Battery life / warranty

Battery life / warranty

What is the life expectancy of the batteries for the Tesla S?
I've have already reserved one, but this is probably my biggest concern.

Secondly, does anyone know what the warranty will be on the batteries?


Straight Shooter | 28 juli 2010

You will not get solid answers from Telsa on this one. The car is not even in production yet, so solid factual data is not avaialble yet and it would be refuted/bullied/slandered by all the nay-sayers out there too. Add in all the variables like car weight, speed of discharge and depth of discharge and it confuses the matter entirely.

I think what we need to see from manufactures is a highway and city discharge rates along with its impact on batery life. We all know real world usage is never included by auto manufactires, so we need to know discharge rates in hot and cold temps with a/c or heater running, stereo blasting, sitting in grid lock. It would be nice to see it at 70mph too.

If Telsa wants to ellivate fears about batties they need to provide that, as well as replacement costs and most importanrtly what I beleive to be the real ' sales advantage'......battery upgrade costs. In other words, when newer and better battery tech is added to the cars, what is the cost Telsa will give to me to permanantly swap out my older batteries for the newer ones? Some type of sliding scale costs based ob years of use would be nice.

FYI......I'm not slagging the Model S either, quite the opposite. I'm trying to convnce my wife to buy one with me.

trydesky | 29 juli 2010

Thanks Straight Shooter. I agree with your comments.

I'd also like to know from Tesla if "topping off" will lessen the battery life. If I get the 300 mile version, I won't NEED to top off every evening...and I won't if it will extend their life.

Mike_ModelS_P457 | 30 juli 2010

trydesky that is a great question! I am planning on the 300 mile battery, but given my normal commute is 12 miles round trip, I don't know it makes sense to charge each night. I am interested if there are negatives / positives to this approach. Also, I am going to charge off of my solar system (42 panel double array), so I would prefer to charge during the weekends during the day than during the week at night...

bw | 30 juli 2010

I can't figure out how the S can get 300 mile range when other smaller EVs are struggling to get 100 miles with batteries that cost $15K! Also a newbie question - is the S expected to have regenerative braking to help extend the range?

dsm363 | 30 juli 2010

I may have this wrong but given that Tesla uses lithium ion batteries (same cells as in a laptop), there isn't a penalty for plugging it in every night to have a full charge. In fact, I think that's what they recommend. Also, I was told the 300 mile pack may not be available immediately when production begins. If you only have a 12 mile commute, you may be able to save some money and get the 160 or 230 mile pack anyway. You can always upgrade to a larger pack later.
The model S will probably have regenerative breaking as well (the Roadster has it).

trydesky | 30 juli 2010

bw, I do not know if they will use regenerative breaking or not, but I read that the 160 mile version is battery type A (A = some battery I don't know the name). The 230 mile will be more of battery type A, while the 300 mile will be battery type B...a different battery that can store more energy.

dasky4eva | 30 juli 2010

bw - definitely the Model S will have regenerative braking. Based on early test drives, reports indicate taking your foot off the accelerator will cause the car to slow enough that the brake lights come on.

Can't provide an answer to your first question, but I believe Tesla has some competitive advantages in its electric vehicle platform.

Todd Burch | 30 juli 2010

To answer all of your questions:

Life Expectancy of the batteries: Although nobody knows for sure, and Straight Shooter is right in that it's a little too early for that information, we can deduce based on what Tesla's released (and on the Roadster) that you can expect your battery to last 7 years on average...10 years if you treat it nicely, 5 years if you're really bad to the battery. I think I remember an early Model S website alluding to this 5-7-10 year value. Based on what Roadster owners are saying, their batteries are still holding charge pretty well (near the original range) after 30,000 miles.

Warranty: No idea...Tesla will tell us when they've done the testing and the math on that one.

Regarding "Topping Off": Charging to max capacity will indeed degrade the battery faster. Like the current Roadster, the Model S will most certainly have a "range" versus "standard" mode. "Range" would allow you to charge the battery fully--but since it degrades the battery faster, only use it when you feel you need it. "Standard" would charge to something like 85-90% charge (don't know the number exactly)...and would treat the battery the nicest.

Check out for *LOADS* of information on the Roadster, battery technology, and whole lot more.

As far as time of charge is concerned: You can program the car to charge at only certain times of the day. So, if you have solar panels, you can plug it in, set it to charge during daylight hours, and forget it. (Again, this is based on how the Roadster works...the Model S will almost certainly have this feature as well).

bw: Tesla is able to achieve their range for several reasons, but primarily because they hired a bunch of very bright electrical engineers, and have designed systems to take very good care of the battery. Ever wonder why laptop batteries die so quickly? After all, they're lithium ion too. The reason is because they get hot...really hot...sitting on your lap next to all those boards. If you control the battery's temperature closely, as they do, batteries can last much longer.

And yes, the Model S will definitely have regenerative I imagine *all* electric cars will have into the foreseeable future. It's an excellent thing--get energy you would've lost in a regular car, **plus** your brake pads last much longer! A lot of Roadster owners drive their cars so that they rarely ever need to use the brakes!

meloccom | 1 augusti 2010

trydesky wrote: I'd also like to know from Tesla if "topping off" will lessen the battery life. If I get the 300 mile version, I won't NEED to top off every evening.

It's widely believed that it's best to keep Lithium Ion batteries at a state of charge between 20% and 80%.
The Roadster will charge your batteries only to 80% unless you put it into range mode. If you read the owners manual, downlodable from the Teslamotors site, it warns you that using range mode will reduce battery life. I imagine it will be the same for the Model S.
If for example your commute uses 20% of the capacity of the battery you can charge every night or every 3 nights to stay in the 20 - 80% range. This should result in no perceptable difference in battery life.

William13 | 1 augusti 2010

The batteries work well in the Roadster. Toyota claims that the Prius battery (different type) lasts longer because of not completely charging or discharging. The Roadster has different modes: range, standard, and performance. I expect this has a similar purpose.

The first year will only offer max 230 mile range. This is thought to be due to need for improved technology for the 300 mile range.

The timing of the release is partially to allow for the expected drop in price for batteries. (Often quoted at 10-15% yearly.) The lowest price is for the 160 mile pack.

ChadS | 1 augusti 2010

@trydesky, in addition to what Straight Shooter says, the 300-mile version of the car will likely be a different chemistry, which I doubt Tesla has enough testing on to estimate lifetime.

"Topping off" all the way to 100% is kind of bad, but on the Roadster by default the car stops charging at 90%. Current recommendation is to go ahead and "fill" it that level every night, although that could change, especially with different chemistries.

@Mike_ModelS, I know it's cool to charge during the day when you get the actual bits from your solar system. But while it's not intuitive, it helps the grid more if you feed your solar power to the grid during the day during high-demand time, and then pull a charge for your car at night when the grid has excess capacity. Although if you are only charging during weekends, maybe demand is low...I guess it depends on where you live, temperature, etc.

@bw, Tesla is partly planning on battery prices to come down in the next two years. And note that the $57k price is only for 170-mile range; you'll have to pay extra to get 300 miles.

The S (and pretty much any future EV, I would think, except maybe some no-name ones competing solely on price) will have regenerative braking. Using regen is much better than braking, because you recycle some energy rather than discarding it. However, it's better to keep using the energy rather than recycling it--regen is nowhere near 100% efficient, so it's much better to maintain your momentum rather than brake (via regen or the brake pads) when you can. You probably know this, but some people that are new to regen thinks it magically adds range and that you should use it all the time.

Rustybkts | 4 augusti 2010

Chad S is correct that a solar cell installation is best fed into the grid during the day, then charge at night as the solar cell array is not used at all when not charging the car which spoils efficiency.

Regarding regen, I do not know the efficiency but my own EV car ( has regen current of over 75A at 330v at speeds over 60mph which of course drops as speed reduces.
Even if you have 50% battery conversion efficiency this must offset the energy needed to accelerate back up to the previous speed as steady speeds use far less energy.
Stop start traffic would I guess be most efficient for regen.

An earlier post from "bw" suggested that manufacturers cannot achieve 100 miles from $15,000 battery packs.
My own 60 mile range 50Ah set of 94 cells cost around £5,000 (GBP) two years ago and can be sourced now for around $5,000 or less.
Surely a manufacturer can halve that price for the huge quantity they use.

rreinman | 14 augusti 2010

I had heard that the on board computer will read back information such as slow down to MPH to reach your destination so as to not run out of a charge. Is that true?

Timo | 15 augusti 2010

@Rustybkts "Regarding regen, I do not know the efficiency but my own EV car ( has regen current of over 75A at 330v at speeds over 60mph which of course drops as speed reduces."

Regen rate depends of deceleration rate, not speed.

@rreinman, I know that Leaf has such display, and making one is pretty trivial thing to do, so I would be rather surprised if Type S on-board computer doesn't have that

jmalcoun | 17 augusti 2010

I manage several EV initiatives for a major US utility, including several million in research funding. One of the major outcomes of the work we're funding is in the realm of battery health. Reports will be out soon, but I'll share one of the most interesting findings...

Battery health is most optimal when charge occurs as near use as possible. Therefore, you not only want to delay charging until off peak (for environmental and financial reasons), but you want to delay until the early morning, just prior to leaving your house.

WRT the question on how can Tesla manage to squeeze so much range out of their battery system when other OEMs are struggling at what appear to be major costs...Tesla does not actually have any special sauce in the battery area (as of right now at least). In fact, most in the business are blown away by the fact that they are basically packaging together actual laptop cells - read: not very progressive technology. Yes, there is likely some snazzy stuff going on in the battery management side. But as far as I can tell, they simply have an enormous cell array at work. That is how they achieve higher ranges. A very large portion of the cost of the Model S (and really any EV) is locked up in the battery.

This brings us back to battery health...very important to devise optimal battery charge/discharge habits as this will have enormous impact on the residual value of your vehicle. Whether or not there is a secondary battery market (jury is out and will be for a while) you'll want to maintain a strong charge if you intend to sell your car.

gacoka | 18 augusti 2010

Could someone from Tesla say something please...

gotwins | 18 augusti 2010

Just wondering, since I haven't had an experience with electric cars, what is the cost comparison to gas and your electric bill. Basically, I'm trying to weigh the cost of gas to electricity.

Timo | 18 augusti 2010

@gotwins; that depends of cost of electricity and gas in your area. Roadster uses about 53kWh for 220 miles or so so that is 53000Wh/220 = about 240Wh/mile. In here one 1kW costs about 10 cents (euro cents), so that would be 2.5 cents for mile. A little under 2 US cents

If you have a car that gets 30mpg that translates to 1/30 of gallon times gas cost for one mile. In California one gallon costs about 3 dollars. So you would be 10 cents (US cents).

In addition to that EV requires practically no engine maintenance. No oils to change, no belts, plugs, pistons etc. to wear out. Maybe after some 200000 miles you might want to change bearings, that's all.

Calculate yourself.

Rrroger | 10 december 2010

I agree with with gacoka. How often does Tesla monitor all of these Forum comments to make improvements, or answer the questions?

And how will we know?

ConnorO79 | 10 december 2010

@Timo, i'm intrigued with that calculation, of the 5kwh for 220 miles, if that goes into the model s, (using 50kwh/220miles, overestimation) i got it as 60 miles in one hour, as 13.6kw per hour it uses.

is speed taken as a variable in there somewhere?

Timo | 11 december 2010

At 60mph Roadster uses roughly 15kW. For that range is... 3.5hours * 60 = 212 miles. It's different for different speeds.

qwk | 11 december 2010

Wall to wheel, the roadster gets about 3 miles per kwh.

Timo | 12 december 2010

Which depends of the average speed and conditions.

qwk | 12 december 2010

I guess

qwk | 12 december 2010

I guess I should have included the word average in my previous post.

Brian H | 13 december 2010

Stay around 20 mph and you'll get a lot more! But it will be boring all the way.

Bubba2000 | 15 januari 2011

Tesla has the roadster for a few years and they should have the data regarding:
1. Charge and discharge cycles for various types of driver habits.
2. Effect of regen braking.
3. Environmental changes regarding temperature, environment, etc.

They could simulate - close enough, but not exactly - the conditions on a static battery pack with multiple cycle and get 5, 7 and even 10 year data. I suspect they have done so and have the data regarding the operational life of the battery packs.

Battery life it the most critical part in the purchase decision of the Model S. Not range... especially with the 300 mile pack. Charging stations are cheap to set-up, especially the 240V kind... any hotel, motel chain, could do them cheaply. Range is a problem with the Leaf... any long distance trip is impossible with a 100 miles max and then having to recharge. Heck, that is camel range.

I am confident that Tesla has mastered the rest of the technology including the design of the car, drive train and electronics. They proved that with the Roadster. With the Toyota expertise - or without - they can produce 100 cars/day. They are doing this kind of thing even in Mexico. They have the finances.

They need to address the Achilles heel - battery life.

Bubba2000 | 15 januari 2011

Would the addition of super capacitors increase the life of the battery? Since the life of the battery is dependent on the charge and discharge cycles, regenerative braking power would go the super capacitors and then discharge to the motor. It would smooth the flow of current for the Li battery.

I read that the expected mean life of the battery is only 100,000 miles. Give the hi cost of replacement of the batteries, that is too short life. That the biggest impediment to adoption since with 300 mile/charge there is to range anxiety for most trips... in the EU, there are charging stations all over the place, so it will happen here.

I do not know much about this area of engineering. May be somebody with expertise could comment?

Timo | 16 januari 2011

Problem with supercapacitors is that they still have only about 1/100th or less of the capacity of the batteries, and braking can easily overload them unless you use so big ones it starts to hurt the range of the car. Otherwise idea is good.

ckessel | 16 januari 2011

"300 miles/charge there is to range anxiety for _most_ trips"

Who the heck travels 300 mile for "most" trips? I think I've driven 300 miles in a day maybe twice in the last 5 years. Granted, I take fewer long distance trips than most, but 300 miles in a day is a long distance.

The problem isn't range at that point, it's your usage profile. If someone is regularly driving 300+ miles a day, then EV isn't for them. At least, not until 45 minute recharge stations are plentiful.

Bubba2000 | 16 januari 2011

ckessel - Sorry that was a typo. I meant to say that for most trips with a 300 Mile range, there is no model anxiety. The longest trip I have made in the last 5 years was a 250 mile. It is a matter of time before quick charge stations show up.

If I were to order a Model S, I would have to prepay ($12,000) for the replacement battery. This way the car would be good at least for 150,000+ miles and some residual resale value. More important, I would not get stuck if the battery went dead in 5 years. Such as package would cost around $75,000 with the 300 mile option. This is the BMW 7 price range.

I think Tesla needs to tweak the chemistry, charging/discharging electronics and temperature control to extend the battery life... which I suspect they are doing. In time, they may offer a plan to refurbish the battery pack.

discoducky | 16 januari 2011

Q: How long will it take you to rack up 100K miles?

Typically, about 15K/year, so about 7 years.

Q: What will the price of a replacement battery be in 7 years?

A: Most forecasts show a linear drop in prices around 20 to 30% Y/Y, so the price should be about 30% of what it is when you take delivery.

So, if it's 10K in 2012, it should be about $3K in 2019, roughly.

ckessel | 17 januari 2011

It's hard to see a reason to prepay for a battery replacement. Batteries are likely to be cheaper when you need it. Plus, you might not have the car due to an serious accident or you sold it for some reason. Or Telsa may not be in business, though I hope that won't happen.

Ramon123 | 14 februari 2011

One of the fallacies I hear over and over is the rather
silly assumption that "batteries will cost a lot to replace."
Now, really! We've seen the price of batteries come down over 8% per year for quite some time. It wasn't that long ago when the quote was over $1000 per kWhr capacity, which lately has been quoted (for Tesla, NOT GM, which pays three times as much) as
$200 per. So tell me, why does anyone believe that when the time comes to replace batteries 10 years down the road, it will require huge sums of money? If that $200 figure is accurate (it came from a stock analyst) for Tesla's costs, then presumably, a 300 mile range pack, which will require somewhere around an additional 35 kWhrs worth of cells beyond what's included in the 160 mile pack, would add roughly $7,000 to the cost of the vehicle. For what it's worth ....

Timo | 15 februari 2011

I believe that this 8% is underestimate for next few years. There has been serious technological breakthroughs in battery tech which have not yet reached manufacturing, and also increase of manufacturing volume is accelerating fast because BEV:s are getting more and more common, which also drops the price of the batteries.

Al Hook | 15 februari 2011

Prefer to think there is the same difference between sales ads and reality for EV range as for gas/diesel mpg. In real life I assume the numbers are 20-40% less.

Which means an EV with teoretical range 100 miles should serve you well as a commuter car if the distance to work one way is 30 miles or less. Or 60 miles if you are able to recharge at work.

With teoretical range 200 or 300 miles you of course multiply these figures by 2 or 3.

Will an EV save you money compared to a high mpg diesel?
Depends not on price of electricity only. In addition you will have battery replacement cost per driven mile.

And here uncertainty prevails until some thousand EVs have furnished average data.

Some (wild) examples of how much to add to the price of electricity:

100K miles and 10K dollars = 10 cent/mile
100K - 5K = 5
200K - 10K = 5
300K - 10K = 3.3

With 3$ a gallon and 50 mpg a small diesel car will cost you 6 cent/mile. Fuel price will in the future probably increase more than cost of electricity and of battery packs.

Fuel price increase and battery pack life span are probably the most important unknowns that bingo comparisons.

What about second hand value of EVs?
Two completely opposite possibilities:
- Demand greater than supply = prices far above fossil fuel used cars
- Rapid technological development makes EVs like laptops, TV's etc out of date the moment you leave the shop. Hence impossible to sell above give-away price.

Volker.Berlin | 15 februari 2011

"Prefer to think there is the same difference between sales ads and reality for EV range as for gas/diesel mpg. In real life I assume the numbers are 20-40% less."

I used to agree with that statement until I found that there is hardly a Tesla Roadster owner who reports that he consistently does not have the mileage as advertised. More like the opposite. It seems like Tesla is trying to build a reputation that their mileage figures can be taken literally, and from what I read on the web (here and elsewhere), I tend to believe in their promises until proven otherwise.

perbakken | 15 februari 2011

I have tested the Mitsubishi i-Miev in Norway. This is an pure EV and Mitsubishi claims its range is 100 miles.

Without using any heating and in plus three degrees centigrade on bare asphalt with four persons in the car, it was only possible to drive 45 miles. Less than half of what Mitsubishi said. I really hope that Tesla is more honest with the driving range!

A winter in Norway is normally snowy and the temperature can easily drop down to minus twenty degrees centigrade...

Samuel H. | 15 februari 2011

EVs work slightly better at colder temperatures than they do at warmer temperatures. Mitsubishi obviously overstated their range as your experience proved. However, the extra weight of four people decreased your range. So, the 45 miles you drove was representative of part lie and part load.
However, Tesla owners have been reporting ranges that met or exceeded the published range numbers. Tesla has been honest in everything. Why try to discount what has been proven by over 1500 Roadster owners across the world? The Roadster does what they say it can do and more. The Model S will as well.
I expect that it will be a better car than the Roadster for this reason. The Roadster was based on an existing car. The Model S is being designed from the ground up to be the best car ever! Their goals for the Model S are to have the safest, smoothest, quietest, best handling car ever produced. They met their goals for the Roadster. I can't wait to see them do the same with the Model S!

perbakken | 15 februari 2011

Samuel H. I am not, in any way, trying to discount Tesla, as I was just telling you about my experience with Mitsubishi. I have already made my reservation for the Model S and this I did after my test-drive of i-Miev. :-)

Samuel H. | 15 februari 2011

Sorry if I was a bit blunt. The i-Miev is okay for some people, I guess.

Douglas3 | 16 februari 2011

Speaking as a Roadster owner, I can state categorically that Tesla does not exaggerate their range claims. The car does what they advertise.

In fact, they provide very detailed curves showing the effect of driving at different speeds on the car's range.

msiano17 | 16 februari 2011

@ ckessel - I'd agree with you on if your 300+ mile a day driver, the technology is just not there yet for them to switch to an all EV. Either we need a boost in battery capacity/density or we need all the local municipalities and private sector to invest in Phase 3 chargers which would give the batter a huge boost real quick.

On a separate note, what has anyone heard regarding any affect a side impact crash would have on the batter consider the location. Would a side impact total the batter? (If so I would had to be the other driver ha!)

imhsar | 16 februari 2011

Sometimes it depend upon how we drive and how much we are driving, the product itself should be good. The way you are using can change its capacity.

Volker.Berlin | 21 december 2011

Now that battery warranty conditions for the Model S have been released, it turns out that they much more favorable than many expected:

The warranty is 8 years and
100,000 mi (161.000 km) for the 40 kWh
125,000 mi (201.000 km) for the 60 kWh
*unlimited mileage* for the 85 kWh battery pack!

I think that sounds fair although it remains to be seen which the actual terms of warranty are. How much degradation within those 8 years is deemed acceptable?

Timo | 21 december 2011

I think Tesla defines it as 70% of initial capacity. IIRC that's what it is for Roadster.

David M. | 21 december 2011

That means most folks could resell with the battery still under warranty! I've never owned a car for 8 years despite my original intentions.

Brian H | 21 december 2011

The first 'S' resales should be very interesting. How soon do you think the first will happen?

Timo | 21 december 2011

Usually if there are enough buyers that happens pretty soon, no matter what kind of car is in question. It is matter of numbers, take big enough sample and unexpected things start to happen to some of them.

This is rather expensive car so I would believe "need for money" would be the first reason. Someone that wanted to be green but didn't really have the money and/or stable enough finance base gets kicked by RNG.

Brian H | 21 december 2011

Real Number Generator? It kicks?