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40kwh Battery Degradation?

Has there been any official information about how battery degradation works on the software limited 60kwh battery? For example, if the software limits the battery to 2/3 of the capacity of the battery, there will be degradation. If the software limits to 40kwh, there should be no degradation.

How is it taken away? Just moved to the buffer, so you KNOW you're pushing it when you go "sub-0".

I have 5.8 and now my max charge is only 132 down from 145 when I got the car.

Tesla has silently reduced my range by 13 miles or 11.2% through software updates.

Toyota just modified my fuel gauge, now my idiot light starts blinking when I have 2 gallons left instead of only one. I think I'm going to sue them for taking away my range.

With 5.8, my last 2 charges maxed at 141 IDEAL miles. That is not just shifting the buffer. (160-141)/160 is an 11% reduction in charge capacity. That is a good size reduction for just 12,000 miles.

It would be nice if there a reading of the of the State of Charge in kW, not just in Ideal or Rated miles. Then we would know for sure if the range reduction is due to battery degradation, or a change in the algorithm used to calculate the range.

Ideal or rated? Only Ideal counts.

If you drive one, only rated counts because that's how far it will drive.

Wrong. Comparing battery charging levels requires a non-flexible measure. Only Ideal is standard, and hasn't been fiddled by updates, etc.

@eAdopter - Did you get your V5.6 or V5.8 update yet? The release note specifically mentioned better algorithm in calculating battery range. I infer this to the rate range and not ideal range.

So is seems the release note agrees with Brian H on this one.

Let's relax a little bit on the rate range.

My personal observation is that the latest 5.8 release calculation in range is more accurate than previous versions. For example, my most recent 23 miles commute actually used 26 rated miles.

The latest calculation is more accurate by about 6 miles. That is quite impressive with the way that I drive...

Just updated to software 5.8 , rated range is now 129 , on my limited 60kWh battery.
On delivery (May 2013) rated range was 147. The last full charge on Nov 17 , before software update
135 rated range.

@Brian H
Things such as battery charge are important to bloggers.
Range is important to owners/drivers.

I installed the software upgrade (.28) last night and lost another 3 miles of range. Dang! No wonder the stock is falling.

I went from a fully charged 129 rated at the start of the 5.8 update to 127 upon completion. Time to start emailing upper management, methinks.

I find it fascinating that the theory that rated range drops are due to tinkering with the way rated range is calculated has been repeated so often that it is now accepted as fact by many.

There has been a fairly consistent definition of rated range presented by Tesla reps, that being soc divided by a fixed number determined by the EPA to be typical energy usage per mile. It does seem that the rated range goes down faster than you would expect from that calculation while driving due to the gradual buildup of a reserve so that when you hit zero rated miles you are not dead in the water.

I have not seen any explanation as to why new cars would show the published, unchanged EPA rated range if this calculation has changed. Or course, it is an assumption on my part that they do, but I think it is a reasonable one.

As I believe I have stated earlier in this thread, it is my theory that, if anything has changed, it is that the algorithm to compute soc has become more accurate with software updates. Of course, all of this speculation could be put to rest if Tesla simply published definitions of rated and ideal miles, but I no longer expect that to happen.

With 4.5 I had a max filled range of 227 km (141 mi), as of 2 days ago when I got 5.8 (.22), my range dropped to 218 km (135mi) max.

I can only assume that this sudden drop is to do with the fact no longer lowers at highway speed, thus it must use more power to compensate for the increased drag.

In addition to this the car's vampire power drain has increased significantly from 4.5, in the past 36 hours the car has lost 24 km (16km/day or 10 mi/day) - I have not driven the car since Saturday 11pm.
Previously w/ 4.5 it was losing ~10 km a day.

I reset both consoles yesterday and the burn continues, I set "energy save" off and reset them again this morning and then set "energy save" to back on (it was not sleeping at all, instantly ready when I got in), hopefully that will activate the energy saving.

5.8 (v .22 at least) is not a good release at all...

On 5.8, I get 125 rated miles and 142 ideal. Not quite the 160 ideal promised.

The other variable is buffer (below 0). If that has been expanded, the only place it can come from is "off the top". That would represent no change in actual total charge, though.

On my 40/60, prior to 5, I lost 8 miles from 9PM to 12PM the next day.

After 5.8, I lost 4 miles from 4PM to 12PM the next day.

My rated range right after charging went from 140 to 135. When the car was brand new, the rage was 141.

I have 1527 miles on the car after 6 months.

Your ideal range readout is more accurate when considering battery performance. My car is a year old this week and the recent update coincided with its anniversary so I monitored the charging closely to see how things changed over the past year.

Keep in mind that I have a P85. When new, the car had an ideal range with full charge of 302 miles. Friday I did the same charge to see how things were going and I topped off at 300 ideal miles. I was quite impressed.

Rated miles and projected miles are calculated differently because of the firmware updates so they are not the best indicator for evaluating overall battery performance. They have been working on refining the readouts.

The point I'm trying to make is that you want to compare apples to apples and the ideal range setting is best tool we have for the job that I have found.

I understand the apples to apples comparisons and why some prefer to measure Ideal Range.

However, I'm much(!) more concerned with Rated Range performance than battery performance.

If after a few years the Ideal Range is 300 miles and Rated Range is much less, isn't Rated Range the measurement that will have owners contacting TM to complain?

In other words, I think owners are more concerned about how many miles they can drive. The Ideal Range number is interesting, but not very relevant to me.

@eAdopter - You do have valid concerns about the Rate range. On the surface it does seem like a big drop since your S40 delivery.

OTOH, wouldn't you prefer more accurate Range based on your personal usage versus a more inflated number?

Whenever I ask my wife how long it'll take her to finish getting ready, she would reply in 10 - 15 minutes. We never manage to leave the house for at least another hour after her response.

What kind of answer would you like to hear? Imaginary but sounds good on the surface or realistic but not what you want to hear?

To put it simply, I only care about how far I can drive the car when it's fully charged.

Details regarding the algorithms or battery health aren't usefull or meaningful to me and I couldn't care less about them. I'm not even curious.

I only care about the bottom line: How far I can drive on a full charge.

Precisely why I purchased the 40 kWh battery , it was advertised at 160!
I have lost 18 miles of range in six months , 7500 miles.
May 29 , delivery was at 147
At this rate , it will be at 111 by Spring.

A change in Rated Range which is not matched by a change in Ideal Range is not a change in reality, only in the car's interpretation of a given charge, or even a change in the charge reported.

I was at 133-135 Rated on 4.5 and now I'm still at 133 (just after charging, or 151 Ideal) in 5.8.
I really think that my true range is about 129 at 289 Wh/mi.
If Ideal is 300 Wh/mi, why can I only go 129 miles at 289 Wh/mi?

Ideal range for S40/S60 is about 270 Wh/m. Ideal for S85 is 300 Wh/m.

Try to match the battery usage and look at the instant mileage graph and you'll see parity between range and ideal miles at 270 Wh/m.

I think the bottom line is that even driving below 300Wh/mi, I'm not going to get even the rated range of 126 miles, let alone ideal. And neither is anywhere close to 160 miles. It's not a huge deal for me at the moment, but if this continues it will be. And like eAdopter, I couldn't care less about anything but the actual range I can drive the car. Which as an owner of one, I can say from experience what that is. At 300Wh/mi I can drive about 115 miles.

@fluxemag -- I'm seeing almost the same as what you're getting. I think we can't go further than 115 or 120 miles at 300 Wh/mile. Which is confounding because at 72% charge cap for the 60kWh, that amounts to: 43.2 kWh, or 43200 Wh. So one would think that you should be able to drive: 43200 Wh/(300 Wh/mile) = 144 miles. But in reality, we're seeing 25 to 30 miles less than that. My lifetime average of over 5000 miles when I go to the Energy Settings is 316 Wh/mile. Even at that, I should be able to drive over 136 miles. But the cap is 20 less than that on real results.

The lack of transparency into this discrepancy is very frustrating and concerning to say the least. It allows the company to always attribute the falling This could be fixed if Tesla would display a "Remaining kWh" metric in addition to rated+ideal miles, so we could see how much charge we have left.

Don't forget about the 15 miles reserve once the car goes below zero.

Arg, sent my 2nd paragraph prematurely. Should say:

The lack of transparency into this discrepancy is very frustrating and concerning to say the least. It allows Tesla to always attribute the falling numbers to refinements in their algorithms, where it could also be battery degradation. We can't tell because we have no window into the actual charge level. This could be fixed if Tesla would display a "Remaining kWh" metric in addition to rated+ideal miles, so we could see how much charge we have left.

After the latest update 5.8 My S has dropped from 139 rated to 131 in about two weeks. I was at the service center yesterday and they told me the drop was the way I drive the car. This I don't believe to be correct.. The car has 5000 miles and the kwh used average 301 for the life of the car over 6 months. Why the drop in such a short time? The only real answer I can surmise is the Elon added to the range past zero. Maybe 10 miles that would account for the loss. Several from Tesla ownership have told me that if you drive like a little old lady the mileage will come back. I find this to be not true.


Are you talking about rated range or ideal range? Also, from the numbers you've given I doubt you're doing max range charge. Rated range changes all over the place for me. They're doing a different calculation for rated range now. If you really want to know, do a max range charge with ideal miles set. See how that compares with stated max ideal range stated for you battery pack.

Also, has the weather changed in the last two or three weeks?


The 40's don not have the max range charge option, we can only charge to 72%, that is our max (and my standard charge).

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