Recent Articles Slamming Tesla for Battery Pack Issues

Recent Articles Slamming Tesla for Battery Pack Issues

I own Tesla stock and am a Model S reservation holder. I have noticed over the years several regular of online investment bloggers that consistently disparage Tesla as a company (e.g. Seeking Alpha, Motley Fool, Bloomberg). And more recently, (since the first deliveries of the S last week) I have seen several articles questioning "known" issues with the Tesla battery packs including implications that it will run down significantly after 100,000 miles and owners will need to spend $20,000 to buy a new battery, leading to a lower future resale value. The number of battery pack hit articles and the consistency of the language leads me to think that they might be coming from a Speaking Points memo. Any thoughts? Also what do you know about the battery pack charge issues? Has Tesla put out any official responses to these issues at all?

I know you guys are pretty connected and would love to get your thoughts.

Steve841 | June 27, 2012

Well I know nothing and don't claim to be any expert. But, Li Ion batteries go bad eventually. All batteries do. And, so do all combustion engines for that matter.

My hope is that an 8 year / unlimited mile warranty is good (Tesla still around and batteries actually making it that long) and there is no fine print hidden there somewhere.

Also, its my hope that Tesla will have progressed with newer battery technology and incorporate it into a replacement battery pack years down the road (pardon the pun) that offers even greater range and is reasonably priced.

Teoatawki | June 27, 2012

For Tesla's response, see the plug it in blog post.

As for battery life, the battery pack gradually lose capacity over time and charging cycles. You won't wake up some morning to find the battery has died. So, as long as the current capacity is sufficient for your needs, there is no reason you have to replace the battery pack.

Teoatawki | June 27, 2012


Edit feature, wherefore art thou?

Sudre_ | June 27, 2012

To answer your other question, I do think they have an agenda. It seems they take turns printing the same material. You can look at what some are invested in and understand why they trying to discredit Tesla. I recall one was heavily invested in lead acid type systems so he needs to destroy Li-ion because his choice is not looking like a good one.
They should already know their statements are misleading, if they did any research at all (like read the comments on the other guys article) they would have discovered answers to all their exaggerations.

Soflauthor | June 27, 2012

At the risk of sounding paranoid, it's very important for those holding significant short positions (or other competive positions) to dampen any broad-based enthusiasm for TM. After the generally rave reviews of the Model S in the automotive trade press this past weekend, its not the least bit surprising that factually-challenged articles appear in the financial blogs. For the "short" community (and others), rave reviews about the Model S are a very dangerous thing. They must be offset with negative comments, immediately.

Vic M | June 27, 2012

As an engineer with a lot of experience in testing Li-Ion batteries, I may have some useful comments here. Modern Li-Ion cells rate to about 500 full discharge cycles with a loss of about 10-15% capacity. Multiply that by miles per charge (300 in the 85 kW-hr case), and you can see the useful life of the pack with little degradation. This is why Tesla warranties the big packs for longer. So, the smallest packs are expected to have the biggest issues.

The good news is that I have personally cycled cells to 800+ cycles and though there is capacity loss, they still keep working nicely. I plan on at least 160,000 miles on my P85

ThorensP | June 27, 2012

Thanks for your post. That gives me a good sense of what I can expect for the first 150,000 miles. Do you have any data on what happens in the next 500 full discharge cycles? Does the loss continue at the same approximate pace or is there an accelerating drop off? The reason I ask is it seams like the longer the packs last the higher the resale value will be, which will impact market demand for the Model S, and things like lease rates (when lease programs crank up), etc.

phb | June 27, 2012

In the case of these investor blogs, any claims made without citation and any quotes given without citation should be immediately ignored as, at best, supposition and, at worst, outright self-interested lies. I would also be highly suspicious of any claim to technical expertise coming from investment "experts."

All Li-ion batteries degrade somewhat over time and all ICE vehicles lose power and become less efficient over time. New things work better than old, highly used things. This should not come as a surprise.

As to the edit feature, I asked several at Tesla for that at the Get Amped event over the weekend.

Timo | June 27, 2012

@akimball, All the different charts for different Li-Ion chemistries that I have seen show that loss is continuous and drop slows down, not accelerates. There might be some point where electrolyte between electrodes goes bad and kills the battery completely, but it's so far in the future that none of the charts show that. Not even those that show 2000+ cycles, which would be something like half a million miles it 85kWh Model S. By then you would want to have new battery anyway, and probably would get it as cheap as new set of tires if you get only 85kWh.

BYT | June 27, 2012

@phb, although I agree with you, many others are highly influenced by theses self proclaimed experts and therefor make lame decisions as such. As an investor I can't ignore the lies because I know the influence the bottom line regardless of how false and self serving they may be.

Vic M | June 27, 2012

@akimball and Timo

The data I have shows about 18% loss at 800 cycles. This is unlikely the same chemistry as Tesla is using (I have not found out what it is), and for lower peak currents. That said, the capacity loss should be quite muted for the large packs, and I fully anticipate that the battery will take me to the scrap heap (or museum!)

ddruz | June 27, 2012

Vic M, What constitutes a "cycle?" If you drive 30 miles then recharge in standard mode to 90% maximum as you might in a typical commuting day, what part of a "cycle" did you use? Does the fact that you used and recharged the battery at all count each 30 mile day as cycle, or since a full cycle might be 300 miles on an 85 kwh pack does each day count as 1/10 of a cycle, or is "cycle" determined some other way? We need to know what constitutes a cycle to make projections based on your numbers. Thanks.

Mark K | June 27, 2012

Its very simple:

Some folks in a position to benefit from negative news on TM did not get what they needed at launch.

So they paid for negative headlines to blunt the boffo success, and buy time to unwind their positions.

The transparency of the misdirection was palpable.

The headlines "Trouble ahead for TM" and others were crafted for alarm, yet the facts did not comport with the headlines.

The video on Bloomberg was also contrived to put a spin on everything said, by using staged reaction comments from the anchor. It was pretty embarrassing.

Look no further than the timing of the piece. The battery performance data has been an open book for half a year, but the headline appears right after TM hits the launch out of the park.

TM never hid the fact that all things wear out, including batteries. The responsible journalistic role would be to compare the maintenance costs relative to ICE cars. If you do, the Model S EV comes out a clear winner because it has far fewer parts, that last longer.

If you kept a Mercedes for 8 years, you'd already be 10-20k into maintenance costs. Even if batteries never got any cheaper (inconceivable), I can't imagine the eventual replacement cost being more than what you'd actually pay to keep your ICE premium sedan alive.

Example: two weeks after my Mercedes 4yr warranty expired, it was diagnosed with a "strut leak". The fancy computerized active hydraulic suspension that gives it amazing handling is very complex. Repair cost: $10,000.

The Bloomberg crew knew what they were doing. They clearly intended to miscast the facts, and went out of their way to do so.

Mike Bloomberg is a man I respect, but that news staff I can't. What was readily observable in this case demonstrates they dont have the ethical qualifications to rate as real journalists.

Whether you love or hate EV's, all of us have an obligation to tell the truth. Not half of it, but all if it. This crew did not.

One very positive sign: whomever paid for this wouldn't go out of their way to make stuff up unless they're worried that TM is the real deal.

To all the bums willing to lie to shackle us to the bad old days - be afraid. Be very afraid.

Physics cannot be bought.

Timo | June 28, 2012

@ddruz, "cycle" usually means from full to empty and back to full. Two half cycles is nearly same as one full, but in reality if you don't go from completely full to completely empty and back again it is less damaging to battery cells. Your 30 miles from 90% full 300 mile battery and then back to 90% is then a bit less than 1/10 cycle.

Vic M | June 28, 2012

A cycle is a full discharge. I am unfortunately not aware of how partial discharge will affect life, but the first assumption would be that partial discharges would result in correspondingly less degradation. I am not aware of too many great studies on partial discharge though.

Teoatawki | June 28, 2012

What Tesla seems to be telling us is that the "stress" on the battery is worst when you charge the top 10% or drain from the bottom 10% or Supercharge. If you mostly manage to avoid those, you should get excellent battery performance for a very long time.

My plan is to stick with my original battery pack for 10+ years, by which time I'm hopeful a 500+ mile pack is available for $20K in 202x dollars. Basically $10K in today's dollars.

Beaker | June 28, 2012

Teoatawki +1

ddruz | June 28, 2012

Vic M and Timo, thanks for clarifying the term cycle. Very helpful.

DanD | June 28, 2012

I have a lot of complaints about Tesla as a reservation holder and stock owner but a battery that costs $20K (at today's prices) to replace in 100K miles isn't one of them.

Just in the reading I've done on iON battery technology it seems likely that performance will increase substantially and that I'll perhaps get to replace my 65 kWh battery in a few years with a 100kWh battery that costs maybe $10K.

I look forward to the the rest of the car holding up better because of fewer parts and my engine replacement NOT being a major operation like it would be on an ICE.

bshortell | June 28, 2012

At the Newport Beach Fashion Island event, an engineer stated that they already had an 85kW battery pack with over 165,000 miles and it is at 85% capacity.

Brian H | June 29, 2012

According to the Rule of 72, your halving of real value of the dollar in 10 yrs requires a 7.2% inflation rate (compounding annually). Nasty!

Teoatawki | June 29, 2012

That's good news. So I can be pleasantly surprised when it's only $15K in 10+ years.

Brian H | June 29, 2012

That would still require 4.1%. Possible. 2½% would come to about $13K in 10 yrs.

Teoatawki | June 30, 2012

Even a happier surprise. In terms of actual time I was thinking more on the scale of 15 years.


Brian H | June 30, 2012

Close. 2½% for 15 yrs. is about $14.5K.

Teoatawki | July 1, 2012

Here's some more interesting information I just found over on TMC:

The info below comes from a Tesla engineer group leader named Lars.

Whereas the LEAF battery pack is series-parallel, composed of 96 cell-pairs wired in series, the Tesla arrangement is reversed: parallel-serial. 14 modules, each containing enough cells in series to generate the full voltage of 400V or so, with the 14 modules in parallel. Temperature of each of the 14 modules is tracked and controlled independently.

The design intent, not guarantee, is for the temperature-controlled battery pack to lose no more than 30% capacity over 18 years. Compare that to the disappointing capacity decline being reported for LEAFs after just one year in warm climates.

There will be adapters to allow both the 85 kWh battery, and the 60 kWh battery, if equipped with the Super-Charger option, to charge from CHAdeMo or SAE Quick Chargers. The 40 kWh battery will not have support for DC through the Tesla charging port.

Brian H | July 1, 2012

It's interesting that, AFAIK, the "little" 40 kWh battery is larger than the biggest competitor on the market. Comparing apples and grapes!

BYT | July 1, 2012

"lose no more than 30% capacity over 18 years" WOW! I would really justify the price of my Signature if the 85KW battery can run me that long! I was anticipating 50% battery loss after 10 years when calculating my ROI and will still be super conservative in my estimations so that I get increased returns when the car goes beyond my expectations. I would never have guess however only 30% loss after even 12 years! My guesses if course are based on laptop batteries and not those of a car.

Brian H | July 1, 2012

Yes, the impossibility of controlling temps in a skinny laptop put the batteries thru the wringer. Tesla made a real point of keeping them in "long-life" range, and the effect is dramatic.

Timo | July 1, 2012

I think 30% over 18 years is without cycling IE. "shelf life". I think it will lose capacity much faster with use, but warranty is for 8 years anyway.

GoTeslaChicago | July 1, 2012

"The design intent, not guarantee, is for the temperature-controlled battery pack to lose no more than 30% capacity over 18 years."

I have to think that is a typo, or misunderstanding. 30% loss over 8 years seems more likely.

Robert22 | July 1, 2012

This is no small point and should be clarified. Is the above quote a typo, based on a non-cycling "shelf battery", or with real world highly conservative one discharge per day use?

What time is it in Berlin? I bet Volker might have some light to shed on this.

jerry3 | July 1, 2012

Roadster owners seem to be losing about 2% to 2.5% per year. However, the rate of loss is supposed to slow down. But even if it doesn't, 2.5% * 12 years is 30%. The Model S has better thermal control than the Roadster, so 30% at 18 years doesn't sound unreasonable to me.

jerry3 | July 1, 2012

--supposed to slow down with age. Edit function missing (proofreader broken too).

Brian H | July 1, 2012

No, Timo, "no more than" suggests in all (reasonably normal use) conditions, and never recharging is hardly that!

eq1 | January 19, 2013

fyi, the calculations a couple posts up are inappropriate; you need to use a growth rate formula, not just multiply the rate of capacity decline by the number of years... At 2.5% loss of battery capacity per year, 26% capacity will be lost after 12 years; 30% loss happens at 14 years; at 18 years the loss is 37%...

lolachampcar | January 19, 2013

I read a Roadster thread a few days ago dealing downloading logged data from the car and using data from as many cars as possible to chart battery degradation. I'll keep looking for it and try to post a link but the short of it was as mentioned above 2 -2.5% per year.

You can bet Tesla improved the battery with Model S so I think the Roadster data is promising to say the least. What we have here is article by someone with an agenda versus Roadster owner experience. I'm going with the latter.

lolachampcar | January 19, 2013

dealing with downloading .......

Getting Amped Again | January 19, 2013

Are there documented details for the battery warranty? Is it only based on a "complete failure" or just performance less than "spec"? Is it prorated like aftermarket ICE car batteries are? If my battery loses 90% of its ability to charge in year eight, will I get a new battery?

lolachampcar | January 19, 2013

This was a post on TMC
by johnchamplinhall
As you might expect, Model S has attracted more than a few customers that are also engineers :)

I would like offer an expert comment on the issue of the life of the Model S battery. I am a Model S reservation holder and also lithium ion battery expert. In my most recent battery assignment I lead over a 10 year period the qualification of a Li/NCA system for used very expensive autonomous satellites. This effort succeeded through a combination of careful life testing, detailed analysis of test articles and development of a heuristic model based on quantum mechanics which provides a high confidence prediction of operation life.
To answer the question which kicked on this thread battery degradation with time basically follows Pguerra case 3 as illustrated below with experimental and theoretical data for a real NCA system.

While I have not worked with the Panasonic NCA system I believe my experience is close enough to provide some useful rules of thumb. First, all degradation process are a function of applied stress. Three common stresses that a battery sees are temperature (the Tesla battery is water cooled for a reason), voltage (the maximum mileage you charge the battery to) and depth of discharge (miles per day, note this is why the only 85 kWh variant has an year warrantee).
I have employed my battery models to predict Model S life and the results are outstanding. I believe that if routine charging is limited to about 80% of maximum mileage (~200 miles) and average daily use to 60 to 70 miles (my present commute) the battery life to 70% capacity will be on the order of 20 year in the Southern California climate. I can still drive to San Francisco, I just won’t do it every week (I don’t now for that matter).

johnchamplinhall, R3937

Brian H | January 19, 2013

That corresponds to the statement I saw somewhere that the engineers actually expect about half the degradation being promised. Good old safety margin principle!

lolachampcar | January 19, 2013

I just wish the crap being thrown at Tesla had fact next to it (ala Jon Stewart). There are a lot of people that simply will not look further to learn the truth and may be turned off :(

Robert22 | January 19, 2013

Can I extrapolate those results to my iPhone and iPad battery?

DJay | January 19, 2013

@lolachampcar. Just curious, would you change your approach if your daily usage were 30 miles, i.e.consider keeping the charge lower then 80% or charging every other day.

Brian H | January 19, 2013

Yeah, if you add a heat management system! ;)

Anthony H | January 19, 2013

Brian H
+1 I get it!

sergiyz | January 19, 2013

It's mostly the unknown that scares people.
Would I be upset if I've lost 30% of capacity in several years ?
Yes I would be... if I had 40kWh battery pack.
With 85kWh pack I frankly wouldn't care much.

Robert22 | January 20, 2013


Either it all becomes moot without meticulous heat management or Apple's charging recommendations don't provide for maximum battery longevity. Gee, I wonder why they don't want their batteries to last 20 years?

Mark E | January 20, 2013

When your iphone has a liquid cooled and heated battery then it may last as long as a model s. it might be a bit heavy to carry though.

Robert22 | January 20, 2013

Tesla meet Borealis, Borealis meet Tesla. Borealis has the most efficient electric motor on the planet and the lightest heat management system in existence. Surely you guys could get together for tea.