Max Pack chemistry and quad motor

[NineElectrics]

Givan that the Max Pack is just a chemistry/BMS tweak, and doesn't change the mechanical form of the pack, it is clearly compatible with quad motor.

So, why does the Quad Motor Max Pack product *really* no longer exist anymore?

Clearly the Max Pack can't achieve a significant range boost without use of Enduro dual motors. Does it go beyond that, though? Do the dual motors in the Max Pack have some added efficiency improvements that the non-Max Pack duals don't? Is there a gear change? A transmission?

Can the Max Pack battery not drive the quad motors with enough peak power/voltage? Or do quad motors just kill the efficiency of the Max Pack?

Sponsored

 

[carsly]

I don't work at Rivian, but my answer would be pricing.

If you add the pricing for Max Pack on top of the Quad Motor you're way up there. If it had the interior of a Range Rover Sport then maybe Rivian can find enough demand but with Tahoe quality interior materials and a $100+K price point is a tough ask when prices for EV's are sliding across the board. The answer is to get volumes up by moving downmarket - thus the regular 'dual motor' becoming available at effectively the same time as the 'performance dual motor' and I suspect Rivian will want to get the Standard Range battery out as soon as they can - even if it's just a large pack missing some cells.

 

[zefram47]

Nope...efficiency of all dual-motors is going to be the same. It's just the trickery of the new rear axle disconnect system in the dual that allows for auto-conserve mode over the quad that is the difference. If they'd actually made a 180 kWh pack, quad would've been amazing with max pack, but then you'd have a weight problem. At this rate, I wouldn't expect a "real" max pack offering until battery chemistries allow for a lot greater energy density. Again...glad I changed to Large pack in December, but I do wish the 180 kWh capacity had been real for those that want to tow. I've said it in a few threads already, but with a very minor bump in pack capacity the efficiency changes for dual won't show through when towing in part because both motors will be engaged 100% of the time and because pulling a giant sail behind the truck doesn't allow one to defeat physics.

 

[usofrob]

I highly suspect Rivian is trying to keep the number of variations of the vehicle down and just hit the target market. And they assume the target market wants the max range when the select max pack. And the dual motors are still likely a few percent more efficient than the quad in conserve. I don't believe it's price because even at the newest prices the dual performance is only $3k less than quad. It could also be that the new max pack chemistry can't handle as much current output for the 835 hp, but it can for 665 hp.

 

[NineElectrics]

Nope...efficiency of all dual-motors is going to be the same. It's just the trickery of the new rear axle disconnect system in the dual that allows for auto-conserve mode over the quad that is the difference.

Interesting. Why does the incremental range come in at 4 miles/kWh? It seems the pack energy doesn't increase enough to account for the range boost one gets over the dual non-max pack. That's why I wonder about some kind of additional tweak.

 

[Supratachophobia]

Givan that the Max Pack is just a chemistry/BMS tweak, and doesn't change the mechanical form of the pack, it is clearly compatible with quad motor.

So, why does the Quad Motor Max Pack product *really* no longer exist anymore?

Clearly the Max Pack can't achieve a significant range boost without use of Enduro dual motors. Does it go beyond that, though? Do the dual motors in the Max Pack have some added efficiency improvements that the non-Max Pack duals don't? Is there a gear change? A transmission?

Can the Max Pack battery not drive the quad motors with enough peak power/voltage? Or do quad motors just kill the efficiency of the Max Pack?

I made a spreadsheet last night to figure out this exact thing. If you had a quad max, the difference in range between the dual max would be ridiculously small. Not only would it confuse people, but it would create another production option. And it would canabalize sales from high margin vehicles. My guess is that Rivian wants to steer away from outsourcing motors.

 

[Supratachophobia]

I posted this in another thread and I think it's relevant here:

So ever since I heard someone mention that LG makes a 5800mah battery and that's what could be in the max pack, I've been wondering what the downsides of that would be. It's actually a bit of a unicorn when you go search for 5800mah 21700 cells. But here is the highest one I found, the INR21700-M58T. Apparently there is some theoretical max in cylindrical cells, 800 Wh/l. Not sure what that means, but no cylindrical batteries are able to overcome that. With the INR21700-M58T being the largest 21700 I can find right now, it has an energy density of 768 Wh/l. And they kinda cheat to get there: This particular battery is actually 71mm tall instead of 70. Some sites list it at 5800mah, but it's actually 5570mah according to LG.

Here are some bad things that happen with batteries that try to squeeze in higher capacities:
1. faster degradation
2. increased heat when discharging
3. lower cycle life

I'm going to go out on a limb and say that if the max pack is using these cells that have super-high mah, then not only would the cost not be worth it, you could risk having a less reliable battery on your hands after a few years. The only other anecdotal evidence I can offer to this is the 90kwh batteries vs. the 85kwh batteries that were options on early Model S. The 90's degredad faster and greater than their 85kwh counter-parts.

 

[Electrified Outdoors]

All we can do is speculate. I would say its a combination of pricing and efficiency. Its only an extra 14 kwh gross or 13 kwh usable most likely based on the C&D article.

Someone posted a window sticker that showed significantly higher EPA numbers (84 mpge vs 78 mpge for dual motor large). Battery can't really make the truck more efficient.... so... my guess is drive mode tuning was done to increase the numbers on Max pack variant. Above 20 mph the dual motor is a front wheel drive truck unless you lose traction or step into it.

Rivian has much more control over dual motor since the rear motor can be disengaged and reengaged at will. The quad is not designed for this which is why it has a separate conserve drive mode to decouple the rear motors. My understanding is EPA tests in AP mode so quad would only see a few miles increase.

I don't see any other way Rivian got an extra 58 miles (48mi on R1S) out of an extra 14kwh gross energy gain.

Rivian claims a "more capable" version of quad motor is in the works that will pair with max pack. More capable could mean the ability to decouple rear motors at will like the dual.... we will have to see.

Real world testing needs to be done. Im hoping to get a max pack owner to team up with me to test it out.

 

[NineElectrics]

Someone posted a window sticker that showed significantly higher EPA numbers (84 mpge vs 78 mpge for dual motor large). Battery can't really make the truck more efficient.... so... my guess is drive mode tuning was done to increase the numbers on Max pack variant. Above 20 mph the dual motor is a front wheel drive truck unless you lose traction or step into it.

Why isn't that tuning done for the dual motor large pack, I wonder? Does it require a beefier motor? Is it going to increase warranty repair costs?

And does this EPA fiddling mean we'll see much less than advertised real world range?

So many questions.

 

[Electrified Outdoors]

Why isn't that tuning done for the dual motor large pack, I wonder? Does it require a beefier motor? Is it going to increase warranty repair costs?

And does this EPA fiddling mean we'll see much less than advertised real world range?

So many questions.

Here is a hypothetical....if I already submitted my DM large pack to EPA and it has a higher number than quad...and I now have a max pack that I want to charge a premium for...would I submit the DM for testing again or would I submit max pack with the new tweaks? If I do the ladder that means it will appear to be a more significant gain.

Again I can only speculate but based on Rivian's statements I don't think they are using different hardware because they are going for simplification so they can pump out more units and get the cost down while also increasing their margins.

It could also be that they created software tuning specific to the max pack equipped vehicles. Maybe the battery can handle regen longer or can do more regen at a higher soc? Its really hard to say but I dont't think they are using different motors or anything like that as it would complicate the manufacturing process.

 

[NineElectrics]

Why was this thread moved? This is a general topic, not a battery specific topic.

 

[Supratachophobia]

So I'm still looking into this, but I received information that Rivian went with a ~5200mah Samsung 21700 cell for max pack. Whereas their large pack is based on a 4800mah Samsung 21700 cell. I'm not sure how to do the math on that, but reading elsewhere here on the forums, I think that would make the max pack 146kwh vs large pack 125kwh usable. Someone feel free to correct my math. My concern has been slightly abated now that we know the cell isn't operating at the bleeding edge of theoretical cylindrical cell technology.

 

[HaveBlue]

So I'm still looking into this, but I received information that Rivian went with a ~5200mah Samsung 21700 cell for max pack. Whereas their large pack is based on a 4800mah Samsung 21700 cell. I'm not sure how to do the math on that, but reading elsewhere here on the forums, I think that would make the max pack 146kwh vs large pack 125kwh usable. Someone feel free to correct my math. My concern has been slightly abated now that we know the cell isn't operating at the bleeding edge of theoretical cylindrical cell technology.

Well 350×146÷125=409 miles so that would jive perfectly.

 

[Epicloop]

~5200mah Samsung 21700 cell for max pack. Whereas their large pack is based on a 4800mah Samsung 21700 cell.

5200/4800= 1.083 x 352m is only 381miles (8% increase)

352m/135kw=2.607m/kw
410m/2.607=157kwh (16% increase)

Well 350×146÷125=409 miles so that would jive perfectly.

352/125=2.816m/kw x 146 = 411 miles

411/352=1.17(17%)
5200/4800= 1.08(8%)
17 > 8 = does not jive

 

[Donald Stanfield]

Me looking at all these math problems.

Sponsored