# Forums

## battery mileage

lets say you drive in moderately hilly roads
lets say you drive during winter half the year
lets say half your battery charges are supercharges and half are regular
lets say that most of the time you fully discharge the battery (when about 30 miles is left in the charge) before charging

how many miles would the battery give me before I'd have to replace it with a new one?
thanks!

P.S. did I miss any other factors affecting the battery life?

Brian H | January 20, 2013

If you can tolerate reduction to 70-80% of new capacity, how many miles can you drive in 8 years? 200K?

Timo | January 20, 2013

Other than this I understand:

"lets say that most of the time you fully discharge the battery (when about 30 miles is left in the charge) before charging"

Why would you want to fully discharge before charging? Just plug it in every day.

drp | January 20, 2013

Timo

I think he implies that is the daily commute and if almost uses all the juice

Timo | January 20, 2013

That's d*mn long commuting. 250miles at 60mph would take over four hours, two hour drive each direction. To me that would get old really fast, so I would be looking for apartment closer to whatever the reason for that long commuting is.

ylyubarsky | January 21, 2013

To calculate it, first of all we need to know the percentage that considers to be replacement point. For instance 50% left, it should be replaced and so on. Then if every year the battery looses 3%, let's give it 5%. So 10 years to be replaced. Every year an average of 25,000 miles. So we have 250,000 miles before battery replacement. It's only a guess. But tell me, how many of you drove your car 250,000 miles. I change my car every 3 years. So I think that more than 90% will sell the car and buy a new one long time before the battery is dead. That's my personal opinion. What do you think?

Sudre_ | January 21, 2013

Some people don't have a commute. They work from their car and drive place to place all day and they don't want to beg their customer for a plug. A realtor in the country for example might easily drive 200+ miles a day.

drp | January 21, 2013

I drive about 34,000 miles a year and sold my Euro van with 283,000 miles on it after 3 1/2 years. The more I read however the less range anxiety I have. It seems like the degradation of the battery is nowhere near what the naysayers seem to suggest. A 110 plug in at work is the worst case scenario and that can go along way. Only time will tell and it's pretty much just mental masturb.... at this point.

Deanhuff.fl.us | January 21, 2013

First let me say I'm rationalizing the MS purchase to myself as spending on the car rather than gas (with some mid-life crisis dollars thrown in). Right now I spend between \$350 - \$400 a month on fuel.

I have the same questions about mileage and degradation... My work commute is 125 miles a day (62 each way) I live in FL and all of my driving is on the highway. So the conditions would be something like:

95 degrees
A/C running
72 - 75 mph
125 miles a day

My office has been very receptive to the idea of putting in a Level 2 J1772 charger (220 - 30Amp). There are a couple of Volt owners @ work and I think we could work out a schedule to share. I am guessing a work recharge would take 3-4 hours a day (replenish 62 miles). Then @ home I'd have another 2 hr recharge off the 50Amp at night (replenish another 62 miles).

In theory the 45kWh should do fine... but I put 35k - 40k miles on a car each year. I'm weighing the benefits of upgrading the battery to the 60 or 85 VS purchasing a replacement 45kWh battery down the road.

Brian H | January 21, 2013

The 40 (not 45) kWh would be pushing it. You'd be pretty much completely dependent on that work charge. The 60 would give you the safety margin; likely you could do the RT without trouble when necessary.

Deanhuff.fl.us | January 21, 2013

Yes, 40 not 45.

I spoke with my sales guy today....he also recommended the 60. 10K is a pretty big option to my pocketbook.....decisions, decisions

Brian H | January 21, 2013

And then, of course, you'd have the option (on finalize date only) to opt for Supercharging, for a mere \$2K more! |9-/

Timo | January 21, 2013

If you drive for living, then I suggest getting SC capability, no matter which battery version you finally choose. So 60kWh at min 85kWh performance at max (current max).

so the general guess is 200k - 250k miles before the battery would need replacement (when the battery reached 50% meaning every charge would now give half the miles the battery was initially offering per charge) ?

Brian H | January 26, 2013

The general standard is 70% remaining is "end of life" for the original application of the battery. But of course an owner can use his own.

Neech | January 26, 2013

Can we expect that the battery must be replaced at 8 years even though there is ~70% charge left?

Brian H | January 27, 2013

It would be about the same as a new 60 at that point, and degradation would be proceeding more slowly than at first. If that's enough mileage, I don't see why you'd need to. But you might want to.

Brian H | January 27, 2013

I mean, of course, an 85 would be about the same as a new 60. Don't know about the power draw and accel.

Damian | January 27, 2013

I am told to discharge the battery as much as possible (95-98%) once a year. This will prevent the battery from losing it's overall charge of 3% a year. This falls under the heading of maintenance. Has anyone else heard this?

drp | January 27, 2013

At 170 miles a day at least four times a week I'm probably going to be discharging my battery a lot more frequently than that! I can't imagine I'll resist the temptation to open up on the long stretches of expressway that I have during my typical commute!

Damian | January 27, 2013

Selling an MS every 3 years???

When the car is getting better through its updates and you have been taking the car from being almost perfect to a place where all the pesky annoyances are now all gone, sounds counter-intuitive, but that's me.

teddyg | January 27, 2013

I really wouldn't be buying a Model S if I frequently did long range trips requiring a near full discharge and near full recharge. This would represent a full charging cycle...I think Tesla is relying on the fact that 95% of people drive less than 50 miles per day so that the vast majority of the time you are only using around 20-25% of the total capacity each day...therefore they are banking on one full cycle of the battery every 4-5 days on average. I imagine this is how they arrive at the 25% average capacity loss over 8-10 years.

I might do a long road trip three or four times a year so the first gen Model S is fine for me. If however I was someone who road-tripped every weekend I would hold off to see what the effect of frequent full cycle discharges and supercharging really has on these cars and batteries.
I love Tesla and I wish them all the best...I just wouldn't be able to afford taking a chance right now if I were a frequent road-tripper...I'm not so I'm all in...but just giving my 2 cents.

Brian H | January 27, 2013

I thought the "full discharge occasionally" meme just applied to NiCad, etc, not to LiIon?? No memory effect with LiIon, e.g.

EVTripPlanner | January 27, 2013

I've created a quick-reference sheet covering charge rates/times, range, etc at www.hannelconsulting.com/tesla - I've noticed quite a few people downloading it...it also covers estimated actual capacity vs. spec given your range/consumption

teddyg | January 27, 2013

Brian...its not really about memory effect...its about how many charging cycles you can get out of a battery.
When a battery goes from 100% to 0% and then is recharged to 100% that is one full charging cycle.
High end lithium ion batteries might get 750-1000 full charging cycles before capacity is significantly reduced.
So by me only using 20% of my Model S capacity every day I complete a full charge cycle every 5 days...5 x 750 = 3,750/ 365 = about 10 years of driving before my range is significantly reduced (say to 25% of original capacity as Tesla states).

However if I had a much longer commute and was road tripping often with SC use it might I might be going through a full charging cycle every 2 days...2 x 750 = 1,500/ 365 = about just over 4 years of driving before my range is significantly reduced.

Battery cycle life will improve over time (perhaps much more rapidly than overall capacity) which is why I wouldn't be ready for the first gen Model S right now if I was a frequent road tripper or had a 100+ mile daily commute. Since my daily commute is less than 40 miles...I'm ready now but others who frequenetly road trip or have long commutes should take this into consideration.
Not saying Tesla isn't on top of all this already its just I couldn't afford to take a \$75,000+ gamble on it just yet...I would wait until more data comes back on this for long range commuters or frequent road trippers intending to use superchargers often.