New Roadster Goodies for 2014

[spaceballs]

The car and electronics are not designed for high current DC.

Well PEM can suck out what 300KW from the ESS, so to me that high current DC

- - - Updated - - -

I'm no engineer so can someone explain why they can't just bypass the PEM and onboard charger and wire directly to the battery to make Supercharging possible?...

What I suggested is basically this.

- - - Updated - - -

... *The only exception I can think of is if the cell count were lowered, in order to make room for a coolant line to snake through the rows/layers of cells....

This already exists, ESS has active water cooling between cells, wouldn't be too hard to put in better battery pump if it required it.

Also with newer battery tech, with lower cell IR, it will have lower heat generated at higher C rates.

- - - Updated - - -

... It would be a lot more challenging to change the cell count or add DC bypass, ...

DC bypass wouldn't be too hard for Tesla to do, firmware change, and HV wire tap between ESS and PEM.

- - - Updated - - -

They'd need to upgrade most of the supporting systems to do this:

- New Model S charge port
- Rewiring charge port, PEM and battery
- Add DC bypass contactors
- New firmware
- Possibly increased cooling

Plus all the testing needed to bring it to production. It's a lot easier to do a 1:1 swap of the battery cells to create a long-range pack.

Some notes of your list.
- New Model S charge port - Agreed needed.
- Add DC bypass contactors - Not needed already in ESS
- New firmware - Agreed would need updated firmware to enable DC bypass contactors to SC.
- Possibly increased cooling - Unlikely needed with latest Cell IR technology.

 

[Kevin Sharpe]

And is battery extended warranty now a good idea???

What do you think??

I'm struggling to get any value out of my extended battery warranty despite most people agreeing that I've had a long term battery problem. Historically I recommended everyone buy the extended battery warranty because this is complex technology that isn't yet fully supported by the community but today I'm not convinced the warranty has any value :crying:

See more background info here...

Trying to see if our CPO Roadster ideal mile range loss/CAC value decrease is real... - Page 5

I think the real questions we need answering before making decisions on warranties are how much will the "400 mile" battery upgrade cost? What's the real EPA range? When will Tesla deliver this? What warranty will they offer on the new battery?

 

[djp]

Some notes of your list.
- Add DC bypass contactors - Not needed already in ESS
- Possibly increased cooling - Unlikely needed with latest Cell IR technology.

The current contactor connects and disconnects the ESS from the PEM. It does not bypass the PEM to allow DC charging, a new contactor would be needed for this.

I'm referring to increased cooling capacity of the HVAC system. Supercharging pumps out a lot of heat and it's likely the Roadster compressor would not be able to keep up.

Bottom line - adding Supercharging to the Roadster is not a wise use of Tesla engineering resources or shareholder capital. They're better off focusing on Model X and Gen III to grow the company.

Tesla has a contractual obligation to honor the battery replacement agreements and they've taken the path of least resistance by doing a 1:1 battery cell replacement. Don't expect them to invest any more than they need to on the Roadster.

 

[JRP3]

I thought the Model S cells were about 3100 mAh, instead of the 3400 mAh "off the shelf" Panasonic cells.

The numbers don't seem to support this. 3.1ah x 3.6V = 11.16Wh x 7104 = 79,280.64 Wh. 3.4ah x 3.6V = 12.24Wh x 7104 = 86,952.96 Wh

 

[techmaven]

The numbers don't seem to support this. 3.1ah x 3.6V = 11.16Wh x 7104 = 79,280.64 Wh. 3.4ah x 3.6V = 12.24Wh x 7104 = 86,952.96 Wh

Alternatively, it could be that these cells have a nominal voltage of 3.7 volts. We simply don't know until someone pulls a production charged cell and does some measurements.

BTW, various places show either 3.6 or 3.7 volt nominal voltage. For instance, this is supposed to be based on a Panasonic NCR18650A and has markings with 3.7v:

Test/Review of Intl-outdoor NCR18650A 3100mAh (Black))

 

[JRP3]

Yes it's possible that the NCA cells operate at a slightly higher nominal voltage of 3.7V but that still does not allow a 3.1ah cell to create an 85kWh pack using 7104 cells. It would mean a 3.4ah cell at 3.7V gives the Model S an 89,368.32 Wh pack, and the Roadster an 85,933.98 pack.

 

[Kevin Sharpe]

We simply don't know until someone pulls a production charged cell and does some measurements.

we are getting close... some packs from the Tesla Rav 4 EV have been taken apart...

Real Tesla Batteries - eSamba EP 35 - YouTube

 

[Botbldr45]

@Kevin Sharpe

Concerning EBW..... I agree with your statements. We need to wait for more info from Tesla concerning availability, cost, feasibility. Buying EBW now may prove premature and from your experience wasteful!

 

[djp]

400 Mile Pack (Was New Roadster Goodies for 2014)

Yes it's possible that the NCA cells operate at a slightly higher nominal voltage of 3.7V but that still does not allow a 3.1ah cell to create an 85kWh pack using 7104 cells. It would mean a 3.4ah cell at 3.7V gives the Model S an 89,368.32 Wh pack, and the Roadster an 85,933.98 pack.

Agreed, Model S is probably using a 3.4Ah cell at 3.7V nominal and derated to 85kWh. This is in-line with similar ratings for the Roadster:

Model S

Total capacity = 7,104 * 3.4Ah * 3.7V = 89.4kWh

Rated capacity = 95% of Total = 85kWh

Usable capacity = 90% of Total = 80kWh

Roadster

Total capacity = 6,831 * 2.4Ah * 3.6V = 59kWh

Rated capacity = 95% of Total = 56kWh

Usable capacity = 90% of Total = 53kWh


Using the Model S cell in a Roadster pack would give a useable capacity of about 77kWh, or about 357 ideal miles.

 

[Botbldr45]

Now that's what I'm talking about!!
Ocean City and back without worrying about charging stations.
WooHoooo!!! :biggrin:

 

[Eberhard]

Agreed, Model S is probably using a 3.4Ah cell at 3.7V nominal and derated to 85kWh. This is in-line with similar ratings for the Roadster:

Model S

Total capacity = 7,104 * 3.4Ah * 3.7V = 89.4kWh

Rated capacity = 95% of Total = 85kWh

Usable capacity = 90% of Total = 80kWh

Roadster

Total capacity = 6,831 * 2.4Ah * 3.6V = 59kWh

Rated capacity = 95% of Total = 56kWh

Usable capacity = 90% of Total = 53kWh


Using the Model S cell in a Roadster pack would give a useable capacity of about 77kWh, or about 357 ideal miles.

my calculations:

85kWh / 7104 * 6831 = 81,73kWh

 

[Kevin Sharpe]

Using the Model S cell in a Roadster pack would give a useable capacity of about 77kWh, or about 357 ideal miles.

still a long way from Elon's 400 mile target

 

[djp]

my calculations:

85kWh / 7104 * 6831 = 81,73kWh

Yep, the Model S cells would give 85.9kWh total, 81.7kWh rated and 77.3kWh usable in a Roadster pack.

 

[dsm363]

I thought the Roadster left a much smaller buffer than the Model S (allowed more of the capacity to be used)?

 

[djp]

I thought the Roadster left a much smaller buffer than the Model S (allowed more of the capacity to be used)?

As far as I've seen they both charge to 95% in range mode and have a buffer below the zero line. The difference is the Model S will disconnect the battery at low SOC to protect against bricking, whereas the Roadster will keep the vampire drain going to absolute zero.

 

[spaceballs]

The current contactor connects and disconnects the ESS from the PEM. It does not bypass the PEM to allow DC charging, a new contactor would be needed for this.

It doesn't need to bypass the PEM, PEM at idle can handle seeing HV DC, all it needs is firmware update to think it's in Park when SC is being done.

I'm referring to increased cooling capacity of the HVAC system. Supercharging pumps out a lot of heat and it's likely the Roadster compressor would not be able to keep up.

IF HVAC can't handle the heatsoak from the cells, the BMS firmware can be updated to notify to slow down SC charging rate to maintain proper temps. i.e. so it would limit SC, but it would be significantly more than 70ah.

Bottom line - adding Supercharging to the Roadster is not a wise use of Tesla engineering resources or shareholder capital. They're better off focusing on Model X and Gen III to grow the company.

Depends on how much they allocated resources for support of their last gen car. From a outside perspective we have no idea of how much.

Tesla has a contractual obligation to honor the battery replacement agreements and they've taken the path of least resistance by doing a 1:1 battery cell replacement. Don't expect them to invest any more than they need to on the Roadster.

Yes a cell swap update is pretty much expected since they already signed up to do it. For expectations I would base it of their history, but my personal feeling is the same as yours (i.e. they likely will not do more than what is needed). My only note is that it really wouldn't take a big effort to add limited SC ability, I'm pretty sure they could do it with an firmware coder, engineer, and an tester in a month.

 

[djp]

It doesn't need to bypass the PEM, PEM at idle can handle seeing HV DC, all it needs is firmware update to think it's in Park when SC is being done.

The Model S charge port uses the same pins for both AC and DC charging. You need a relay to either connect AC to the PEM or DC to the battery.

I agree with most of your other points, but your estimate of one month to do the work is a lot more aggressive than Tesla's estimate. DC bypass was part of the original proposal for the Roadster, but scrapped when they realized how much work it would be. If Elon says it's not happening, it's not happening.

 

[spaceballs]

The Model S charge port uses the same pins for both AC and DC charging. You need a relay to either connect AC to the PEM or DC to the battery.

I agree with most of your other points, but your estimate of one month to do the work is a lot more aggressive than Tesla's estimate. DC bypass was part of the original proposal for the Roadster, but scrapped when they realized how much work it would be. If Elon says it's not happening, it's not happening.

Well my idea would be separate plug where you have to lift the trunk lid to access, so more of a hack I guess. Yeah my estimate is aggressive, I'm prob forgetting all the management meetings so 2x that.

 

[qwk]

Well my idea would be separate plug where you have to lift the trunk lid to access, so more of a hack I guess. Yeah my estimate is aggressive, I'm prob forgetting all the management meetings so 2x that.

I'm pretty sure that Tesla isn't going to go the separate plug route because that is not the way the company does things. The only way that I could see supercharging making it's way to the Roadster, is via retrofitting a Model S HV box into the PEM. Since that would take nearly a complete PEM redesign, this is very unlikely to happen.

 

[chickensevil]

So I keep seeing people throw around hard numbers on how many cells are in the packs... My understanding was that was a very good guess. Did someone actually get the chance to rip apart either of the packs to confirm these numbers? If so, then why didn't they also take the time to pull the real measurements off the cells (volts and amps)?

I only say this because everyone seems pretty set on making these numbers work and guessing how many amps the cells have based on a possibly flawed number. If that value was actually settled somewhere then I will go back to the peanut gallery.