Decreasing rated range.

[tomas]

I don't think this is necessarily true. For instance, there is no way that I experienced 4% degradation 5 months and 7,000 miles after doing my first 100% charge in March. I have a B pack. When I max charged a few days ago, the display showed 289 miles but the car continued charging for a good 30-40 minutes after it hit 100%. That current went into the pack even though the miles didn't increase beyond 289, so there is more charged capacity than the display is showing. The first time I max charged in March, I could drive 11 freeway miles before the display dropped by 1 mile. After max charging a few days ago, I immediately lost range as soon as I started driving.

The algorithm seems to be pretty wonky and unreliable when it comes to determining actual pack capacity.

You need to watch number of kW during charging. That final 40 min on range charge is balancing and it is charging at very, very low rate. Algorithm has clearly changed over firmware releases but is not wonky!

- - - Updated - - -

At 24,000 miles and 2 years, on the original A pack, I get 255 range miles on a 100% charge. If I do a few 100% charge, more than 50% discharge cycles on a trip, I can occasionally see 256 range miles.

This is consistent for me. 18 k mi, A pack, 100% charge is 250 to 260 EPA rated. Not far off the original 265.

 

[Mnlevin]

My MS 60 has 32k miles on it. We just drove it to Western Mass from Ft Lauderdale Fla using the Superchargers all the way. I know that some of what I am going to say has to do with it being summer and warmer and wondering how it will effect the return trip early Oct. However I found that traveling highway speeds 65-73 mph I got within 5% of the rated range but I noticed that my Kwh/mi was lower as I drove north and was in more hilly terrain. (?) But I still get 200 miles on a full charge and 180 on a 90% charge. Over the 16 months we have had the car we have charged it to 90% almost every night and I do about 2 full charges per month, but when I do, I top it off in the morning and start my drive right after it gets full. I was told not to let the battery ever sit at 100%. Currently I left the car at the Albany airport. When I left last Tuesday it had 144 miles, but in checking my phone app, it is losing about 4 miles per day. Not worried I will be back there Wed night and have over 110 miles left to do a 55 mile trip. The Superchargers worked perfectly, in some places I was able to charge to 110% of what I needed to get to the next SC in less than 15 minutes. Got a full charge in 45 min at Savannah. All in all it it has been great.:biggrin:

 

[mknox]

So I'm trying to figure out what this all means. I'm now getting 214 Rated Miles at 90%. I used to get about 245 at 90% when the car was new(er). I usually charge to 70% and end the day at 30 or 40% and have maybe done 3 full Range Charges in 1 1/2 years. So maybe my pack is "out of balance" or maybe it's a firmware thing. But does all this mean my car still has the range (or most of it) that it did when new? How does this work? If I drive to 0 Rated, will the car continue on for 20 or so extra miles? Will my Wh/mi start to get lower (better) and I'll get my range back that way? It hasn't become a "problem" for me, but I am just curious as to what to expect if my range still is there, but just isn't showing on the battery screen.

 

[gaswalla]

So I'm trying to figure out what this all means. I'm now getting 214 Rated Miles at 90%. I used to get about 245 at 90% when the car was new(er). I usually charge to 70% and end the day at 30 or 40% and have maybe done 3 full Range Charges in 1 1/2 years. So maybe my pack is "out of balance" or maybe it's a firmware thing. But does all this mean my car still has the range (or most of it) that it did when new? How does this work? If I drive to 0 Rated, will the car continue on for 20 or so extra miles? Will my Wh/mi start to get lower (better) and I'll get my range back that way? It hasn't become a "problem" for me, but I am just curious as to what to expect if my range still is there, but just isn't showing on the battery screen.

I used to charge to 70% also and had ranges like you mention. My service center said balancing only occurs at 90+ percent and asked me to charge to 90 for 6 weeks. My range at 90% went from 212 to 228 over a month. Try it out.

To answer your question. Your battery is out of balance, and when it goes to zero, you'll be stuck.

 

[AmpedRealtor]

This is just my pet theory... In a perfect world, the range algorithm would be 100% correct. Assuming a perfect battery, that means 265 miles of rated range and the car stops moving when you hit zero. This reflects a perfect range calculation from 100% to zero. The range algorithm only knows the endpoints of the battery by charging to 100% and then driving the car until it is completely discharged and stops moving. At that moment, the algorithm will be very accurate because it knows where the real zero is and where the real 100% is. But nobody drives that way.

If the algorithm knows where the top is, but doesn't know where the bottom is, it makes sense that zero is not really zero. When my algorithm drifts out of balance and shows 289 miles instead of 301 miles, I'm pretty sure that what's missing will magically appear as being able to drive 12 miles past zero. Again, just my pet theory, but Tesla has said nowhere publicly or in writing that there is any reserve range past zero. In fact, if you ask Tesla, they tell you that zero is zero and to not count on any buffer capacity. I think the perception of a reserve past zero is nothing more than a symptom of an inaccurate range calculation where whatever appears to be lost is still in the battery and can be driven past zero.

 

[Klaus]

Agree 100%!

All that agonizing about the (generally) few single-digit mile discrepancies at the top end of range assumes that the algorithm is much more perfect than it can possibly be. Tesla has done a marvelous job with range estimation, but it's an estimate. Just as others have reported, I've seen days when I start driving and my range doesn't drop for several miles. Other days it drops right away. This is in California, with pretty consistent summer temperatures in the morning. What happened to my battery between those days? I'm pretty sure nothing, just the estimation algorithm thinks different The charge stop point anywhere below a full charge also has to be an estimate.

mknox's range drop may be another issue, but I'd like to know how far he can really drive with his diminished range estimate. Might be worth checking into a detailed battery health diagnostic to make sure one of his modules isn't acting abnormally.

 

[badgerlake]

After reading this thread, I decided to do a 90% charge (normally do 60% each day and only drive 30 miles/day) and see what I would get. I am an early VIN (1776) but only 12k miles and have a P85. Not sure I like my results and not sure this can all be explained by algorithms and balancing, but I only have 204.7 rated miles at 90% (monitored closely via VisibleTesla).

 

[apacheguy]

All that agonizing about the (generally) few single-digit mile discrepancies at the top end of range assumes that the algorithm is much more perfect than it can possibly be. Tesla has done a marvelous job with range estimation, but it's an estimate.

Not doubting that there is inherent uncertainty in the range calculation. But if it is so uncertain, then why don't we have any D packs reporting less than 250 miles on a range charge? If it is as simple as you make it out to be then there shouldn't be discrepancies between the various revisions of the batteries. The same uncertainty should exist in the measurement of all packs.

After reading this thread, I decided to do a 90% charge (normally do 60% each day and only drive 30 miles/day) and see what I would get. I am an early VIN (1776) but only 12k miles and have a P85. Not sure I like my results and not sure this can all be explained by algorithms and balancing, but I only have 204.7 rated miles at 90% (monitored closely via VisibleTesla).

Seems low to me. My 80% = 200 rated.

 

[Klaus]

Not doubting that there is inherent uncertainty in the range calculation. But if it is so uncertain, then why don't we have any D packs reporting less than 250 miles on a range charge? If it is as simple as you make it out to be then there shouldn't be discrepancies between the various revisions of the batteries. The same uncertainty should exist in the measurement of all packs.

I'm not making anything out to be simple ;-) I'm saying it's more complicated than relying on a single number that we don't know how it is being derived.

One possible explanation is that that the range estimation is derived from the cell or pack voltage and the newer pack design may retain a slightly higher voltage after charging is finished. Or I may be completely off the mark with that guess ...

What I'm certain of is that measuring available energy stored in the battery is extremely complicated, and even integrating voltage * current over time during charging wouldn't necessarily give an accurate result because of the chemistry involved as well as inherent losses in the storage process. Personally, I am extremely satisfied with the way Tesla provides a reasonably accurate and reproducible estimate, such as it is. For reference, we also drive a Leaf with the extreme opposite in range estimate accuracy ...

 

[Gear]

Not doubting that there is inherent uncertainty in the range calculation. But if it is so uncertain, then why don't we have any D packs reporting less than 250 miles on a range charge? If it is as simple as you make it out to be then there shouldn't be discrepancies between the various revisions of the batteries. The same uncertainty should exist in the measurement of all packs.

Because they're newer?

 

[apacheguy]

Because they're newer?

Well, yes, of course but that would imply degradation or cell imbalance is the cause. Klaus was saying there is uncertainty introduced in the measurement of pack voltage and capacity. I said, ok, but if that true, then by extension we should see some (not all or most, but some) D packs getting 250 or less. Alas, this is not the case.

I have no doubt that uncertainty exists in the way rated range is computed, but I still think we are seeing other effects at play.

 

[Klaus]

Well, yes, of course but that would imply degradation or cell imbalance is the cause. Klaus was saying there is uncertainty introduced in the measurement of pack voltage and capacity. I said, ok, but if that true, then by extension we should see some (not all or most, but some) D packs getting 250 or less. Alas, this is not the case.

I have no doubt that uncertainty exists in the way rated range is computed, but I still think we are seeing other effects at play.

You keep (slightly) misunderstanding and/or misquoting me. I didn't say that there is uncertainty in the measurement of pack voltage. I am saying that available pack capacity (energy) is difficult to determine and that the range display is an estimate for that available energy. Not being a battery expert by any means, but knowing physics and chemistry to some degree, I'm convinced that the least significant digit (i.e. the individual miles of estimated range) is of doubtful accuracy. Many of us have experienced that with a firmware update where all the sudden the estimated range was different than before, while the battery remained precisely the same and its state of charge mostly the same, save some vampire draw.

Regarding the D packs, it could be that they have better cells, better battery management systems, or whatever. The fact that these newer packs tend to give higher range estimates may reflect that the range is actually better, or is better preserved compared to older generation packs, but it could also be that the estimate ends up being more optimistic. The only way to know with reasonable accuracy would be to run down each pack to the low cut-off voltage and measure the energy extracted. Even that depends on the rate of discharge, i.e. hypermiling or lead foot.

I didn't read all the relevant posts, but most of the time owners seem to be reporting the high end (i.e. 90% and "100%") range estimates, and not the actual range.

Again, with all that complexity, I'm very impressed that Tesla manages to give is such a reliable range gauge. A lot of R&D must have gone into that estimation algorithm.

 

[Gear]

Well, yes, of course but that would imply degradation or cell imbalance is the cause. Klaus was saying there is uncertainty introduced in the measurement of pack voltage and capacity. I said, ok, but if that true, then by extension we should see some (not all or most, but some) D packs getting 250 or less. Alas, this is not the case.

I have no doubt that uncertainty exists in the way rated range is computed, but I still think we are seeing other effects at play.

Firstly, of course the D packs are going to be an improvement. That's how progress works. Secondly, my point was that they're newer, not that they're a redesign. The average D pack would obviously have fewer miles than the average A pack, and therefor less chance to become imbalanced. Finally, there are enough people who are doing deep cycles on their A packs and still have high rated range numbers that I think you and a few others are worrying about nothing. Stop worrying so much and just enjoy the car.

 

[tomas]

Firstly, of course the D packs are going to be an improvement. That's how progress works. Secondly, my point was that they're newer, not that they're a redesign. The average D pack would obviously have fewer miles than the average A pack, and therefor less chance to become imbalanced. Finally, there are enough people who are doing deep cycles on their A packs and still have high rated range numbers that I think you and a few others are worrying about nothing. Stop worrying so much and just enjoy the car.

This is not about averages, it's about clear trend in reporting that many A packs seem to report lower range @ 100% and few or no D or later packs do. Age is no longer relevant, as there are D packs with many more miles and roughly same chrono age as A packs. As for me, my A pack was showing low miles @ 100% after almost a year of 70% charges, which supposedly do not balance. After firmware updates (currently 5.11) and return to frequent 90% charges to balance, I'm back to high 250s @ 100%. Beginning to suspect it's less that A packs degrade, more that they imbalance easily.

suggest A owners charge at 90%. Not once, not twice, but for a month. Then see what you've got.

 

[rlang59]

I used to charge to 70% also and had ranges like you mention. My service center said balancing only occurs at 90+ percent and asked me to charge to 90 for 6 weeks. My range at 90% went from 212 to 228 over a month. Try it out.

To answer your question. Your battery is out of balance, and when it goes to zero, you'll be stuck.

I can confirm seeing the same thing with respect to charging below 90% then going back.

 

[Darth Fedor]

But after charging to 90% for a month do you go back to what you were previously charging it at? When I first got my MS60 July 3rd it was placed at 90%. I left it there until roughly 2 weeks ago, where now I charge to 80%.

Should I go back to 90% at all times or keep it at 80%? What's the right % people?!?!?!?!

 

[WarpedOne]

Imbalance does no damage to the battery.
Always charging to the 90% does more damage than always charging to 80%.
When you see drastic drop in estimated range (more then 5% total range i.e more than 15 miles) you do few consecutive range chargers. And then return to 80% or even a bit less depending and usual range demands.

Range estimation is range ESTIMATION, that must always err on the safe side i.e. report less than the real number.

 

[tomas]

But after charging to 90% for a month do you go back to what you were previously charging it at? When I first got my MS60 July 3rd it was placed at 90%. I left it there until roughly 2 weeks ago, where now I charge to 80%.

Should I go back to 90% at all times or keep it at 80%? What's the right % people?!?!?!?!

Who knows but suggest 90% at least once a week and more if range seems to ebb.

 

[rlang59]

But after charging to 90% for a month do you go back to what you were previously charging it at? When I first got my MS60 July 3rd it was placed at 90%. I left it there until roughly 2 weeks ago, where now I charge to 80%.

Should I go back to 90% at all times or keep it at 80%? What's the right % people?!?!?!?!

You are going to get all kinds of opinions on this and many of them will be based on assumptions. The only real answer is charge to what you need.

 

[ckessel]

Imbalance does no damage to the battery.
Always charging to the 90% does more damage than always charging to 80%.
When you see drastic drop in estimated range (more then 5% total range i.e more than 15 miles) you do few consecutive range chargers. And then return to 80% or even a bit less depending and usual range demands.

Range estimation is range ESTIMATION, that must always err on the safe side i.e. report less than the real number.

As I noted before, I have 26k miles on my A pack and my range charge is 253 and my 90% is 226. I've range charged a few times over the last year. At one point, I was charging to about 70% or 80% (don't recall) to "be good to the battery" and only did that for maybe a month because I found it annoying. However, it did seem like my estimated range dropped decently even after I went back to always charging to 90% and range charging a few times.

To me, it really doesn't matter if the loss is real or just estimated because either way it's range I can't use. If I leave the house with 200 estimated miles, I have to believe it's really 200 and plan accordingly. It of no value to me if it's secretly 220 due to estimation errors.

At this point, I'm on pace for 20% loss in 100,000 miles. I guess that's ok since it's more or less what Tesla originally was guessing. It's unsettling though to see later packs, ones with as many or more miles, showing substantially better max charge.