kWh. There may be voltage restrictions involved as well, if each module is 200V (which I think is likely) then you will have to add 2 modules at a time, increasing the minimum increment size to ~18kWh.
Of course I could be completely wrong about module size etc. but I think all evidence points in the direction of the big pack being 75kWh/8 modules, which puts the base pack at 55kWh/6 modules. (Exact numbers that I expect are 73.5kWh big pack and 55.1kWh base pack)
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JRP3
Hyperactive Member
"LHC,"
Where do you get the 9.2 kWh per module?
As for 200 V per module, I think that would be highly unlikely. To keep BMS cost down automotive packs are almost always one string. Multiple high voltage strings in parallel require a BMS for every string, or some other way to balance the 92-100 cell groups (single cells or multiple cells in parallel) in each string.
GSP
PS. This is (sort of) on topic for pricing the larger battery option
The advantage of having 200V modules is that you can have two packs with 6 and 8 modules, where all the modules are identical, and both packs are 400V. But the BMS would be more complicated.
The disadvantage of having 50V modules is that using identical modules and dropping two modules results in a 300V pack. That's fairly low, and would probably cause problems with the superchargers, the slow charger and the drive inverters. The alternative would be to still have eight 50V modules, where you remove some cells from each module. This would likely be more costly and heavier. But the BMS would be simpler.
I think Tesla would be willing to put in the extra effort to find a good BMS design that would allow them to connect modules in parallell without much fuss. Some extra effort in the design phase should allow them to simplify battery pack production substantially.
The disadvantage of having 50V modules is that using identical modules and dropping two modules results in a 300V pack. That's fairly low, and would probably cause problems with the superchargers, the slow charger and the drive inverters. The alternative would be to still have eight 50V modules, where you remove some cells from each module. This would likely be more costly and heavier. But the BMS would be simpler.
I think Tesla would be willing to put in the extra effort to find a good BMS design that would allow them to connect modules in parallell without much fuss. Some extra effort in the design phase should allow them to simplify battery pack production substantially.
JRP3
Hyperactive Member
No, but they didn't simply remove a sufficient number of modules either. They removed (I think) two modules, dropping the voltage to around 350V and also removed a buch of cells from each of the remaining modules. Tesla could keep all the modules identical if they upped the voltage to 200V.
LargeHamCollider
Battery cells != scalable
These are good points, my responses would be the same as what Yggdrasill posted above. I'd like to add that these modules will likely be used in MS/X eventually, without something like 200V/module the module voltage won't scale well from base M3 (6 modules) to top MX (~12 modules).
9.2kWh comes from ~75kWh/8 modules.
Edit: @GSP I'm interested to hear if you have an alternative module layout, any speculation of your own?
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