Battery cell/pack specs

[Rivianmd]

Starting a thread to discuss specs around the 2170 cells and overall pack capacity. I am fascinated with the tech side and specifically the cell chemistry and the wh per cell. I am also intrigued with the change in language using “large” pack vs. actual kwh capacity. Recently we’ve received information that the pack will be somewhat less than 135 kwh. This concerns me because there are no 2170 cells in mass use today that have the wh capacity @ 7777 cells for the large pack which would allow for a proper buffer at 135 kwh. So either Rivian has developed a proprietary cell with LG Chem that outperforms all other commercially available cells today, or the average wh per mile has dropped significantly from ~ 425 which has been the running assumption. (Or maybe they’ve upped the cell count?) I remember a tweet from RJ stating that they got 318+ out of a 135kw pack on the long way up. Maybe we are underestimating the vehicle efficiency? Also, if the are marketing the vehicles at 300+, my assumption is that the vehicle new will exceed that threshold for all wheel/tire combinations. I can’t imagine they would have the 20’s for instance come in less than 300. I also hope that they are engineering with a significant buffer so they can offset degradation. Again, all pointing back to wh’s per cell. Do others have thoughts on this or additional info to share?

Sponsored

 

[DucRider]

We don't have any information on how the pack has evolved, but the LWU vehicles had <135 kWh packs.
The original release specs had a design of 15 kWh "modules" with 864 cells (two layers of 432 with a cooling plate separating them). The 105 kWh pack would have had seven modules, the 135 kWh would need nine, and the 180 would require twelve.
They would have been arranged in a 108s configuration giving a nominal voltage of ~390 to 400.
An example of an LG cell in the 2018 timeframe of the battery pack details is the LG INR21700 M50T. It has a nominal energy rating of 18.2 Wh (and a 17.6 Wh "minimum")
https://www.batteryspace.com/prod-specs/11514.pdf

A "large" pack (formerly 135 kWh) with the original design and the M50T would have had a nominal energy rating of 141.5 kWh (or a minimum rating of 136.9 kWh). 9 modules of 864 cells is 7776 total cells.

It is a fair assumption that things have changed from the original pack specs, either in physical layout , increased buffer size, or some of each. But we have no details at all. And Rivian appears to be following Teslas lead and giving no kWh numbers. How much technical info they release is yet to be seen.
Sandy Munro has an LE on order and will tear it apart upon delivery and we will get far more info than Rivian is likely to provide.

 

[Rivianmd]

Thanks for the detailed response - the more I think about it the vehicles must be more efficient than 425 wh per mile.

 

[skyote]

Sandy Munro has an LE on order and will tear it apart upon delivery and we will get far more info than Rivian is likely to provide.

I didn't realize that! Just googled though & watched his config video (for anyone else considering doing the same, don't waste your time).

I think it will be very interesting to see what Sandy has to say. Now I just want to know when he placed his preorder so I can get an idea of where he stands in line to get his truck!

 

[DucRider]

One possible scenario I see is a switch to the more common 96s configuration (Tesla, GM, etc).
This would reduce the cell count and thus both the energy rating and physical size of the "modules" (if they stuck with that design).

96s 8p modules would have 768 cells and be ~350V nominal and energy of ~14 kWh (using the M50T specs from above).
The "large" pack would be ~126 kWh nominal, with an unknown actual usable capacity.

If we go with the Tesla method, I expect to see Wh/mi in the 375 to 425 range (with the 21s at the low end of the range, the 20s on the higher side and the 22s somewhere in between)
That equates to ~2.3 to 2.7 mi/kWh (common display in most vehicles)

 

[mkennedy1996]

Thanks for the detailed response - the more I think about it the vehicles must be more efficient than 425 wh per mile.

They have published some data that guides us to the efficiency. While this information is still the current information posted, we don't know if it has evolved as the vehicles have developed.

They publish charging speeds for two different chargers. They do not specify which vehicle these are for, nor do they give specifics on the wheel configuration, which can have an impact on range.

The mobile charger provides 7.68kW of power and adds 16 miles per hour of range.
You have to deduct a percentage of that power that is lost during the charging process in order to come to the power available to add range. In this case I use a charging loss of 8% and 10%.

At a 10% charging inefficiency loss, you have 6,912 watts available to add range. Their spec indicates this would add 16 miles of range (with rounding this could be 15.51 to 16.49):
432Wh/mile - with rounding this could be between (419 to 446Wh/mile)

At an 8% charging inefficiency loss, you have 7,066 watts available to add range. Their spec indicates this would add 16 miles of range (with rounding this could be 15.51 to 16.49):
442Wh/mile - with rounding this could be between (428 to 456Wh/mile)

The hard wired charger provides 11.5kW of power and adds 25 miles per hour of range.

At a 10% charging inefficiency loss, you have 10,350 watts available to add range. Their spec indicates this would add 25 miles of range (with rounding this could be 24.51 to 25.49):
414Wh/mile - with rounding this could be between (406 to 422Wh/mile)

At an 8% charging inefficiency loss, you have 10,580 watts available to add range. Their spec indicates this would add 25 miles of range (with rounding this could be 24.51 to 25.49):
423Wh/mile - with rounding this could be between (415 to 432Wh/mile)

This at those scenarios:
432Wh/mile - with rounding this could be between (419 to 446Wh/mile)
442Wh/mile - with rounding this could be between (428 to 456Wh/mile)
414Wh/mile - with rounding this could be between (406 to 422Wh/mile)
423Wh/mile - with rounding this could be between (415 to 432Wh/mile)
The average of these comes to 428Wh/mile or between (417 to 439Wh/mile)

Based upon available data, that is my best guess.

 

[Trandall]

https://www.batteryspace.com/prod-specs/11514.pdf
the spec's state >or= to 80% initial cycle energy after 300 cycles and 70% at 14 degree F also 80% at 32 F. If this info translates from the individual cell to the pack assembly that would mean degredation of 20% after only 90,000 miles and only 210 mile range when 14 F for the large pack. Hopefully I'm missing something those numbers are horrible.

 

[mkennedy1996]

If we go with the Tesla method, I expect to see Wh/mi in the 375 to 425 range (with the 21s at the low end of the range

The Tesla method would be to engineer to the test rather than the real world and get a range projection that cannot be realistically achieved in the real world.

I sincerely hope that they do NOT follow Tesla's lead. It mispresents the capability of the car in the real world. Other companies have adopted a testing formula that is much closer to the real world.

 

[Rivianmd]

They have published some data that guides us to the efficiency. While this information is still the current information posted, we don't know if it has evolved as the vehicles have developed.

They publish charging speeds for two different chargers. They do not specify which vehicle these are for, nor do they give specifics on the wheel configuration, which can have an impact on range.

The mobile charger provides 7.68kW of power and adds 16 miles per hour of range.
You have to deduct a percentage of that power that is lost during the charging process in order to come to the power available to add range. In this case I use a charging loss of 8% and 10%.

At a 10% charging inefficiency loss, you have 6,912 watts available to add range. Their spec indicates this would add 16 miles of range (with rounding this could be 15.51 to 16.49):
432Wh/mile - with rounding this could be between (419 to 446Wh/mile)

At an 8% charging inefficiency loss, you have 7,066 watts available to add range. Their spec indicates this would add 16 miles of range (with rounding this could be 15.51 to 16.49):
442Wh/mile - with rounding this could be between (428 to 456Wh/mile)

The hard wired charger provides 11.5kW of power and adds 25 miles per hour of range.

At a 10% charging inefficiency loss, you have 10,350 watts available to add range. Their spec indicates this would add 25 miles of range (with rounding this could be 24.51 to 25.49):
414Wh/mile - with rounding this could be between (406 to 422Wh/mile)

At an 8% charging inefficiency loss, you have 10,580 watts available to add range. Their spec indicates this would add 25 miles of range (with rounding this could be 24.51 to 25.49):
423Wh/mile - with rounding this could be between (415 to 432Wh/mile)

This at those scenarios:
432Wh/mile - with rounding this could be between (419 to 446Wh/mile)
442Wh/mile - with rounding this could be between (428 to 456Wh/mile)
414Wh/mile - with rounding this could be between (406 to 422Wh/mile)
423Wh/mile - with rounding this could be between (415 to 432Wh/mile)
The average of these comes to 428Wh/mile or between (417 to 439Wh/mile)

Based upon available data, that is my best guess.

Seems reasonable - so if we take 428Wh the usable pack size would need to be at least ~128.5Kwh. If you assume they will have a buffer this gets us right back to 135 pack size.

 

[Rivianmd]

https://www.batteryspace.com/prod-specs/11514.pdf
the spec's state >or= to 80% initial cycle energy after 300 cycles and 70% at 14 degree F also 80% at 32 F. If this info translates from the individual cell to the pack assembly that would mean degredation of 20% after only 90,000 miles and only 210 mile range when 14 F for the large pack. Hopefully I'm missing something those numbers are horrible.

Read that too.

 

[mkennedy1996]

If this info translates from the individual cell to the pack assembly that would mean degredation of 20% after only 90,000 miles and only 210 mile range when 14 F for the large pack. Hopefully I'm missing something those numbers are horrible.

On three of my Teslas, I have seen range loss of 5.6, 7.7 and 8.5 miles per 10,000 miles driven. In percentage, that is 2.2%, 2.7% and 2.9% per 10,000 miles driven.

 

[Rivianmd]

I just hope they aren’t reaching for the 21’s to be right over the 300 mark with minimal to no buffer. We know that in the first 50k or so we will see 2-5% degradation. That is why I am concerned that they’ve come out with the pack being less than 135kwh

 

[DucRider]

https://www.batteryspace.com/prod-specs/11514.pdf
the spec's state >or= to 80% initial cycle energy after 300 cycles and 70% at 14 degree F also 80% at 32 F. If this info translates from the individual cell to the pack assembly that would mean degredation of 20% after only 90,000 miles and only 210 mile range when 14 F for the large pack. Hopefully I'm missing something those numbers are horrible.

That is for a true 100% to true 0% with no thermal management during charging/discharging. All EV manufacturers stop discharge well above the lower cutoff voltage (2.5V in this case), and most (except Tesla?) don't allow charging to the fully charged voltage (4.2V in this case and pretty universal).
This is a pretty standard way to spec cells and I've seen a similar spec sheet on one of the Panasonic cells designed for Tesla with similar test cycling. IIRC, the cutoff on that cell was actually listed at 3.0V. I'll see if I can find the link.

The reduced range at lower battery temperatures is the reason that Rivian is implementing the ability to warm the pack (see the cold weather testing video).

 

[Rivianmd]

That is for a true 100% to true 0% with no thermal management during charging/discharging. All EV manufacturers stop discharge well above the lower cutoff voltage (2.5V in this case), and most (except Tesla?) don't allow charging to the fully charged voltage (4.2V in this case and pretty universal).
This is a pretty standard way to spec cells and I've seen a similar spec sheet on one of the Panasonic cells designed for Tesla with similar test cycling. IIRC, the cutoff on that cell was actually listed at 3.0V. I'll see if I can find the link.

The reduced range at lower battery temperatures is the reason that Rivian is implementing the ability to warm the pack (see the cold weather testing video).

And they are using resistance heat and not a heat pump which makes no sense in most use cases. Today you can find heat pumps that operate in low single digits F

 

[DucRider]

And they are using resistance heat and not a heat pump which makes no sense in most use cases. Today you can find heat pumps that operate in low single digits F

They were testing to as low as minus 40° F

Sponsored