Battery replacement dependent on charges? Time? Both?

Battery replacement dependent on charges? Time? Both?

I've hunted in the FAQs and articles, but I'm not sure I found an answer. I know the battery doesn't have a memory and 7 years is the replacement timeline if you pre-purchase the battery when you buy the car. What I'm trying to figure out is what actually governs the battery life? If I drive a relatively low amount, say 7500 miles a year, is the battery still going to need replacement at 7 years?

Or is it more dependent on how often you charge it? Is it better to top the battery off all the time or limit the charging to when it's necessary? My typical driving profile is maybe 20 miles a day, so I could easily not charge it all week, then charge it over night on a weekend as my standard procedure, only doing cop offs if I'm on the road frequently and for more extended periods (like on a vacation or a busy weekend).

So, I suppose, in short I'm trying to figure out how much the battery longevity depends on time versus use. My actual driving is often well less than 10k per year, so I'm wondering if it's better for me to NOT pre-purchase the 7-year battery swap.

BYT | 10 januari 2011

How about we just run the cars off a couple of these Bloom Energy boxes?

cablechewer | 10 januari 2011

AFAIK batteries have both a recharge life and a calendar life. Check the side of any consumer battery you buy and it will have a date on it. That doesn't mean it will be dead at that point - just that the manufacturer won't promise it will be 100% at that point.

I am no chemist, but I have read in various places over the years that all batteries suffer from very gradual deterioration that takes place inside just from aging. One explanation I saw said that deposits can collect on the ?anode? and gradually inhibit energy transfer. I forget which specific Lithium chemistry the author was discussing.

I have had a Tesla rep tell me that they have been finding battery deterioration to be less than the 30% over five years that they originally predicted back in 2006. I have also seen similar hints elsewhere on the web, but that is hardly a quantifiable, hard fact you can take to the bank.

ckessel | 10 januari 2011

The shelf life of a consumer battery though doesn't typically mean it won't charge well, just that's lost it's charge. I certainly wouldn't expect the battery, even if rarely used, to be going strong after 50 years :). That said, if it's # of charges that's the predominant factor in battery life, then I can tailor how/when I charge based on how I actually use the car.

discoducky | 10 januari 2011

In short, Lithium Ion batteries (in laptops and in the Model S) will last a bit longer if you drive less and charge less often. Batteries degrade over time due to the positive and negative poles essentially become less effective at engergy transfer.

With all that being said, I'm very confident in Tesla will do all the right things to ensure the battery lasts longer than it should.

and breakthoughs seem to happen every day:

Roblab | 10 januari 2011

You forgot one key battery degenerant: Heat. High charge rates are hotter, and all batt mfg people will tell you that fast charging lowers your battery lifespan. Charge at home overnight, take as long as you can.

Timo | 10 januari 2011

@BYT, bloombox is not suitable for cars. Too big, too heavy, too slow operations, too expensive to make it short. Could work for apartments at least until we have aneutronic fusion generators (which might be a lot closer than people realize).

Vawlkus | 11 januari 2011

If the battery is properly cared for, not drained to 0 before it's charged, not overheated, not overcharged (although Tesla's onboard gear should keep that from happening), etc, then the battery will probably last a lot longer than the 10 years that Tesla's tests have shown.

The more charge/discharge cycles the battery goes through the lower it's lifespan will be. That doesn't mean it'll just stop working one morning, it just won't be quite as able to hold it's charge anymore. It's a gradual degradation, something like 1% per year (not an acutal figure). Say you get the 160 mile battery and drive the Model S heavily. After 5 years, instead of 160 miles, you might be getting 144 miles max instead of the full 160.

Brian H | 11 januari 2011

Timo, he was suggesting charging, not running, with the Bloombox. But I think the B-Box is a dead end; it's basically a NG-fuelled fuel cell. Very expensive power. Maybe suitable for someplace that gets NG but is not on the grid. I hear some of the first adopters have abandoned it, and aren't finding buyers for their used Boxes.

VPLACE | 11 november 2011

Most of my battery usage will be about 30 miles/day, with a few 200mi trips.
If I recharge each night using 110v/20amp outlet, will the battery degrade faster, than if I installed and used a 240v/50amp breaker/outlet??
If so, by how much??....approximatly!

Also what is the time it would take to recharge (after a 30 Miles usage)using 110v vs 240v??

I heard that it would take 1 Hr to recharge a 35 Mile usage, but I don't know what size of a charger was used!?

Mycroft | 11 november 2011

The car's computer will charge the pack ideally, regardless of what you plug it into. Just plug it in each night and everything will be fine. I'm sure Tesla will be a bit more explicit in the manual for the car.

Leofingal | 11 november 2011

@VPLACE - estimates are ~300Wh/mile, so 30 miles should be ~ 9 KWh - assuming 90% efficiency (maybe high?) that means you will need to provide 10 KWh. A 20 Amp, 110V outlet (pretty basic) would provide 2.2 KW, so it should take under 5 hours to recharge this, and given overnight charging, this should allow the computer to optimize this comfortably.

I think for normal daily use (as you define it) plugging your car into a 110V outlet should be adequate. However, if running a 220V 40 or 50 Amp line to your garage is not overly complicated, it probably makes more sense to do so. If your panel is way on the other side of the house, you might get by on your standard 110V. One of the more EE savvy posters can correct my math if I left out something (like really it will limit to 15 Amp on a 20 Amp circuit? I kind of remember hearing this somewhere else).

Robert.Boston | 12 november 2011

My understanding is that the more slowly you charge the battery, the less degradation they incur. So, 120v would be less harmful, not more. That said, unless you're putting on very few miles, the 120v option is going to be painfully slow; it will be adequate for recharging overnight from a commute (30-40 miles), but if you take a long drive on Sunday, you're going to be playing catch-up all week.

Ramon123 | 13 november 2011

The size of the battery pack will be the overriding factor of how many miles a battery pack might be good for, since number of recharges is the most often quoted factor with respect to battery longetivity. MIT did some studies and found that speed of recharge
has zero effect on battery lifespan, good news for fast chargers.
The Tesla battery pack likely regulates its temperature during recharge the same as it does at all other times. If the cells are good for 500 (full) recharges, then theoretically the 300 mile pack could take you 150,000 miles.

VPLACE | 16 november 2011

@Ramon123 "If the cells are good for 500 (full) recharges"

Claification: (Battery Life)
Does it matter if I recharge,(300mi battery), (using a 240v/50A Outlet) every night after 30 miles, or once a week after 210 miles??

brianman | 16 november 2011

My understanding is...

For a 160 battery, how did you eek out 210 miles?
For a 230 battery, you'll be dipping into the bottom 10% of the battery which is generally bad for it.
For a 300 battery with an 80% starting charge, you'll be right at the 10% mark on the battery which is not a good idea either.

If you change the question...

Every night after 15miles, or weekly after 105 miles, all but the 160 battery should be fine for weekly charge instead of daily charge.

Brian H | 16 november 2011

You can eke out 210 miles if you just drive downhill, like these powerless walkers:

VPLACE | 17 november 2011

My Previous question was:
"Does it matter if I recharge,(300 mi battery), (using a 240v/50A Outlet) every night after 30 miles, or once a week after 210 miles??"

Notice that I did specify that I was using a 300 mile Battery!

210 mile usage is only 75% of battery capacity, so I don't understand your reference to "the 10% mark"!??

Also, I still don't know which is best for battery life ...daily charging or weekly charging!!??

brianman | 17 november 2011

Sorry I missed the 300mi battery in your original question.

In one of the other threads, I posted a link discussing battery life for the Roadster from another forum. Many (most?) of us believe similar battery characteristics will apply for the S.

Some quick points from that discussion:
1. normal charging doesn't top off your battery at 100%, it does something more like 80% or 90%
2. range charging brings the number higher (95% perhaps)
3. draining your battery below 10% or 20% is generally bad for the battery

Combining those 1 and 3, you find 60%-70% of capacity is the most you should aim to drain your battery between normal topoff charging.

As such, the 75% amount doesn't really fit.

In short, daily charging is much better for the battery than weekly in this scenario.

That's my understanding at least. Hope this helps.

rdgreene | 18 november 2011

I'm a little scared of battery memory/degrade (I know lithium ion is supposed to cure this). The reason is that I've noticed in most current solid state devices (ie: iPhone 4, recent laptop) -- if the use profile is slight use and constant "top off", this leads relatively quickly (in 6-9 months) to a battery that has very minimal charge capacity. As an example, my 6 month old laptop battery -- which goes in the docking station "all the time" so it's always constantly topped off, now only lasts about 30 minutes.

On the other hand, if I follow the "full discharge" use pattern -- ie: don't allow the device to charge until the battery is near total depletion, then I don't see this type of charge capacity degradation.

I'm curious what other folks think about this (and whether they have corresponding "real world" experience that matches mine) -- of course, with the thought of "should I charge the Tesla every night or should I run it all the way to zero, and only THEN charge it"

Kallisman | 18 november 2011

Don't worry, rdgreene. The Tesla charging is designed to not charge the battery to 100% on a daily basis to prevent serious degradation. In standard mode it will only charge to 80-90%. The car will also prevent u from discharging the battery completely for the same reason.

Computer manufacturers don't care about the longevity of the battery. They simply tell you to buy a new one, so they make more money. Not covered by warranty since it's considered a consumable part. It would be really nice if laptops could be more nice to the batteries too, not keep them at 100% over time.

Daxz | 18 november 2011

There is a good article on charging batteries at:
...a performance drop of recoverable capacity caused by environmental conditions and not cycling. The worst condition is keeping a fully charged battery at elevated temperatures, which is the case when running a laptop on the power grid.
.... a Li-ion battery can also fail because of undercharge

So keep your batteries cool and with enough power.

- maybe this should be argument against solar panel roof too. The increase in solar heat absorbed by the car may kill the battery faster than any small charge you could give it. Just try to park in shady cool spots whenever possible.

EdG | 18 november 2011

While parking in a shady cool spot seems excellent advice (in warm to hot weather), I hope the car will cool the battery even when parked to protect itself. Then being in a shady spot will be good to conserve charge.

VPLACE | 18 november 2011

Thanks all-for the Charging frequency info!
I must say, I a little concernd about the limitations of the "usable" 300 mile battery trip max driving mile range.
(I'm not disputing the data, only the consequences.)

For example, best case 10% top and bottom battery protection buffer, limits a realistic maximum driving range of 240 miles (300-10% top & 10% bottom).
Similary, the max driving range for a 20% top & 20% bottem buffer would limit the max driving range to 180 miles.....not what I was expecting!!

Mycroft | 18 november 2011

300 miles is the maximum range. It is NOT the daily range.

Hopefully Tesla will be honest in their materials and won't let people assume they can drive up to 300 miles every day.

Using the Roadster as a guide, the maximum standard charge will be around (300*.80)-30 = 210 miles. So you would safely be able to drive a bit over 200 miles every if you so choose to do so.

When you need to drive long distance, you would charge in max-range mode immediately prior to going. Then you would have the full 300 miles available. Although I would want to plan on charging somewhere around 250-280 miles unless the destination was within 300.

Robert.Boston | 19 november 2011


The 300-mile range is not a theoretical "if we let you over-charge the battery and then run it to 0%" number; 300 miles will be achievable with a new battery at Range charge and running the battery down to the "safe" bottom. There's no need to deduct 10% at top and bottom.

VPLACE | 19 november 2011

Thanks again.
Bottom line, with a 'new' battery, and normal driving conditions, I should feel 'comfortable' in reaching my drive destination, with a 'Full Battery Charge', if my destination is within 300 miles, ...including all battery charging safety requirements, which are built into the battery and the Tesla charger!!??

Do I have it right!!

Mycroft | 19 november 2011


Timo | 20 november 2011

There is a catch in that 300 mile range: it is with normal weather and paved road distance. If you drive bad roads at winter you won't get that much unless you drive rather slowly. OTOH by driving slowly you could have 400+ mile range...

Volker.Berlin | 20 november 2011

If you drive bad roads at winter you won't get that much unless you drive rather slowly. (Timo)

...which might be advisable on bad roads in winter anyway... ;-) SCNR
(The argument you make is of course entirely valid.)

Brian H | 20 november 2011

Nah; I'll bet Timo likes to do 70 mph+ on snow-packed roads and mountain passes. Some people live for cheap (or expensive) thrills!

Timo | 20 november 2011

More like 65, though I have driven faster than that when needed. Snow and ice is nothing odd here so every Finn knows how to drive in it.

Fun is not with the speed but the slides ;)

Brian H | 21 november 2011

Yeah, I grew up and learned in Eastern Canada, and was horrified at what happens here in Vancouver on the Wet Coast when it snows (every year or two). People gun their motors trying to get uphill (the city is mostly hills) on summer tires. That produces instant ice, and doowwwnn they go, bouncing off whatever happens to be lining the road as they head for the next intersection.

The ones who drive to the mountains to ski eventually learn (or die). But the rest ...