Battery life concerns

As I reach for the charge cord more frequently for my cell phone every passing day I worry about the implications for my future Model S. I know the battery capacity will diminish every year. Even TESLA puts a NEW battery (<1y/o & <25k miles)as one of their prerequisites for getting the stated mileage. We have had enough TESLA battery powered cars out for a sufficient amount of time to see some data start to come in. At least we should be able to see if the degradation is linear or curved over time.

My cell phone battery's life span is about a year. At that point its down about 2/3 of what it was. I would think the same would be said for a car battery. If 260 miles was what you bought your car for and all of a sudden you could only drive 156 miles, you would probably have major problems doing the things you bought the car for. Or at a the very least, a major reworking of how you get them done. So if my Model S's battery drops below 2/3 of the stated range I would be looking for a new battery. When is that 2/3's number going to be hit?
I understand that supercharging has an effect. Lets assume 2 super charges a month to full capacity. The rest of the charges would be thru twin charging 240volt 100 amp circuits. Driving on average 15k miles a year in south Florida.

Any ideas on battery life degradation projections?

Plug-in America did a limited survey of Roadster owners recently - no discernable degradation with owners who had 10K-30K miles. Wouldn't worry about it - enjoy your car, instead!

Dude, why don’t you pose this question to a physics professor in your local university then report back to us?

In the mean time, let me guess.

For simplicity, worst case scenario: No name, generic Lithium battery would last for about 300-500 cycles.

That fits with your cell phone example. You charge it 365 times a year, then it dies.

Transfer that very simple example to your car. You run your car 300 miles a day, deplete it every day, and it dies after 90,000 miles (300 miles x 300 recharges=90,000 miles) in a year.

That may explain why Tesla guarantees your 85kWh battery for 8 years or 100,000 miles.

Sure, you can try to Broder your battery down by running in a circle around a parking lot. However, the worst scenario applies when you practice 100% DoD Depth of Discharge. Most of us don’t or can’t because by default, the software prevents us from completely discharge or completely recharge your Model S battery.

Most of us only let our car partially discharge and we don’t “max charge” so that don’t count as one complete discharge/recharge cycle.

Thus, your Model S battery may last you a long time :)

I've heard number of 1.5-3% loss per year, not sure how many miles, but assume it is 15-25K. Linearity? Don't know, but given the amount, not much difference between linear and curve. I don't sweat it at all. Had a Prius before, and have not noted any decline with battery/milage over 8 years 187K miles. MS battery is of better quality.

Also, MS85/P85 has 8 year/unlimited miles battery warranty! (not 100K miles). I got a 85 and love it.

There have been some posts here and on TMC from Roadster owners who report minimal degradation. These are admittedly anecdotal, but should give you some confidence.

Unless you are max charging every night, and fully depleting every day, you won't frequently be operating the car in the more damaging ranges of >85% and less than <15% of max charge.

As a Ph.D. physical chemist with 40 years of lithium battery development experience and Model S owner I think I am in a pretty good position to reassure you. The Panasonic cell used in the MS is probably one of the best in the world. I am very familiar with its electrochemical design (LNCA) and have developed physics based models for predicting LNCA life. Providing that your daily driving pattern is reasonable (<100 miles) and its not too hot where you live I predict the battery will last (70% of new range) for > 20 years.
If you want further reassurance get a copy of the paper below by some Panasonic researchers (you have to buy it for $31). Their results equate to 400,000 miles of life even with 160 mile per day driving cycle
“Prevention of the Micro cracks Generation in LiNiCoAlO2 Cathode by the Restriction of DOD” Transactions, S. Watanabe, T. Hosokawa, K. Morigaki, M. Kinoshita, and K. Nakura, ECS Transactions 41 (41) 65-74 (2012).

@john - good info - thank you very much! If I get 20 years out of my MS85, that would be awesome and the gas savings much greater than first thought...


read about the original Toyota RAV4 which was tested to 300,000 miles by Toyota. The MS is 40% to 50% more capable and far more advance.

AFAIK, no one, even high-mileage types, has reported any loss of range so far.

That 100 miles per day or less is actually right where I am. And I live in South Florida so we are fairly temperate. Hardly ever above 100 degrees like the south or southwest gets.

What does the unlimited battery cover?

Unlimited mileage battery warranty.....

Abnormal failure, range loss beyond expected due to manufacturing flaw, etc. Normal loss of range, possibly about 30% in 8 yrs., is not covered.

I've also heard that active thermal management (which Tesla employs and it one of their trade-secrets and a barrier to entry for competition) also dramatically extends the battery life and cycles…I'm sure @ johnchamplinhal will chime in and correct me if I'm off the mark.

Also a battery engineer and PHD from Cern I happen to work with also has few if any concerns about the Tesla battery from a chemistry/design/longevity point of view. Any degradation would be on order of 100,000+ miles of usage and replacement is possible and supported. Cost is documented to be inline with similar high mileage ICE wear-tear problems.

Also Tesla has an 8 year/unlimited milage warranty.

The early Rav$'s were NiCad batteries and they did require some maintenance (I have a co-worker with a 2002 RAV4 with 150,000 miles) and do fail as my friends did at 150,000 miles. Replacement is $9,000. You can't compare those battereis to the new MS LithiumIon.

In talking to Raodster owners in our area and Tesla mechanics that have worked on them for years, they've seen almost no battery degredation yet. I am confident they'll do fairly well and most likely will surpass older ICE vehicle issues that we've seen in our cars after about 100,000 miles.

Doctor is right. Keeping the battery at the right temperature does wonders for life and safety. Fourty years ago my PhD major subject was thermodynamics.

I don't have any documentation to prove this; however, I believe there is a deliberate reason why laptop and cell/smart-phone Li batteries don’t last long, and it makes perfect since why.

Laptop and cell-phone manufactures don’t want their products to last very long deliberately, as it almost guarantees if the Li battery starts to go bad, most will just buy the newer product, verses try and replace the battery (never mind, they don’t make it easy to replace the battery on the new cell/smart-phones, or cheap by any means). However, just cheap enough, that we all end up buying the next newer version anyway.

This is fairly common with many products built today. Unlike the toaster I grew up with in the 1960-70’s, and never broke down even after I left home in the late 1980’s, products back then were designed to last forever. Today, these companies have wised up, and engineer many products to fail deliberately. You would think, “why would they do that, I will never buy that product again if it fails in a few years”. If you do a little research, you will find that a great deal of these products are all owned by the same corp. So when one fails, and you choose another, chances are, it’s still the same corp that gets the money in the end.

On the flip side, an EV car battery that degrades quickly in a few years or after 50k miles would be a nightmare for the company that designed and built it. Nissan has made billions just off the fact that their motors last well over 250k miles without any problems, and has given them a reputation worthy of getting repeat business for decades by loyal customers.

Thus, in a nutshell… don’t compare ‘built to fail’ cheap consumer products, with ‘built to last’ expensive vehicles.

Excellent point TikiMan.

I got to the point that I now replace small household appliances that have failed with used ones that were built pre-1980. I'm done with the planned obsolecence and disposable mentality.

I couldn't find a new toaster that was well made and had decent heating elements at any price. New toasters today just dry out bread slowly. A new hand mixer I bought didn't have enough power to make it through a batch of hot buttered rum batter.

I buy products that I think will stand up to the test of time. Model S included.

Don't get me started with new dishwashers.
The 80s ones would take paint off dishes,
But these new ones do not even take the food off.

I long for my 1980's Washer, Dryer and Dishwasher.

Cheap basic cell phone batteries die quickly because it is more expensive to take the steps necessary to make them last then it is to just replace them. Think of the average cell phone battery, its temperature is allowed to wildly swing from 30 degrees in your pocket to far lower in the ambient air dozens of times a day, the Tesla buffers the temperature keeping it strictly within the desired temp range. A cell phone battery is generally cycled fully each day, a Model S battery is on average cycled fully once every 5-7 days. A cell phone battery employs a minuscule compact charger with a requisite lack of more complex control circuitry, the Model S uses sophisicated charging and diagnostic control systems to control the charge tightly and refuse any power which is suboptimal hence the issues using generators to charge etc.

The sum effect of all of these and many other factors is despite everyone's experiences and hence worries resulting from short ifespam cell phone batteries the much better managed and sized Model S battery will have a lifespan which will eclipse most people's experiences with batteries.

I believe the concern about Max Range charging is overblown, as long as the battery is not allowed to sit in that state. Start using/drawing it down right away and there is little impact. It's the sitting that hurts.

I bought my wife a Cuisinart food processor in the late '70s. It had a 30 year warranty! It still works great.

@TikiMan - Excellent response and dead-on correct.

@GLO: the first gen Rav4-EVs used NiMh (nicke metal hydride) batteries, not NiCad. And yes had very long life as you pointed out.

@Docrob - OT, but is there an issue with charging the Model S from a stationary generator?

Brian: re max range and letting it sit - my Model S was charged to 197 miles in max range mode for unknown reasons when at the Fremont service center. I called them Nd asked them about it, but they assured me that it was in accordance with their procedure. Then I see it lost 10 miles per night sitting in their lot while waiting to be picked up by me on Monday. (I am out of town at the moment)

The battery will drain a few miles every night, so it might not be all that bad? I don't know. I'd never personally charge to max unless absolutely necessary.

The average person drives about 12,000 miles/year, especially families with 2 cars or more. That is about 30 miles/day. Optimally the Tesla owner would set the battery charging for optimum life and connect the car to power every night. The battery would be operating in the optimum range with a daily discharge of only 20% at the most depending on the driving conditions.

The battery would be stressed may be 4 times/year during long trips at max change, with partial SC use may be 2 times per trip. Rest of charging does at a hotel under optimum conditions. In many cases, I would just use the ICE auto since there are no SC in my area. Hotels do not have charging ports yet.

Under these conditions, most of the MS batteries will last a long time. Very different from my iPhone5 where the charge does not last the whole day. Charge it to max every night, discharge to less than 20% and got to be charged again. I got the iPhone4 for 3years and I have not noticed any degradation, but it needs charging 1/day.

I would like johnchamplinhal to comment on what is over the horizon in battery tech. Do you see the batteries improve capacity gradually at the usual rate of 6-7%? Or are there disruptive advances that can increase capacity and lower cost in the next 3-5 years? TIA.

You can look at the 18650 cell degradation curves on the Panasonic web site.

It's all in the cycles, not the number of years. IIRC (too lazy to look for it now), after 500 cycles you are down to about 70% capacity.

So if you drive a full charge every day, including weekends (that's over 100K miles a year), you will be down to 70% in 18 months.

But most people don't drive nearly that much. At 20K per year, you need some seven years to reach the 70% capacity. At 10K per year, over a decade to get to that point. (10K per year is only about 40 charge cycles).

I drive less than even that(6 to 8K miles), so this is a total non-issue to me. But for high mileage drivers, it's something you need to know. That said, high mileage drivers blow out the useful life of any car, regardless of technology. How much life is left in an ICE after 200K miles? How much was spent on fuel?

With all the speculation around the next announcement being SuperCharger specific I am confused again. I thought SuperCharging was hard on the battery. And doing it more than 4 or 5 times a month was discouraged. With more data coming in from real world supercharging is that turning out not to be the case. Why would they hype up supercharging so much if it is hard on the battery. Adding more centers, uping the Amps, reducing the charge time etc seems to be asking for deteriorating batteries.

@Tim. You may be thinking of using the "max charge" option when charging, which is not the same as using the supercharger network. Although most people on a long trip would most likely max-charge at some point.