USA MY RWD has soft limited LR battery!

[bzobzo]

Just picked up my MY RWD today. It has been already established that it does not have the LFP battery pack, but there was some speculation on whether it was a soft limited LR battery or a new smaller capacity NCA battery. From what I am seeing, I'm pretty sure that it is the Long Range battery software limited down to 260 rated miles.

At the supercharger at 99% charge it was still charging at a 35kW rate. As we know, a battery actually charged to 99% would be charging slowly, not anywhere near 35kW. Also, at 100% charge, there is no limited regen warning, indicating that the battery can absorb the full regen charge.

Charge rates that I managed to note: (battery was only preconditioned for about 10 minutes in 30F temps, so it can probably do better)
80% - 53kW
85% - 51kW
90% - 45kW
97% - 37kW
99% - 35kW

For MY RWD owners this is awesome news. When charged to a displayed 100%, the actual battery is around 80%. This means 100% of the range can be used without concern about battery degradation just like the LFP battery in the M3 RWD. And better than a LFP pack, you can charge quickly to 100% when Supercharging. Really, the RWD is almost as good as the LR in practical range since one will not often charge above 80% in the LR.

Some other data points:

• The MY RWD weighs 4,154lbs and the MY LR weighs 4,416lbs, a difference of 262lbs. The front motor unit alone weighs over 200lbs, so you would expect a greater weight difference if the physical battery was smaller.
• The Shanghai LFP MY RWD weighs 3,920lbs. With a similar battery capacity, you would expect the NCA MY RWD to weigh signicantly less than this, since LFP is less energy dense.

 

[David99]

Awesome news if all of this turns out to be the case. Does your VIN indicate it's not a LFP?

 

[bzobzo]

Awesome news if all of this turns out to be the case. Does your VIN indicate it's not a LFP?

VIN is 7SAYGDED9PF946XXX, so battery type is "E". I believe it would be "F" for LFP

 

[jcanoe]

If you set the daily charging limit above 80% does the vehicle display the usual "80% charging limit recommended for daily driving"?

 

[MP3Mike]

Does your VIN indicate it's not a LFP?

No, VINs do not have anything in them to indicate the battery type.

VIN is 7SAYGDED9PF946XXX, so battery type is "E". I believe it would be "F" for LFP

E just means Electric, all Model Ys have the same digit.

 

[arni]

You can finish strongly with LFP, ref chart 2022 Model 3 SR LFP Supercharging speed

 

[bzobzo]

If you set the daily charging limit above 80% does the vehicle display the usual "80% charging limit recommended for daily driving"?

Yes. This is consistent with other Tesla trims that have had software limited batteries, even though it should be safe to charge above that.

 

[jsight]

That makes this trim look like a pretty good deal, TBH. I bet a lot of people with the LR rarely go above 80% anyway.

 

[mborkow]

That is good news…awfully tempting. Thanks for the info!

 

[mborkow]

Do we know what strategy is used in the software lock Tesla uses? It occurs to me that the software could restrict the battery a couple (maybe more?) different ways:
- all cells are charged but capped by the software (at around 75%)
- the software only charges 75% of the cells in the battery pack (leaving the remaining cells unused)
The first strategy would be fantastic (it means charging to 100% is really only charging the whole battery to 75%)…but the second strategy means charging to 100% is actually charging each cell being used to its max (which would not be a great thing to do your car regularly).

 

[David99]

Do we know what strategy is used in the software lock Tesla uses? It occurs to me that the software could restrict the battery a couple (maybe more?) different ways:
- all cells are charged but capped by the software (at around 75%)
- the software only charges 75% of the cells in the battery pack (leaving the remaining cells unused)
The first strategy would be fantastic (it means charging to 100% is really only charging the whole battery to 75%)…but the second strategy means charging to 100% is actually charging each cell being used to its max (which would not be a great thing to do your car regularly).

Since there is no way to divide the battery pack up and charge only some cells while not others, it is most likely just a charge limiter. That's what Tesla did with the old 70/75 packs for the S.

 

[E90alex]

- the software only charges 75% of the cells in the battery pack (leaving the remaining cells unused)

This is not possible

 

[mborkow]

This is not possible

Why wouldn’t it be possible (or do you mean for Tesla’s battery back architecture it’s not possible)?

 

[E90alex]

Why wouldn’t it be possible (or do you mean for Tesla’s battery back architecture it’s not possible)?

Cells are not individually addressed. They are all wired together in series and parallel so they can’t selectively charge one cell higher than another. To the car it essentially just looks like one giant battery.

 

[David99]

Tesla might also change the battery configuration at any point. By doing the software limit, they are putting cells in the car they are not getting paid for. Back in the day when they did that for the 70/75 pack, it was a small amount. Here it is quite a lot. With the Model S battery pack it was easier to manufacture different sizes as it was put together from smaller identical modules. The 3/Y battery it not made to be broken up easily.

Maybe Tesla wasn't able to get enough LFP packs and instead of not building these cars at all, they put in the normal packs and added the software limit. Once they get more LFP packs, they might switch that again.

Can someone verify the cell voltage via ScanMyTesla?

 

[mborkow]

Cells are not individually addressed. They are all wired together in series and parallel so they can’t selectively charge one cell higher than another. To the car it essentially just looks like one giant battery.

in that case, then yes, the software wouldn’t be able to selectively charge only certain segments of the pack. Thanks

 

[mborkow]

Tesla might also change the battery configuration at any point. By doing the software limit, they are putting cells in the car they are not getting paid for. Back in the day when they did that for the 70/75 pack, it was a small amount. Here it is quite a lot. With the Model S battery pack it was easier to manufacture different sizes as it was put together from smaller identical modules. The 3/Y battery it not made to be broken up easily.

Maybe Tesla wasn't able to get enough LFP packs and instead of not building these cars at all, they put in the normal packs and added the software limit. Once they get more LFP packs, they might switch that again.

Can someone verify the cell voltage via ScanMyTesla?

From my POV, a software limited NCA pack and an LFP (w/o software lock) offer many of the same advantages. I think I’d be happy with either. The only scenario I wouldn’t like the current RWD is a smaller NCA pack.

 

[gsmith123]

Id love to see a full charge curve, or at least a test of peaking charging speeds from 10-20%. If it can hit 250kw that’s also very strong evidence it’s a big pack (although I guess they may limit charging speed artificially as well)

 

[chipdex]

Id love to see a full charge curve, or at least a test of peaking charging speeds from 10-20%. If it can hit 250kw that’s also very strong evidence it’s a big pack (although I guess they may limit charging speed artificially as well)

Id love to see a full charge curve, or at least a test of peaking charging speeds from 10-20%. If it can hit 250kw that’s also very strong evidence it’s a big pack (although I guess they may limit charging speed artificially as well)

since they publicly state max charging speed as 170kw wouldn't it follow that they would also software limit that?

 

[bzobzo]

Tesla might also change the battery configuration at any point. By doing the software limit, they are putting cells in the car they are not getting paid for. Back in the day when they did that for the 70/75 pack, it was a small amount. Here it is quite a lot. With the Model S battery pack it was easier to manufacture different sizes as it was put together from smaller identical modules. The 3/Y battery it not made to be broken up easily.

Maybe Tesla wasn't able to get enough LFP packs and instead of not building these cars at all, they put in the normal packs and added the software limit. Once they get more LFP packs, they might switch that again.

Can someone verify the cell voltage via ScanMyTesla?

I have a CAN cable on order for use with ScanMyTesla, so hopefully I'll be able to report some more data soon.

I think the use of the LR battery was primarily motivated by trying to keep the RWD eligible for the tax credit. However, since they didn't have an off the shelf smaller NCA pack, they used the existing LR one. From the teardown videos I've seen of the battery pack, it doesn't look like a simple change to simply leave out some cells. And given the transition to the new 4680 cells, they probably didn't want to engineer, certify and stock a new smaller NCA pack on the soon to be outdated 2170 cells. I'd be surprised if they didn't transition to a cheaper smaller capacity battery pack soon though, because at $100/kWh, the roughly 20kWh extra in the larger pack is a fair chunk of change. But given the effective $7500 off the purchase price of the vehicle with the tax credit, I suppose they deemed the extra cost tolerable for now.