-
Want to remove ads? Register an account and login to see fewer ads, and become a Supporting Member to remove almost all ads.
Pure speculation: nothing to do with positive/negative per se, but one of the contactors needs to have breaking capacity to be opened under full load. The other one can be sequenced so that it only opens/closes under no load, and so can be smaller.
This is probably right - it's a very, very remote chance your failsafe would need to be opened under load. The chance of your primary contactor welding closed along with the drivetrain experiencing a critical error requiring open-under-load simultaneously seems pretty remote. However, given Tesla's supply chain optimization, the question is whether that'll continue. I wonder what the spec difference is.
glhs272
Unnamed plug faced villian
Does anybody have any good pictures of the 60kWh battery with the covers removed (including the hump) but not disassembled? I am curious of the feasibility of adding 2 more 60kWh type modules to the battery to make it a 70 (or a 60+ as I would call it). I am not saying I am going to do this, just wondering if it would be technically feasible. The additional modules would be wired in series with the existing modules which would make it operate at the same voltage as the 85kWh battery. This would significantly improve fast charging capability as well as make the 60 perform close to or better than the standard S85. Obviously some software details would have to be sorted out and the BMS board in the battery might not have available unused channels to talk to those new modules (assuming they used different hardware on the 60 vs. 85). I think it would be cool upgrade package if offered by Tesla. It would keep all of those 60 batteries on the road instead of having to take in used batteries in order for someone to upgrade. For those who have had their hands inside Tesla's batteries I think they would have a good feel if this idea has merit.
Maybe the coil wires are of different length?
Maybe the arc blow-out magnets are of differing polarities to help with packaging the DC bus bars by removing the need to arrange DC current to flow in a specific direction?
thegruf
Active Member
Hi wk057, just found the battery wiki page on here.
http://www.teslamotorsclub.com/showwiki.php?title=Battery table&redirect=no
Looks like S85/P85/P85+ shared the same battery near enough.
May be just rolling upgrades, but from the latest results it does look like the P85D battery could be different (fuses?), and also the 85D is up-revved against all the others so could be just another variant or something altogether new?
Cue the new cells speculation, though imho I doubt it. Need a few mor recent reports eg 70D tbh.
Do you have any insight on this?
http://www.teslamotorsclub.com/showwiki.php?title=Battery table&redirect=no
Looks like S85/P85/P85+ shared the same battery near enough.
May be just rolling upgrades, but from the latest results it does look like the P85D battery could be different (fuses?), and also the 85D is up-revved against all the others so could be just another variant or something altogether new?
Cue the new cells speculation, though imho I doubt it. Need a few mor recent reports eg 70D tbh.
Do you have any insight on this?
My standing guess, until I see evidence to the contrary, is that the 70D simply uses 14 of the same modules used in the 85 pack (which uses 16) and they're just marketing it as the 70D instead of the 74.375D. This would just give it a hair extra buffer for low discharge vs the 60/85 which is fine.
It's possible the 70 pack could have 13 of the 85kWh type modules instead (12 in the back and one in the nose for balance) which would be 69.0625kWh... round up to 70 for marketing.
Either way, the only thing that makes sense is just switching to using the same modules as the 85kWh pack, since it eliminates the 60-type module, which has fewer cells, entirely. Streamlines pack production a bit more. Now the only choice will be 14 or 16 modules.
The P85, P85+, and S85 definitely have the same battery pack. The two packs I received were from an S85 and P85, and they were the same modules and same main pack fuse.
The P85D/85D packs likely have slightly larger main pack fuses and *maybe* slightly larger cell level fuses... but I doubt the latter now that I've tested the cell level fuses.
As for new cells, speculate all you want, but I'm guessing we won't see any new higher density cells until Model 3.
thegruf
Active Member
Agree totally re 70D structure.
Curious that the last entry in the table (at the time of writing) ie the first 85D has a noticeably different pack nr though.
In theory this is just an 85KWh pack capable of same power as the other 85 models before it.
Would be interesting to see a teardown of a P85D pack to see which details are changed (if any), this would unfortunately mean a P85D write-off, so liely no volunteers!
Curious that the last entry in the table (at the time of writing) ie the first 85D has a noticeably different pack nr though.
In theory this is just an 85KWh pack capable of same power as the other 85 models before it.
Would be interesting to see a teardown of a P85D pack to see which details are changed (if any), this would unfortunately mean a P85D write-off, so liely no volunteers!
Well, unfortunately I'm personally pretty much done with tearing packs down. Two and a half packs should be enough for me. lol.
Definitely would also be interested if someone pops the cover on a P85D pack though.
Next time you blur out your S/N, you might want to do the same to the Datamatrix code.. Because it says your serial number is ST13L0027159
Very extremely small nit: the "S" is probably a field name, so the serial # probably just starts with "T" (and may even be the first letter of the name of the company).
I'm having a hard time going with your 70kwh design theory. Fewer modules would require a re-designed charger, re-designed inverter, different BMS, and far more differences in firmware. There's a reason the 60 used the same number of modules. So many things rely on the voltage being the same across models. Tesla has already set a precedent with keeping the voltage the same across pack sizes. I see no reason why they would change that, and lots of reasons why they would go with the same number of modules in the 70, just fewer cells.
llavalle
Member
JRP3
Hyperactive Member
And I thought the 60 only used 14 modules instead of 16. I too assumed Tesla would keep voltages the same across all vehicles, but in fact they did not.
Yes, so there are two venues toward 70kWh:
- 16 modules of those 'fewer-cell' modules (69kWh)
- 14 '85kWh-pack modules' (74kWh)
Part of the answer will be packs nominal voltage. If it stays at 350, it will say 14 modules. If it says 400V, it will mean 16 modules.
The other part of the equation will be weight - how will its mass relate to S60, S85 and S85D.
What doesn't ring right is why would tesla increase price of the battery for 16% (assuming same cells as in 85 just more of them) and only increase end price a tiny bit, reducing earnings / car.
As others have already answered, the 60 didn't use the same number of modules as the 85kWh pack. It used 14 moudles for a nominal voltage of something like 302V. The 85kWh packs use 16 modules and have a nominal voltage of ~346V. The BMS is per module, also. So no changes needed there since the voltages are the same for both module types. Aside from that, the chargers can output a DC voltage from 50VDC to ~410VDC (can't recall the exact upper number off the top of my head). The 60 and the 85 share the same drive units, and they're rated to operate from a large voltage range (something like 200VDC to 425VDC).
So no real changes are needed besides just changing the modules.
I had considered the 16 of the 60-type modules as a solution, but it wouldn't have any real production advantage vs eliminating it.
I'm wanting to lean more towards the 13 module solution the more I think about it. 12 in rear, one in nose, 69kWh. Slightly lower nominal voltage and voltage range (280V nominal, ~327V charged, ~234V dead) but within spec of all of the other components. However, this would add a bit more complexity (new bus bar configuration in the pack vs just using the same ones from the 60 pack with 14 modules). So, not sure until I see a 70D supercharge voltage screenshot.
As for the price... in the absence of any verifiable data, I think everyone tends overestimates the battery cost to Tesla for some reason. Even using a high estimate like $400/kWh, adding 10kWh would be ~$4000. The cash price of the 70D is something like $6000 higher than the 60. So, I don't really think they're taking a hit.
I don't think Tesla would make that decision anyway. They're not in that mode to cannibalize.
The other option 16 of the "fewer cell" modules, but with less cells removed. Currently there are 64 cells in stead of 74 per group in the 'lite' modules... if they made this 65, it would add another ~1.1KW to a 16 module pack for a total of just over 70KW.
However, I'd agree with wk057 that simply standardizing on a single "full" module is the likely answer... even if that does mean the pack is slightly over it's advertised rating.
stopcrazypp
Well-Known Member
Right, if someone supercharges the 70D it'll be very easy to tell from the peak voltage how many modules it has. Just for reference:
60kWh 352V (14 modules in series *6 series group per module*4.19V)
85kWh 402V (16 modules in series *6 series group per module*4.19V)
Of course, that still doesn't tell how many cells is inside each module, but we can probably make a good guess depending on the module count.
Similar threads
