40kwh Battery Degradation?

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.

mbergman | November 8, 2013

Matthew98, that can only be done once, right? How about 3 or 4 years later, when the battery has again lost an unacceptable amount of range?

And I am sure that this is also a problem with some 60/85 batteries, and their owners' don't have this relatively inexpensive, but still expensive, option.

I was told by my local service manager when I asked about my apparent range loss (slightly over 1% for each 1000 miles of driving) that I was not the first to express concern about this.

After an engineer in Fremont examined my logs, my service mgr was told that my battery was operating within the expected range. No further explanation was offered. He said he would escalate my concern to the next level and I expect a response sometime next week.

At this rate I will have lost 50% of my usable range in 4 years. Certailnly not what I had expected or was led to believe.

If Tesla dismisses owners' concerns regarding this rather fundamental issue, I do not have a lot of hope for the company's future.

Chuck Lusin | November 8, 2013


10K cost just to upgrade an old pack. If I had to replace my pack, I would also want a new one first and possibly a larger one.

The S40 started with 145 so to go to 188 (+43) for 10K, I don't think that is a good deal.

Mathew98 | November 8, 2013

Perhaps I just don't get it. You'll be unlocking the rest of your battery pack. You're not getting a refurb pack. It's your own pack that you've been driving.

I think all this degradation gloom and doom maybe premature. I received the 5.6 updates two nights ago. One of the specific release items mentioned that the algorithm for the range calculation has changed again. Speculations from other threads also alluded to the algorithm changes between the version have accounted for much of the "loss of range" since V4.0 instead of real loss.

My S60 used to have 188 miles ranges after a 90% charge. Now the same charge shows 178 miles after 5 months and two software upgrades. I'm sure there's some real battery degradation in between. However, my range has remained the same for the last two months since I programmed the schedule charging to end right before my commute to work each morning.

BTW, 5.6 sleep mode pretty much addressed the battery drain issue with 1 mile loss per 24 hours.

mmm | November 8, 2013

In CT, the morning charge is now only reading 128, it has dropped 2-3 miles per month since getting the car in early June. I hope it levels off soon!!

Chuck Lusin | November 8, 2013

In my case, it is not a software range calculation. My car started with version 4.5 and has three minor upgrades to the final release of 4.5.

Maybe Tesla could randomly remove the 72% limit, so the pack could receive a full charge. Just a thought!

Also if everyone is losing 1% per 1K miles, at some point the pack will have to be replaced.

So is the S40 warranty 100K or 125K miles?

eAdopter | November 8, 2013

I would consider paying an upgrade fee if TM hadn't reneged on their promise to offer an Extended Warranty for owners in my state (WA). For me, owning a car with such expensive parts isn't a viable financial risk. Reliability of my car has not been good, and I don't want to be paying for parts and service when it ages beyond 50k miles.

It's a personal financial decision, and I understand others will need to decide for themselves.

I agree with you. The gloom and doom may be premature. I hope you're right.

An open question to all 40 owners:
If the car loses an average of 2 miles of range per thousand miles driven ... when is it no longer viable transportation for you?
(of course, answers may vary)

Chuck Lusin | November 8, 2013

A quick number for me would be 80-85, I could still use it for work, but it would kill any weekend micro trips. Dam, that is just years away! I'm driving about 1K miles per month, and the car is just about 6 months old.

eAdopter | November 8, 2013

@Chuck +1
I hope this trend doesn't continue. I was planning to keep the car for eight years, but that's now very doubtful.
The MS is by far my favorite car and I enjoy it daily. I'll be disappointed if forced to sell it back to TM.

Chuck Lusin | November 8, 2013

Call me cheap, but I was hoping like 10 plus years. I was thinking that the drive train, was more like an electric diesel locomotive requiring minimal maintenance. But then I have Ryobi Lithium batteries, that are totally dead, when I made the reservation for the Model S.

eAdopter | November 8, 2013

Sorry, Chuck, but I can't call you cheap. You're smart and frugal. Keeping a car tens years is a great way to make the cost/benefit calculation work for an expensive car.

Mathew98 | November 8, 2013

I wonder what label you have for someone striving for 15 years of MS ownership?

BTW, I missed out on the boat for S40 so I had to settle for the S60 instead...

bish | November 8, 2013


10 years? That's all? Before I got my MS, I was driving a 1995 Dodge Intrepid with well over 300,000 miles. With some TLC, I hope my MS will get me to at least 200,000 miles.

Chuck Lusin | November 9, 2013

Thanks everyone, Yes let's hope for a long life! Both us and the cars.

MS-lover | November 9, 2013

from my reading and experience with 2 leafs and our MS, the first year you can expect 6% reduction in capacity (may 4.5% in the first 6 months) followed by about 3% per year after that . I think most of what is written here follows the first year pattern. Our course the leaf does poorly compared to the MS in warmer environments.

eAdopter | November 9, 2013

I wish you the best with a 15 year plan, but some of the MS technology may be completely unusable by then.

For example, will 3G and 4G still be available?

Also, I think manufacturers are only required to supply parts for ten years. What happens in year 11 if a new screen or dashboard is needed? I'm not sure these are parts I'd want to retrieve from a salvage yard.

Due to things such as low volumes and technical constraints, I doubt non-OEM manufacturers will make/remanufacture parts.

These are some of the reasons I decided to keep my MS only while under warranty.

Today I'm writing this on a iPad, not a five-year old Pentium via AOL dial-up modem.

Chuck Lusin | November 10, 2013

OK, here is some data from my last little trip.

I started with a full charge of 135 (rated). So when I got home the, since last charge stats are 122.6 Miles, 35.4 kWh, and avg 289 Wh/mi. The Rated range was down to just 6 miles left.

Now for the math part, here is what I was thinking. Rated is calculated at 300Wh/mi so with 6 miles left I still had 1.8 kWh left, which gets me a total of 35.4 + 1.8 = 37.2 kWh, and the hidden amount of 2.8 kWh or 9 miles under zero, assuming zero vampire drain. Version 4.5 (1.33.61) Total trip time was 8 hours, 2 hours driving and 6 hours sitting. I found a thread that stated the vampire drain at 4.5kWh per day, so 4.5 / 24 * 6 = 1.125 kWh. This works out to 2.8 - 1.125 = 1.675 kWh or 5.6 rated miles below zero. Temp when I arrived at home was 65 degrees F.

The weird part is that we charge to 72% which should be 43.2 kWh, so maybe 1.675 + 3.2 kWh or 8.9 miles under zero.


The car is just about 6 months old (5 more days) and 6,400 miles, and of course a 40/60.

Chuck Lusin | November 10, 2013

OK after a 72% charge, from all the way down to 6 miles rated range last night, now the rated range is 136. Not really different from the 135 yesterday.

Just testing some theories.

Chuck Lusin | November 11, 2013

Last night I charged at 5A 245V and today I'm showing a 133 Rated (just the vampire drain).

Any other thoughts?

Jewsh | November 11, 2013


The later firmwares have become much more realistic about range. The earlier, higher numbers could be considered fairly optimistic... It's entirely possible you've lost a tiny fraction of range or even nothing at all.

Brian H | November 11, 2013

But many playing with coasting etc. are getting wh/mi in the mid-200s, and have switched to Ideal display to better reflect what they're getting.

mbergman | November 12, 2013

I may be missing something obvious here, but I don't really understand the theory that apparent battery degradation is due to a revised method of calculating rated range.

If I am not mistaken, the epa rated range for 60/80 batteries has remained constant since the introduction of the S. It seems extremely unlikely to me that new owners would quietly accept the fact that their brand new cars cannot charge to the advertised epa rated range, which would be the case if the drop in fully charged range is due to software revisions.

If drops in fully chargerated range occur immediately after software revisions, it seems much more likely to me that the algorithm for calculating battery soc was revised to improve accuracy.

And by the way, @jewsh, until the recent drop in temps here in NY, I always exceeded the rated range without any effort.

So what am I missing?

Brian H | November 12, 2013

The only reason Max Range would drop after update is if the buffer was increased, AFAIK.

Chuck Lusin | November 12, 2013

I have been on the same software version since July 28 version 4.5 (1.33.61). Use to charge to 147 rated, now 133.

Longhorn92 | November 12, 2013

I was at 144-145 rated miles originally, now typically at 138-139 rated miles at time charging ends. Every once and a while, it only charges to 135-136, but that is usually when it doesn't need to charge much (already at 125+ when I plug in). I have been on v4.5 (1.33.61) since 7/27.

eAdopter | November 12, 2013

@mbergman @chuck +1
My range has dropped from 147 to 137 while on the same minor version of 4.5. The timeframe was a little more than three months due to receiving a new battery in late July. To be fair, it's colder now so that may account for some of the loss. TBD next summer...

makemeupkc | November 12, 2013

I have about 14k miles on my car since June 5. When the car was delivered to me my range was about 147 miles of range. 5 months later, I only get 129 miles of range. Have anyone else experienced the same amount of decreased range?

mrspaghetti | November 12, 2013

Can you guys please report ideal rather than rated so we can compare apples to apples?

makemeupkc | November 12, 2013

San Diego, Ca ..range between 59° to 75°

Chuck Lusin | November 12, 2013

Sure, 133 Rated = 154 Ideal.

Koz | November 12, 2013

Full charge rated comparison is just as good an apple as comparing full charge ideal. They are both based on fixed metrics, just different metrics.

mbergman | November 13, 2013

I've gone from 141 +-1 to 130 +-1 rated. (129 this morning.)

mrspaghetti | November 13, 2013

@Koz - Full charge rated comparison is just as good an apple as comparing full charge ideal. They are both based on fixed metrics, just different metrics.

That is not correct in my understanding. Ideal is a simple conversion of battery state-of-charge to a mileage number, without taking into account your prior driving or any other factors. Rated tries to account for many other variables.

Mathew98 | November 13, 2013

@eAdopter | NOVEMBER 9, 2013
"I wish you the best with a 15 year plan, but some of the MS technology may be completely unusable by then.

For example, will 3G and 4G still be available?"

I have been using my 4G MIFI router for over two years. Now I actually get to use it to tether to the MS with V5.6. I'll upgrade the MIFI router to whatever latest and greatest technology when the time comes for replacement. No changes will be needed for the MS.

I do agree with you that technology will get outdated rather quickly. However, software will be continually updated for the MS so that's covered.

The introduction of other features this summer are certainly nice to have but none that I needed as an experienced driver. I would not pay for retrofitting to any of the hardware anyway.

For those who like to get a brand new car every 3-5 years to avoid dealing with repairs and play with the latest features, all the more power to them. I'm sure if a real leasing program is available, sales of the MS will at least double.

For me, I like to keep my cars for the long haul and maximize the value of the cars. The depreciation of the car take the biggest hit during the first 4 years of it life. With the low maintenance of the MS, I may even keep it longer than 15 years...

robgoodin | November 13, 2013

My Rated range has decreased from 144 to 133 over past couple of months. I feel this is not actual battery degradation but the software Tesla is using to limit the 40kers. A bit of a disappointment since I wanted the 40 k battery due to 50% less weight then 60k battery pack. Now I have the extra weight of 60 K battery pack and a software limiting program that may be using faulty data and assumptions for limitations.

fluxemag | November 13, 2013

126 Rated, 144 Ideal. I agree that the last drop from 134 to 126 rated was due to moving to 5.6, but prior to that I had the same software revision, and lost 2 miles per 1000 driven just like the others. So at this rate, the car will have 0 rated range at 72500 miles. I do believe however that the degradation will taper off, despite the very linear trend I have now.

Chuck Lusin | November 13, 2013

This new range calculation looks to be more accurate.

Brian H | November 13, 2013

Rated doesn't use personal driving history. That's Projected. Rated originally used the 2011 EPA 5-cycle test range of 265 mi. as its base (for the 85). If they reserved more buffer below the 0 mile mark, that would come directly off the 265 AND the Ideal max of 300.

Tracking degradation would have to be done with a consistent max peak charge (i.e. before or after the changes).

Koz | November 13, 2013


My understanding is that it is based on the state of charge and the mile/kwh calculated by the EPA and used in the cars rating (rated miles) along with a fixed buffer reduction factor. Since our 40's are really 60's with a software tweak, I'm guessing since 4.5 we start with 1/3 of the buffer. The 60's start with zero buffer and it is built as the battery is drained. There is a thread that details this. Several drivers have run tests and calculated the reduction factor to build the buffer. I forget but I think it is about 6kwh that gets built up over discharge to zero miles rated. This allows for some additional driving below zero and is where our "missing" capacity from 4.5 went. The ~2kwh buffer baked into our 40's full charge equates to about 7 miles. This is about what my full charge rated miles dropped after the 4.5 update.

mbergman | November 14, 2013

@Koz, I'm not convinced that is the explanation.

First, some of us have always been on 4.5. While there have been one or two minor software revisions since I received my car, significant range loss has occurred after the last update.

Second, if I recall correctly, when RodandBarbara first discovered this through testing, they reported that the buffer, initially zero, was built up gradually when driving. Your theory would necessitate them always having starting off with a maximum range charge during their "investigations", and I don't remember that being the case.
I could be wrong, though.

murraypetera | November 14, 2013

We were told on the website before we ordered that the 40 would give us 135-145 miles per charge. If tesla decides to buffer some of that so they have fewer tow calls the. They need to give us more of the battery to use to give us the range advertised.

You cannot just start taking usable battery away after we have the car and expect us to just accept it.

Brian H | November 14, 2013

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

murraypetera | November 17, 2013

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.

mrspaghetti | November 17, 2013

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.

bish | November 17, 2013

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.

Brian H | November 17, 2013

Ideal or rated? Only Ideal counts.

eAdopter | November 17, 2013

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

Brian H | November 17, 2013

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

Mathew98 | November 18, 2013

@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...

ramtaz | November 18, 2013

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.

eAdopter | November 18, 2013

@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.