Pics/Info: Inside the battery pack

[wk057]

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.

It should be pretty simple to interpolate the charging curves of the 60 and 85 packs for comparison to the 70D pack to come up with a pretty good guess on cell count.

Someone get a 70D to a supercharger and video it already!

Maybe one of you folks close to Fremont could go for a test drive...... to the Fremont supercharger. Even a single snapshot of the charge screen would at least get us the module count. hehe.

 

[bxr140]

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.

I may have missed the apples to apples cart, but my 60 peaks at 361-362V when supercharging. If I extrapoate to 0% SOC it would be somewhere between 325 and 350.

 

[wk057]

I may have missed the apples to apples cart, but my 60 peaks at 361-362V when supercharging. If I extrapoate to 0% SOC it would be somewhere between 325 and 350.

Not sure where 362 would come from, since that would be ~4.31V per cell using 14 modules...

The range for the 60 should be ~353 down to ~252 for 4.2V and 3.0V per cell respectively.

 

[hcsharp]

Humm... The voltage is not the same on a 60 and a 85...

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.

I didn't know that. I thought they had the same number of modules with fewer cells in each one. Sorry for taking things off-course.

 

[bxr140]

Not sure where 362 would come from, since that would be ~4.31V per cell using 14 modules...

The range for the 60 should be ~353 down to ~252 for 4.2V and 3.0V per cell respectively.

<shrug>

Perhaps there's a sizable difference between charging voltage and pack voltage? I have no idea.

 

[wk057]

<shrug>

Perhaps there's a sizable difference between charging voltage and pack voltage? I have no idea.

It's possible. I've seen the supercharge voltage around 403-404V, which is a little high (2-3V) but I haven't seen it read 10V high... *shrugs*

 

[bxr140]

Just to round out the dunno-what-to-do-with-this-data angle, here's what I've seen during charging. Of note:
--Charging voltage plateaus around 90% SOC. Could be some kind of balancing?
--Occasionally it bounces back and forth between 361 and 362. I don't think this is a significant piece of analysis.
--Points below the denser field are supercharger pairing events. I don't know enough about the hardware to speculate on the reason why this happens.

 

[arg]

Just to round out the dunno-what-to-do-with-this-data angle, here's what I've seen during charging. Of note:
--Charging voltage plateaus around 90% SOC. Could be some kind of balancing?

I think this is just the charging switching from being limited by the maximum current that the cells can take to being limited by the maximum voltage that they can take. This is normal behaviour for Lithium charging.

--Points below the denser field are supercharger pairing events. I don't know enough about the hardware to speculate on the reason why this happens.

Also to be expected. The voltage at the terminals of the battery can be considered to be the actual standing voltage of the cells, plus the voltage dropped across the internal resistance of the cells and all the connecting wires by any current that is flowing (V=IR). So if you were able to measure the voltage of the idle pack at a given state of charge you would see figures a bit lower than your graph; in practice we only ever see voltage readings when charging is in progress, so the readings are higher than 'true' in proportion to the charging current.

When you are paired at a Supercharger you are getting less than the usual current, so the reading is lower than usual.

 

[yobigd20]

can some rich folk with money spewing out their butt just buy a 60, a 70, an 85, and a new P85D and dissemble them all and check voltage and then count and let us know the answer so we can stop speculating?

 

[wk057]

can some rich folk with money spewing out their butt just buy a 60, a 70, an 85, and a new P85D and dissemble them all and check voltage and then count and let us know the answer so we can stop speculating?

I'd be broke if I did that

 

[thegruf]

and speculating much more fun

 

[woof]

can some rich folk with money spewing out their butt just buy a 60, a 70, an 85, and a new P85D and dissemble them all and check voltage and then count and let us know the answer so we can stop speculating?

Perhaps query the guys on the investor's threads? You may have a better chance of finding said spewer there. But, if I had that particular predicament, I don't think I'd be sitting around (or able too!) reading these forums so chances are slim.

 

[stopcrazypp]

Not sure where 362 would come from, since that would be ~4.31V per cell using 14 modules...

The range for the 60 should be ~353 down to ~252 for 4.2V and 3.0V per cell respectively.

There are some cells that charge at 4.35V. If Tesla is using those it'll complicate things, but that difference is still not enough to account for a whole module (15 modules at 4.2V is already 378V), so the module count will still be 14.

 

[JRP3]

What if the series cell count per module in the 60 is different than we are assuming?

 

[yobigd20]

What if the series cell count per module in the 60 is different than we are assuming?

Wasn't a 60 battery pack disassembled by the NHSTA during their crash testing with pics posted online that proved less number of modules in the pack?

 

[scaesare]

What if the series cell count per module in the 60 is different than we are assuming?

Here's a pic. You can see the 10 blank spacers that make up two of the 6 parallel groups of cells that make up a complete module:

 

[stopcrazypp]

What if the series cell count per module in the 60 is different than we are assuming?

As scaesare posted, we have disassembled pictures of the 60kWh module that show 6 groups in series. And we know from NHTSA pictures that there are 14 modules.

I can't really think of a reason to change the number in series per module, since keeping it the same allows them to use the same battery plate for all the different modules (just leave some cells blank per group, as with the 60kWh).

Also, if you assume 7 per module, that means 14*7*4.2V = 411V which is even higher. 13*7*4.2V = 382V, which is also higher. 12*7*4.2V = 353V but would be no different from at 14*6*4.2V assumption (which we have evidence of already).

 

[JRP3]

Obviously we are missing something that explains why it looks as if Tesla is charging the 60 cells higher than the 85 cells. I would be very surprised if that were actually the case.

 

[gorgasyang]

wk057,
some information about tesla battery pack of this post have been reposted to chinese website.
sb are

interested to know the exact mass of the whole battery pack, although Tesla said the mass is 544kg.

a independent measurements is​

very important for compare with other battery, i.e chinese BYD E6 and denza.
thx!​

​

 

[Otmar]

Tesla said the mass is 544kg.

The value I heard from Tesla for a 85 kWh pack is 569kg (1254lb). I was glad to hear it was less than the 600kg that I read in some article, Car and Driver maybe?