Decreasing rated range.

[tomas]

It is. You charge the car 100%, you drive it to the end and look at the trip meter's energy consumption.

No, in most cases it is not. It would only work if you charged to 100%, immediately set off, drove til exactly empty (to avoid distortion from vampire loss) and timed your zero to happen in safe proximity to charger. A lot of trouble to get just another data point that will probably not prove or change anything!

there have been a few real incidents posted of true rated range aberrations, but most of us are in a very narrow 5% +/-2 range. We must be sweating bullets because we like to, I guess.

 

[scaesare]

There are 3 things in play when it comes to range:

1) Actual range loss due to battery degradation- This is to be expected as per Tesla. It's understood to be most significant early on in battery life and then taper more gradually over the remaining life of the cells.

2) Temporary range loss due to pack imbalance- This is a known issue with series style battery packs such as Tesla's. The loss is real in that the total pack range is diminished until the pack can be rebalanced. It's understood that the Model S can re-balance the pack, but when and under what circumstances is not completely known. Once the pack is in balance the range is restored.

3) Apparent range loss due to algorithm inaccuracy- This is simply visual inaccuracy due to the fact that "at rest" estimates of battery capacity are calculations, with a number of variables (temp, cell age, etc...). The greater the extremes of charge and discharge, and thus the larger sampling extent, the more accurate the algorithm may be. The converse is that shallower charge cycles result in less accuracy.


As I've written before regarding issue #3, because of the evidence supporting the concept of shallower charge cycles being better for the pack, I don't believe it's worth attempting to charge or discharge to greater levels than necessary just to see a different number on the dash is worth it.

With issue #2, the range loss can impact a person if they really need it, even if for a single long trip where you are really pushing your range limits. If you really are down to counting a few extra miles to make your journey it may be worth-while to try and force a pack rebalance. Anecdotal evidence suggests this happens at the tail end of range-charges (where the last percentage point of charge can take an hour or more). As range charges are harder on the battery, I recommend this only if you have no other alternative. It's uknown to what extent the Model S attempts to balance at <100% charges

For issue #1, it's a fact of life with Li-ion cells. However, given that deeper carge cycles, time at 100% charge state, and high temps are all hard on the battery, I make the above recommendations with the aim of minimizing this real degradation.

 

[Madartist]

There are 3 things in play when it comes to range:

1) Actual range loss due to battery degradation- This is to be expected as per Tesla. It's understood to be most significant early on in battery life and then taper more gradually over the remaining life of the cells.

2) Temporary range loss due to pack imbalance- This is a known issue with series style battery packs such as Tesla's. The loss is real in that the total pack range is diminished until the pack can be rebalanced. It's understood that the Model S can re-balance the pack, but when and under what circumstances is not completely known. Once the pack is in balance the range is restored.

3) Apparent range loss due to algorithm inaccuracy- This is simply visual inaccuracy due to the fact that "at rest" estimates of battery capacity are calculations, with a number of variables (temp, cell age, etc...). The greater the extremes of charge and discharge, and thus the larger sampling extent, the more accurate the algorithm may be. The converse is that shallower charge cycles result in less accuracy.


As I've written before regarding issue #3, because of the evidence supporting the concept of shallower charge cycles being better for the pack, I don't believe it's worth attempting to charge or discharge to greater levels than necessary just to see a different number on the dash with issue is worth it.

With issue #2, the range loss can impact a person if they really need it, even if for a single long trip where you are really pushing your range limits. If you really are down to counting a few extra miles to make your journey it may be worth-while to try and force a pack rebalance. Anecdotal evidence suggests this happens at the tail end of range-charges (where the last percentage point of charge can take an hour or more). As range charges are harder on the battery, I recommend this only if you have no other alternative. It's uknown to what extent the Model S attempts to balance at <100% charges

For issue #1, it's a fact of life with Li-ion cells. However, given that deeper carge cycles, time at 100% charge state, and high temps are all hard on the battery, I make the above recommendations with the aim of minimizing this real degradation.

Thanks for the excellent summary of the factors affecting range degradation. It is what I've learned as well from reading through the various threads about this subject. Based on what you've said, it sounds like you are in favor of setting the charge limit at 90% and charging every night. Is that your personal practice as well?

 

[scaesare]

Thanks for the excellent summary of the factors affecting range degradation. It is what I've learned as well from reading through the various threads about this subject. Based on what you've said, it sounds like you are in favor of setting the charge limit at 90% and charging every night. Is that your personal practice as well?

You are certainly welcome.

I actually only charge to 60-70% (depending on how cold the weather is) during weekdays as that's sufficient for my work commute and any evening driving I typically do. On weekends I charge to 90% as my needs are more varied, and I like to have the range for impromptu trips.

With Superchargers now being within a couple of hours of me on major routes out of town, I haven't range-charged in quite a while...

VisibleTesla makes all this a snap to set up to have happen automatically...

 

[hans]

It is. You charge the car 100%, you drive it to the end and look at the trip meter's energy consumption.

Does the trip meter energy consumption figure include vampire drain, HVAC, battery heating, and other misc consumption not related to driving?

 

[tomas]

Does the trip meter energy consumption figure include vampire drain, HVAC, battery heating, and other misc consumption not related to driving?

Lotsa people going to answer like they know. But unless tesla engineers hiding in here, we do not know.

 

[islandbayy]

My update;

43,000 miles on my car, 9,000 on replacement battery pack. Rated Range is 200. And that is charging from Charge Now to 100%.
Comparison: Original pack had 202-203 Rated at 34,000 miles when it kicked the bucket. Tesla insists nothing is wrong with the new pack.

 

[scaesare]

My update;

43,000 miles on my car, 9,000 on replacement battery pack. Rated Range is 200. And that is charging from Charge Now to 100%.
Comparison: Original pack had 202-203 Rated at 34,000 miles when it kicked the bucket. Tesla insists nothing is wrong with the new pack.

Assuming that you were at 34K miles when the replacement occurred, with over 26% additional miles on the replacement pack, what makes you feel that a 1-1.5% variance is indicative of a problem?

 

[FredTMC]

Perhaps. But I'm not willing to risk being stranded simply to get the number. It's certainly inconvenient at best. I would much rather tackle the issue via a sensible charging strategy. That is the reason why I posed the question.

Ive used this method to get an accurate assessment of my battery's total KWH output. This method is the best "true" method (IMO)

actually, it's not required to drive all the way to Zero miles left in order to get a good assessment. It's perfectly okay to end the excerise with a few miles left. For example, if the car is showing 6 miles of rated range left, then you can simply assume that you have an additional 2 KWH of remaining energy until you reach zero rated range. Simply add this final 2 KWH to the KWH expended on the trip meter.

 

[David99]

For issue #1, it's a fact of life with Li-ion cells. However, given that deeper carge cycles, time at 100% charge state, and high temps are all hard on the battery, I make the above recommendations with the aim of minimizing this real degradation.

Agreed. The best thing we can do is avoid things that we know cause faster battery aging. Everything else is something Tesla will optimize and improve.

- - - Updated - - -

Does the trip meter energy consumption figure include vampire drain, HVAC, battery heating, and other misc consumption not related to driving?

As long as you drive, everything is included. Once you park your car or it's just sitting there running the AC or heater going, it's not added. You will see the rated range go down of course, but it is not included in the trip meter energy consumption.

 

[islandbayy]

Assuming that you were at 34K miles when the replacement occurred, with over 26% additional miles on the replacement pack, what makes you feel that a 1-1.5% variance is indicative of a problem?

not sure I'm following you. at 34,000 miles on it, my original pack had 96.65% of it's original range. With only 9,000 miles on my current pack, the replacement, it has 94.78% of it's original range. My problem isn't the range per say. my problem is the rate at which the range is declining.
Original pack rated range declined at a rate of approx .2 miles per 1000 miles driven. in comparison, my current replacement battery is loosing range at a rate of approx 1.2 miles per 1000 driven. that is where my problem lies.


My math is not the best. if I screwed it up please correct me.

 

[tomas]

not sure I'm following you. at 34,000 miles on it, my original pack had 96.65% of it's original range. With only 9,000 miles on my current pack, the replacement, it has 94.78% of it's original range. My problem isn't the range per say. my problem is the rate at which the range is declining.
Original pack rated range declined at a rate of approx .2 miles per 1000 miles driven. in comparison, my current replacement battery is loosing range at a rate of approx 1.2 miles per 1000 driven. that is where my problem lies.


My math is not the best. if I screwed it up please correct me.

evidence is pretty conclusive that a) packs decline ~5% early in lifetime, b) then they stabilize and decline at very low rate, c) each pack is slightly different. You seem worried that new pack is slightly different from old and projecting linear decline. seems to me too early to be worried about too small a difference.

 

[bhuwan]

not sure I'm following you. at 34,000 miles on it, my original pack had 96.65% of it's original range. With only 9,000 miles on my current pack, the replacement, it has 94.78% of it's original range. My problem isn't the range per say. my problem is the rate at which the range is declining.
Original pack rated range declined at a rate of approx .2 miles per 1000 miles driven. in comparison, my current replacement battery is loosing range at a rate of approx 1.2 miles per 1000 driven. that is where my problem lies.


My math is not the best. if I screwed it up please correct me.

Is your pack really a new pack, or a refurbished pack?

 

[scaesare]

As long as you drive, everything is included. Once you park your car or it's just sitting there running the AC or heater going, it's not added. You will see the rated range go down of course, but it is not included in the trip meter energy consumption.

This doesn't seem to be the case at least initially after charging. If I trigger the car to "power up", by either starting HVAC preconditioning, opening the doors to put some stuff in the car, etc... the car counts the energy usage while it was there idle in my garage against the total energy usage on the trip meter. This is easy to see initially because the average after the first tenth of a mile is something ridiculous like 1,400 Wh/mi, os it's easy to see.

Of course as you build more milse up on your trip, that initial energy usage is averaged over the longer distance, so you don't see that spike as prominently, but I'm not sure that if I park again later in the trip and use a lot of energy while idle it's not represented... it just may be harder to see.

 

[liuping]

Just to throw another data point out there.

Tomorrow my car will be 1 year old, and I hit 20000 on the way to work this morning.

I also did a range charge last night (first in quite a while) as a data point. I got a pleasantly surprising 262 miles.

Most days I charge to 80% and drive to about 60%. I've done 10 Range charges total.

The very first range charge I ever did was 272 miles (one month after pickup @ 1732 miles), but the next one was 266 (2.5 months @ 5040 miles).

 

[scaesare]

not sure I'm following you. at 34,000 miles on it, my original pack had 96.65% of it's original range. With only 9,000 miles on my current pack, the replacement, it has 94.78% of it's original range. My problem isn't the range per say. my problem is the rate at which the range is declining.
Original pack rated range declined at a rate of approx .2 miles per 1000 miles driven. in comparison, my current replacement battery is loosing range at a rate of approx 1.2 miles per 1000 driven. that is where my problem lies.


My math is not the best. if I screwed it up please correct me.

OK, I see.. the concern is the rate of decline... is the rate of decline lessening at all after 9K miles?

My assumption is that this is a refurbished pack. And from those here who have had such pack replacements I believe that the stance Tesla takes is that you will receive a pack of comparable health/capacity.

Thus, I expect that the cells in the pack you got would have also already had ~34K miles worth of "wear" on them. Thus an additional couple of mile of degradation in nearly 10K wouldn't seem to be that out of the norm.

I also suspect that a refurb pack may present the car with an initial "learning curve" where the algorithm SOC estimate may need some time to acquire enough charge cycle sampling points to determine the actual capacity. This would make it appear the pack was rapidly losing capacity initially, whereas it may have been initial estimate error.

 

[walla2]

My pack boost experience is sadly over now. My range stayed up for 3 weeks but after three range trips seems to be back to about a 10% degradation at 10k miles. My real world trip revealed I have 66.8 kwh in my pack down from the original 74 or so available in the 85 kwh pack. The 66.8 / 74 is a 10% loss equivalent to the 10% rated range drop.

One confounder was that I was upgraded to .180 after my third range charge and that's when the range went back down so I can't say what really reset things. What I do see is that my pack is showing some real world degradation if it only has 66.8 kwh left in it.

 

[apacheguy]

Sorry to hear, walla2. It did seem odd to me that your MS regained so much range immediately after the tech visited. 67 kWh from full to empty is a bit concerning. Have you pressed that issue with Tesla? Rated range is based on calculation, but kWh used is based on measurement.

 

[walla2]

I haven't pressed the issue for now. Tesla has said the pack is healthy and that it is not something wrong with the pack. I will await their proposed fix (software) before asking for further evaluation.

 

[mknox]

I'm interested to know what Tesla does to determine pack health. Even if I had to pay for it, I think some sort of report directly from Tesla would be extremely useful. For example, it may be very beneficial to someone looking to purchase a used Model S.