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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.

"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.

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.

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.

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

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

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%...

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.

dealing with downloading .......

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?

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

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

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 :(

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

@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.

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

Brian H
+1 I get it!

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.


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?

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.

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.

Nice, very nice! Lots of potential collaborations there.

I live in Texas. My garage probably gets 120+ degrees in summer. Is that going to significantly increase degradatoin?

The battery will cool just fine

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