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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?


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.

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.

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...

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?

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).

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.

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.

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!

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.

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.

@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.

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.

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?

@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

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.

Could someone from Tesla say something please...

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.

@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.

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?

@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?

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

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

Which depends of the average speed and conditions.

I guess

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

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

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.

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?

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.

"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.

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