This is why you can't get 'rated range'

[N..8]

David, I agree that many factors are at play. I believe that the cell packs voltage "droop" under load which is how the you get those power limits. I believe the perfect temps for all the cells is 80 degrees. So as you've stated if the battery is not at operating temps the batteries "droop" faster and cause the power limit differently. I think when we are talking about a hard limit we are referring to when the car shuts down and this seems to be after/during the 4kw buffer depending on when the first cell pack hits certain voltage, possible 2.9 - 3.0v. I'm wonder if this might be why those with a new car can go into this range and see no affects then as the battery gets older people all of a sudden get caught off guard. Then a shut down happens and they can't understand why it happened when they have been doing it all along with no symptoms.

 

[Snerruc]

I don’t understand you guys. You CAN get rated range or better. I’m at 271 wh per mile lifetime and rated is approx 290. Jerry33 is at 245 after 120,000 miles. I drive normally- speed limit + definitely keep up with traffic flow and no hypermiling stuff.

 

[Lukez]

I don’t understand you guys. You CAN get rated range or better. I’m at 271 wh per mile lifetime and rated is approx 290. Jerry33 is at 245 after 120,000 miles. I drive normally- speed limit + definitely keep up with traffic flow and no hypermiling stuff.

You obviously don't drive in the cold and in high winds very often.

 

[ran349]

I don’t understand you guys. You CAN get rated range or better. I’m at 271 wh per mile lifetime and rated is approx 290. Jerry33 is at 245 after 120,000 miles. I drive normally- speed limit + definitely keep up with traffic flow and no hypermiling stuff.

Nobody is saying you can't get rated range. Most people will get rated range if they are driving at 270 to 280 Wh/mile, but not at the 290 or 295 Wh/mile rate.
I get rated range at 270 Wh/mile.

 

[shred86]

I'd like to mention a few things based on my experience with driving down close to 0 or below.

There is no hard limit. Its ambiguous. I have driven my car down to almost 0 countless times and the power limiter comes on at different times. It depends on temperature and SoC which makes perfect sense. But it also depends on how recent the battery has been used, how much it has been used and and how recent it was charged. Maybe that's partly explained by temperature but I think it doesn't explain it entirely.

Here is an example that illustrates it. On a road trip I drive and charge back to back. The battery gets cycled a lot in a short period of time. The power limiter comes on very late when I drive down low.

When I drive little and don't charge my car for days and then drive it down low, the power limiter comes on much earlier.

I also thought battery voltage would be the main determining factor but I see different behaviors at the same voltage depending on the previous use patterns.

In other words, yes SoC, temperature, power draw all play a role, but I see different battery health even when all the above are the same. The term 'recent cycle amount' would describe it best. The BMS definitely knows about it as it adjusts accordingly. It determines mostly the power limits and how deep into the buffer you can go. It definitely isn't balancing. My cells are alway closer together after long resting periods.

Battery capacity seems to be a complex issue with many variables.

Great info. I’ve seen some folks mention similar behavior with charging to 100%. If you haven’t charged to 100% in a while, it is very slow to charge as you approach 100%. If you’ve charged to 100% recently or frequently, it still throttles as you get closer to 100% but not as much, likely because it has better confidence on not overshooting the limits. Perhaps it’s similar to the bottom end - if the battery hasn’t been to lower SOCs in a while, it’s going to limit the power earlier.

My guess is you could still draw all ~4 kWh from the buffer, but you’ll just be power limited earlier/more aggressively, probably to the point the vehicle is almost undrivable. I’d be curious if anyone has actually seen the vehicle shutdown with nominal energy remaining >0.0 (assuming no other battery balancing issues). It’s also apparent you don’t always arrive at 0% displayed with exactly 4 kWh of nominal energy remaining, so that also adds to the variability.

 

[supratachophobia]

I'd like to mention a few things based on my experience with driving down close to 0 or below.

There is no hard limit. Its ambiguous. I have driven my car down to almost 0 countless times and the power limiter comes on at different times. It depends on temperature and SoC which makes perfect sense. But it also depends on how recent the battery has been used, how much it has been used and and how recent it was charged. Maybe that's partly explained by temperature but I think it doesn't explain it entirely.

Here is an example that illustrates it. On a road trip I drive and charge back to back. The battery gets cycled a lot in a short period of time. The power limiter comes on very late when I drive down low.

When I drive little and don't charge my car for days and then drive it down low, the power limiter comes on much earlier.

I also thought battery voltage would be the main determining factor but I see different behaviors at the same voltage depending on the previous use patterns.

In other words, yes SoC, temperature, power draw all play a role, but I see different battery health even when all the above are the same. The term 'recent cycle amount' would describe it best. The BMS definitely knows about it as it adjusts accordingly. It determines mostly the power limits and how deep into the buffer you can go. It definitely isn't balancing. My cells are alway closer together after long resting periods.

Battery capacity seems to be a complex issue with many variables.

I would submit that pack temp is a very large factor here. High temps, lower resistance, battery happier to discharge.

 

[supratachophobia]

Nobody is saying you can't get rated range. Most people will get rated range if they are driving at 270 to 280 Wh/mile, but not at the 290 or 295 Wh/mile rate.
I get rated range at 270 Wh/mile.

I am. I am saying you can't get rated range using EPA consumption and setting zero on the dash as your stopping point. You can't, I can't, no one can.

 

[N..8]

I believe you have to use the 4kw buffer to get it, that's what the math says. Which for my S75 would mean me going another 6.5% SOC.

With TM-SPY if my car reads 0 SOC, TM-SPY says I have 6.5% left or 4kw.

 

[ran349]

I am. I am saying you can't get rated range using EPA consumption and setting zero on the dash as your stopping point. You can't, I can't, no one can.

I didn't say EPA consumption. I said 270 to 280 Wh/mi will give most people rated range, but not 290 or 295, which you call EPA consumption. And that is assuming you stop at 0% dash SOC. We're saying the same thing.

 

[ran349]

I believe you have to use the 4kw buffer to get it, that's what the math says. Which for my S75 would mean me going another 6.5% SOC.

With TM-SPY if my car reads 0 SOC, TM-SPY says I have 6.5% left or 4kw.View attachment 379108

Have you ever tried taking it below the 6.5% value?

 

[N..8]

Have you ever tried taking it below the 6.5% value?

Just so we are talking them same thing. At this level my car was reading 0 SOC on the dash and TM-Spy was showing 6.5%. I've driving another mile or so but never down to 0 kw. When I did drive it down a little I was showing power limited so I think at 0kw the car will shut off and also believe that if cell pack gets to 3.0v that it will shut down.

 

[ran349]

Just so we are talking them same thing. At this level my car was reading 0 SOC on the dash and TM-Spy was showing 6.5%. I've driving another mile or so but never down to 0 kw. When I did drive it down a little I was showing power limited so I think at 0kw the car will shut off and also believe that if cell pack gets to 3.0v that it will shut down.

So the 0% dash is not a hard shut down point, but you are running in risky territory at anything below 0 % dash SOC. In your case, maybe you had a few more miles, but hard to tell how many.

 

[N..8]

So the 0% dash is not a hard shut down point, but you are running in risky territory at anything below 0 % dash SOC. In your case, maybe you had a few more miles, but hard to tell how many.

You are correct on this, with TM-Spy up it will show what the pack remain is. What we are seeing here in this thread is what we believe the Total Rated miles at 100% is using this buffer for it's calculation. Also when watching TM-SPY with the cars dash SOC is scaled not to Pack Zero but pack with 4kw remaining.

 

[supratachophobia]

I didn't say EPA consumption. I said 270 to 280 Wh/mi will give most people rated range, but not 290 or 295, which you call EPA consumption. And that is assuming you stop at 0% dash SOC. We're saying the same thing.

You can't call it "Rated Range". Rated Range is a number based on the EPA test results. I think it's an important distinction to keep. Especially since the consumption equation changes as you approach zero. And I'm not the one calling it EPA consumption, the EPA is. They did the test, Tesla made the algorithm (and lied), so here we are.

And yes, I'm a bit sour on the whole thing.

 

[David99]

I recently provoked a shutdown when i kept driving passed 0%. My car would allow me to take another 0.7 kWh after it showed zero usable left. 0.7 out of the 4 kWh buffer is not much and definitely doesn't make up for the missing energy to get the full rated range. SO be prepared to have your car shut down soon after it shows zero.

 

[ran349]

I recently provoked a shutdown when i kept driving passed 0%. My car would allow me to take another 0.7 kWh after it showed zero usable left. 0.7 out of the 4 kWh buffer is not much and definitely doesn't make up for the missing energy to get the full rated range. SO be prepared to have your car shut down soon after it shows zero.

So how did you get back up and running again? Any clue on why it didn't let you use more of the 4kWh?

 

[N..8]

I recently provoked a shutdown when i kept driving passed 0%. My car would allow me to take another 0.7 kWh after it showed zero usable left. 0.7 out of the 4 kWh buffer is not much and definitely doesn't make up for the missing energy to get the full rated range. SO be prepared to have your car shut down soon after it shows zero.

Do you think the shut down was because of one of the cell packs hitting 3.0v or lower and were you watching it on TM-SPY or the dash?

 

[Rocky_H]

Any clue on why it didn't let you use more of the 4kWh?

As has been pointed out before, that's probably because it's supposed to be an anti-bricking reserve, not a driving reserve. The car is intended to shut down with some energy left in the pack to prevent people from permanently destroying their batteries.

 

[shred86]

I recently provoked a shutdown when i kept driving passed 0%. My car would allow me to take another 0.7 kWh after it showed zero usable left. 0.7 out of the 4 kWh buffer is not much and definitely doesn't make up for the missing energy to get the full rated range. SO be prepared to have your car shut down soon after it shows zero.

Out of curiosity, when you were at 0% displayed, what was TM-Spy or Scan My Tesla showing you for "SOC UI" and "Nominal energy remaining"? Thanks again for testing this stuff.

As has been pointed out before, that's probably because it's supposed to be an anti-bricking reserve, not a driving reserve. The car is intended to shut down with some energy left in the pack to prevent people from permanently destroying their batteries.

While I agree with you the car is supposed to shut down with voltage left, it's not what we're necessarily talking about. I've already explained it once with sources but I have yet to see an explanation that says otherwise. I'll explain it again. In general, lithium-ions can not go below 2.5V, else they become unusable because you can't charge at those levels without compromising safety. This is where the term "brick" comes from, your battery turns into a brick. Lithium-ion batteries typically have a protection circuit from 2.6-2.9 volt where the battery will stop "working" (can't be used), which is this "anti-bricking buffer" so you don't get near the 2.5V level mentioned earlier. The higher your anti-bricking buffer is, the more "pad" you have to preserve the battery if it isn't charged for an extended period of time because you will slowly lose energy over time.

As it's already been proven, Tesla's appear to shut down the vehicle around ~3.0V. The range from 2.5-3.0V is what I would consider the anti-bricking buffer; you can't use it... because it's an anti-bricking buffer...

What we're talking about is another 4 kWh buffer that the BMS is obviously tracking because 1) it reports "nominal energy remaining" which has consistently shown is around 4 kWh at 0% displayed SOC, 2) it also reports "SOC UI" which corresponds to the amount of "nominal energy remaining" and 3) we have several examples of vehicles actually shutting down (or extremely close to) at 0.0 kWh remaining or 0% "SOC UI", and dozens of examples of vehicles driving 10-17 miles past 0% displayed.

We also have examples of vehicles shutting down a mile or two after 0% displayed, and this is what I'm curious about and David99 is providing some insight on with actual BMS data.

In no way am I suggesting to drive below 0%. I think it actually makes perfect sense you would put a pad on the bottom end, on top of the anti-bricking buffer, because the car becomes so power limited now safety becomes questionable. For example, driving 20 mph on a 65 mph freeway... probably not smart. Not being able to go up a hill, probably not good. Strong head winds or very cold weather with high energy draw... not good as well. So this buffer makes sense such that folks get a fairly consistent driving experience down to 0% displayed (still going to be slightly power limited as you get to those levels).

 

[David99]

Do you think the shut down was because of one of the cell packs hitting 3.0v or lower and were you watching it on TM-SPY or the dash?

In my experience it's not as simple as the voltage alone. I often hit 2.9 Volt when driving at low SOC but it doesn't shut down. Voltage highly depends on power load. When it's low and accelerating, it drops down to 2.8 or lower depending how hard you push. On top of that the warmer the battery, the less the voltage sags when drawing power. I believe the shut down point is voltage dependent of SoC, temperature and power draw. All these numbers combined matter.

Here is a screen shot from the relevant CAN bus data. BTW, battery temperature was 40 C / 108 F which is ideal to get the most out of the battery. The lowest Voltage was 2.88 and when it shut down it was 2.91